Power in Flux

What's on your mind?


[140]

Live Feed

Richard230 created the thread BMW's Vision DC Roadster electric motorcycle.
" Here is a link to an article regarding the new BMW Vision electric motorcycle concept that was just announced, published by Electrek:
https://electrek.co/2019/06/25/bmw-f...n-dc-roadster/
Personally, I am not a fan of the styling or the riding position. But I do like the idea of BMW finally entering the electric motorcycle market - if they actually do. "

18 Hours Ago

frodus replied to the thread What I've been working on: Palatov D2EV.
" I've been in it, but the driving has lately been for testing at race-speeds and I've not been part of the testing crew. I'm just the electron-herder. "

19 Hours Ago

Stevo clicked Likes for this post: WORX.VOR.EMC.v3.3 by Spoonman

20 Hours Ago

Stevo replied to the thread What I've been working on: Palatov D2EV.
" Very very cool Trav.... Have you driven it? "

1 Day Ago

Stevo clicked Likes for this post: What I've been working on: Palatov D2EV by frodus

1 Day Ago

Stevo clicked Likes for this post: 50cc Scooter conversion by 3DRoboGuy

1 Day Ago

cmcnall created the thread PSA: Reminder to all for maintenance.
" My Chain popped off on the on ramp to the highway today.
I was lucky and stupid, Remember to check your bike often and do your maintenance! "

1 Day Ago

EVcycle clicked Likes for this post: Electric Motorcycles 2019 book review by Richard230

1 Day Ago

3DRoboGuy replied to the thread 50cc Scooter conversion.
" Wow !
So this is an EV grin ! I'm still picking the flies out of my teeth (yeuch) !

I'm not quite sure where to start. I realise this project was only for a 50cc scooter and by many standards it was pretty simply / basic but I am blown away - not by my work but rather by the result; quiet, cheap to run, non CO2 polluting, low maintenance...
Incredible.
It's true, you HAVE to try electric before knocking it and then... well, after a a try, you most definitely won't be knocking it !
Attachment 8350
Attachment 8355

Anyways, I'm a pretty 'picky' kinda guy and, normally, the first to criticise my own work and the results of it so, let's start with the criticisms :

To be fair, at this stage, after 34km on Scoot-ee, I don't have many criticisms :

1: take-off is a little... 'vicious' / quick. There seems to be no gentle / soft-start I guess I'd call it. Just have to be careful when starting off that you're pointing in the right direction. To be fair, it's nothing horrible, just not quite the soft / gentle start I'd have preferred for normal kick-offs...

2: the batteries are hard to remove - I'll re-design them from long'n'thin (20 18650 cells long and 4 cells wide) to short and fat (10 cells long and 8 cells wide). The new size is just within the capabilities of Prusa mk3 printer and should allow me to fit 3 (3Kw) (in lieu of 2 - 2Kw) if I want / need to. To be fair, 34km and not dead is better than I imagined... so... 3 packs most likely will not be necessary but...

3: the V / A 'test' meter could be better. I'd like to improve upon this with a coulomb counter type meter or maybe a full screen / instrument panel to replace the one that's there... it's not a 'requirement (especially as I scraped in, just under the 800Euro budget) to be fair but if such a display could be fitted and look good then it would definitely be better.

4: in an ideal world I'd have been able to keep to a belt drive. Much quieter, but really... it's a little like a turbine powering up... not loud or annoying... I'd have simply preferred EVEN quieter !

Having said that...
Attachment 8351

Top Speed
the top speed is in excess of 60kmh down hill (rev limiter cuts in again at around 65-68Kph) and easily 57kmh on the flat (wind or no wind) VERY happy !

Acceleration
seems more than adequate.
0-30Kmh in 5.1 seconds
0-45Kmh in 9.8 seconds
0-50Kmh in 19.9 seconds
250metres from standing start 21.6 seconds
Definitely NOT blistering but better than stock. It probably didn't help that my mouth was wide open in an electric / ecstatic kind of grin - must have increased drag / resistance
I'm also pretty sure that a Kelly KBL72101X controller would make a huge difference but then it would add an additional 300Euro to the budget ! But... once I receive thoughts from you, more experienced guys, I'd be more than happy now to swap out the controllers for a test... Currently max amps through the controller is 'limited' to 40A - it's just the controller. Loading up the two battery packs through their BMS's and breakers delivers in excess of 75A so... Kelly controller upgrade would seem to be appropriate if I need / want more dazzling performance.

Noise
Impressive, almost none, just a chain 'rattle'... and a turbo-style whine... not bad at all and a HUGE improvement over the original !! I'd still like a belt though. This motor just won't accept a belt very easily...
Again, if I were doing another conversion I would spend more time researching the motor and get something that could handle a belt pulley, maybe with an additional end-of-shaft bearing for less shaft stress... thoughts anyone ?

Having said all the above, I still can't quite believe it all works so well.
I'm monitoring controller temperature (fishtanks style digital thermometer clamped to two controller fins and heat paste. Currently, (just 34Kms) the max recorded temperature is 36'C / 97'F. I think that's OK but, again... thoughts... I'm also going to do some decent hill work this week to test and check controller amps / temperature / volts...
Attachment 8352

What more can I say ?

Time
Conversion work (give or take a wee bit) : 40 Hrs

Costs
Original RPS Scoot purchase price : 200 Euro
Batteries (2 x 20S4P LiFePo4 / 1Kw ea) : 498 Euro
Throttle, DCDC converter, SSRs : 75 Euro
Cable, Plugs+Sockets, Meter+Shunt : 50 Euro
Fibreglass, paint, clips... : 25 Euro
Total (give or take a wee bit) : 850 Euro


Bear in mind,
I have never undertaken a conversion before...
I am only your standard electrician / electronics engineer...
Granted, I have a pretty extensive set of tools but...
I solder and braze regularly but, although I have a MIG welder, I have less than a full day's welding experience (slightly more now !) ...
I can fibre glass (used to build beach-rescue canoes etc) but there wasn't much to do on this project anyways and anyone can make a cardboard template or two and apply some fibreglass, so...

Tools
90% of this project could be undertaken without any specialist tools; a 'standard' toolbox (spanners, screwdrivers & files etc), a drill, a grinder, a multi-meter and a soldering iron.
The last 10% would involve a welder (stick would be fine, I used a MIG), a method to make up your battery pack(s) or you could buy it (them) ready made, a hot air gun and a glue gun...
Granted, I DO have use of a 3D printer and I have extensive experience with both it and Sketchup BUT neither are absolutely necessary...

Registration
Re-registration in France is all but impossible BUT in the UK, it took less than 30 minutes to arrange, the road tax is zero and the insurance cheaper than the original ICE scooter. Having said that, I live in France and haven't physically done a re-registration BUT I have spoken at length to DVLA (thanks Bob) and various insurance brokers...
I have no idea as to how difficult it is in Germany, Netherlands or the US but, remember there were ZERO frame, swingarm, brake or original equipment mods - all I did was remove the ICE kit...

Cost Justification
As if we need one nowadays to switch from fossil fuels, not to mention the fun to be had during the project and the amount I learnt... but...
All of the work was completed for a total expenditure of (give or take) 1,000 Euro. That includes the original ICE scooter purchase !!! There are quite literally thousands of 50cc / 125cc scooters, mopeds and motorcycles in Europe alone that don't work but could be brought back to life for less than a thousand Euro / Pounds with almost zero running charges ! It might be illegal (strictly speaking) to ride a conversion on the road today in France and, maybe, other countries, but in 12 months, 2 years or 5 years time and as governmental Co2 reduction targets come into force ??? Who knows ?!
Additionally, Low and Ultra-Low Emission Zones are on the increase. Two to three months riding in one of these zones would pay for the conversion.

Charging
Finally, I put an OWL (energy power) meter on the charger last night. The 2 x packs were showing 67V at the start and were fully charged this morning (I think it should only take 4 to 5 hours tops from empty to full) and the meter displayed 1.7Kw of energy at 26cents (0.26 Euro) cost - for 34Kms !!!! Incredible.

Solar
I can't help but get all fired up over this and think I could run for free if I had roof solar - and not much of it at that !! No cost to me, reduced noise, almost zero servicing costs and no Co2 emissions damaging the planet ! What's not to like ?
Attachment 8353
Attachment 8354

Next
I guess now, it just remains for me to :
do a lot more tests,
make a video and You-Tube it,
undertake the mods (when I've stopped grinning) and
monitor how Scoot-ee performs over the next couple of hundred kilometres...

RESULT ! Delighted, I think that says it all - I'm converted !! "

1 Day Ago

flo replied to the thread What I've been working on: Palatov D2EV.
" Wow
awesome good luck at pp.

flo "

1 Day Ago

flo clicked Likes for this post: What I've been working on: Palatov D2EV by frodus

1 Day Ago

supercub50 replied to the thread Honda C50 conversion.
" Thanks for the interest! Sorry I was away on vacation for two weeks so nothing new on the project I am afraid.

For the battery, I was thinking of using NCR20700B cells, 10 pcs in parallel and then 16 groups in series. Have them positioned vertically, basically two packs in 10P8S configuration in series, one pack on top of the other. Should have quite compact dimensions and therefore fit relatively easily.

QS recommends max 6 kW peak power for the 205 motor so my battery current will be less than 150 A at all times, which that cell type should manage easily I think.

I have access to a 3D printer so definitely I would like to design and print my own cell holders. For the BMS I was thinking of the Energus tinyBMS.

Gesendet von meinem Nokia 7.1 mit Tapatalk "

1 Day Ago

supercub50 clicked Likes for this post: Sachs xtc 125 conversion by flo

1 Day Ago

frodus created the thread What I've been working on: Palatov D2EV.
" It's been an exciting year or two for me. I sold my Brammo Empulse in 2018 to make room for a Model 3. The Model 3 took too long and I ended up with a Chevy Volt last December. Then, early this year, I decided to quit my job at Leviton to work full time in the EV industry. I was approached by 2 local companies, EVDrive and Rinehart Motion. Ultimately I took the Rinehart Motion job during their acquisition by BorgWarner. At the same time Rinehart was acquired, AMRacing was also acquired and both companies were combined into one and renamed Cascadia Motion.

The hiring processes took a while, and my manager-to-be asked if I was interested in helping out with a project. Last year, Palatov, Rinehart and EVDrive began a project to build an electric hypercar. I gladly accepted and went over to Palatov to volunteer for about week before I started officially.

In the last 4 months, I've spent many long days updating schematics, specifying parts, wiring the car, adding functionality and programming the DC-DC, charger, BMS and uploading code to the VCU. We've got a great team and I'm happy to have gotten the chance to work on such an exciting project.

Now, the cat is out of the bag and the car is now at Pikes Peak and just passed Tech inspection. We'll be racing this Sunday to the top of Pikes Peak. It looks like a Zero SR-F, University of Nottingham UoN-PP, RIT Electric Vehicle Team REV 2 and the TEAM MIRAI Mark Coverdale IdatenX HC will be there to represent Electric Vehicles. I don't see any other EV Cars.

And here's some great blog posts by Dennis Palatov about the D2EV:
http://www.dpcars.net/d2x/index.htm

Anyway, here's pics of the car we built, and a few pictures of the development along the way:
[IMG]http://elmoto.net/attachment.php?attachmentid=8343&d=1561405285

http://elmoto.net/attachment.php?att...4&d=1561405343

http://elmoto.net/attachment.php?att...5&d=1561405380

http://elmoto.net/attachment.php?att...6&d=1561405418

http://elmoto.net/attachment.php?att...7&d=1561405445

http://elmoto.net/attachment.php?att...8&d=1561405493

http://elmoto.net/attachment.php?att...9&d=1561405519 "

1 Day Ago

3DRoboGuy replied to the thread 50cc Scooter conversion.
" Having experienced the results of my NOT having done some math (I guess, at the outset, I had just 'hoped' all would be well because it was the simplest solution - not to mention that the conversion itself seemed pretty daunting and I was impatient to start. D'Oh !! ) and having just recently worked out the chain / sprocket ratio I was looking for, I ordered up and received three T8F / double 'D' sprockets; 9tooth, 11tooth and 17tooth.
The 17tooth is for the motor sprocket
The 9tooth is for the rear sprocket along with the 11tooth sprocket should the 9tooth be, as expected, simply too small for the chain / shaft diameter... it IS sold for this chain but maybe not this shaft diameter and I'm loathe to reduce the original diameter of the shaft on the gearbox side of the sprocket. Each sprocket was around was 7Euro, so why not give the 9tooth one a go anyways ?!

So, in steps (always easier for my tiny brain ! ) :
I'm going to need to :
shorten the existing input shaft,
reduce its diameter, creating a 10mm shoulder for the T8F sprocket,
reduce the shaft diameter still further (to 8mm) so that the T8F sprocket fits over it and up to the 10mm shoulder,
cut two flats on the 10mm portion of the shaft to suit the T8F sprocket, ensuring they are 6mm deep - the depth of the sprocket,
cut an 8mm / M8 thread onto the newly created 8mm portion of the shaft,
slide the sprocket into place, followed by a lock washer and then the M8 nut (the lock washer not only helps prevent the nut from backing off but also takes up the 'slack' between the 10mm-to-8mm shoulder and the thread on the 8mm shaft due to the shoulders on the thread cutting die).

When put like that, it all sounded pretty simple but how to achieve concentric faces on the shaft whilst the shaft is still fixed to the gearbox ? I really needed to remove the shaft and lathe it up... but... that's definitely NOT within the realms of your average DIY'er I thought and most certainly outwith my budget to have it professionally done (not to mention that it's outwith the original scope of the project)...

What I came up with was slightly simpler: reassemble and back-drive the gearbox with a drill. So, attaching a suitable socket to the drill and driving the gearbox from the wheel end gave me a rotational advantage of 14:1 (the gearbox ratio in reverse) and the ability to rotate the input side of the shaft just like it was on a lathe ! Well, that was the idea... So, sticking to my step-by-step approach, I :

1: reassembled the gearbox and removed the existing clutch / variable-drive unit for the gearbox input shaft :
Attachment 8335

2: measured the required offset; the distance between the shaft bearing face and the end of the 'to-be modified-and-threaded' shaft, taking into account the depth / thickness of the sprocket, lock washer and nut (+ a wee bit).
3: attached the drill to the output side of the gearbox and had my 'helpful assistant' on the drill trigger ! And now, cut the shaft to suit. No going back now !!
Attachment 8336

4: carefully re-measured the offset of the 10mm shaft shoulder and, with the help of a spinning gearbox input shaft (drill and helpful assistant), a grinder (for the initial 'get-me-close' work) and a file and some digital callipers (for the finishing / precision work), reduced the shaft diameter to 10mm (for the sprocket).
5: carefully measured a 6.5mm offset on the newly created 10mm shaft and reduced the shaft end to 8mm, thereby creating a second shoulder for the washer and nut...
6: locked the shaft and filed two opposing flats on the 10mm portion to accept the T8F sprocket.
Attachment 8337

7: threaded the 8mm portion of the shaft getting as close to the 100mm/8mm shoulder as was possible.I was very careful here to get as close as possible but not to have the die come up hard against the shoulder and thereby damage the newly cut thread. The split / spring washer is here to 'take up' that 'slack'.
Attachment 8338

8: offer up the sprocket and make any adjustments. This was slow work, you can't add a bit back onto the shaft after taking too much off... slow but sure, testing and measuring all the time.
9: fit the split / spring washer and the nut !!
Attachment 8339

10: Use a rule for the check the final lateral alignment between the motor pinion and the gearbox sprocket. There is around 15mm of lateral movement in the 4 x motor mountings so final alignment was simple enough.
Attachment 8340

11: Cut and split-link the chain to suit and then tension in the usual 'alternator-style' way at the motor. In the case of a scoot and particularly in the method I'd selected to mount the motor, there is no 'play' needed in the chain to take up suspension travel. The motor, chain and rear wheel all move on the same swingarm / frame... No idler, sprung tension sprocket needed - one of the clever design features of a scoot's transmission.

All in, from start to finish (once I had the math pegged), this took the best part of an afternoon ! Nice 'n' steady was the name of the game here, like I said, I was very aware I couldn't easily remedy removal of too much of the shaft...
As it happened, all worked out just fine and, remember, I'm an electrician (of sorts) to trade, not a machinist or mechanic ! If I can do it, then anyone can !
I should have done this from the start but feared messing about with the mechanical stuff - just go nice and slow, take your time, better to get a good result and take your time than to rush a mistake... especially as a 'mistake' on the shaft work is not easily recovered from.
Attachment 8341

That's me for the initial conversion. All-in-all around 37 hours work. The next one would be MUCH quicker (barring any mistakes) IF I was ever to do another scoot - what I'd REALLY like to do is a Kawasaki VN 650 or similar - now that would be fun !
Attachment 8342

Anyways, I'm off to have some fun and (gently) road-test the Scoot-ee !!

There will undoubtedly be some alterations and additions but they're for another day as is whether this could ever be documented with a view to creating a 'kit' of parts. I'm also keen to make a small video of Scoot-ee on the road after some basic road-tests. Maybe it could indicate the performance, how it sounds and behaves and. . . and whether I feel it was all worth or not... "

2 Days Ago

Richard230 created the thread Electric Motorcycles 2019 book review.
" My daughter gave me a copy of "Electric Motorcycles 2019" by Michah Toll as a father's day present. I just finished reading it. What you have here is something like a book full of electric motorcycle brochures of models that are currently available. It is quite up to date and contains information that became available as late as April 2019. So it is a nice overview of the current market and also contains models that might be available within the next couple of years. At around $15 on Amazon, the price of the book is certainly reasonable.

Most of the information presented seems to have been obtained from official factory sources, however the author has also included comments from his personal experience riding some of the bikes along with information obtained from owners of the models, when available. I think the book makes a good resource for historians that might be interested in an overview of the state of the electric motorcycle market in the spring of 2019. For the price, I thought it was a good value and provided several hours of light entertainment.

The only model that I missed in the book was information regarding that European "lady bug" scooter that has been around for a few years and seemed to have been selling fairly well in the EU. Perhaps it is no longer for sale? The book does not mention discontinued brands, such as Mission Motors, Brammo, Victory, Electric Motorsport, Native, etc. Although it does have a page regarding the Alta Redshift EXR, while at the same time mentioning that the company is defunct. ??? I guess the author has a soft spot for Alta. "

2 Days Ago

3DRoboGuy replied to the thread KwSAKI Mk1 (Ex 500).
" That looks AWESOME !
Once I finish my current Scoot project (on the forum, nearing completion - hopefully later today / tomorrow) I want to convert a Kawasaki VN650 Vulcan but the donor price is HUGE !
Anyways, good luck with your controller configuration and, hell, the whole project.
Simply AWESOME ! 10 / 10 !! "

2 Days Ago

3DRoboGuy replied to the thread 50cc Scooter conversion.
" After 'playing about' with the Volt / Amp meter it was time to re-visit the motor 'stutter' and the un-modified clutch.

I grabbed my hand-held tacho (nothing special here, 15-oddEuro on Amazon), removed the chain between front / rear sprockets and applied a little reflective tape the motor shaft / gear.
Attachment 8331

Ahhhh.... All became apparent... The 'stutter' kicked in at between 5700rpm and 5850rpm. The light dawned... with ears alone, I had absolutely no idea the motor was spinning that fast !! Oops ! The stated maximum motor revs is stated as being 5000rpm and 5900rpm absolute tops ! OK the controller was either deliberately limiting the revs of I'd reached the motor / controller capability limit... either way... " I have a problem Houston ! "

So, using the tacho it became apparent that the onboard clutch only kicked in at around 3000 motor rpm.

The motor arrived with a 13tooth sprocket and the lowest rear (driven) sprocket I could find with a large enough centre through-hole (to pass over the rear vari-drive / clutch drive shaft) was 69tooth. I should have done some more math... Idiot !

Anyways, couple the 13 / 69 sprocket ratio, the clutch and the, internal-to-rear-wheel, gearbox ratio of 14:1 and... nothing surprising here... high motor revs = low wheel revs ! I should have thought of this way before now. Idiot (again!).

OK. I immediately reverted to a plan I'd been concocting that was to simply lock off the clutch by welding 4 short studs between the outer (driven) clutch bell-housing and the inner (drive) clutch pad plate. That took 10 minutes; I popped then off the end of the gearbox input shaft, slipped the bell housing off, welded on 4 short 10mm studs and reassembled (the studs simply located in 4 similar holes in the driven (inner) section of the clutch.
Attachment 8332

Stand up, wheels back on the floor and... OK... 11kmh max speed but.. although I'm disappointed at the, not-so-dazzling, top speed, I'm also grinning - I <b>have</b> converted a petrol scoot to an, albeit rather slow, electric scoot !!

After a poodle (I wanted to say 'whiz' but that really wasn't the case) around the garden and patio with my wife saying... 'Nice dear... but won't won't the milk have gone off by the time you get it home ??? " I reverted to the garage. I stripped down the clutch assembly and started to re-work the plan... but this time with some math first !

Accepting that there is very little I can do with the internal-to-rear-wheel gearbox (14:1) ratio and that the maximum motor revs are 5000 (forget about the over-rev portion (that can simply be a later date 'Brucie' bonus ! ) and the rear wheel circumference of 1.45m I calculated for a 45Kmh top speed (matches the original top speed - although still not dazzling) :
Attachment 8333


5000rpm x chain/sprocket ratio (CSR) x internal gearbox ratio (GBR) x 1.45 = speed (mtrs / min)
=> 5000 x CSR x GBR x 1.45 x 60 = Speed (mtrs / hr)

convert revs per minute into revs per hour (because I need Km per hour - kmh - at the end)
=> (5000 / 1000) = 5

=> 5 x CSR x GBR x 1.45 x 60 = Speed (Kmh)

I know GBR = 14:1, so 1 / 14 = 0.0714 (GBR = a multiplication factor of 0.0714)
=> 5 x CSR x 0.0714 x 1.45 x 60 = Kmh

to isolate the CSR (chain sprocket ratio)
5 x 0.0714 x 1.45 x 60 x CSR = Kmh
=> 31.1 x CSR = Kmh

... or...
=> CSR = Kmh / 31.1

so, for a top speed of 45Kmh :
=> CSR = 45 / 31.1
CSR = 1.45

and, for a top speed of 60kmh - illegal :
=> CSR = 60 / 31.1
=> CSR = 1.93

and for 75kmh - also illegal but fun to work out :
=> CSR = 75 / 31.1
=> CSR = 2.41

That's to say;
for 45kmh, the front sprocket has to have 1.45 more teeth than the rear sprocket
for 60kmh, the front sprocket has to have 1.93 more teeth than the rear sprocket
for 75kmh, the front sprocket has to have 2.41 more teeth than the rear sprocket

So, math over, the motor arrived with a T8F sprocket / shaft fitting, that's to say a double 'D' fitting on a 10mm shaft or a 10mm shaft with two flats cut into it, 180' opposed.
Attachment 8334

The challenge here is that for the (theoretical) power involved (3000W / 3Kw) this type of fitting doesn't allow for larger than 17tooth sprockets (not unless custom built - or someone has a source I haven't found ) To be fair, above 17tooth is probably placing a HUGE amount of stress (even with the 14:1 rear gearbox ratio) on the motor shaft and as the number of teeth are increased so too does the sprocket diameter and, therefore, so too does the side or cross stress and the torsional stress.
The long and the short of all this ?
17 teeth front sprocket is (probably) the limit (but, if I could find a 19tooth sprocket I wouldn't mind a try !).

So, taking the 17tooth front sprocket and the CSR for the three 'required' top speeds above :
to calculate the drive ratio of these two sprockets :

Front Sprocket Teeth (FST) / Rear Sprocket Teeth (RST) = CSR

FST / RST = CSR
=> RST = FST / CSR

Front sprocket teeth (FST) = 17teeth

feeding the numbers into the final equation :
for 45Kmh and a CSR = 1.45 :
=> RST = FST / CSR
=> RST = 17 / 1.45
=> RST = 11.7
obviously, a sprocket can only have a WHOLE NUMBER of teeth. A 12tooth sprocket will provide a top speed of slightly under 45kmh, whereas an 11tooth sprocket would provide a slightly greater than 45kmh top speed.

for 60kmh, CSR = 1.93
=> RST = FST / CSR
=> RST = 17 / 1.93
=> RST = 8.8
A 9tooth sprocket will provide a top speed of slightly under 60kmh, whereas an 8tooth sprocket would provide a slightly greater than 60kmh top speed.

for 75kmh, CSR = 2.41
=> RST = FST / CSR
=> RST = 17 / 2.41
=> RST = 7.1
An 8tooth sprocket will provide a top speed of slightly under 75kmh, whereas an 7tooth sprocket would provide a slightly greater than 75kmh top speed.

NOTES
It should be noted here that a 9tooth sprocket is the smallest I was able to find BUT I'd be very surprised if the chain ran smoothly over it on a standard shaft. Obviously, sprocket tooth stress increases with a lower number of teeth on that sprocket - there are simply fewer teeth for the chain to engage with and transfer power to.
It should also be noted that whilst some even number sprockets exist within the available 9-17 tooth range, there are more odd numbered ones that there are even numbered ones. I believe this is because sprockets with an odd number of teeth wear, both themselves and the chain, more uniformly that sprockets with even numbers of teeth. If a sprocket has an even number of teeth, then the same tooth will be engaged by the same pair of chain rollers upon each rotation. This, in turn, leads to uneven wear on the chain and sprocket and a shortened service life for both... as I understand things.

I thought about the above for a good few hours whilst I was away on business someplace else and couldn't see any other, relatively simple (DIY) and low cost approach to my speed dilemma...
As I was originally 'aiming' to replicate the original / standard scoot I decided to settle for slightly improved 45kmh performance and opted for an 11tooth sprocket.

Working out the math on this one from the original formula :
5 x CSR x 0.0714 x 1.45 x 60 = Kmh
CSR = 17/11 = 1.55

=> 5 x 1.55 x 0.0714 x 1.45 x 60 = Kmh
= 48Kmh
...and... the max motor rpm was stated (and seen on the tacho as the 'limiter' cut in) as being 5900
=> 5.9 x 1.55 x 0.0714 x 1.45 x 60 = Kmh
= 57Kmh

So, with a 17tooth sprocket up front (on the motor) and an 11tooth sprocket on the rear (gearbox input shaft) I should expect a top speed somewhere in the region of 48 to 57Kmh.

That was OK. I was 'happy' again... the question though was how to get an 11tooth T8F sprocket onto an overly long, 38mm diameter shaft !!

In the end, the solution was pretty simple, if a little drastic. But, hey, what the heck, I'd already gone way past the point of no return...

Adapt the shaft !
So, I'm off to do just that !! "

3 Days Ago

3DRoboGuy replied to the thread 50cc Scooter conversion.
" At the outset I decided it would be really handy to be able to see battery voltage and motor / controller current primarily for test purposes but also whilst riding. However, because I hadn't found a relatively in-expensive meter and because it was simpler at the time and because I really had no idea where I would fit such a meter on the bike and because I didn't want to 'invest' in 'just' a V/A meter without knowing if I would later wish for more (power, temperature and maybe speed...) and because... because... because...
all I did was fit a 100A shunt and a 5 pin test port (both of which I had) ;
pin 1 = Gnd
pin 2 = 12V (DCDC converter
pin 3 = 72V (Battery pack)
pin 4 = Shunt 'A'
pin 5 = Shunt 'B'
All in all a really simple 'test port'...

Later down the line, I found a volt / amp meter on eBay (about 10 euro) using the same 200mA shunt. Needless to say, I ordered one and here it is cabled up and plugged in to the test port :
Attachment 8325

Now though, some 6 weeks into the build, I've arrived at this point and I really think I'm going to need to see this stuff whilst riding. So, whilst I had the covers / fairings off (to add an earth cable to the charge IEC socket - good point Bill), I'm revisited my 'test port' idea and ran a multi-core, screened, cable from the port up to the instrument panel and terminated it with a standard cable socket. In fact, at the same time, I ran a second multi-core, screened, cable from the port up to the instrument panel although not having any immediate real use for it - I'm bound to want it later and, if not, nothing lost !!

Keeping to my original, circa 800Euro costs, I still couldn't find a waterproof V/A meter, that could be retro-fitted on the scoot and be seen whilst riding, for any reasonable price. There was, however, a clock built into the instrument panel... maybe I could remove it and re-task the vacated space for the new V/A meter...
Attachment 8326

Anyways, like I said, I already had all the covers off again, so I removed the instrument panel and stripped it; 3 screws and it was off, 4 more screws and it was opened up, 2 more screws and disconnect 3 cables and the clock was out. No damage done...
Unfortunately, no matter how I tried I couldn't fit the V/A meter in it's place - it was simply too tall. What I came up with though was to split the two 3-digit displays into two, and site them separately.
Attachment 8327

I left the voltmeter on the PCB - it fitted just fine in the available space - then added 100mm of cable between the, now removed, 3-digit display panel (Amps) and the original solder pads on the PCB. I then re-sited (with a little help from Sketchup and the 3D printer) the Amps 3-digit display within the housing...
Attachment 8328
Attachment 8329

I then fitted a matching cable plug to the previous one I'd fitted on the end on the new cable from the controller / battery area to the instrument panel, connected it up and tested it all out...
Attachment 8330

Result !

All's good... ready for testing !

So... back onto the motor 'stutter' and clutch... "

4 Days Ago