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View Full Version : Brutus's 5-speed El Moto (transmission discussion)



Brutus
04 May 2011, 1741
Everyone here is left to guess about the usefulness of a transmission and its benefits. I am the only one who has a working prototype with 5 gears. To be quite honest you all don't know what you have been missing! It is like riding an ICE bike and I am glad Brammo has seen the light. If any of you doubt me you are welcome to come take Brutus for a spin around the block. :)

EDIT: Nuts&Volts here, I moved the first 15 posts to a new thread to suit the discussion

jpanichella
04 May 2011, 1743
Everyone here is left to guess about the usefulness of a transmission and its benefits. I am the only one who has a working prototype with 5 gears. To be quite honest you all don't know what you have been missing! It is like riding an ICE bike and I am glad Brammo has seen the light. If any of you doubt me you are welcome to come take Brutus for a spin around the block. :)

Aw man, then where are the high resolution pictures and videos for us to salivate over?

Edit: duh, found your build thread.

Richard230
04 May 2011, 1759
I may be the odd man out (as usual), but one of the things I like about electric vehicles is that they don't have a transmission. I have been shifting and clutching all my life and find that not having to do so is relaxing and lets me better concentrate on the traffic and scenery around me. I sure hope the Empulse motor doesn't sound like the one in the video above. That thing sounds like a hive full of killer bees. I never cared much for bees. Maybe they can sell some playing cards as an accessory to attach to the spokes.

cycleguy
04 May 2011, 1807
Everyone here is left to guess about the usefulness of a transmission and its benefits. I am the only one who has a working prototype with 5 gears. To be quite honest you all don't know what you have been missing! It is like riding an ICE bike and I am glad Brammo has seen the light. If any of you doubt me you are welcome to come take Brutus for a spin around the block. :)

I'd be very interested in some details of what it's like to ride, in particular, how quickly does the torque fall off when holding it in gear? Do you find that downshifting when already at speed, forcing the motor way past it's torque knee results in slower acceleration?
Do you find it most effective when short shifting? Does it accelerate faster at times by upshifting vs. holding it in gear? How often do you find yourself in the wrong gear?

Thanks in advance for the info. I think it would give everyone a better idea of the benefits.

DaveAK
04 May 2011, 1823
Everyone here is left to guess about the usefulness of a transmission and its benefits. I am the only one who has a working prototype with 5 gears. To be quite honest you all don't know what you have been missing! It is like riding an ICE bike and I am glad Brammo has seen the light. If any of you doubt me you are welcome to come take Brutus for a spin around the block. :)
Unfortunately this is true, but it's not from a lack of interest, just a lack of money and the skills that you clearly have. I'm waiting for a full, (and hopefully Brutusly honest :) report on how well it operates. Do you need all five gears for example. What you would have done diferently if anything. Stuff like that.

Brutus
04 May 2011, 1842
First gear pulls hard right to the top and struggles to hit the last 6mph. Second gear picks up and pulls the same and struggles to get to the last few mph and 3,4,5 are the same way. That was today with a dead pack. Pretty much it downshifts and feels like a ICE motor with low compression, as for the downshift thing, yes it pulls horrible if it falls off the torque knee(much better to let the next gear pull it vs. downshifting like an ICE) and shifting short is the best way to make it accelerate to higher speeds.

I should probably qualify what I consider to pull hard, I ride a Suzuki Hayabusa daily so when I say it pulls hard I am not joking.

cycleguy
04 May 2011, 1902
First gear pulls hard right to the top and struggles to hit the last 6mph. Second gear picks up and pulls the same and struggles to get to the last few mph and 3,4,5 are the same way. That was today with a dead pack. Pretty much it downshifts and feels like a ICE motor with low compression, as for the downshift thing, yes it pulls horrible if it falls off the torque knee(much better to let the next gear pull it vs. downshifting like an ICE) and shifting short is the best way to make it accelerate to higher speeds.

I should probably qualify what I consider to pull hard, I ride a Suzuki Hayabusa daily so when I say it pulls hard I am not joking.

I'm assuming you still have a clutch, if so, do you find it difficult getting it into gear at a standstill without the transmission shaft turning?
The powerband sounds similar to a low revving diesel, lots of torque but power flattens out quickly.

Brutus
04 May 2011, 1926
The clutch exploded on me after a few drag race style standing starts, it was only rated for 50ft.lbs and the motor I am using pulls 80. Rolling forward or backward a few inches will handle the synchro and it falls into gear with no clutch and no application of the throttle. shifting at speed is as simple as letting off the throttle and shifting the lever.(weather down or up) If you ever rode a Honda 185s ATC then it is very similar, except the thumb throttle :)

And I think you nailed it with the diesel analogy, that is why I completely changed the primary and final ratios to better space, and use the amount of torque available.

DaveAK
04 May 2011, 1932
So do you think all five gears are worth it? If you redid the design do you think you'd use fewer or more gears, or keep it at five?

harlan
04 May 2011, 1937
Everyone here is left to guess about the usefulness of a transmission and its benefits. I am the only one who has a working prototype with 5 gears. To be quite honest you all don't know what you have been missing! It is like riding an ICE bike and I am glad Brammo has seen the light. If any of you doubt me you are welcome to come take Brutus for a spin around the block. :)

My first EV conversion was a car and it used the original 5 speed gearbox with aluminum racing flywheel and racing clutch. It would have been undriveable without the gearbox however I only needed two speeds, 2nd and 3rd. If I had to do it all over again though I would just use a bigger motor and lost the gearbox altogether.

Brutus
04 May 2011, 1946
My first EV conversion was a car and it used the original 5 speed gearbox with aluminum racing flywheel and racing clutch. It would have been undriveable without the gearbox however I only needed two speeds, 2nd and 3rd. If I had to do it all over again though I would just use a bigger motor and lost the gearbox altogether.

Did you play with the rear end gearing or leave it stock?

Brutus
04 May 2011, 1957
So do you think all five gears are worth it? If you redid the design do you think you'd use fewer or more gears, or keep it at five?

Yes all 5 are worth it, 6 might be overkill and 4 would limit your top end. It really boils down to what the bike is going to be used for and then gear it accordingly. I have the ability to choose 4,5, or 6 and am quite pleased with my choice of 5 because it will do everything I need it to.

Nuts & Volts
04 May 2011, 1958
Yes all 5 are worth it, 6 might be overkill and 4 would limit your top end. It really boils down to what the bike is going to be used for and then gear it accordingly. I have the ability to choose 4,5, or 6 and am quite pleased with my choice of 5 because it will do everything I need it to.

Any idea of the weight of the transmission?

Brutus
04 May 2011, 2008
Mine weighs around 50lbs. with oil. a 6 would be a few pounds more, but it would never get over 60lbs. with my primary.

Nuts & Volts
04 May 2011, 2025
I think a good test would be for you to get a 0-60 time or a 1/4 mile time with shifting and then a time without shifting (maybe in a few different gears). That would kinda show a difference in performance

OR a more representative test would to get a time without the transmission at all, but that is asking a lot.

Oh oh or do the first test, but have someone 50lbs lighter ride the bike on the no shifting run ...please :D

Also any idea of cost? sorry I like data :)

DaveAK
04 May 2011, 2026
Yes all 5 are worth it, 6 might be overkill and 4 would limit your top end. It really boils down to what the bike is going to be used for and then gear it accordingly. I have the ability to choose 4,5, or 6 and am quite pleased with my choice of 5 because it will do everything I need it to.
So what you're saying, and please correct me if I'm wrong, is that a well designed system performs well. Who'd a thunk it? :D

My hat's off to you sir. Besides performing to your expectations it's a beautiful piece of work.

Brutus
04 May 2011, 2036
I think a good test would be for you to get a 0-60 time or a 1/4 mile time with shifting and then a time without shifting (maybe in a few different gears). That would kinda show a difference in performance

OR a more representative test would to get a time without the transmission at all, but that is asking a lot.

Oh oh or do the first test, but have someone 50lbs lighter ride the bike on the no shifting run ...please :D

Also any idea of cost? sorry I like data :)

I do believe a guy name podolefsky here has the Identical setup as me but his batteries are waaay better then mine. so for no trans data I would look to him as for my data I will do a full test on Saturday morning and post video and data no matter what the outcome.

I do know that 0 to 60 is 5.4 and top speed in 5th was 119mph, but I changed my rear sprocket so those numbers are going to change again. This is part of the reason I don't keep posting numbers, because they keep changing. ;)

Brutus
04 May 2011, 2038
Thank you DaveAk, that really means a lot. :)

Nuts & Volts
04 May 2011, 2057
I do believe a guy name podolefsky here has the Identical setup as me but his batteries are waaay better then mine. so for no trans data I would look to him as for my data I will do a full test on Saturday morning and post video and data no matter what the outcome.

I do know that 0 to 60 is 5.4 and top speed in 5th was 119mph, but I changed my rear sprocket so those numbers are going to change again. This is part of the reason I don't keep posting numbers, because they keep changing. ;)

You the man!

I would install a tranny if i could get a 3 or 4 speed for 30lbs and a 2 speed for 15-20lbs. But I am looking at a 80HP system. Lower peak HP than more gears makes sense.

Oh and I agree with Dave (thats twice in one day!)

chef
04 May 2011, 2138
The tranny wars sure have gotten alot tamer :D

teddillard
05 May 2011, 0238
Yeah, it's a little different when you're talking to someone who's actually done it, huh? HAahahaaa

GREAT info man, thanks for posting. I think, like everything else on an electric motorcycle, we gotta "think different". It doesn't seem to be about using the peaks of the power curve, as with ICE, it's more about extending the top and the bottom of the curve... is that a fair analogy?

...not enough coffee yet to make an illustration of what I mean. o_0

Square Wave
05 May 2011, 0312
Now you understand, Ted. That's what I've struggled to find a way to say. The Square Wave CVT was fragile and terribly inefficient last year but it clearly improved acceleration.

teddillard
05 May 2011, 0355
So, OK, coffee's starting to kick in... here's what I gotz, kick away:

This is my little totally simple-minded visual. The first is an ICE motor power curve:

http://evmc2.files.wordpress.com/2010/11/attachment.jpg?w=462&h=268

This, in it's simplest form, is what a three-speed does to an ICE motor power curve:

http://evmc2.files.wordpress.com/2010/11/attachment-1.jpg?w=473&h=267

Now, what a tranny on an electric motor gives you is better mechanical advantage at the low end, right? So the motor can accelerate the bike faster, with less load. At the top end it's a different challenge- re-gear the bike so the top RPM of the motor doesn't top out before you want it to, assuming the motor has the horsepower to keep pulling at speed...

Here's my stab:

http://evmc2.files.wordpress.com/2011/05/picture-1.png?w=593&h=595

This is just trying to show the load (thus, the heat) on the motor. With a transmission, you're getting a more dramatic drop in load at low speeds (the motor is working less, so it stays cooler) then it averages out to be more even- you're putting more load at the top speeds than without the tranny (so you can keep pulling) yet you're putting less on it at low speeds (so you can accelerate faster).

What becomes totally clear when I was working on this graph is that the more gears you add, the more you spread out the power. You can literally distribute it to wherever you want it to be. If you gear it really low, the load drops really fast, and by adding more gears you can keep it low.

Obviously there are other factors, and I'm sure the engineers and physicists are gonna go nutzo on the details... for instance, when you add more gears you add more weight... yeah, fine. I like pictures. (...and strawberry ice cream.) :D

edit: I think it just dawned on me why this is so hard to get my head around. With a gas motor you're looking at the output, because that's basically fixed over the RPM range. You're looking to take an available resource and put it where you need to. With an electric motor you're dealing with a powerplant that will draw as much as it needs to do the work, and the issue isn't as much delivering a resource, but keeping the thing from drawing more than it can handle before it goes all melty... Like I said, we gots to tink different.

chef
05 May 2011, 0704
There have been other 2-wheel conversions that retained the transmission. I believe one was based on a Yamaha sport bike. Not well documented and no controlled comparisons, making it tough to claim indisputable advantages. The owner liked the performance but that's subjective, opening up endless debate. As was stated before, it just takes one company releasing product to sway public opinion.

Warren
05 May 2011, 0729
Ted,

Try more coffee. Here is a dyno plot from the infamous Jack Richard.

http://1.bp.blogspot.com/-N8TxG8PbAu0/TarwTzURfbI/AAAAAAAACKg/wTVUrnlPrDk/s1600/spyder7601horsepower.jpg

Notice that it looks a lot like your second plot. With a gear box, you can run the motor at it's highest power over a greater range, for maximum acceleration, and top end. Or you can run it at it's most efficient for maximum range....just like an ICE.

Early ICE machines had a single cylinder engine with a huge bore, and stroke. They could run with no clutch or gearbox. They pretty quickly learned that a better compromise was a smaller higher speed motor, with a clutch and multi-gear transmission.

Whether EV designers will eventually come to the same conclusion, I can't say. But for on-road vehicles, I can definitely say that, as long as the battery is such a huge part of the weight and expense of an EV, aerodynamics is where you want to put your emphasis.

Cedric Lynch, the ultimate EV geek, figured this out. He had a wimpy controller, and battery to start, so he used six gears on his bike. Once he had a system that could produce higher volts and amps, he dumped the gears. But he kept the aero fairing!

Warren

markcycle
05 May 2011, 0738
Tesla also eliminated the gear box

teddillard
05 May 2011, 0740
Ted,

Try more coffee. Here is a dyno plot from the infamous Jack Richard.


Due respect, I don't follow... want to try that again? It seems we're in agreement, but I can't really tell. (Were we talking about aerodynamics here? ... and I certainly am not even bothering with anything Jack posts... who knows anything about where that came from?)

Anyway, my illustration is far from proof, it's more a way to visualize the motor's load distribution over the speed of the vehicle. And it makes sense to me. :D

edit: Let me just make a very simple point here. What I'm looking at is load. Tell me if that's wrong.
I've seen the comments over and over again... in gearing discussions. Too high a gear ratio and you pull great accelerating, but don't reach top speed. (The motor has less load and can pull it well at slow speed, but the motor reaches RPM limit at the top speed.) Too low a gear and you get your top speed, but the motor works too hard at low speed acceleration and heats.)

Simple solution. Gear it low, to give the mechanical advantage so the motor isn't overworked at low speeds, and then switch it to higher gearing to spread the load to the top speed range. Transmission. Spreading load over the speed range... a little, slightly different concept than spreading a narrow powerband over the same speed range. Just different because you're concerned with overheating due to over-loading, rather than simply distributing available power.

jpanichella
05 May 2011, 0753
Tesla also eliminated the gear box

I read that they were having tons of reliability issues with their transmission due to the amount of torque their motor was producing.

teddillard
05 May 2011, 0801
I read that they were having tons of reliability issues with their transmission due to the amount of torque their motor was producing.

Yeah, they also aren't as much concerned with running the smallest, lightest motor they can. The simple answer = bigger motor, which we don't want to do on a bike.

Nuts & Volts
05 May 2011, 0807
Tesla also eliminated the gear box

Its not that they eliminated. It was that they didnt have the time and resources to design it so that it wouldnt keep breaking. I know there was a lot of tension caused internally. I believe this tension was due to some engineers wanting to put more time into solving this issue and other engineers saying we need stop so that we can get this car to market.

Yeah, they also aren't as much concerned with running the smallest, lightest motor they can. The simple answer = bigger motor, which we don't want to do on a bike.
Thats very true, unless your Chip Yates :)

cycleguy
05 May 2011, 0817
Here is a plot of the torque curves of a Honda CRF450 and an AC15 motor.
I picked the CRF 450 because it has similar HP to the AC15. The Honda is geared for a max top speed of 75MPH, which is about 1000 rear wheel RPM. The AC15 gearing is adjusted to match the top speed of the Honda CRF which ends up being approx. 8:1

Max torque of the CRF is 36 lb/ft. The overall gear ratio for each gear is calculated and the total rear wheel torque is plotted in red for each gear of the CRF against the AC15 rear wheel torque with an 8:1 ratio.

http://i32.photobucket.com/albums/d27/roehrcycleguy/MotorToquecomparison-1.jpg

I think we can see that despite the much lower torque of the CRF engine, when multiplied by the 19:1 overall 1st gear ratio, it ends up with significantly more torque to the rear wheel, so in this case the CRF would accelerate faster than the AC15, through out it's range. It should be noted that this is assuming that the engine is shifted at just the right RPM.

It's pretty clear that the CRF would outperform the AC15 in it's present configuration, however, we are comparing a highly developed and optimized ICE engine to what is essentially an off the shelf fork lift motor/controller setup. There is lot's of room for increased performance of the electric motor, that would easily allow it to outperform the ICE.

For example. Doubling the voltage, along with the appropriate controller could double the RPM capability of the electric motor which would allow the motor to be geared at 16:1 rather than 8:1, and achieve the same top speed but double the amount of torque to the rear wheel. At twice the amount of torque, it would blow away the ICE, no question.

Concentrating on higher voltages and high speed controllers is much more useful towards improving EV performance than adding a transmission, in my opinion.

teddillard
05 May 2011, 0829
But again... please show me the error of my ways. I'm not looking at torque, I'm looking at load on the motor, and that's the significant difference between an electric motor and a gas motor.

And you can't look at just torque, anyway, it doesn't tell the whole story. You have to look at HP vs speed too, in your model, right?

cycleguy
05 May 2011, 0835
Both examples have the same horsepower, roughly somewhere around 45HP. Gearing doesn't effect HP, you are just trading between speed and torque. Given two sources with equal HP, the one that transmits more torque to the rear wheel will accelerate faster.

Brutus
05 May 2011, 0858
Now if you added a transmission to your electric motor and geared it right for an electric motor it would walk all over that 450 with the same HP and torque right?

teddillard
05 May 2011, 0859
Both examples have the same horsepower, ...

OK, I see you deftly avoided my question about my illustration, though... :D Is it valid to equate current load on a motor to torque output?

My guess... no.


Now if you added a transmission to your electric motor and geared it right for an electric motor it would walk all over that 450 with the same HP and torque right?

...exactly. :D

Nuts & Volts
05 May 2011, 0904
OK, I see you deftly avoided my question about my illustration, though... :D Is it valid to equate current load on a motor to torque output?

My guess... no.

Its better to look at torque. That's what tells you how fast you can accelerate. The speed simply tells you know long/far you can accelerate. I dont think your illustration is completely ted, but for me it is difficult to interpret. I am guessing you are displaying road load? why does that go down with speed, it should go up do to aero drag??


Now if you added a transmission to your electric motor and geared it right for an electric motor it would walk all over that 450 with the same HP and torque right?

Exactly. Instead of zigzags like the ICE, you would have a number of torque steps. So overlay a 16:1 and a 8:1 AC15 curve on the graph and you have a two speed torque curve. Which will kick that 450's ass

cycleguy
05 May 2011, 0916
OK, I see you deftly avoided my question about my illustration, though... Is it valid to equate current load on a motor to torque output?

Sorry Ted, I didn't mean to avoid your question. I just don't understand your graph, mainly regarding load. I don't understand why you are plotting load on the left side of the graph.

DaveAK
05 May 2011, 0919
What kinds of ratios are you runnning and/or how are they spaced? 1--2--3--4--5 or 1-2---3---4-5 or 1---2-3-4---5 kinda thing?

I'll let these other bozos argue theory til they're blue in the face, I'm interested in the practical application. :D Remind me of the motor/controller/voltage your running.

teddillard
05 May 2011, 0921
Sorry Ted, I didn't mean to avoid your question. I just don't understand your graph, mainly regarding load. I don't understand why you are plotting load on the left side of the graph.

Yeah, I get it. It's the trouble with being a photographer... everything is visual. :D

I'm not sure if I can even explain it more, just that at low speeds if a motor is geared too low it has too much load on it. I think I'm using the idea of load in a way that's just too removed from the way you engineer guys are looking at things.

Maybe not a good illustration... but it's totally in line with the notion that Brammo is using a tranny to help keep the motor cooler, yet pull high speeds.

I think.

cycleguy
05 May 2011, 0926
Now if you added a transmission to your electric motor and geared it right for an electric motor it would walk all over that 450 with the same HP and torque right?

Why not just add an additional motor? Not only would you have twice the torque, you'd also have twice the horsepower, in the same space taken up by the transmission and clutch. I don't disagree that adding a transmission would be beneficial, I just don't think it's worth it compared to adding a second motor, or raising the voltage substantially on a single motor.
The transmission does not add horsepower, only torque, sooner or later you'll be in high gear where the transmission won't help you at all, instead it will hurt you with all the added weight and parasitic drag doing nothing to make you go faster.

Brutus
05 May 2011, 0933
What kinds of ratios are you runnning and/or how are they spaced? 1--2--3--4--5 or 1-2---3---4-5 or 1---2-3-4---5 kinda thing?

I'll let these other bozos argue theory til they're blue in the face, I'm interested in the practical application. :D Remind me of the motor/controller/voltage your running.

1--2-3-4-5 d&d es 15-6 alltrax 7245 and 72v 21ah sla (for now)

Brutus
05 May 2011, 0937
you keep saying added weight...where? a motor and extra batteries has more weight than a trans period. And one more thing rpm requires voltage with your way so do you want 300v between your legs to go 150 mph or 96v to go 150?

cycleguy
05 May 2011, 0949
you keep saying added weight...where? a motor and extra batteries has more weight than a trans period. And one more thing rpm requires voltage with your way so do you want 300v between your legs to go 150 mph or 96v to go 150?

Explain exactly how adding a transmission would allow the same top speed at 1/3 the voltage?

teddillard
05 May 2011, 0953
Explain exactly how adding a transmission would allow the same top speed at 1/3 the voltage?

Yeah, see, here we go again talking theory vs practice. Here we have a guy with a bike with a tranny... let's stick with the facts, mebbee?

DaveAK
05 May 2011, 0957
I really want to take you up on your offer of trying it out. It's just so intruiging to me. Not that you used a transmission, I've always thought that warranted some investigation, but that you used 5 gears and not 2 or 3. Did you start out with 5 in mind?

Nuts & Volts
05 May 2011, 0958
you keep saying added weight...where? a motor and extra batteries has more weight than a trans period. And one more thing rpm requires voltage with your way so do you want 300v between your legs to go 150 mph or 96v to go 150?

Brutus you can add 40HP in both a motor and batteries for the same 50lbs and space your transmission takes up. Actually for enough money you could add a 100HP in both motor and battery for 50 lbs.
So you dont do a transmission or another motor/batteries because of a weight advantage. You do it for a cost, simplicity, and "cost-effective" performance advantage.

1 agni will do 40HP peak, but that is only at 1 single speed. If I use a 2 speed I can now get that 40HP and all the torque leading up to that point at 2 speeds in my speed band. Instead of spending $2000 to increase my battery (more batteries), controller(another controller) and motor power (another motor), I used a $500 transmission to utilize my maximum power of my current setup twice (or 6 times for Brutus) as much as a single speed system.

If you want effeciency then dont use a transmission or build a new one

Brutus
05 May 2011, 1004
Explain exactly how adding a transmission would allow the same top speed at 1/3 the voltage?

How about you answer a question for me and then you might get a little insight without me writing a book.

How many gear ratio's do you deal with if you have a 5 speed trans added to a standard Brammo enertia?

frodus
05 May 2011, 1014
in the end, the motor is still the limitation of top speed. Without enough HP, you're still **** outta luck.

119mph is impressive though, good job.

cycleguy
05 May 2011, 1014
so do you want 300v between your legs to go 150 mph or 96v to go 150?

I'd much rather go 150MPH on 96V, but please explain how adding a transmission is going to do that for me? Just asking you to explain the reasoning behind your claim.

jpanichella
05 May 2011, 1017
in the end, the motor is still the limitation of top speed. Without enough HP, you're still **** outta luck.

119mph is impressive though, good job.

119mph with lead acid batts make it even more impressive.

teddillard
05 May 2011, 1017
in the end, the motor is still the limitation of top speed. Without enough HP, you're still **** outta luck..

Right, but we want top speed and acceleration too.

Brutus
05 May 2011, 1025
I really want to take you up on your offer of trying it out. It's just so intruiging to me. Not that you used a transmission, I've always thought that warranted some investigation, but that you used 5 gears and not 2 or 3. Did you start out with 5 in mind?

My whole point in building Brutus was to use parts that already exist as much as possible to keep costs down and also have the ability to customize and change things to suit the owner. Basically build an electric motorcycle that can be customized off the shelf much like motorcycle riders tend to do. There are only 7 parts that I have to make to put this bike together, other than that the aftermarket already exists for my bike and that keeps build costs down and options high. Going with 5 speeds was always the plan from the start.

DaveAK
05 May 2011, 1032
I had a 99 TransAm that was specifically designed to go from 1st to 4th under normal driving. If you wanted 2nd you had to gun it. What would the Brutus be like if you say stuck it in 3rd and rode at a sedentary pace, like you were a law abiding citizen or something equally as boring? :D

Harold in CR
05 May 2011, 1119
Right, but we want top speed and acceleration too.

By golly, I believe Ted has got it.:D

Where can the build thread be ?? I have looked in many places, just not the correct one ???

Nuts & Volts
05 May 2011, 1126
By golly, I believe Ted has got it.:D

Where can the build thread be ?? I have looked in many places, just not the correct one ???

http://brutusmotorcycle.com/

Harold in CR
05 May 2011, 1225
Thank You, Sir.

podolefsky
05 May 2011, 1352
in the end, the motor is still the limitation of top speed. Without enough HP, you're still **** outta luck.

119mph is impressive though, good job.

I agree - with the same motor, controller, and voltage as me...I want to go 119 mph (actually, that scares the crap out of me).

The max HP is what will limit your top speed. The thing is, electric motors have a HP peak, it's not flat. The peak is at the torque knee, which is (generally) way below the max RPM. So to get to, say, 100 mph you need to gear so that you're at the HP peak at 100 mph. If you do that, it's going to be a dog off the line.

I've played with lots of gear ratios, so I don't have a transmission but I know what different gearing feels like on the same bike. I had 65:13 (5:1) and it was a blast...to about 35 mph, then it just kind of putted up to 50 or so and that was it. I've also geared it 52:16 (3.25:1) and it was a blast between 40-75 mph (or so). The increase in power above 40 mph was huge...but it bogged down accelerating from a stop.

That's my experience, and why I would love to have at least 2 speeds...putting aside issues of efficiency and what not.

Now, I could get an AC motor and run it at 120V. Then I could gear it down, have good acceleration from a stop and have lots of high end power as well (because of how the high voltage extends the torque knee). But still, for the same reasons as above, having 2-3 speeds could (maybe) make it even better. It would just be faster across the board.

Now, there are a few things that make this more complicated. First is that if you gear too low (as I did at 5:1) you may not load the motor enough, meaning you don't pull as many amps as you could. That means you're missing out on available torque - you could gear lower, pull more amps and still have the same low end performance, and get a higher top speed. That's the sweet spot for a 1-speed bike. I could never pull more than ~300A when geared 5:1. My controller will do 450A and my batteries can handle that. I had 50% more torque available that I wasn't using.

The other thing to keep in mind is that even if you can gear down and go 100 mph, the question is whether and why you want to do that. The range takes such a massive hit at that speed that, unless you are doing very short runs, it's just not practical. Even at 70 mph I have about 1/3-1/2 the range as at 45 mph. I almost never go faster than 60 mph, but with my gearing (about 4:1) I can hit 70 mph. I do this for three reasons

-I like to have a bit more headroom at 60 so I'm not stuck there red lined.
-it gives me more power from 35-50 mph or so, which is nice for typical driving around town where you need to accelerate through traffic.
-I can tell people my bike does 70mph. If I say it does 60, they look a little nonplussed.

My 2c.

DaveAK
05 May 2011, 1407
Well from experience 120mph is very, very fun. :D

I'm aiming for about the same as you - 70mph top end so that I can say it can, and as quick off the line as I can get it while still reaching the top end, but most of my riding will be at 45mph so I'd like to also be able to say I can get 50 miles out of it. I like the idea of a transmission so that I can extended any of those numbers, even though I know it will be at the expense of something else.

DRZ400
05 May 2011, 1414
I like the two motor configuration. Adding series and parallel switching of the motors sounds worth looking into. Motors are in series with the pack then switch to parallel for max HP and speed (like my sons ride on Jeep). A 2 speed gear box would make sense too....just be sure you have a big pack. 120 mph sustained would be pulling over 20kw easy.

jpanichella
05 May 2011, 1423
I like the two motor configuration. Adding series and parallel switching of the motors sounds worth looking into. Motors are in series with the pack then switch to parallel for max HP and speed (like my sons ride on Jeep). A 2 speed gear box would make sense too....just be sure you have a big pack. 120 mph sustained would be pulling over 20kw easy.

You've seen Jozzer's Ducati, right? He has videos of him riding with a series/parallel switch on 2 agnis.

http://electricmotorcycleforum.com/boards/index.php?topic=504.0

DaveAK
05 May 2011, 1528
I've looked at series/parallel switching as well. As far as I'm concerned there's more than one way to skin this particular cat and I've no real preference at this stage. Personally I just think that a single motor and single gear ratio covers 100% of what I need but only 80-90% of what I want. So to get that extra 10-20% becomes a time/money/effort vs. reward question. I'd love to be in a position to try multiple options and report back. With Brutus having actually built a bike with a transmission now I'm waiting for some reports on a series/parallel switching setup. Jozzer's is a manual system right? I'll have to check that link again. I'd forgotten about it.

jpanichella
05 May 2011, 1540
I've looked at series/parallel switching as well. As far as I'm concerned there's more than one way to skin this particular cat and I've no real preference at this stage. Personally I just think that a single motor and single gear ratio covers 100% of what I need but only 80-90% of what I want. So to get that extra 10-20% becomes a time/money/effort vs. reward question. I'd love to be in a position to try multiple options and report back. With Brutus having actually built a bike with a transmission now I'm waiting for some reports on a series/parallel switching setup. Jozzer's is a manual system right? I'll have to check that link again. I'd forgotten about it.

I tend to agree, if I ever wanted more speed I would probably swap my sepex set up (same as yours) for an AC-15 set up. I walked into this project admiring the simplicity and lack of moving parts, adding a transmission defeats that.

DaveAK
05 May 2011, 1558
I tend to agree, if I ever wanted more speed I would probably swap my sepex set up (same as yours) for an AC-15 set up. I walked into this project admiring the simplicity and lack of moving parts, adding a transmission defeats that.
It's not really (just) about speed though. If it was then just up the voltage and/or bigger motor.

teddillard
05 May 2011, 1737
OK, more graphs. It occurred to me it's really simple... just graph the acceleration.

First graph, two gearings. One tops out at 60 mph, but gives you 0-60 in 6 sec. The second gives you taller gearing, and lets the motor reach top speed (limited by HP of course) but accelerates slower.

http://evmc2.files.wordpress.com/2011/05/picture-2.png?w=589&h=560

So, take the top of the tall gearing and put it on the lower gearing, you got a top speed of 75 and a 0-60 in 6 sec, total ET is 8.25 rather than 12. (all made-up numbers for the illustration, but I think in the ballpark...)

http://evmc2.files.wordpress.com/2011/05/picture-31.png?w=588&h=554

Nuts & Volts
05 May 2011, 1758
Now you're gettin it Ted! Now try that with 6 speeds and see how fast you get...

podolefsky
05 May 2011, 1910
I may have posted this on another thread, but here it is anyway.

First plot is rear-wheel-torque vs speed for two gear ratios using my D&D (14:65 and 16:52), compared to a Ninja 250 shifting through the gears. D&D is rated at 80 ft-lb. 2nd plot is HP (dashed line is theoretical required power vs speed).

Interpret as you will...

http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/ICE_gears.png

http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/ICE_HP.png

Barron
05 May 2011, 2055
Brutus - how many horsepower does your bike make?

chef
05 May 2011, 2157
A minor tangent...

This and a few other threads got me thinking (scary, yes). A gearbox is a mechanical method of smoothing out available power. For a given acceleration, lower gears reduce peak power drawn from the batteries (or conversely for given power draw, it can improve acceleration). The electrical approach is ultracaps or mixed-chemistry battery configurations (http://www.elmoto.net/showthread.php?500-Mixing-High-Powerand-High-energy-cells.&p=5905&viewfull=1#post5905). Very different approaches with the same goal. These may only be comparable for low-end acceleration. I'm not sure how ultracaps or hybrid packs would improve top speed.

I know, oversimplified in too many ways, but this intrigued me. Maybe there's a way to incorporate the best of both the electrical and mechanical approaches.

teddillard
06 May 2011, 0249
Now you're gettin it Ted! Now try that with 6 speeds and see how fast you get...

HA! (I should say, no, now you're getting it*, but that would be cruel...) But yeah, on the function of a transmission to maximize acceleration while allowing the top speed of the motor, sure, this is why I've been saying it's really very simple (and pretty obvious), after seeing the same comments repeatedly here on gearing ratios.

Adding gears is just as obvious, you're just adding more steps like this.

http://evmc2.files.wordpress.com/2011/05/picture-4.png?w=561&h=579

The theory would be that, once you've added the overhead of a tranny, it won't add that much more weight to add a few more gears. (Which is why my bicycle has eleventy million more gears than I use...)

The thing I can't figure out how to show is the effect on the motor temperature. Back to my "Load" graph... if the motor is being loaded too much at low RPM it's going to heat up. Gearing helps avoid that, right? I showed the load as very high, then tapering off, because that's what I saw the current draw to act like on my bike. Anybody have a graph of that somewhere - current/speed? Noah? (Awesome graphs, thanks, btw!)

(Editorial Comment: Can we keep this thread on-topic, that being transmissions? Aerodynamics, battery chemistry, motor design, stuff like that, that's all cool "go-fast ideas" stuff, but not really about the topic, which is real-world transmissions, and I really feel like we're getting somewhere with this subject - that is to say, I'm finally getting this through my thick head. Not to be a bitch or anything... I'd love to hear more about all that other stuff in another thread.)

* "it" being the tortured inner workings of my poor, shriveled brain...

teddillard
06 May 2011, 0328
I did just find this graph, showing a "Heat" curve that looks just like my "Load" curve:

http://www.motoredbikes.com/attachment.php?attachmentid=26512&stc=1&d=1275744935

http://evmc2.files.wordpress.com/2011/05/picture-1.png?w=593&h=595

Funny thread: http://www.motoredbikes.com/showthread.php?p=276965

BaldBruce
06 May 2011, 0613
Noah - Why don't your curves go through zero?

Allen_okc
06 May 2011, 0655
is anyone building a two speed transmission for a ice motor, that an everyday fellow like me can purchase...

BaldBruce
06 May 2011, 0732
is anyone building a two speed transmission for a ice motor, that an everyday fellow like me can purchase...
yes and no...

Yes peole have built 2 speed transmission. Check out drag racing transmission specialists. Very common to use a two speed tranny.
No they are not cheap! Monster sized to handle mongo power.

teddillard
06 May 2011, 0740
is anyone building a two speed transmission for a ice motor, that an everyday fellow like me can purchase...

yes, THAT is the question... I've seen transmissions on the surplus sites, but they're friction-type for lawn tractors. I've toyed with making a simple two-speed project with no clutch, just to get the "overdrive" effect for a speed run. Like this:

http://www.chiefdelphi.com/media/img/7a7/7a7dedf7928ab8c78054909be7a518ff_m.jpg

http://www.chiefdelphi.com/media/photos/25967

Barron
06 May 2011, 0804
Brutus,
I don't understand how you are getting 119mph from the d&d es 15-6 alltrax 7245 and 72v 21ah combination.
A faired sportbike would normally require > 40 horsepower to achieve that speed.
The motor you are using is rated for 30hp peak.
So it seems like it couldn't do that speed unless the motor is being run at > peak, the bike is streamlined etc ... ...?

frodus
06 May 2011, 0815
So if I understand right..... if you have a motor of sufficient HP, you don't need gears, but if you have a lower HP motor, its beneficial to add gears to help keep the motor in the higher power part of its curve and closer match the curve of a Gas bike.

I think for me, my AC20 ought to handle what I need, both high and low RPM..... but its interesting to think about how it'd change if I had one more gear.

jpanichella
06 May 2011, 0817
Here's some 2 year old 2-speed snake oil.

http://www.gizmag.com/new-multi-speed-electric-vehicle-transmission-improves-ev-performance-and-range/11670/

cycleguy
06 May 2011, 0829
is anyone building a two speed transmission for a ice motor, that an everyday fellow like me can purchase...

There are a number of 2 speed spindle drives used in the machine tool industry that would work and are made to bolt onto the motor face, can handle the torque and speeds. Many are also shifted electrically.

Here's one example:
http://www.andantex.com/products_andantex.php?id_product=331

They're quite expensive though

Brutus
06 May 2011, 0841
Brutus,
I don't understand how you are getting 119mph from the d&d es 15-6 alltrax 7245 and 72v 21ah combination.
A faired sportbike would normally require > 40 horsepower to achieve that speed.
The motor you are using is rated for 30hp peak.
So it seems like it couldn't do that speed unless the motor is being run at > peak, the bike is streamlined etc ... ...?

The best way to explain this whole horsepower debate is to look at the specs of a ninja 250. In the real world a ninja 250 makes about 23hp at the rear wheel and it will also get to 125mph. The advantage of streamline fairings will only help with getting to the top speed faster not actually hitting the top speed. An easy way to prove this is go strip all the fairings off your bike and see what little difference it makes when you take it for a ride. What I have found is that the rider is the biggest wind resistor and simply ducking down will correct that.

teddillard
06 May 2011, 0844
So if I understand right..... if you have a motor of sufficient HP, you don't need gears ...

I'm going out on a limb and saying that a transmission would help any motor (motorcycle), by giving you your absolute top end and your fastest acceleration. But I can't prove it.

Now, if you have a motor of sufficient HP for what you want, that's another story, but you're going to lose efficiency in heat. Maybe.

my hed hurtz.

Nuts & Volts
06 May 2011, 0845
There are a number of 2 speed spindle drives used in the machine tool industry that would work and are made to bolt onto the motor face, can handle the torque and speeds. Many are also shifted electrically.

Here's one example:
http://www.andantex.com/products_andantex.php?id_product=331

They're quite expensive though

Any idea of the price? Or weight


I'm going out on a limb and saying that a transmission would help any motor (motorcycle), by giving you your absolute top end and your fastest acceleration. But I can't prove it.

I tend to agree here. Accel (rear wheel torque) and Top end can always be increased with 2 speeds or more. Bc of weight, performance may not increase a lot (includiong handling and maybe even 0-60 times).

teddillard
06 May 2011, 0848
... The advantage of streamline fairings will only help with getting to the top speed faster not actually hitting the top speed. ...

Sorry, you lost me there. You got that reversed maybe? ...goes against everything I know.

Nuts & Volts
06 May 2011, 0854
Sorry, you lost me there. You got that reversed maybe? ...goes against everything I know.

I believe he is explaining that full fairings only makes a minimal advantage. But from an engineering/physics standpoint his statement does not seem correct

Brutus
06 May 2011, 0859
Sorry, you lost me there. You got that reversed maybe? ...goes against everything I know.

I guess that was way too broad of a statement. Let me just say motorcycles are not as streamline challenged as people believe them to be.

Sorry, I need a redbull

teddillard
06 May 2011, 0902
I guess that was way too broad of a statement. Let me just say motorcycles are not as streamline challenged as people believe them to be.

Sorry, I need a redbull

"A brick with a parachute on it..." was how I've always heard a motorcycle's aerodynamics described.
http://www.schultzengineering.us/aero.htm

I'm with ya on the redbull tho. :D

I think your statement says more about the fairings that are sold on sport bikes more for appearance (sales) than actual aerodynamics, than the realities of drag etc...

Nuts & Volts
06 May 2011, 0904
"A brick with a parachute on it..." was how I've always heard a motorcycle's aerodynamics described.
http://www.schultzengineering.us/aero.htm

I'm with ya on the redbull tho. :D

As Ted stated, lets leave aero out of it for now :) here we only talk about trannys and gears

teddillard
06 May 2011, 0905
oh i did say that didn't i. :O

frodus
06 May 2011, 0905
Sorry, you lost me there. You got that reversed maybe? ...goes against everything I know.

Yeah, aero is the limit of top speed. The less the coefficient of friction, the higher the ability of top speed with a limited HP drive.

Back to Trannies!

that sounded bad.

podolefsky
06 May 2011, 0940
Noah - Why don't your curves go through zero?

The HP curves should go through zero - they were made using the El Moto spreadsheet (and then combined in Illustrator). It just doesn't plot the zero point.

[edit] Through the magic of vector graphics, HP curves now go through zero. :)

ZoomSmith
06 May 2011, 1129
Back to Trannies!

Maybe we could come up with an alternative term that doesn't trigger the Content Filters?

harlan
06 May 2011, 1205
Maybe we could come up with an alternative term that doesn't trigger the Content Filters?

Transmissions?

Barron
06 May 2011, 1316
I cannot find any information where a 23hp Ninja 250 achieves 125mph. The example review below shows it makiing 110mph maximum with 32.5hp (I'm assuming at the crank although this particular artiicle doesn't say).

http://www.motorcyclenews.com/MCN/bikereviews/searchresults/Bike-Reviews/Kawasaki/Kawasaki-250R-Ninja-2008-current/

I have a 2009 Ninja 250R that I bought new and before I converted it to electric the only way it would do 125mph is if it was pushed out of a plane.
Where are you getting the 125mph at 23hp statistic from?

My comment about the streamlining was just in relation to how you achieved such a high top speed with such little power. I understand that you'll be limited by max motor rpm and gearing for top speed, but streamlining would allow you to run taller gearing and hence achieve a higher top speed. Anyway, sounds like you are not using streamlining, so I'm just surprised you got a higher top speed than any other non streamlined motorycle I know of for the amount of power you had.


The best way to explain this whole horsepower debate is to look at the specs of a ninja 250. In the real world a ninja 250 makes about 23hp at the rear wheel and it will also get to 125mph. The advantage of streamline fairings will only help with getting to the top speed faster not actually hitting the top speed. An easy way to prove this is go strip all the fairings off your bike and see what little difference it makes when you take it for a ride. What I have found is that the rider is the biggest wind resistor and simply ducking down will correct that.

Nuts & Volts
06 May 2011, 1346
I cannot find any information where a 23hp Ninja 250 achieves 125mph. The example review below shows it makiing 110mph maximum with 32.5hp (I'm assuming at the crank although this particular artiicle doesn't say).

http://www.motorcyclenews.com/MCN/bikereviews/searchresults/Bike-Reviews/Kawasaki/Kawasaki-250R-Ninja-2008-current/

I have a 2009 Ninja 250R that I bought new and before I converted it to electric the only way it would do 125mph is if it was pushed out of a plane.
Where are you getting the 125mph at 23hp statistic from?

My comment about the streamlining was just in relation to how you achieved such a high top speed with such little power. I understand that you'll be limited by max motor rpm and gearing for top speed, but streamlining would allow you to run taller gearing and hence achieve a higher top speed. Anyway, sounds like you are not using streamlining, so I'm just surprised you got a higher top speed than any other non streamlined motorycle I know of for the amount of power you had.

I agree that I am hesistant to believe the 120 on the Brutus with only 30HP. A video would convince me thou :) time will tell.

I could care less thou , I just want to learn more about the transmission! Brutus, do you really need a clutch at all? Would simply rolling off the throttle allow you to shift up and down?

teddillard
06 May 2011, 1401
... do you really need a clutch at all? Would simply rolling off the throttle allow you to shift up and down?

You can shift pretty easy on any bike without a clutch... just gets tricky when you're trying to squirt the power on. Starting from stop would be a lot easier on an electric though. :)

Brutus
06 May 2011, 1501
I cannot find any information where a 23hp Ninja 250 achieves 125mph. The example review below shows it makiing 110mph maximum with 32.5hp (I'm assuming at the crank although this particular artiicle doesn't say).

http://www.motorcyclenews.com/MCN/bikereviews/searchresults/Bike-Reviews/Kawasaki/Kawasaki-250R-Ninja-2008-current/

I have a 2009 Ninja 250R that I bought new and before I converted it to electric the only way it would do 125mph is if it was pushed out of a plane.
Where are you getting the 125mph at 23hp statistic from?

My comment about the streamlining was just in relation to how you achieved such a high top speed with such little power. I understand that you'll be limited by max motor rpm and gearing for top speed, but streamlining would allow you to run taller gearing and hence achieve a higher top speed. Anyway, sounds like you are not using streamlining, so I'm just surprised you got a higher top speed than any other non streamlined motorycle I know of for the amount of power you had.

Simple really, for an extra 15mph on that baby ninja just drop the rear sprocket 2 teeth, slightly less acceleration and slightly more top end and it will take slightly longer to get there.

podolefsky
06 May 2011, 1504
According to the El Moto spreadsheet calculations, 120 mph requires about 27 kW, or 36 HP. That's with a 550 lb bike/rider, rolling drag coeff of 0.02, 614 in^2 frontal area, and air drag coef of 0.65.

If the air drag coef is dropped to 0.5, then 120 mph requires 30 HP. Coef = 0.35 requires about 24 HP. That doesn't seem unreasonable with a decent fairing and tucked rider (but I'm not certain). [edit] Actually, just read a bit more, and getting below 0.4 seems really hard without a fairing that encloses the entire bike.

Here is some info about air drag coefficients. I know we tried to steer clear of this, but it seem relevant to the argument about whether 120 mph is possible with 30 HP. A motorcycle is probably somewhere between a long cylinder (0.82) and a sphere (0.47). If the streamlining were very good (approaching an airplane wing), it could be as low as 0.04.

http://en.wikipedia.org/wiki/Drag_coefficient

podolefsky
06 May 2011, 1529
I added curves for an AC-20 at 96V to my plots a few pages back. This would be about 35 lb of batteries over a 72V system.

I geared the AC 12:72 (1:6), since it has a bit less low end torque, but much higher RPM.

You'll notice that the torque curve for the AC-20 destroys the Ninja 250 all the way to 100 mph and beyond. It also more than makes up for the high speed power advantage of a gear box (compared to the Ninja or the 72V system). That's not to say a gear box couldn't help flatten this curve as well...just that if you're going to add 35 lb to the bike, batteries *might* be as-good-as or better than gears. Just sayin'.

Barron
06 May 2011, 1559
Coef is 0.6+ for a faired sportbike. Which is a little worse than a Hummer H2 (0.57). Only saving grace for the bike is much smaller frontal area.


According to the El Moto spreadsheet calculations, 120 mph requires about 27 kW, or 36 HP. That's with a 550 lb bike/rider, rolling drag coeff of 0.02, 614 in^2 frontal area, and air drag coef of 0.65.

If the air drag coef is dropped to 0.5, then 120 mph requires 30 HP. Coef = 0.35 requires about 24 HP. That doesn't seem unreasonable with a decent fairing and tucked rider (but I'm not certain). [edit] Actually, just read a bit more, and getting below 0.4 seems really hard without a fairing that encloses the entire bike.

Here is some info about air drag coefficients. I know we tried to steer clear of this, but it seem relevant to the argument about whether 120 mph is possible with 30 HP. A motorcycle is probably somewhere between a long cylinder (0.82) and a sphere (0.47). If the streamlining were very good (approaching an airplane wing), it could be as low as 0.04.

http://en.wikipedia.org/wiki/Drag_coefficient

Barron
06 May 2011, 1616
Simple really, for an extra 15mph on that baby ninja just drop the rear sprocket 2 teeth, slightly less acceleration and slightly more top end and it will take slightly longer to get there.

I'm still not getting it.
Stock sprockets (on 2008+ models) are 14/45 which is a ratio of 3.214 (:1)
Dropping two on rear to 14/43 gives a ratio of 3.071

Change in ratio is 3.214 / 3.071 (about 4.6% change)
Multiplying this by the 110mph top speed gives a new top speed of 115.1mph

So dropping two teeth on rear would only increase top speed by just over 5mph.

Where is my math wrong?

frodus
06 May 2011, 1634
I added curves for an AC-20 at 96V to my plots a few pages back. This would be about 35 lb of batteries over a 72V system.

I geared the AC 12:72 (1:6), since it has a bit less low end torque, but much higher RPM.

You'll notice that the torque curve for the AC-20 destroys the Ninja 250 all the way to 100 mph and beyond. It also more than makes up for the high speed power advantage of a gear box (compared to the Ninja or the 72V system). That's not to say a gear box couldn't help flatten this curve as well...just that if you're going to add 35 lb to the bike, batteries *might* be as-good-as or better than gears. Just sayin'.

linking helps

http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=13731&viewfull=1#post13731

:)

That makes me smile though, I'll be at ~96V (102.4V nominal) and should be able to pump out 550A long enough for an acceleration to a comfortably fast speed.....

Nuts & Volts
06 May 2011, 1659
I added curves for an AC-20 at 96V to my plots a few pages back. This would be about 35 lb of batteries over a 72V system.

I geared the AC 12:72 (1:6), since it has a bit less low end torque, but much higher RPM.

You'll notice that the torque curve for the AC-20 destroys the Ninja 250 all the way to 100 mph and beyond. It also more than makes up for the high speed power advantage of a gear box (compared to the Ninja or the 72V system). That's not to say a gear box couldn't help flatten this curve as well...just that if you're going to add 35 lb to the bike, batteries *might* be as-good-as or better than gears. Just sayin'.

Yea, but an AC-20 costs almost as much a Ninja costs new :) So in my mind, buying a agni, alltrax, and a gearbox will give you almost as much performance as a AC-20 while being about the same price. I would need to plot out the agni torque curve over an AC-20, but I think you could make it 0-60 in about the same time :) top end would definitely be a little off. Anyone wanna plots those together?

Or Noah can plot your motor with 5 gear steps against a single gear AC-20 curve. NV, i say the new graph. It looks like your motor cant beat the AC-20 with an infinite number of gears. :(

DaveAK
06 May 2011, 1708
But if your agni, alltrax and gearbox costs the same as an AC20, but only gives you almost the same performance, then wouldn't you better off with an AC20? :D Just nitpicking now. It's Friday. :)

But in all seriousness it's the same old story of working with what you've got or what you can afford. Say an AC20 is equivalent to an Agni with a gearbox, then what's an AC20 with a gearbox going to be like?

podolefsky
06 May 2011, 1728
linking helps

http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=13731&viewfull=1#post13731

:)

That makes me smile though, I'll be at ~96V (102.4V nominal) and should be able to pump out 550A long enough for an acceleration to a comfortably fast speed.....

Thanks, couldn't figure out how to link to my post.

It makes me want your set up...

podolefsky
06 May 2011, 1740
Yea, but an AC-20 costs almost as much a Ninja costs new :) So in my mind, buying a agni, alltrax, and a gearbox will give you almost as much performance as a AC-20 while being about the same price. I would need to plot out the agni torque curve over an AC-20, but I think you could make it 0-60 in about the same time :) top end would definitely be a little off. Anyone wanna plots those together?

Or Noah can plot your motor with 5 gear steps against a single gear AC-20 curve. NV, i say the new graph. It looks like your motor cant beat the AC-20 with an infinite number of gears. :(

Keep in mind that AC-20 curve is at 96V. So you not only get more power, you get more kWh (33% more) and thus more range. At 72V, the D&D and AC are pretty well matched, except that the AC can eek out a bit more power above the base speed (I think because it's able to field weaken). The AC is also a tad more efficient overall.

I've plotted Agni vs others - compared to an AC-20, it's not even close. The AC hits a higher RPM, so you can gear it just as low (or lower) than the Agni. It has about twice the torque, and will handle more voltage. The AC-20 is just a big motor (by el moto standards).

This is comparing a single Agni...dual Agnis is a different story.

GUFF
06 May 2011, 1826
Great discussion guys, I am seeing valid points by many!

I would agree that a transmission is beneficial in an EV with a smaller motor. Helping to reduce heat build up and pushing more torque at higher speeds. Makes perfect sense why Brammo is doing it! I agree it will also draw people in who prefer the shifting!

After looking at Noah's great graphs its clear to me that once you have a large enough electric motor, a transmission seems less inviting due to weight and its associated drivetrain losses. So, for performance applications I don't think its worth it. For street riding applications with smaller bikes and smaller electric motors they seem like a good fit.

I think the AC-20 is fine in a larger bike. It looks good in a 600, feels lonely in my liter bike, but looks out of place on a 250. So in my bike I would say that an AC-20 is not a large motor.

We really haven't even tapped into the good stuff yet when it comes to motors and controllers. I do think AC will dominate production EVs since the motors are easier to make mass production and they are dam near timeless. Imho BLDC is the way to go for low vol performance apps. I also think Mark is 100% right, wye/delta switching or something like it, is the future.

Why ride the past when you can ride the future? :)

magicsmoke
06 May 2011, 1911
I see two very different scenarios being mixed i.e. adequate performance vs maximum attainable.

A loosely termed 'large' motor is likely to provide an adequate performance but doesn't mean it wouldn't be enhanced by the addition of a gearbox.
Whether the cost, weight, space etc. constraints are deemed worthwhile or even desirable is down to the individual's own judgement.

As for maximum attainable performance, i.e. with a multispeed box, the two 'ratio markers' I would suggest are those which allow for the front wheel to just float with the rider leant forward under hard acceleration, and at the other end, that which when the motor is spinning at its maximum safe mechanical rpm (and at its continuous current limit) equates to a roadspeed dictated by the power developed vs aero drag etc.
Dependent upon the range between these two ratios, additional gears would likely prove useful.

Remember, because power developed by a motor is directly proportional to its speed (rpm), the sole advantage of a gearbox is to allow the motor to run at its maximum speed and therefore make available maximum power at any roadspeed up to that which is limited by drag and other losses. A single speed box running at a quarter or half max rpm can by definition only be making a quarter or half max power respectively.

podolefsky
06 May 2011, 2112
Remember, because power developed by a motor is directly proportional to its speed (rpm), the sole advantage of a gearbox is to allow the motor to run at its maximum speed and therefore make available maximum power at any roadspeed up to that which is limited by drag and other losses. A single speed box running at a quarter or half max rpm can by definition only be making a quarter or half max power respectively.

Just a point of clarification, power is proportional to speed up to base speed, then it drops.

If you look at my graphs (http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=13731&viewfull=1#post13731), with 6:1 gearing you're RPM limited to about 100 mph (8000 RPM). There's power to spare, so if the motor could go beyond 8000 RPM you could go faster, but then you're power limited because HP drops past the peak. Your top speed is where the power curve intersects the dashed line. You get the maximum speed possible if the dashed line intersects the HP peak, which means gearing down to move the peak to the right.

For the AC-20 at 96V, playing around with the numbers gives a top speed of 133 mph when geared about 2.3:1.

magicsmoke
07 May 2011, 0217
Just a point of clarification, power is proportional to speed up to base speed, then it drops.

Only if you don't have enough pack voltage.

i.e. The pack voltage must equal the motor back emf at max rpm PLUS sufficient to permit maximum armature current at that rpm. (95V or so total supply for an Agni 95R).
This setup presents straight line power with respect to rpm, right up to the motor max.

Because you now have an 'excesive' pack voltage, be careful not to over rev the motor when not fully loaded. (motor that is, not you :) )

But yeah, you're right, if the pack voltage isn't high enough to run the motor to destruction then gear for the roadspeed equivalent to the max power, wherever it may be.

teddillard
07 May 2011, 0324
... for an acceleration to a comfortably fast speed.....

Isn't that one of those oxymoron things? :cool: (Who the hell want's to go comfortably fast? lol!)

podolefsky
07 May 2011, 1002
Only if you don't have enough pack voltage.

i.e. The pack voltage must equal the motor back emf at max rpm PLUS sufficient to permit maximum armature current at that rpm. (95V or so total supply for an Agni 95R).
This setup presents straight line power with respect to rpm, right up to the motor max.

Because you now have an 'excesive' pack voltage, be careful not to over rev the motor when not fully loaded. (motor that is, not you :) )

But yeah, you're right, if the pack voltage isn't high enough to run the motor to destruction then gear for the roadspeed equivalent to the max power, wherever it may be.


True, if the motor can handle that voltage. My D&D is rated to 72V, it might be able to handle 96 (although I've asked D&D and they said don't go over 72V). Mechanically limited RPM is about 5000, I believe. Base speed at 72V is about 2000 RPM, and since it increases linearly with voltage, I'd need more than 180V to maintain full torque to 5000 RPM. With that voltage, I believe the arcing would destroy the brushes and commutator. Or it would overheat very quickly, or both.

I could be wrong - actually, I'd love to be wrong (because of the possibilities).

GUFF
07 May 2011, 1308
Noah, I am not seeing the AC-20 graph you mentioned earlier. Am I missing something?

podolefsky
07 May 2011, 1405
Noah, I am not seeing the AC-20 graph you mentioned earlier. Am I missing something?

It's here (http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=13731&viewfull=1#post13731), overlaid on the other graphs.

You might need to refresh your browser to see it.

larryrose11
07 May 2011, 1649
Great discussion!!!
Noah, I too love to me wrong. It is an opportunity to learn, and i LOVE to learn.
I think I'm sold on the AC-20@96+V

All of this theory vs Brutis first hand experience reminds me of an engineering proverb:
-The difference between theory and practice is much smaller in theory than in practice.

podolefsky
07 May 2011, 1729
I like

"Theory without practice is empty; practice without theory is blind." - Immanuel Kant

GUFF
07 May 2011, 1939
It's here (http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=13731&viewfull=1#post13731), overlaid on the other graphs.

You might need to refresh your browser to see it.

Thanks man!

How did you calculate the Wheel torque? Was it Motor Torque output x Gear Ratio? I have seen the AC-20 spec'd at both 105 and 110 ft/lbs which would bring it to 630 and 660 respectively.

podolefsky
07 May 2011, 2203
Exactly, motor torque * gear ratio.

I've also seen those specs for the AC-20. I asked EMS about it and they said they were "updating" the spec on their website. The data for those motors is all screwed up. The AC-20 shows about 72 ft-lb on the curve from HPEVs (http://hpevs.com/), but then they have a curve for the AC-12 (which uses a smaller motor) that goes to 85 ft-lb (and 60 HP!).

If you look at the AC-20 curve, it goes to 700A *DC*. This is with a 48V controller, which is rated to 650A (RMS). If you use the higher voltage controller, then you're limited to 550A (RMS), so less torque than shown. I think...none of their data is consistent. I mean, it all looks like real data, it's just really hard to compare across motors since they're all different set ups.

So I did the best I could with the data available to make the graphs. I think they are probably close to correct, the numbers all look about right. Just keep in mind that all motor data out there is suspect. (Especially the graphs from Agni that look like they were drawn, not real data.)

EVcycle
09 May 2011, 1055
So if I understand right..... if you have a motor of sufficient HP, you don't need gears, but if you have a lower HP motor, its beneficial to add gears to help keep the motor in the higher power part of its curve and closer match the curve of a Gas bike.

I think for me, my AC20 ought to handle what I need, both high and low RPM..... but its interesting to think about how it'd change if I had one more gear.

I echo that comment. I think 2 gears would be nice, but after reading most of the post, I have not seen much on the effects of the transmission on range. ( I am still reading)

It is great to go fast but at what cost?

Monkey wrench Ed

podolefsky
09 May 2011, 1110
I echo that comment. I think 2 gears would be nice, but after reading most of the post, I have not seen much on the effects of the transmission on range. ( I am still reading)

It is great to go fast but at what cost?

Monkey wrench Ed

That's right - a transmission won't give you any more range. (I can think of one argument that *maybe* you could get more range with a transmission, but it's kind of complicated, has to do with the Peukert effect and whether this is greater than the transmission losses...)

It's basically about performance...and yeah, better performance always comes at a cost.

frodus
09 May 2011, 1111
well, since a transmission doesn't change power, just torque/RPM, you will decrease RPM and increase torque by changing the ratio, but the power at xxmph should remain fairly unchanged between the two. But consider that higher amp draw is more inefficient, but I can't imagine that you're drawing enough current with a single speed compared with a dual to really notice much losses, and it should be similar to the losses in a transmission.

So the power from your batteries should remain the same, I'd think. I doubt there'd be much difference in range, but the ability to accelerate may be better with a transmission, but its still the same power.

EVcycle
09 May 2011, 1114
well, since a transmission doesn't change power, just torque/RPM, you will decrease RPM and increase torque by changing the ratio, but the power at xxmph should remain fairly unchanged between the two. But consider that higher amp draw is more inefficient, but I can't imagine that you're drawing enough current with a single speed compared with a dual to really notice much losses, and it should be similar to the losses in a transmission.

So the power from your batteries should remain the same, I'd think. I doubt there'd be much difference in range, but the ability to accelerate may be better with a transmission, but its still the same power.


We will see.....I hope. Really thin transmission oil would help.

The range would be less since you are taking up battery room with the transmission? (or did you say that?)

teddillard
09 May 2011, 1122
Yeah, I gots to weigh in on this one too... :D

I think the transmish would increase your range if you're riding under hard acceleration. Using the same theory that it would keep the motor from overheating.

Push the motor too hard, it heats and becomes less efficient. Put a transmish in, you gets motor not working as hard, so staying cooler. More efficient. More range. Maybe a little.

podolefsky
09 May 2011, 1123
well, since a transmission doesn't change power, just torque/RPM, you will decrease RPM and increase torque by changing the ratio, but the power at xxmph should remain fairly unchanged between the two. But consider that higher amp draw is more inefficient, but I can't imagine that you're drawing enough current with a single speed compared with a dual to really notice much losses, and it should be similar to the losses in a transmission.

So the power from your batteries should remain the same, I'd think. I doubt there'd be much difference in range, but the ability to accelerate may be better with a transmission, but its still the same power.

Looking at a TS data sheet, going from 1C to 3C loses about 10% capacity. From 3C to 5C loses about 5% more. But that's at constant discharge rates. If you're usually at 1C and just pull 5C for short durations, and not very often, it's going to be a lot less. Maybe a couple %. Lithium does a really good job handling high amp draw.

EVcycle
09 May 2011, 1138
Yeah, I gots to weigh in on this one too... :D

I think the transmish would increase your range if you're riding under hard acceleration. Using the same theory that it would keep the motor from overheating.

Push the motor too hard, it heats and becomes less efficient. Put a transmish in, you gets motor not working as hard, so staying cooler. More efficient. More range. Maybe a little.

I agree if it is a low HP motor. The proof is in the pudding?

P.S. I made some high speed runs with the ME1003 and it barely got warm.


"It is all about the combination and the bike's ultimate purpose"

Ed

teddillard
09 May 2011, 1319
So. Something just dawned on me. Many of the TTXGP bikes are RUNNING A TRANSMISSION. :O

It's a reduction gearbox. It weighs about the same as a shifting transmission, no? Yet. They seem to think it's worth it.

Now. If they could only shift the damn things... :D

Nuts & Volts
09 May 2011, 1336
So. Something just dawned on me. Many of the TTXGP bikes are RUNNING A TRANSMISSION. :O

It's a reduction gearbox. It weighs about the same as a shifting transmission, no? Yet. They seem to think it's worth it.

Now. If they could only shift the damn things... :D

Only one I know of is Lightnings bike from last year. Square Wave had alLayshaft only because their CVT didnt work out. Any other teams running one?

I also think a tranny would be about another 5 lbs due to the addition of more gears and bearings.

cycleguy
09 May 2011, 1340
So. Something just dawned on me. Many of the TTXGP bikes are RUNNING A TRANSMISSION. :O

It's a reduction gearbox. It weighs about the same as a shifting transmission, no? Yet. They seem to think it's worth it.

Now. If they could only shift the damn things... :D

Ted, I'm not sure you realize that your bike has a transmission too, it's your motor sprocket, chain and rear wheel sprocket.

The reason the fast TTXGP bikes have an additional step down ratio is because they are using high voltages which allow the motors to rev very high, some as high as 15000 RPM. An additional step down ratio of 2:1 doubles the torque to the rear sprocket, and since the motor revs so high, it doesn't over rev at top speed.
Once again proving my earlier point that if you have a motor with enough power to pull a top speed of 150MPH, you are not going to need a transmission.

EVcycle
09 May 2011, 1341
and clutch, and shifter and .... :)

teddillard
09 May 2011, 1353
Ted, I'm not sure you realize that your bike has a transmission too, it's your motor sprocket, chain and rear wheel sprocket.

Oh, you can be sure I realize lots of things. Please spare me, seriously.

Kyle, I'll have to look it up, but I thought there were more.

podolefsky
09 May 2011, 1357
Once again proving my earlier point that if you have a motor with enough power to pull a top speed of 150MPH, you are not going to need a transmission.

Aaaaahhhhh!!!!! This is driving me crazy.

These absolute statements about not *needing* a transmission are missing the point. There are lots of ways to get good performance at the high and low end. One is adding batteries, one is getting gobs of current to the motor, and another is to use a (mechanical) transmission.

All of them add weight and complexity. All have their pros and cons. There's a lot of knowledge of the different approaches - maybe it would be better to just document the pros and cons, the different methods, and then people can read the facts and decide. It's such a complex problem that no one approach is going to be decisively better under all circumstances.

teddillard
09 May 2011, 1404
Yeah, I think we should just start an "i can haz trasmisshion?" elmoto club. :cool:

cycleguy
09 May 2011, 1410
Aaaaahhhhh!!!!! This is driving me crazy.

These absolute statements about not *needing* a transmission are missing the point. There are lots of ways to get good performance at the high and low end. One is adding batteries, one is getting gobs of current to the motor, and another is to use a (mechanical) transmission.

All of them add weight and complexity. All have their pros and cons. There's a lot of knowledge of the different approaches - maybe it would be better to just document the pros and cons, the different methods, and then people can read the facts and decide. It's such a complex problem that no one approach is going to be decisively better under all circumstances.

Agreed 100%, I think the question here is whether or not adding a multi speed transmission is an effective solution to increasing the performance, compared to other means. I think it is not. Not that a transmission would not give you any benefit at all, but that you would be far better off in efforts towards increasing voltage and motor RPM capabilities. As proven by looking at all the fast TTXGP bikes.

A transmission is simply a torque multiplier , it does not increase HP. So no matter how many speeds you have, a 20 HP motor is only going to give you so much.
If all you care about is topping out at 60mph, then by all means knock your socks off putting a transmission on it to get you there faster, but if you want an Elmoto to perform like a real motorcycle, a transmission is a waste of time and effort.

podolefsky
09 May 2011, 1423
but if you want an Elmoto to perform like a real motorcycle, a transmission is a waste of time and effort.

An el moto IS a real motorcycle! I want an el moto to perform better than a ICE motorcycle :D

Actually, I don't care that much about the EV vs ICE thing. I just want an el moto to perform the best that it can, given certain constraints (like size, weight, cost, etc...)

Nuts & Volts
09 May 2011, 1430
Yeah, I think we should just start an "i can haz trasmisshion?" elmoto club. :cool:

Agreed!!

Here is my simple proof. You have a battery, motor and controller that are perfectly matched to give the exact same peak power.

400 lb motorcycle, you add a 40 lb 2 speed tranmission with a 1:1 ratio and a 2:1 ratio. So you can get 100% more wheel torque while adding 5% more weight. Torque is a force, so...

Force= mass*acceleration OR acceleration= Force/mass

With no transmission and a 1:1 ratio you have lets say 400 units of force (torque), that makes (400/400) 1 unit of acceleration.
Add the 2 speed, you get (2*400)/440 = 1.81 units of acceleration.

So no matter how F'ing big of a motor you have, even a huge ass 40lb 2-speed transmission will improve your accleration performance and give you any top speed you want. No compromise.

cycleguy
09 May 2011, 1430
An el moto IS a real motorcycle! I want an el moto to perform better than a ICE motorcycle :D

Actually, I don't care that much about the EV vs ICE thing. I just want an el moto to perform the best that it can, given certain constraints (like size, weight, cost, etc...)

I'm with you 100%. I think all of us here want to see the Elmoto be able to perform on an even level with ICE motorcycles some day. The sooner we get there the better, and a transmission is not a path to that end.

ZoomSmith
09 May 2011, 1432
Aaaaahhhhh!!!!! This is driving me crazy.

Me too. My brain hurts from trying to follow you guys.

podolefsky
09 May 2011, 1446
Agreed!!

Here is my simple proof. You have a battery, motor and controller that are perfectly matched to give the exact same peak power.

400 lb motorcycle, you add a 40 lb 2 speed tranmission with a 1:1 ratio and a 2:1 ratio. So you can get 100% more wheel torque while adding 5% more weight. Torque is a force, so...

Force= mass*acceleration OR acceleration= Force/mass

With no transmission and a 1:1 ratio you have lets say 400 units of force (torque), that makes (400/400) 1 unit of acceleration.
Add the 2 speed, you get (2*400)/440 = 1.81 units of acceleration.

So no matter how F'ing big of a motor you have, even a huge ass 40lb 2-speed transmission will improve your accleration performance and give you any top speed you want. No compromise.

Yes! Exactly! Except.... :rolleyes:

This all assumes the load on the motor is enough that you are pulling the most amps you can in low gear. I just did a calculation knowing that when I was geared 5:1 I only pulled 300-330A. geared 4:1 I hit around 400A, and at 3.25:1 I think I'll hit my 450A controller limit. Yes, those are battery amps, but that's at full throttle so (at least with my controller) batter amps = motor amps.

So my calculation basically told me that when geared lower at 5:1, the load on the motor is so low that switching to 4:1 I get *more* rear wheel torque because it is pulling sufficiently more amps. At 3.25:1, it will probably hit the 450A limit and get about the same rear wheel torque as 4:1, but it will give me more high end power. (And as Travis said, if I had a 600A controller it would go even higher.)

Just another wrench in the works.

Someone should just take this thread, edit it up and make it a book (Ted).

lugnut
09 May 2011, 1451
A transmission is simply a torque multiplier , it does not increase HP.

So is the chain and sprocket. Transmission as I see it infers multiple selectable ratios. And you're right. It cannot increase HP. In fact it decreases it due to losses. Maybe not by much, but still some loss. And it adds mass. And consumes space.

The multi ratio transmission is a valid means to alter the drive ratio. If that is what a guy chooses to build into his bike, good for him. All I have been doing here is trying to point out alternatives like increasing the current limit to accomplish the same performance and to dispel some incorrect beliefs which I see like the transmission will increase your range or lighten the load on your battery.

cycleguy
09 May 2011, 1512
Agreed!!

Here is my simple proof. You have a battery, motor and controller that are perfectly matched to give the exact same peak power.

400 lb motorcycle, you add a 40 lb 2 speed tranmission with a 1:1 ratio and a 2:1 ratio. So you can get 100% more wheel torque while adding 5% more weight. Torque is a force, so...

Force= mass*acceleration OR acceleration= Force/mass

With no transmission and a 1:1 ratio you have lets say 400 units of force (torque), that makes (400/400) 1 unit of acceleration.
Add the 2 speed, you get (2*400)/440 = 1.81 units of acceleration.

So no matter how F'ing big of a motor you have, even a huge ass 40lb 2-speed transmission will improve your accleration performance and give you any top speed you want. No compromise.

No, it will not. Your top speed is limited by the HP of the motor. A transmission will not increase your top speed, only how fast you get there.

Lets work this backwards for arguments sake. Chip Yates' bike goes 194 MPH, it can get there because it has 194HP. It also has 295 lb/ft of torque. 194MPH is just under 3000 rear wheel RPM. The motor revs to 8000 rpm, so a gear ratio of 2.66:1 would give that top speed at max motor RPM. 2.66 x 295lb/ft= 785 lb/ft of torque to the rear wheel!
A production superbike (R1, CBR1000 etc.) puts almost 1000 lb/ft of torque to the rear wheel with a 6 speed gearbox. Lowering the top speed of the Yates bike a bit with a 3:1 ratio would put you at the same rear wheel torque.
The question is, what benefit would Yates get in adding a two speed transmission to his bike? None!

frodus
09 May 2011, 1519
Take 2 motorcycles, each the same aero, same weight, same rider, each with different gear ratios. How much Power does it take to move one compared to the other? It takes the same amount of output shaft power. One has a high RPM (higher PWM) and lower current, the other has lower RPM and more current, but both require the same power to push the motorcycle at that speed.

Now let’s say for it’s a K91 at 72V. Now look at a couple different RPM’s, and the efficiency difference is only a few percent. Likely the same difference as a transmission would lose.

But until someone measures equivalent motor/controller/batteries with and without transmission, we're all theorizing.

teddillard
09 May 2011, 1519
Brutus, you started it, you can make it stop.

Go get a 50lb weight off your weight bench sitting under the pile of junk in your cellar. Strap it into a backpack, and strap that video camera to your hat, point it at the speedo, and do a run through all the gears to your top speed.

Then lose the backpack and do a run in only one gear, full throttle up to top speed. Pick one. Hell, go ahead... you can do it in three different gears, one that doesnt get you to top speed, one that just gets you there, and one that can't get you any faster, but bogs in the low speeds.

Post the video. Discussion over. :O

EVcycle
09 May 2011, 1523
"Discussion over"

One EV motorcycle does not make any statement of proof. (now you sound like a politician.... ) :O

When the discussions end, so does the creative learning....

frodus
09 May 2011, 1525
No, it will not. Your top speed is limited by the HP of the motor. A transmission will not increase your top speed, only how fast you get there.

"sorta" right, but only to a point. Your top speed is limited by HP AND the mechanical RPM limit, if you hit one before the other, that one is the limiting factor. A transmission CAN increase your top speed if you have not maxed out the HP, but run out of RPM.

frodus
09 May 2011, 1527
"Discussion over"

One EV motorcycle does not make any statement of proof. (now you sound like a politician.... ) :O

When the discussions end, so does the creative learning....

you sound like Yoda....

A statement of proof does not a single motorcycle make..... mmmhhhmmmmm

EVcycle
09 May 2011, 1528
LOL..... Much better!!!!

Nuts & Volts
09 May 2011, 1533
No, it will not. Your top speed is limited by the HP of the motor. A transmission will not increase your top speed, only how fast you get there.

Lets work this backwards for arguments sake. Chip Yates' bike goes 194 MPH, it can get there because it has 194HP. It also has 295 lb/ft of torque. 194MPH is just under 3000 rear wheel RPM. The motor revs to 8000 rpm, so a gear ratio of 2.66:1 would give that top speed at max motor RPM. 2.66 x 295lb/ft= 785 lb/ft of torque to the rear wheel!
A production superbike (R1, CBR1000 etc.) puts almost 1000 lb/ft of torque to the rear wheel with a 6 speed gearbox. Lowering the top speed of the Yates bike a bit with a 3:1 ratio would put you at the same rear wheel torque.
The question is, what benefit would Yates get in adding a two speed transmission to his bike? None!

Ok you missed my point entirely. I am not trying to increase top speed. With or without a transmission your top speed is limited by peak HP, so that does not need to be discussed at all in my mind. The point of the transmission is to increase accel without effecting top speed.

My point is that with a transmission Chip Yates can get even more rear wheel torque and accelerate even quicker. If he starts to spin his tires then he can can get a bigger tire and still increase his acceleration.
OR he could use the transmission to increase his top speed without hurting his acceleration.

Also I do not believe that Chip used 194HP at 194mph. Ill look back at the Hell for Leather article to confirm.

PS - he actually has 240HP and 365 ftlbs now

teddillard
09 May 2011, 1538
"Discussion over"

One EV motorcycle does not make any statement of proof. (now you sound like a politician.... ) :O

When the discussions end, so does the creative learning....

Gee. Sorry (yoda). :p

My point being that the original post was an offer to show some real-world experience. As Brutus posted, we're all left to guess. This would answer a whole lot of questions... As far as learning goes, at some point we all learn more by doing, or seeing what's been done.

Brutus
09 May 2011, 1549
Since Friday I have been busting my rump to get a video of proof up and Murphy's law has taken hold of my project. It started with my charger, moved to the batteries and ended with a broken shift cable(which I should have never used). Some of the discussion here has been excellent and very insightful along the way. I will fix everything and post a video when it all happens. A few of you are real close to figuring it all out to where I am at with all this but you are missing a few key elements in the transfer of everything to the final output or at least no one has mentioned anything about it.

Here is how I feel about a transmission and its usefulness in el moto's.

For drag racing, top speed runs, or track racing a transmission will be useless because you can get what is needed out of a direct drive to suit the racing application. For low speed 50mph or less street riding with no emphasis on performance than a transmission is useless. For a street motorcycle dealing with traffic, open highway and trying to satisfy performance minded riders a transmission is a benefit and an easier solution to suit the el moto consumer market.

teddillard
09 May 2011, 1552
Thanks, man, and sorry you've been in Murphyland!

EVcycle
09 May 2011, 1625
Gee. Sorry (yoda). :p

My point being that the original post was an offer to show some real-world experience. As Brutus posted, we're all left to guess. This would answer a whole lot of questions... As far as learning goes, at some point we all learn more by doing, or seeing what's been done.

Agreed, I just have not found a good light weight, strong and cost effective unit. Maybe your other thread will do that. :)

podolefsky
09 May 2011, 1628
You know what's totally friggin mind blowing to me - that we've all sunk this much time into something and haven't been paid a cent. In fact, I'm pretty sure most of us were supposed to be working today :O

EVcycle
09 May 2011, 1630
You know what's totally friggin mind blowing to me - that we've all sunk this much time into something and haven't been paid a cent. In fact, I'm pretty sure most of us were supposed to be working today :O

This is too much fun to be......working!!! :)

cycleguy
09 May 2011, 1650
My point is that with a transmission Chip Yates can get even more rear wheel torque and accelerate even quicker. If he starts to spin his tires then he can can get a bigger tire and still increase his acceleration.
OR he could use the transmission to increase his top speed without hurting his acceleration.


There is a limit to how much torque can be applied to the ground before the front wheel wants to lift too high. Chip Yates is already at that point, so there is no need to look for more torque. His top speed is limited by HP, It's not as simple as gearing taller to get a higher top speed. You reach a certain point where aerodynamic drag is so high that only more HP will get you to go faster. Most bikes don't pull to redline at top speed, because they run out of HP, so even if he had a transmission and could gear higher, he would most likely achieve the same top speed, just at a different motor RPM.

frodus
09 May 2011, 1654
The trick is, finding what the aero HP requirement is for the vehicle, and finding the max HP RPM, and creating a gear ratio (or transmission) who's gearing achieves that max HP at the max speed.

Nuts & Volts
09 May 2011, 1925
There is a limit to how much torque can be applied to the ground before the front wheel wants to lift too high. Chip Yates is already at that point, so there is no need to look for more torque. His top speed is limited by HP, It's not as simple as gearing taller to get a higher top speed. You reach a certain point where aerodynamic drag is so high that only more HP will get you to go faster. Most bikes don't pull to redline at top speed, because they run out of HP, so even if he had a transmission and could gear higher, he would most likely achieve the same top speed, just at a different motor RPM.

I 100% agree Yates doesnt need it. My thought is that his motor and controller wiegh about 140-150lbs together. UQM have been quoted at around $20-25k for a system. For $15k I could buy a motor and controller that can do 130-140HP and weigh about 70lbs. I could then add a 3 speed transmission for 30-40lbs the same amount of batteries and could potentially out-perform him on the same chassis. He could still beat probably beat me in top speed thou. It would probably take a little less or just as much work as it took Chip to build his bike.

I see a transmission in the end as a cheaper means to have more performance out of cheaper, torque limited ride. If motors can become cheaper then a transmission will no longer have this advantage. If I had the money and could source the motor I wanted, I would build a 350lb torque monster and not mess with a tranny, but on my current Agni, GBS, kelly setup. I could add a 20lb 2 speed and get 50% more low end fun :) 20lbs of batteries wouldnt help because of my max controller voltage.

cycleguy
09 May 2011, 2001
I hear what you're saying, but the point I'm trying to make is that a transmission is a band aid for an underpowered motor. It does nothing to increase HP, so yes, your bike will accelerate faster from a stop, but very soon you'll be in high gear and the bike will fall on it's face, because you are now relying solely on it's HP to keep accelerating.

An electric motor's strong point is its low end torque, it's weak point (with current low voltage controllers) is it's low HP and dramatic loss of torque at high RPM. A transmission does nothing to address that shortcoming.

An ICE is exactly the opposite, so a transmission addresses the low torque at low RPM handicap of an ICE perfectly.

We need to look at the positives and negatives of an electric motor, and improve on the negative. A trans is just making the positive even more positive, without doing anything to improve on the negative. The added bonus of improving a motors HP and RPM capability will also improve it's torque range, so you get a double benefit.

Nuts & Volts
09 May 2011, 2021
Ok i see your train of thought. I like to look at it this way. Every motorcycle, be it on the open road, in the city, or on the track will spend the majority of the its time (70-80% is my guess) at 70% or less of its maximum speed. So improving the low end will make a much larger difference in my eyes.

Your improving on the negative is true. If maintaining or gaining top speed is more important then a tranny is not the best choice.

podolefsky
09 May 2011, 2056
OK, here's a (seemingly) simple question.

A Ninja 250 has a top speed somewhere around 110-115 mph, and does 0-60 in about 6 sec. It makes 18 ft-lb of torque and 25 HP.

My D&D makes 80 ft-lb (at 450A) and 30 HP. That's at 72V, 450A controller.

Right now, with single speed 13:52 it has a top speed around 70 mph and 0-60 around 10 sec (or so, I haven't measured it very accurately).

How can I make my bike quicker to 60 and faster top speed than a Ninja 250? It should be able to do that since it has more torque and power.

If I can't have both, I'll take quicker 0-60.

cycleguy
10 May 2011, 0727
OK, here's a (seemingly) simple question.

A Ninja 250 has a top speed somewhere around 110-115 mph, and does 0-60 in about 6 sec. It makes 18 ft-lb of torque and 25 HP.

My D&D makes 80 ft-lb (at 450A) and 30 HP. That's at 72V, 450A controller.

Right now, with single speed 13:52 it has a top speed around 70 mph and 0-60 around 10 sec (or so, I haven't measured it very accurately).

How can I make my bike quicker to 60 and faster top speed than a Ninja 250? It should be able to do that since it has more torque and power.

If I can't have both, I'll take quicker 0-60.

Anything you can do to increase voltage and current would make an improvement.
72V and 450A is fairly low. I think you would be better off upgrading the controller and battery pack to something more capable.
The problem with a DC motor is that they don't rev very high, and have a very short torque range before the knee, so increasing the current would increase torque and raising the voltage would extend the torque curve out further towards max motor RPM.
Based on your specs, it looks like your motor is only revving to about 4000 RPM at top speed of 70MPH. It's capable of 5000-5500 RPM, which tells me you are running out of HP at 4000 RPM to pull any further, because the motor has fallen off the deep end of the torque curve. Increasing the voltage would extend the torque curve out further, giving you more torque at 4000 RPM to keep pulling towards the motor's max RPM, increasing your top speed.
You would be better off spending the extra money on upgrading your controller and battery pack, than spending it on a transmission.

jpanichella
10 May 2011, 0753
Anything you can do to increase voltage and current would make an improvement.
72V and 450A is fairly low. I think you would be better off upgrading the controller and battery pack to something more capable.
The problem with a DC motor is that they don't rev very high, and have a very short torque range before the knee, so increasing the current would increase torque and raising the voltage would extend the torque curve out further towards max motor RPM.
Based on your specs, it looks like your motor is only revving to about 4000 RPM at top speed of 70MPH. It's capable of 5000-5500 RPM, which tells me you are running out of HP at 4000 RPM to pull any further, because the motor has fallen off the deep end of the torque curve. Increasing the voltage would extend the torque curve out further, giving you more torque at 4000 RPM to keep pulling towards the motor's max RPM, increasing your top speed.
You would be better off spending the extra money on upgrading your controller and battery pack, than spending it on a transmission.

But he can't go higher than 72V with his motor due to arcing. We're going in circles...

EVcycle
10 May 2011, 0903
But he can't go higher than 72V with his motor due to arcing. We're going in circles...

Maybe/maybe not. If the amps @72 is dropping off due to a small battery pack the RPMS will drop too and so top speed.
Too low of a gear ratio can cause that.

Been there done that.

podolefsky
10 May 2011, 0928
Maybe/maybe not. If the amps @72 is dropping off due to a small battery pack the RPMS will drop too and so top speed.
Too low of a gear ratio can cause that.

Been there done that.

Right now I'm geared 4:1. I did a test run yesterday, tracking current and speed. Seems like I hit the knee about 40 mph, which is right in line with the motor spec. So it's a lot weaker from 40-60 than from 0-40, and it gets weaker as I approach 60.

So yes, even lower gearing might help bring the knee up closer to 60. I have the gears to try 3.25:1. It will mean losing some low end torque-at-wheel. There's no more current to be gotten from my controller, I'm pegging 500A motor side already.

podolefsky
10 May 2011, 0933
Anything you can do to increase voltage and current would make an improvement.
72V and 450A is fairly low. I think you would be better off upgrading the controller and battery pack to something more capable.
The problem with a DC motor is that they don't rev very high, and have a very short torque range before the knee, so increasing the current would increase torque and raising the voltage would extend the torque curve out further towards max motor RPM.
Based on your specs, it looks like your motor is only revving to about 4000 RPM at top speed of 70MPH. It's capable of 5000-5500 RPM, which tells me you are running out of HP at 4000 RPM to pull any further, because the motor has fallen off the deep end of the torque curve. Increasing the voltage would extend the torque curve out further, giving you more torque at 4000 RPM to keep pulling towards the motor's max RPM, increasing your top speed.
You would be better off spending the extra money on upgrading your controller and battery pack, than spending it on a transmission.

Like Jon said, I can't go higher voltage with this motor. It could probably take more current. What controller could I use? I've seen Kellys that are rated at 600A (but we've been around that and I'm not sure it will actually put out 600A).

Even so, DC motor and "small" battery or no, my bike's specs beat the 250, especially in torque where EVs are supposed to "shine". But the bike is slower. How does that look?

cycleguy
10 May 2011, 0936
It's worth trying a 12/60 (5:1) ratio. It will increase torque to the rear wheel throughout the rev range, increasing acceleration, and may allow the motor to pull max RPM at top speed, provided your battery is up to it, as stated by EVcycle.
What is your battery spec?
A series DC motor is not the best application for a motorcycle to begin with, they just don't have a large enough powerband due to the limited RPM capability. Even though you claim to have as much HP as the Ninja, the difference is that the Ninja's motor is producing progressively more power with increased engine speed as it accelerates in top gear towards it's top speed, whereas your motor is loosing power the faster it spins. At that speed, your motor is far past it's power peak and falling fast.

frodus
10 May 2011, 0936
advance your brushes......

don't go higher current, you'll destroy that motor and brushes.

cycleguy
10 May 2011, 1000
I looked up the specs on the Ninja. It has an overall 1st gear ratio of 23.4/1, that includes the primary reduction of 3:1 x the first gear reduction of 2.6:1 x the final drive reduction of 3:1. The motor puts of 15.5 lb/ft of torque peak, so that would be 23.4 x 15.5 = 362.7 lb/ft of torque to the rear wheel.
All the figures I've found so far show your D&D motor at 65 lb/ft unless I'm wrong. 362.7/65 = 5.58. So, a final drive ratio of 5.58:1 should give you the same pulling power as the Ninja off the line, this is of course not taking overall weight into consideration. 1000 rear wheel RPM is approx. 75 MPH, so 1000/5500(motor RPM) = 5.5:1 ratio for 75 MPH.
If you upgrade the controller to something with 600-650 amps you could lower the gearing to 4.5 or 5:1 and still accelerate as hard as the ninja and get closer to the same top speed. The Ninja tops out at 100-105 BTW.

frodus
10 May 2011, 1003
thats if his batteries don't sag under that kind of load.

podolefsky
10 May 2011, 1013
I looked up the specs on the Ninja. It has an overall 1st gear ratio of 23.4/1, that includes the primary reduction of 3:1 x the first gear reduction of 2.6:1 x the final drive reduction of 3:1. The motor puts of 15.5 lb/ft of torque peak, so that would be 23.4 x 15.5 = 362.7 lb/ft of torque to the rear wheel.
All the figures I've found so far show your D&D motor at 65 lb/ft unless I'm wrong. 362.7/65 = 5.58. So, a final drive ratio of 5.58:1 should give you the same pulling power as the Ninja off the line, this is of course not taking overall weight into consideration. 1000 rear wheel RPM is approx. 75 MPH, so 1000/5500(motor RPM) = 5.5:1 ratio for 75 MPH.
If you upgrade the controller to something with 600-650 amps you could lower the gearing to 4.5 or 5:1 and still accelerate as hard as the ninja and get closer to the same top speed. The Ninja tops out at 100-105 BTW.

Thanks - I've done all those calculations as well (they show up in my graphs of rear-wheel-torque for Ninja vs my bike). The motor is rated to 5500 RPM unloaded, but in reality it maxes out around 4000 RPM. I've had it 5:1, and it did pull hard to about 30 mph, but could barely get above 55 mph (and it took forever to get there).

podolefsky
10 May 2011, 1020
thats if his batteries don't sag under that kind of load.

Good point. I've been testing this to be sure.

Taking data from the Alltrax, at 475 A (battery) and 510 A (motor), battery voltage sags to 68.7V. 2.86 V / cell. That's at about 85% SOC.

GBS are rated down to 2.5V / cell. So I think the batteries have it in them, depends on whether the motor can take 600A.

Also, Travis, I have data the confirms what you were saying about getting very large motor current with small battery current. At 25% throttle, I see 400+ A motor side with ~100A battery side. This is driving around my neighborhood. My butt dyno says this isn't pulling as hard as full throttle, but what does my butt know?

cycleguy
10 May 2011, 1037
Podolefsky, do you have a motor curve, or supply a link to it? You have a really nice bike and did some fine work, I'd love to know that it goes as nice as it looks.

podolefsky
10 May 2011, 1047
Podolefsky, do you have a motor curve, or supply a link to it? You have a really nice bike and did some fine work, I'd love to know that it goes as nice as it looks.

Thanks, nice of you to say. I'd like it to go as fast as it looks as well.

Way back in about 1975 (aka post #66 (http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=13731&viewfull=1#post13731)) I posted graphs of motor curves for my bike with two different gearings, compared to the Ninja shifting through the gears. Is that the sort of thing you're looking for?

(As soon as you see the AC-20 @ 96V curve, you'll say there's your answer...but that's a $5000 answer.)

cycleguy
10 May 2011, 1116
Thanks, nice of you to say. I'd like it to go as fast as it looks as well.

Way back in about 1975 (aka post #66 (http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=13731&viewfull=1#post13731)) I posted graphs of motor curves for my bike with two different gearings, compared to the Ninja shifting through the gears. Is that the sort of thing you're looking for?

(As soon as you see the AC-20 @ 96V curve, you'll say there's your answer...but that's a $5000 answer.)

I was going to suggest going AC induction, but didn't want to bring it up. That's the way to go in my opinion. You don't really need an AC20, an AC15 has very close specs and uses the same controller, In fact the AC15 with the new 1238-7601 650Amp Curtis may even outperform the AC20 @ 550 amps. The AC 20 has slightly more torque but mainly stays cooler due to it's larger mass. An AC15 @ 96V/550A would make a huge difference compared to what you have now and that system is $3100, how much more is that compared to what you paid for your current system? Check with Travis, he may even have a motor he's selling.

podolefsky
10 May 2011, 1141
I was going to suggest going AC induction, but didn't want to bring it up. That's the way to go in my opinion. You don't really need an AC20, an AC15 has very close specs and uses the same controller, In fact the AC15 with the new 1238-7601 650Amp Curtis may even outperform the AC20 @ 550 amps. The AC 20 has slightly more torque but mainly stays cooler due to it's larger mass. An AC15 @ 96V/550A would make a huge difference compared to what you have now and that system is $3100, how much more is that compared to what you paid for your current system? Check with Travis, he may even have a motor he's selling.

Yup, at 96V the performance boost is substantial. At 72V, it's not much different. With AC you trade RPM for torque, but once you regear to get the same wheel torque the curves lie almost exactly on top of each other. The AC system gets a bit more power at high RPM, I think because it can change the timing and field to eek out a bit more. But it's not huge.

My motor, controller, and contactor came out to $1390 shipped. The AC-20 kit is about $3500 + contactor + shipping. (Although I found it on evparts for $3090) (http://www.evparts.com/products/street-vehicle/motors--dot/ac-motor-controller-kits/mt1963.htm).

I have talked to Travis. Bottom line is I don't have cash for an AC kit right now.

frodus
10 May 2011, 1213
I was going to suggest going AC induction, but didn't want to bring it up. That's the way to go in my opinion. You don't really need an AC20, an AC15 has very close specs and uses the same controller, In fact the AC15 with the new 1238-7601 650Amp Curtis may even outperform the AC20 @ 550 amps. The AC 20 has slightly more torque but mainly stays cooler due to it's larger mass. An AC15 @ 96V/550A would make a huge difference compared to what you have now and that system is $3100, how much more is that compared to what you paid for your current system? Check with Travis, he may even have a motor he's selling.

the AC15 package includes a 6501. The AC18 package includes a 7501. The AC20 package includes a 7501. No idea if they have either of those paired with the new 1238R.

No motors for sale ATM, but I can get em.....

DRZ400
10 May 2011, 1231
Thats why I choose the Agni 95 motor over the AC-15. Geared 6:1 (12/72) I get quick accelleration and a 70 mph top end on 84 volts... and its only 22 lbs. Less then 1/2 cost of AC. Now I'm saying this having never ridden an AC bike (other then some hub e-bikes) which I'd like to do.



It's worth trying a 12/60 (5:1) ratio. It will increase torque to the rear wheel throughout the rev range, increasing acceleration, and may allow the motor to pull max RPM at top speed, provided your battery is up to it, as stated by EVcycle.
What is your battery spec?
A series DC motor is not the best application for a motorcycle to begin with, they just don't have a large enough powerband due to the limited RPM capability. Even though you claim to have as much HP as the Ninja, the difference is that the Ninja's motor is producing progressively more power with increased engine speed as it accelerates in top gear towards it's top speed, whereas your motor is loosing power the faster it spins. At that speed, your motor is far past it's power peak and falling fast.

podolefsky
10 May 2011, 1331
Thats why I choose the Agni 95 motor over the AC-15. Geared 6:1 (12/72) I get quick accelleration and a 70 mph top end on 84 volts... and its only 22 lbs. Less then 1/2 cost of AC. Now I'm saying this having never ridden an AC bike (other then some hub e-bikes) which I'd like to do.

Hmmm...I'll have to compare those at 84V. I believe a single Agni 95R makes about 1/2 the torque of an AC-20. At least, that's where the Agni plot ends at 400A. The AC-20 chart says 72 ft-lb at 550A RMS. I believe the AC will go out to 8000 RPM, so it revs higher than the Agni. Don't get me wrong, the Agni is a very nice motor. It's just not an AC-20 (or 15). From looking at TTXGP bikes, AC-20 bikes are comparable to *dual* Agnis.

Correct me if I'm wrong, but the Agni 95R is about $1600 plus a controller, so figure $2100-2200 maybe? The AC-20 kit is $3500 (can be found cheaper), so more expensive but not twice. But if you figure you need two Agnis to equal an AC-20, plus a controller that can handle two motors (either high voltage or current)...then I'm not sure anymore.

frodus
10 May 2011, 1343
Twice the torque and more continuous power (without extra cooling). Higher RPM's, and the simplicity of one motor compared to two+connecting them together.

podolefsky
10 May 2011, 1349
half the torque and more continuous power (without extra cooling). Higher RPM's, and the simplicity of one motor compared to two+connecting them together.

do you mean twice the torque? for the AC-20 over the Agni.

plus, if I understand correctly, the controller can change the timing and field to tweak the torque out further on the AC.

DRZ400
10 May 2011, 1356
Well I paid $1,200 for mine, direct ship from India. My Kelly controller was $450.00 (bought 3 years ago). I see my batterys as my Torque limit not the motor...I'm only going to get 240 amps from them without serious sag....another Agni or AC ain't going to help that! If I wanted more torque with the motor I have I would need A123 prismatics and a beefy-er controller. The Agni geared 6:1 with the 40AH Calibs on a lite bike fit.

frodus
10 May 2011, 1357
do you mean twice the torque? for the AC-20 over the Agni.

plus, if I understand correctly, the controller can change the timing and field to tweak the torque out further on the AC.

oops

Yeah, the controller on AC cna do quite a lot, but that's up to the algorithm they wrote for the controller.

podolefsky
10 May 2011, 1407
Well I paid $1,200 for mine, direct ship from India. My Kelly controller was $450.00 (bought 3 years ago). I see my batterys as my Torque limit not the motor...I'm only going to get 240 amps from them without serious sag....another Agni or AC ain't going to help that! If I wanted more torque with the motor I have I would need A123 prismatics and a beefy-er controller. The Agni geared 6:1 with the 40AH Calibs on a lite bike fit.

Is that because you can't fit 60Ah cells? My 60Ah GBS will do over 450A easily (they sag to about 2.85V / cell, LVC is 2.5V).

magicsmoke
10 May 2011, 1418
The 4 AC-20 motors I bought from Thunderstruck Motors, LLC claim on the sales receipt to deliver 100 ft lbs of torque @ 50 hp. On their website it is 110 ft lbs.! After fighting a low torque-starting problem, I finally got a chance to talk to the manufacturer and was told that 60 lbs. was maximum. That little lie cost me thousands of dollars and hundreds of hours of labor.

The above was from http://www.kisoffroad.com/rockdawg.html

I think that without real data then discussing the relative merits re performance of different motors is somewhat futile.
Perhaps members with different setups could have their bikes dynod and the data collated.

I'm happy to take a couple of Agni's up (although dyno time's a bit tight what with the Southern 100, Northwest 200 and TT all just weeks away :) )

frodus
10 May 2011, 1431
so, with 450A on battery side (7.5C) you're seeing 2.85V? hard to believe, I've yet to see any datasheets from GBS showing discharge curves.

DRZ400
10 May 2011, 1436
We're talking about the same 7C....I've had peaks of 280 amps under up hill accelleration (2.83 cell voltage). My 0-60 is fast...will have to time it this weekend. I could fit 60ah cells but thought it would have looked a little cartoonish.



Is that because you can't fit 60Ah cells? My 60Ah GBS will do over 450A easily (they sag to about 2.85V / cell, LVC is 2.5V).

frodus
10 May 2011, 1438
The above was from http://www.kisoffroad.com/rockdawg.html

I think that without real data then discussing the relative merits re performance of different motors is somewhat futile.
Perhaps members with different setups could have their bikes dynod and the data collated.

I'm happy to take a couple of Agni's up (although dyno time's a bit tight what with the Southern 100, Northwest 200 and TT all just weeks away :) )

Yeah, but that guy doesn't mention voltage, or battery type. There were probably other limitations.

Also, I can't tell, but it looks like they're direct drive. even at 100ftlbs x 4 = 400ftlbs, that thing is going to accelerate like poop. Trying to rock climb with that is just stupid. He'd be better off putting in a hydraulic motor in each wheel and running a large DC motor off the batteries at a continuous RPM.

podolefsky
10 May 2011, 1511
The above was from http://www.kisoffroad.com/rockdawg.html

I think that without real data then discussing the relative merits re performance of different motors is somewhat futile.
Perhaps members with different setups could have their bikes dynod and the data collated.

I'm happy to take a couple of Agni's up (although dyno time's a bit tight what with the Southern 100, Northwest 200 and TT all just weeks away :) )

Thunderstruck still has 110 ft-lb listed for the AC-20. I emailed them and asked directly why this didn't match the motor curves (which only go to about 72 ft-lb). They said "Interesting you should ask. Our supplier is re adjusting their ratings. ...we will be posting some revisions soon."

That was in February. They still have 110 ft-lb listed on their site.

podolefsky
10 May 2011, 1526
so, with 450A on battery side (7.5C) you're seeing 2.85V? hard to believe, I've yet to see any datasheets from GBS showing discharge curves.

Here's data from a hard pull at 100% throttle.
http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/hard_pull_log.png

And just for fun, here's what happens with the rear wheel locked (rear brake on hard), providing maximum load to the motor.

(Not that I want to or should do this very often, but it illustrates the point of motor vs battery amps.)

http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/wheel_locked_log.png

frodus
10 May 2011, 1531
so whats the real freaking rating? Man HPEVS is slow to get this info, how hard is this. bolt two AC20's together and let one spin the other. Then slowly load down one AC20 by "running" the other AC20 against the AC20. Plot voltage and amps on each side. losses will be 1/2 of the total loss.

I mean, you could come up with a cleaner solution, but they have what they need.

podolefsky
10 May 2011, 1548
I emailed Thunderstruck again, and they said "We only post the specs the Manufactures give us and the motor manufacturer has not given us the updated specs yet."

HPEVS website does have data, but none of it is consistent and you can't use it to compare anything. But I don't see 110 ft-lb listed anywhere for the AC-20, so I'm not sure where the EV suppliers are getting this number. Maybe HPEVS gives it to them but doesn't put it on their website?

Time for another email...

frodus
10 May 2011, 1607
yeah, please give me what you get on the AC20, but as of 3 weeks ago, they didn't have it.

podolefsky
10 May 2011, 1657
haha - HPEVS doesn't have an email address on their website (that I could find). Have to call them I guess.

EVcycle
13 May 2011, 0514
I rode in the morning on the Cafe bike because it was

: Friday
: no chance of rain....finally.
: wanted to redetermine if I thought a transmission for THIS particular bike was good or bad.

Conclusion - Nope - due to its light weight and even with its relatively small AH setup, (40 AH) it does just fine.
I had to pass a couple of slow cars this morning and never have a problem even though I have the controller at 280 amps max output.

I did find my analog 600a amp meter that may get temporarily mounted this weekend.

If was going to use it all the time for street/ race, then a 2 or three speed "may" be cool, but even then I would rather have more batteries.

I am interested in the seeing the results (acceleration/top speed/distance) on the other transmission projects.
Since I ride the bike for transportation, not just play, I need the distance as well as acceleration entertainment.

Live to ride - Ed

podolefsky
22 May 2011, 1201
Since the world didn't end yesterday, I thought I'd resurrect this thread.

Here's a plot I made comparing a D&D/Alltrax system (what Brutus and I both have) with an AC-20. All are compared to a Ninja 250 for reference. Both systems are using 72V data. This is plotting wheel torque (motor torque * reduction ratio).

The D&D curves simulate a 5 speed gearbox, set up to have similar shift points to the Ninja, and the same 1st gear torque as the AC-20.

The dashed blue is the D&D with a single 52:16 reduction.

What you can see is that a gear box would really help spread out the effective torque band for the D&D. But, the AC-20 performs better overall without a gearbox (yes, it might be even nicer with a gearbox...but that's not the point here.)

Using the AC would only mean switching out the motor/controller. Same battery pack. The D&D is rated to 72V, while the AC can do 96V or more, so there's plenty more available with the AC and more cells.

http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/DC_shifting.png


Added lines for AC-20 limited to 450A, just to compare apples-to-apples a little better. Dashed blue line is extending the D&D 4.6:1 curve.

http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/DC_shifting_2.png

teddillard
22 May 2011, 1226
NOW we're getting somewhere. Noah, what's the weight difference between the AC20 and the D&D?

The conclusion I draw from this is that, for a given motor/controller, a transmission has a faster top speed and quicker acceleration.

What I'd like to know is if, for a given weight, is a transmission better than a bigger motor and more batteries?

So. If you tell me that the weight difference between your motor and the AC20 is around 50 lbs, then it's an even tradeoff, between your motor with a transmission, and an AC20 without. And you're getting better performance with the bigger motor.

Right?

(For my money, I'd bag the Ninja data altogether... it's irrelevant IMO.)

podolefsky
22 May 2011, 1237
The D&D and AC are nearly the same weight and size (around 55 lb., both 6.7" motors about 12.5" long) The Curtis AC controller is larger, maybe 2x the size of the Alltrax.

I realized I need to state a disclaimer - the D&D Alltrax setup is 450A, the AC-20 setup is 550A.

If you have the room, 8 more cells is about 38 lb and would give you a 96V AC system. Basically take the curve above and extent the knee about 30% to the right (or 30% higher by regearing...all sorts of things you could do).

The AC system is also slightly more efficient, and can do regen...for what it's worth. It also costs more than 2x as much.

teddillard
22 May 2011, 1245
Interesting.

I've been trying to put together an interview of sorts with Richard Hatfield from Lightning, and I asked him about transmissions. This is what he had to say:

"Ultimate power is determined by motor cooling. Properly developed and cooled drive systems are lighter and more efficient than transmissions. The extreme examples are top fuel dragsters. If you make sufficient power you do not need a transmission."

EVcycle
22 May 2011, 1249
Interesting... (part 2) :)

Brutus
22 May 2011, 1250
This is a good time to post an update to what I have found so far. The brick wall of top speed with Brutus is 119mph but it takes for ever to get there and eats battery power fast. The real Issue is rpm of the motor and poor batteries. After some gearing changes to limit top speed to 100mph battery power lasts quite a bit longer and it can get to top speed in a much shorter distance.
In the end I want a bike that is quick from 0 to 100 mph and has good range. I will leave top speed and racing to the guys breaking records. After all I built a sport cruiser not a sport bike.
For now this is what speed I see out of each gear, the only thing that will change from this is the acceleration to these speeds.
1st 0-30mph
2nd 30-48mph
3rd 48-65mph
4th 65-80mph
5th 80- 100mph

podolefsky
22 May 2011, 1255
I added another plot to the above post (http://www.elmoto.net/showthread.php?1246-Brutus-s-5-speed-El-Moto-(transmission-discussion)&p=15269&viewfull=1#post15269) to show AC at 450A limit.

DaveAK
22 May 2011, 1300
I think the Ninja curve is useful as a comparison based on HP, (that's why you're using the Ninja, right?), but I wouldn't use it to base the gearing of the D&D on. I'd like to see the same plot with 2 gears, one with 3 gears etc., with the ratios chosen to get maximum benefit. In my mind we're looking for the best bang for our DIY buck, not a replacement for a similar ICE bike or the perfect motor/controller combo that we can't afford.

Brutus
22 May 2011, 1307
A top fuel dragster is neither efficient or well cooled. A nitro methane motor will melt down if run for more than 12 seconds at top rpm. And 9 gallons to the quarter mile doesn't sound very efficient either.

podolefsky
22 May 2011, 1314
Yeah, that statement about top fuel is just stupid (all due respect). If it were true, F1 cars wouldn't have transmissions either.

podolefsky
22 May 2011, 1326
This is a good time to post an update to what I have found so far. The brick wall of top speed with Brutus is 119mph but it takes for ever to get there and eats battery power fast. The real Issue is rpm of the motor and poor batteries. After some gearing changes to limit top speed to 100mph battery power lasts quite a bit longer and it can get to top speed in a much shorter distance.
In the end I want a bike that is quick from 0 to 100 mph and has good range. I will leave top speed and racing to the guys breaking records. After all I built a sport cruiser not a sport bike.
For now this is what speed I see out of each gear, the only thing that will change from this is the acceleration to these speeds.
1st 0-30mph
2nd 30-48mph
3rd 48-65mph
4th 65-80mph
5th 80- 100mph

Brutus, can you tell me what your actual drive ratios are for each gear?

Those speeds look like they would be just about the same ratios I picked out in my graphs, assuming you shift right at the knee.

teddillard
22 May 2011, 1403
Yeah, good point (cooling), bad analogy, now that I think about it.

EVcycle
22 May 2011, 1417
Yeah, that statement about top fuel is just stupid (all due respect). If it were true, F1 cars wouldn't have transmissions either.

Not really (that stupid). You are comparing apples and oranges there.

Last time I saw, a Top fuel car has 7000 HP and does not make pit stops..... :)

Brutus
22 May 2011, 1424
Your graphs are so close I thought you hacked my computer!

podolefsky
22 May 2011, 1653
Not really (that stupid). You are comparing apples and oranges there.

Last time I saw, a Top fuel car has 7000 HP and does not make pit stops..... :)

True - but so is comparing an electric motorcycle and a top fuel dragster :rolleyes:

F1 cars make about 1000 HP in a 1500 lb car. It's not 7000, but I'd say it's still in the "enough power" category.

EVcycle
22 May 2011, 1704
I may be the odd man out (as usual), but one of the things I like about electric vehicles is that they don't have a transmission. I have been shifting and clutching all my life and find that not having to do so is relaxing and lets me better concentrate on the traffic and scenery around me. I sure hope the Empulse motor doesn't sound like the one in the video above. That thing sounds like a hive full of killer bees. I never cared much for bees. Maybe they can sell some playing cards as an accessory to attach to the spokes.

Me too.... The No tranny club? (Ted would be disappointed as he likes to say "Tranny" ) :):)

Brutus
11 June 2011, 1718
I took Brutus out today, it was quite windy but I managed to get a decent helmet cam video of a 1/3 mile run for some testing on my gauges. Next up is a new battery pack and charging system plus a move into a real shop instead of my garage.
<iframe width="480" height="390" src="http://www.youtube.com/embed/CgbHxLJxKNI" frameborder="0" allowfullscreen></iframe>

jazclrint
11 June 2011, 2319
So maybe a transmission might help a race bike with a limited battery pack get a quicker jump off the line and out of slower corners without using much more power. And if you don't like shifting a cvt would do the trick.

mpipes
12 June 2011, 0920
Brutus, barren desert looks kinda like my digs, what area are you located?

Brutus
12 June 2011, 0943
Brutus, barren desert looks kinda like my digs, what area are you located?

I live in Henderson Nv but the video was shot out at the Solar1 facility off the US 95 in Boulder city. The access road is 3 miles long and not used on the weekends. Boulder city PD comes out to watch me test all the time and I basically have their blessing for weekend use. Where are you at?

podolefsky
12 June 2011, 1005
So maybe a transmission might help a race bike with a limited battery pack get a quicker jump off the line and out of slower corners without using much more power. And if you don't like shifting a cvt would do the trick.

It might help a bike accelerate quicker, but it would actually take *more* power. If you want to accelerate from, say, 0-30 mph in 3 sec, it will take the same amount of power whether you have a transmission or not. The reason is that you have to put the same amount of energy into the bike, and power = energy / time. The only way to use less power is to accelerate more slowly (more time ~ less power)

The only catch is efficiency, which depends on a lot of factors like RPM, current draw, and losses in the transmission. Someone would have to work that out, but I don't think it's enough to actually accelerate faster while using less power.

This has made me think - what a transmission does is get around the inherent limitations in a drive system. Suppose you need 400 ft-lb at the wheel to do 0-30 in 3 sec. If your motor makes 80 ft-lb at 500A, you need a gear ratio of 5:1. 80*5 = 400 ft-lb. If you have a gear ratio of 2.5:1, then then only way to get 400 ft-lb at the wheel is with more current, 1000A since you need twice as much motor torque. If your batteries/motor/controller can only produce 500A than that's your limit.

Or if you want to pop wheelies like in the Brammo Engage video, you need more gears. Chip Yates can do it with one speed because his bike makes 400 ft-lb at the motor. For the rest of us mortals, it's not going to happen with a single speed unless you gear for a top speed of about 12 mph. Maybe that's not your thing, but if it is a transmission makes a lot of sense.

mpipes
12 June 2011, 1446
I live in Henderson Nv but the video was shot out at the Solar1 facility off the US 95 in Boulder city. The access road is 3 miles long and not used on the weekends. Boulder city PD comes out to watch me test all the time and I basically have their blessing for weekend use. Where are you at?

I'm just down the Colorado River at Lake Havasu. I thought I recognized that area around the solar facility in your photos and video! of course, much of the desert looks the same but the mountains in the background looked familiar.

theFREElaker
03 June 2012, 1226
Why ride the past when you can ride the future? :)

THANK YOU SO MUCH! As soon as I read this, I created an account JUST so i could give you my thanks for posting this statement.
Thank you

This just reminds me of why I hate gas powered vehicles so much. Instead of saying, "Shoot, these cars are super inefficient, and gas prices are through the roof and man are the emissions terrible for this planet and wow is maintenance a pain in the booty, lets scrap gas as a source of motive power and start EV mainstream production in 5 years." they say, "Alrighty then people, lets figure out how to make minute positive changes to a REALLY inefficient machine! Whadda ya say!?" And now everyone who sees and wants the future to happen now has to pay ridiculous premiums simply because EV capable electric motors rant being massed produced on a scale suitable for price reductions!
Sorry, I'm done venting!