PDA

View Full Version : Honda CB1100 X11 conversion



teet
07 November 2011, 0851
Hello everyone,

After many years of dreaming about building some EV and even buying my current car (http://www.titusverbeek.nl/a2foto1.jpg) with this purpose in mind I just started with a project a little 'easier' than that and bought a crashed Honda CB1100 X11. I want to turn it into an EV, therefore doing a lot of reading and researching about which parts to use and how to use them. It seems this forum is the place to be to meet other people facing or having faced the same issues that I will, even though I live in Europe, The Netherlands.

I have started a website (http://www.bagdesign.nl/titusverbeek-projects/Project_X11_EV.html) about this project with some pictures and explanations. (written in Dutch, be warned)

Components:
With the motorway in mind (120 km/h or 74 miles/h) regenerative braking, and my limited tooling/electronic skills (I am just a product designer) it seems wise for me to buy a kit which is tested and programmed rather then to buy separate components from various suppliers. Judging the EV's I have seen so far I think that brushless engines sound nicer than brushed ones, please correct me if I'm wrong. Besides that they don't need any maintenance. Therefore, the kit I have in mind is based on a 12 kW (23 kW peak) brushless DC motor running at 48V (http://www.electricmotorsport.com/store/ems_ev_parts_kits_pmac_ds-gen4-48-450.php). A cheaper alternative would be: 6 Hp (19 Hp peak) brushless DC motor running at 72V (http://www.electricmotorsport.com/store/ems_ev_parts_kits_pmac-ss.php). Your opinion about which one to use or if you know another place to get good kits is appreciated.

To be continued...

Bye,
Teet

p.s. EDIT: corrected link to 'cheaper alternative'

Skeezmour
07 November 2011, 1021
Welcome to the fun Teet. Looks like a nice bike and should have lots of room to set it up nicely. One warning though at 48v and that low of power you may have a hard time with 74miles/h sustained speed.

Keep asking questions though there are a lot of great people on here who would love to see another nice Elmoto added to the stable.

jpanichella
07 November 2011, 1107
Welcome!

Good to see another product designer here.

And I second Skeezmour's comment, if you invest in a 48 volt system you'll wish you just went 72. In order to up the voltage you'd need to purchase a new controller, contactor, and charger, so it's a better investment to start with a higher voltage system.

teet
07 November 2011, 1110
Thanks Skeezmour :) Are you saying that 48 volts is probably not enough to reach 74 miles/h?
The alternatives are:
- Induction engine with 29 hp (peak) 82 ft./lbs torque running at 72 V and 550A max (http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac12.php), or
- Brushless engine 12 kW (30 kw peak) 72V 350 Amp (http://www.electricmotorsport.com/store/ems_ev_parts_kits_pmac_ds-gen4-72-350.php),
The induction engine is a little noisy IMO if it is the same as used here (http://www.youtube.com/watch?v=CCUqdBZLRbI&feature=player_embedded#!) but I don't know about the brushless one.

teet
07 November 2011, 1113
Welcome!

Good to see another product designer here.

And I second Skeezmour's comment, if you invest in a 48 volt system you'll wish you just went 72. In order to up the voltage you'd need to purchase a new controller, contactor, and charger, so it's a better investment to start with a higher voltage system.

Thanks jpanichella! And I will do that. It is not that much more expensive compared to buying new parts when changing the voltage later.

teet
07 November 2011, 1134
Regarding the engine power and consumption... do engines, built for more power, also consume more power, even when you drive slow? I mean I don't mind buying a too powerful system but it would be a pity if at the same time that system requires more battery power for a normal, modest drive.

Coninsan
07 November 2011, 1147
Well no, the motor only pulls what it needs too to substain the given speed. This is the same for both a weak and powerfull setup. The only points where the more powerfull setup pulls more juice is during acceleration and substained high speed riding. Theoretically (and most likely practically) both setups should be able to drive the same distance on the same battery pack.

lugnut
07 November 2011, 1214
Regarding the engine power and consumption... do engines, built for more power, also consume more power, even when you drive slow? I mean I don't mind buying a too powerful system but it would be a pity if at the same time that system requires more battery power for a normal, modest drive.

Typically not. A larger electric motor, or more powerful one, may actually run more efficient than the smaller or less powerful one at the same load, meaning less wasted power. A larger motor means more mass to accelerate requiring a bit more energy, but not that much, and the larger motor will be more efficient at that acceleration than the smaller, so will offset that mass penalty. A larger or more powerful motor would run cooler, so you'd think, and cooler motors are more efficient. Aside from space and maybe cost, there isn't much downside to the more powerful motor choice IMO.

teddillard
07 November 2011, 1316
Typically not. A larger electric motor, or more powerful one, may actually run more efficient than the smaller or less powerful one at the same load, meaning less wasted power. A larger motor means more mass to accelerate requiring a bit more energy, but not that much, and the larger motor will be more efficient at that acceleration than the smaller, so will offset that mass penalty. A larger or more powerful motor would run cooler, so you'd think, and cooler motors are more efficient. Aside from space and maybe cost, there isn't much downside to the more powerful motor choice IMO.

Huh. Well... this doesn't make sense to me.

First, it was my impression that most motors, as a sweeping generalization, run at peak efficiency at around 90-95% of their maximum rated load. So, within reason, a smaller motor that's being run at a higher relative load would be nearer it's peak efficiency, right? (Enter Noah, with a graph, stage Left.)

As far as downside, beyond space and cost, the biggest one is weight. By using a "smaller" motor I cut 12 pounds off my bike's weight, and hauling more weight than you need is less efficient. My personal theory is that you want to run the absolute smallest motor you can, without burning the thing up, to keep the weight down.

As for the motor being "powerful", this term used like this is really starting to bug me. The power in the system basically comes from the batteries, and the current they can deliver. The motor isn't powerful (in the sense that it's "full" of power). It's power capable.

ZoomSmith
07 November 2011, 1400
The bike in question here is fairly large, so unlike Ted's batamweight Yammy, this thing will need a "more powerful" motor.

Skeezmour
07 November 2011, 1406
More "power able". System power output would be the better way to put it. If you have a motor/controller that has 50kw potential but batteries that will at best deliver 30kw you have a 30kw system. Find a balance point you will be happy with to start. I personally like systems that allow you to add more voltage. It lets you work your way into your end goal without having to buy the whole thing upfront.

I have a couple of the bigger bikes and as Zoom said you will need a bit more "go" to move it but not that bad.

Hope we are not overloading you.

teddillard
07 November 2011, 1406
The bike in question here is fairly large, so unlike Ted's batamweight Yammy, this thing will need a "more powerful" motor.

Clearly, but the principles remain the same. The question was if a bigger motor is less efficient. Honestly I'm not sure you can answer that theoretically, anyway, without comparing the data on two specific motors... but I'm still convinced that the lightest motor you can get away with is the best bet. It's working at it's peak efficiency, and it's not adding weight to the build.

lugnut
07 November 2011, 1419
Huh. Well... this doesn't make sense to me.

First, it was my impression that most motors, as a sweeping generalization, run at peak efficiency at around 90-95% of their maximum rated load. So, within reason, a smaller motor that's being run at a higher relative load would be nearer it's peak efficiency, right? (Enter Noah, with a graph, stage Left.)



If you take a typical motor out of a product line, say a NEMA induction motor, rated at 5HP and then go to the next larger (more powerful) model in that same product line, say rated at 7.5 HP and look at the motor efficiency of each at 5hp, you'll find the larger (more powerful) motor is running slightly more efficient (maybe just a fraction of a percent). Now look at those 2 motors running at 10HP and I think you'll see an advantage of several percent to the larger (more powerful) motor. But as the question was posed, running a larger (or more powerful) motor at a load capable of a smaller (less powerful) motor does not waste power in the energy conversion process of electric to mechanical in the motor itself and will likely save energy with the larger (more powerful) machine.


As far as downside, beyond space and cost, the biggest one is weight. By using a "smaller" motor I cut 12 pounds off my bike's weight, and hauling more weight than you need is less efficient. My personal theory is that you want to run the absolute smallest motor you can, without burning the thing up, to keep the weight down.

I did mention mass when accelerating, which includes cornering. And that can be considered in efficiency if you define efficiency such. But too small of a motor is a much worse problem than a slightly oversized motor. Ideally you would get it just right and the motor would turn to ashes inches after the finish line with you winning the race :-) But most here want it to last for the season, or for many years on the streets. I say error on the big side.


As for the motor being "powerful", this term used like this is really starting to bug me. The power in the system basically comes from the batteries, and the current they can deliver. The motor isn't powerful (in the sense that it's "full" of power). It's power capable.

The motor is the power conversion machine. Electricity into torque at speed. If it can't do the job, the battery is for naught. And throw in the controller. You have a system. All need to work together. Might as well throw in the chain, and sprocket, etc... Each component needs to be properly sized, or rated, or capable. Sorry if my words bug you :-)

teddillard
07 November 2011, 1432
I did mention mass when accelerating, which includes cornering. And that can be considered in efficiency if you define efficiency such. But too small of a motor is a much worse problem than a slightly oversized motor. Ideally you would get it just right and the motor would turn to ashes inches after the finish line with you winning the race :-) But most here want it to last for the season, or for many years on the streets. I say error on the big side.

Yes, you did... sorry.



Sorry if my words bug you :-)

It wasn't a personal comment, but it's used pretty much across the board to talk about motors. The problem is, for someone new to this, and familiar with the concept of a more "powerful" gas motor, it's a term that causes more confusion than it has to. It took me a long time to figure out that a "more powerful" motor just meant I could give it more power. But I'm a little slow, and stuck in my bad ways. :D

Thanks for the explanation re weight, that now does make sense to me.

DaveAK
07 November 2011, 1544
The problem is, for someone new to this, and familiar with the concept of a more "powerful" gas motor, it's a term that causes more confusion than it has to. It took me a long time to figure out that a "more powerful" motor just meant I could give it more power.
Just out of curiosity what confusion do you think it causes? What did you understand it to mean before you came to the realization you stated?

I don't necessarily agree with your conclusion above, (the second sentance I quoted). But we all see things different ways. If it helps you conceptualize a motor in these terms then that's great, I just don't know if that applies as a general rule to people new to motors and EVs.

In my mind a more powerful motor is one that's capable of delivering more power, as power delivery is what we're after. If a motor is 100% efficient, (as is the entire system), then if it delivers 10HP to the road it's going to take 10HP from the batteries. What you say is true, you can give a more powerful motor more power, but you get more power out of it too. It doesn't just mean you can feed it more, (the point I disagree on). I think we're splitting hairs a little here and pretty much talking about the same thing though.

teddillard
07 November 2011, 1628
I don't think it's splitting hairs at all. It probably does amount to semantics, but as I was told once, words is all we gots. Let me see if I can essplain.

When I started planning a build my first move was to start looking at the "most powerful" motors I could find. But because I've always been into power-to-weight, then I started comparing motors' power vs. their weight. This is all because this is basically what we always did building gas motors. You run a 2-stroke because it had huge power output at the peak, and very light weight. I then started looking for the most "efficient" motor I could find.

When I actually bought and ran the Mars motor with different batteries I started to understand how important the current delivery was, and how that really determined how "powerful" the bike would be. I think the cool thing about the points that have been made here is that you really do have to look at all the parts of the system to determine the power that the motor is going to deliver. The real point is, a guy coming from an ICE background tends to look at the motor as the source, but the motor in an ICE bike is a complete system- intake, compression, combustion, and you can tune each part of that system, and each part has a profound effect on the output. The motor in an electric bike is just part of the whole system.

(light bulb goes on!)

Pointing at the "most powerful motor" is kind of like pointing at "the most powerful piston", I guess.

I'd pass the issue by, but I see it here constantly, and am asked the question constantly as well... it's kind of the basic noob question- and the assumption is if you put in the most powerful motor you're going to get the most power.

So yeah. If you want long life and reliability, you use a motor that's just a bit bigger, heavier, and it will stay cooler. If you want to blow things up, you run small and light and try to cool it to keep it from blowing up before the last lap. Efficiency, however, really doesn't figure into the equation, IMO.

DaveAK
07 November 2011, 1657
Well that's a good explanation. I think it's important for teet and any other newbie to consider each of the main components, (batteries, controller, motor and to a lesser extent gearing), and how they can each be bottlenecks. Depending on how you envision building your system, (I've heard plenty of people suggest starting with SLAs for example), consideration needs to be given when selecting each of these components. I know that with what I've learned on my build I'm glad I went with lithium to start with, but if I was to start a new build there's a lot I would do differently.

teet
09 November 2011, 1006
Wow, thanks for all the explanations!! And no, you are not overloading me.

I have to say that the difference in weight of both motors I was comparing was 5,8 kg. (13 lb) Not enough to worry about, I'd say, compared to choosing the right system voltage and constant 'power transformation capability' of the motor. (I hope I use the right words ;-) ) From your statements I would conclude that using the bigger engine of the two (see my first message with links to both of them) will not have too much effect on the range. This one weighs 15kg (35 lb) but I should use it at a higher voltage because it is a waste to use it 'at half power' (48V).

So I better choose a setup similar to this (http://www.electricmotorsport.com/store/ems_ev_parts_kits_pmac_ds-gen4-72-350.php) one.

Next question: (a little retorical) Can I buy a couple of batteries, just enough to reach the right voltage, and buy the big bunch after I have won the lottery? I mean would it affect the maximum speed instead of just the range?

Saruman
09 November 2011, 1344
Hey fellow Dutchie,
Sure you can buy fewer batteries to begin with, but unfortunately having a series of single batteries (6s1p) instead of a series of parallel batteries (6s2p or 6s3p) means you not only save weight and money, but also add problems; the discharge current for 6s1p is twice that of 6s2p, and three times that of 6s3p, which means that (a) because of Peukert effect (http://www.saruman-electromotive.nl/download/en/Peukert_paper_v1.pdf), the loss of available energy can be substantial, and (b) because of those higher discharge current, your batteries cycle life will be substantially reduced (possibly below 1 cucle :O). So you then have to reduce voltage (run 4s2p or something) and/or reduce power draw by your controller which reduces both topspeed and accelleration...
Maybe you wanna drop by and do koffie&koekje near Utrecht?

teet
09 November 2011, 1815
I was afraid so. (hence 'retorical')
I surely like to drop by and do koffie&koekje (see PM or send me one if I forgot)

My search for the right system is not completely over yet because of two reasons:
1: I'd like to buy it in Europe instead of the USA because of transportation and customs.
2: The company I contacted here (http://www.aep-ehv.nl/) in Holland to supply me the parts says this system is too powerful. (I saw that they used a similar system but running at 120V for a car, guess that's why they say that)

There is one other company (http://www.ev-power.eu/index.php?p=p_56&sName=dc-motors) I just contacted, to check if they have anything else except the displayed Agni brushed engines.

If anyone knows a better company in Europe, please let me know.

teet
11 November 2011, 1637
There is one thing I don't understand:
Suppose I use the PMAC-DS engine that can transform 12 kW (30 kW peak) into pure pleasure,
how can the suggested batterypack (24 cells, lithium, 7,68 kW, 100 kWh) ever deliver that kind of power?
Isn't that batterypack way too weak? (I mean shouldn't the 7,68 be something like 12 or 30? (ignoring the practically impossibility of these numbers for a second)

frodus
11 November 2011, 1729
Different units. 7.68kwh is energy not power. Let's say the batteries can do 5c peak. Assuming you mean a 24 cell 100ah pack, hats 500a and let's say the voltage drops to 2.8v. That's 24 x 2.8v x 500a = 33,600kw. Kw is power. Kwh is energy.

teet
13 November 2011, 1540
..emmm... OK. I guess I miss some technical background to be able to reproduce this. (how to get from 5C to 500A for instance... I have seen 5C mentioned but haven't heard of that unit 'C' before so didn't know what to do with it) Anyway that battery pack will do. That's the most important thing to know. Thanks Frodus!

billmi
13 November 2011, 1731
C is discharge rate in amps relative to the battery's capacity in amp hours. For ecample, if a battery has 40 amp hour capacity, Discharging it at 1C is 40 amps. 2C is 80 amps, 3C 120 amps, etc.

podolefsky
14 November 2011, 0050
Thanks Skeezmour :) Are you saying that 48 volts is probably not enough to reach 74 miles/h?
The alternatives are:
- Induction engine with 29 hp (peak) 82 ft./lbs torque running at 72 V and 550A max (http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac12.php), or
- Brushless engine 12 kW (30 kw peak) 72V 350 Amp (http://www.electricmotorsport.com/store/ems_ev_parts_kits_pmac_ds-gen4-72-350.php),
The induction engine is a little noisy IMO if it is the same as used here (http://www.youtube.com/watch?v=CCUqdBZLRbI&feature=player_embedded#!) but I don't know about the brushless one.

Hey Teet, welcome to elmoto.

Induction motors are actually really quiet. What you're hearing in that video is chain noise...that's going to be the same with any motor.

As far as brushed vs brushless, I think most would agree brushless has advantages (the main disadvantage being cost). You don't have to deal with brushes, but with brushed motors you don't really have to worry about brushes very often (as long as you don't abuse them :) )...and changing them out is pretty simple. It's mostly a calculation of cost / performance and your expectations.

In general, the approach I like is to make sure all the parts (battery, motor, controller) are well matched. None are too big or too small for the others...no major bottlenecks. This way you're not carrying useless weight or throwing away money.

Of all the parts of doing a conversion, connecting the controller to the motor is the simplest by far. The really complicated part is figuring out how to mount the motor, batteries, controller...making it all fit in your frame...and fabricating the custom parts you'll need to get the job done. Not to discourage you at all - this is what makes it tons of fun. Just expect a long process, lots of learning, lots of frustration...mixed with the occasional triumph that makes it all worth it.

teet
16 November 2011, 0530
C is discharge rate in amps relative to the battery's capacity in amp hours. For ecample, if a battery has 40 amp hour capacity, Discharging it at 1C is 40 amps. 2C is 80 amps, 3C 120 amps, etc. Right! All clear now. Thanks Billmi

teet
16 November 2011, 0551
Hey Teet, welcome to elmoto.

Induction motors are actually really quiet. What you're hearing in that video is chain noise...that's going to be the same with any motor.

As far as brushed vs brushless, I think most would agree brushless has advantages (the main disadvantage being cost). You don't have to deal with brushes, but with brushed motors you don't really have to worry about brushes very often (as long as you don't abuse them :) )...and changing them out is pretty simple. It's mostly a calculation of cost / performance and your expectations.

Thanks Noah! That makes sense. And it will not be different with mine unless I use hub engines I suppose. The idea is tempting. No sound, no more maintenance... but I haven't seen the right ones available yet. So why spend more money on a brushless or induction engine then, if changing or adjusting (?) brushes is not much of a hassle? I better save my money for the battery pack then.. And your example shows that paying extra attention to the other parts of the bike is very rewarding too. ;-)


In general, the approach I like is to make sure all the parts (battery, motor, controller) are well matched. None are too big or too small for the others...no major bottlenecks. This way you're not carrying useless weight or throwing away money.

Of all the parts of doing a conversion, connecting the controller to the motor is the simplest by far. The really complicated part is figuring out how to mount the motor, batteries, controller...making it all fit in your frame...and fabricating the custom parts you'll need to get the job done. Not to discourage you at all - this is what makes it tons of fun. Just expect a long process, lots of learning, lots of frustration...mixed with the occasional triumph that makes it all worth it.
I can imagine that. Having a good workshop would make a difference I guess, which I don't. So I will either use the nearby 3D printing facility (maybe they can do CNC milling too, I have to check) or stick to some very simple (but not too pretty) welding.

podolefsky
16 November 2011, 1247
Check out Enertrac (http://www.enertrac.net/). Very nice brushless hub motors, but need high(ish) voltage to get above 60 mph.

I have a brushless hub motor on my scooter, only 3 kW though. It is nearly silent. But I kind of like the chain noise on my motorcycle. The high pitched whine is pretty appropriate (kind of like a Tron light bike).

teet
16 November 2011, 1621
Cool! (both Enertrac and your Tron light bike chain whining noise)
Looks like Enertrac is a very attractive yet pricy alternative indeed.
I think the price will play the main role in my case. ;-)
Rather have some chain whining and better batteries then too little batteries and no sound nor maintenance. Maybe next time. :-)

teet
20 November 2011, 1803
To get an estimated 72V and 350+ Amps for the motor and 100Ah to get a fair range I am comparing different battery setups. Taking into account, in order of importance: Power, energy, cost and weight. I would appreciate your advise about which option to choose or if you see any weird calculations. :-P (voltage drop?)

1: 24 cells of 100Ah all in series.
76V, 100 x 3C = 300 Amp => 22,8kWh (30 hp)
Weight: 84kg (185 lb) - I wonder if I will make my 74 mph max speed with this setup. Maybe not, it is a big bike. But this is the 'cheapest' option.

2: 48 cells of 60Ah in this order: 24S 2P so making a total 120Ah
76V, 60 x 2 x 3C = 360 Amps => 27kW (36 hp)
Weight: 110,4 kg (242 lb) !

3: 240 cells of 10Ah in this order: 24S 10P making a total 100Ah - these are type 38120 (tube-shaped)
76V, 10 x 10 x 10C = 1000 Amps but I will tell the controller to limit to its maximum, say 400 Amps => 30kW
Weight: 72 kg (159 lb) Most expensive option.

I kind of like the second option because a bigger range is a big plus. But I just have my licence and never driven a HEAVY bike. I don't know what it's like. I don't care about acceleration... much.

Since I will probably need to order abroad I am thinking about ordering them in China (http://www.evlithium.com/). They also have a BMS (http://www.evlithium.com/html/7.html). Bad idea?

podolefsky
20 November 2011, 2014
76V, 100Ah would be nice for range, but it's probably overkill. You only need about 8-9 kW (11-12 hp) to make 74 mph on a typical bike. That's about 120A with a 76V system...easily within the continuous (3C) rating of 60Ah cells. You can still have a peak power of over 20 kW or more with that setup.

Most of the standard motors out there won't do 20 kW continuously anyway, so a pack that can do 13 kW continuous and 25 kW peak is usually more than adequate.

More Ah will get you more range, but at a large cost in money, weight, and space. Fitting 72V, 100Ah on most bikes is pretty tight.

Don't know about that dealer. Might be OK, but you're probably better off going with an importer with a good reputation (last thing you want is to get a bad cell or two and have to deal with the distributor in China). But might be OK, depends on your situation.

Saruman
21 November 2011, 0054
Podolefsky, are you certain? My bike doesn't ride yet, but I calculate 15.0kW for 120kmh (74.6mph) for a bike that's about as big and heavy as Teet's bike ('80 Honda CB750F). Your number suggests that I overestimate drag and roll resistance with 40%, i.e. my roll resistance would be only 52N and my drag coefficient would have to be 0.49 - much better than a Hayabusa according to http://www.outyourbackdoor.com/article.php?id=623.

Warren
21 November 2011, 0118
From the man himself, Craig Vetter.

"In Summary: 10-12 horsepower (125-180 cc air cooled engines) is adequate for 55 mph, sitting up and comfortable.
At 70 mph, into headwinds and hills, you need more power. Probably 16-20 hp. (250cc) Liquid cooling seems essential."

http://craigvetter.com/pages/2011-Streamliner/2011-vetter-streamliner-p49.html

Not going to happen with the typical brick-pulling-parachute motorcycle.

teddillard
21 November 2011, 0416
From the man himself, Craig Vetter.

"In Summary: 10-12 horsepower (125-180 cc air cooled engines) is adequate for 55 mph, sitting up and comfortable.
At 70 mph, into headwinds and hills, you need more power. Probably 16-20 hp. (250cc) Liquid cooling seems essential."

http://craigvetter.com/pages/2011-Streamliner/2011-vetter-streamliner-p49.html

Not going to happen with the typical brick-pulling-parachute motorcycle.

This really needs some context, though the link is helpful. This is good:
http://craigvetter.com/images/2011-Streamliner-images/2011-Chap%2049-1mages/1980-1983-2011-Vetter-Streamliners.jpg

"I have made three streamliners. Lets point out pros and cons so you can decide:"
2011 Streamliner
Designed for 70 mph, into a 30 mph headwind, sitting up and comfortable

Not, I suspect, the intention of teet's build. I may have misunderstood, but it seemed he was looking for more typical motorcycle performance along with that top speed.

teet
21 November 2011, 0510
Not, I suspect, the intention of teet's build. I may have misunderstood, but it seemed he was looking for more typical motorcycle performance along with that top speed. Correct, but very illustrative to understand the difference in power need at certain speeds and aerodynamic circumstances.

For my goal I guess I should take Saruman's 15 kW into account. This would mean a 200 Amp demand if there is no voltage drop. And Noah's right, this is way within reach of the first option (24 3,2V cells in series). Plus that speed won't be necessary for long because in my car I can also withhold my enthousiasm and drive 100 km/h. ;-) Thanks guys!

podolefsky
21 November 2011, 0852
"In Summary: 10-12 horsepower (125-180 cc air cooled engines) is adequate for 55 mph, sitting up and comfortable.
At 70 mph, into headwinds and hills, you need more power. Probably 16-20 hp. (250cc) Liquid cooling seems essential."


"into headwinds and hills" is the key line here. and yeah, it will depend on aero and such.

[edit] 15 kW is possible, but i really doubt you need that much for 75 mph, even on an unfaired bike.

a ZEV scooter is 7.2 kW, and they claim a top speed of 75 mph. my R martin is 3 kW and will hit 55 on flat ground, no wind. (it's lead acid, so weighs about 400 lb)

the calculation i'm using says you need about 24 kW to do 110 mph. just as a sanity check, a ninja 250 is about 22 kW and has a top speed of about 110.