50cc auto scooter conversion to electric (with video)

[gwhy!]

I thought I will try and document this as well as I can.
I got it in my head that maybe a outrunner motor.
This one...

large motor.jpg

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can be a direct replacement for the ICE in a small auto scooter.
like this one...

000gilera skp 50.jpg

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Well I picked up the scoot yesterday and today when I got home from work I made a start on stripping it down.
so this is the first installment of pics of the process.

step1.jpg

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My grandson Thought I was going to fix it as the scoot was a non-runner .

step1a.jpg

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He was not expecting that
Hopefully tomorrow I will clean/degrease the transmision and start stripping it down to see what are my options on fitting the motor, I was hoping it will fit inside the crack casing but im not sure it will fit now, but I have a plan B

A000_and its out front.jpg

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Any suggestions/recommendation will be very welcome.

[maydaverave]

Cool I hope this works and works well

[gwhy!]

I have more pictures that I will post later, but for now here is something to think about :

final gear reduction clutch to rear wheel is ~ 12:1
pulling away pulley ratio is ~3:1
top speed pulley ratio is ~1:3
rear wheel circumference is 141cm
being driven by a 170kv motor running at rated voltage 48v which is 8160 rpm


I know this is just numbers at the moment but Im liking the numbers a lot

[gwhy!]

Update: pics

I Degreased\cleaned up the transmission, removed the rear wheel and split the crank casing to remove the crank I also removed the oil pump and kick start gear.

step2.jpg

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The crank shaft need to be cut and extended so it will become just a bar with the splines on the end that the variator fits onto. The motors diameter is just a fraction to large to fit straight into the crank casing but looking at where the bolts hold the 2 halves together I think there will be enough meat still left after opening it up slightly.

step2a.jpg

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Even without making the motor fit into the crank casing it will not stick out to far on the left side so this will also work. Another mounting option for the motor would be to run a 1:1 gear through the piston opening to the modded crank. I think it will need new rollers though, The ones in it have a bit of a flat spot .

step2b.jpg

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Hopefully I will be able to cut the crank tomorrow ready to take to work to try and modify it, I hope to also cut the opening to allow the motor to fit inside the crank casing.

[maydaverave]

Can't wait to see how you connect the motor to the variator. I have thought about doing this for a while and it seems like that would be the only hard part of this little operation. Time to upgrade to dr pulley weights and a kevlar belt.

[gwhy!]

Update:

The crank is now rough cut ready to be lathed. I will also lathe the stator side of the crank, this will keep my options open as regards where and how to mount the motor.

step3.jpg

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I have a 64mm dia outrunner that would be a perfect fit into the crack casing but the motor is only rated @ 3250w BUT on a plus note that motor should be the equivalent of the original 50cc motor. The bigger motor is rated @ 6500w and the can dia is 80mm which I will love to try and make this work cos I have a plan to link 2 of them together and give the drag scoots a run for there money but one step at a time .

Can't wait to see how you connect the motor to the variator. I have thought about doing this for a while and it seems like that would be the only hard part of this little operation. Time to upgrade to dr pulley weights and a kevlar belt.

Tuning the transmission will happen if I think its worth doing ( gut feeling is yes it will be worth doing ), I have some spare rollers kicking about that will be ok for testing for the time being.

[gwhy!]

update:
I have grafted a shaft onto the original output side of the crank. The crank needs to re-visit the lathe in work ( tomorrow )to true it all up and to drill the hole for the motor shaft to fit.

step4.jpg

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step4a.jpg

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I may have to order some sealed main bearings as I don't have the correct size on hand which will hold things up a bit

[vanilla ice]

Great! I was hoping somebody would do this and document it.. A conversion retaining the original case/arm and cvt.

When I rebuilt my scooter, I lathed the old rollers round again and threw them back in. But I don't know if those flat spots matter much. Variators seem to work fine even with the flat spotted rollers. I'd guess lube and balance are all that matters, so grease em and make sure the flat spots all match.

There is even a company marketing pre-flattened rollers and claims they work better.

[gwhy!]

Great! I was hoping somebody would do this and document it.. A conversion retaining the original case/arm and cvt.

When I rebuilt my scooter, I lathed the old rollers round again and threw them back in. But I don't know if those flat spots matter much. Variators seem to work fine even with the flat spotted rollers. I'd guess lube and balance are all that matters, so grease em and make sure the flat spots all match.

There is even a company marketing pre-flattened rollers and claims they work better.

Yes you can get sliders instead of rollers which allow the front pulley to become a slightly smaller dia in the idle position which will give you a little more gear reduction for pulling away . The trouble with having flat spots on the rollers is it can make the gearing inconsistent and more important lose top end speed, but yes they will work. If this works I will fully race tune the transmission but its not worth doing anything yet until we know how well it behaves with stock gearing.

I have been looking over the rest of the scoot and it needs rather a lot of work to get it up to tiptop working order for road use ( so it wasn't such a cheap scoot after all ) But it will be good enough to see if the concept works.

[gwhy!]

The crank mod is now finished for the time being, I have ordered some replacement shielded main bearings but these are 3mm wider than the standard main bearings so the crank will need a bit more work to achieve the correct spacing but this should be not be a problem.

step5 crank finisted (maybe).jpg

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I have opened up the stator side crank casing for a couple of reasons 1: this will allow removal of the complete crank from the scoot without removing the complete transmission. 2: move the motor inwards as far as possible into the crank casing without major modding.

step5a stator side ground out.jpg

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These 2 things would not have to be done to make this work but I think they are a bonus and maybe worth the extra work involved.

as soon as the new bearings turn up the transmission can be re-assembled and fitted back into the scoot.

The next thing to work out the best way to mount the motor.

[gwhy!]

update:
I have been trying some possible motor mounting options, and have come up with this ( obviously it will be a ally plate not a paper one ).

step6 motor mount template.jpg

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And finished the modded crank.

step6a motor fits modded crank.jpg

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I had a e-mail from the bearing suppliers and they have been posted so hopefully I will get them by in the next few days.

[maydaverave]

If this works you should sell small amounts of a bolt on kit

[gwhy!]

If this works you should sell small amounts of a bolt on kit

Modified cranks and replacement sealed main bearings may be do'able as a kit, the only problem will be getting the crank to start with as there are 3 or 4 different types. The bolt patterns for mounting the motor will vary to much on different scoots so the motor mount I think will have to be left up to the person wishing to convert it. Mounting the motor will be so much easier if your not to concerned about how far the motor will stick out . Since I have modded this crank I have thought of a better way (less machining ) to modify the crank. If the bearings turn up and there isn't any unforeseen problems we should know if this works within the next few days .

[gwhy!]

Not much to report today, the bearings still haven't shown up
The motor mount is finished though sorry but no pics ( flat battery on cam, I will post a pic tomorrow ).

[disndat]

This a great build!!!!This is exactly what electric motorcycles/scooters need-a GEARBOX!!!I am really interested with how this turns out.I am really surprised that all these top companies that are trying to build electric superbikes for the FIM and no one has thought of using a gearbox Good luck with this project.

[jmygann]

This a great build!!!!This is exactly what electric motorcycles/scooters need-a GEARBOX!!!I am really interested with how this turns out.I am really surprised that all these top companies that are trying to build electric superbikes for the FIM and no one has thought of using a gearbox Good luck with this project.

How many gears do you need ?

Some say you don't need a gear box with the right motor ?? Just eats up energy ?

[gwhy!]

This a great build!!!!This is exactly what electric motorcycles/scooters need-a GEARBOX!!!I am really interested with how this turns out.I am really surprised that all these top companies that are trying to build electric superbikes for the FIM and no one has thought of using a gearbox Good luck with this project.

How many gears do you need ?

Some say you don't need a gear box with the right motor ?? Just eats up energy ?

But wont this apply to a regular ICE bike ? Its getting the balance between speed and torque and keeping the motor in the most efficient operating conditions ( ICE or electric ). Yes gearing may lose some energy but the gains may out weigh the loses. If a geared transmission will allow slow speed riding ( 0-20 mph ) with boat loads of torque without generating unwanted heat and then be able to take that speed upto 100mph+ whilst still not taxing the motor or controller then this has got to be a good thing .

[disndat]

Yes electric motors can be run without a gearbox BUT if you use a gearbox you will have better acceleration and good top speed-otherwise you have to gear it for one or the other.You do not need a 6 speed gearbox like ICE but a 3 or 4 speed gearbox will go a long way.I am really surprised that all these e-motorcycle builders have not realised that yet.

[fizzit]

The performance gains with a gear box for an electric motor are less than for an ICE because an electric motor maintains torque and efficiency much better across the RPM range... I'm pretty sure you don't know more than companies that make electric motorcycles (neither do I, obviously).

[maydaverave]

The performance gains with a gear box for an electric motor are less than for an ICE because an electric motor maintains torque and efficiency much better across the RPM range... I'm pretty sure you don't know more than companies that make electric motorcycles (neither do I, obviously).

Well he is not an engineer designing a completely new vehicle he is trying to make a cheap, easy, fast, diy electric vehicle and I for one am very thankful for his efforts.

[swbluto]

The performance gains with a gear box for an electric motor are less than for an ICE because an electric motor maintains torque and efficiency much better across the RPM range... I'm pretty sure you don't know more than companies that make electric motorcycles (neither do I, obviously).

Indeed. First, consider that torque at 0 rpm sucks for an gas engine. Than consider an "equivalent" electric motor - it's starting torque is more than 10 times more. That fact alone points to the fact that electric motors have much less to gain from a gearbox than gas engines.

Also, depending on your time to shift and your power system, the overall acceleration might actually be greater if you don't shift during acceleration since you lose time to accelerate during shifting. Ever wonder why Tesla went straight from 2 gears to a single gear? Yes, reliability problems, true, but eventually they improved overall acceleration from 0-60.

[maydaverave]

The performance gains with a gear box for an electric motor are less than for an ICE because an electric motor maintains torque and efficiency much better across the RPM range... I'm pretty sure you don't know more than companies that make electric motorcycles (neither do I, obviously).

Indeed. First, consider that torque at 0 rpm sucks for an gas engine. Than consider an "equivalent" electric motor - it's starting torque is more than 10 times more. That fact alone points to the fact that electric motors have much less to gain from a gearbox than gas engines.

Also, depending on your time to shift and your power system, the overall acceleration might actually be greater if you don't shift during acceleration since you lose time to accelerate during shifting. Ever wonder why Tesla went straight from 2 gears to a single gear? Yes, reliability problems, true, but eventually they improved overall acceleration from 0-60.

Cvts don't shift, so no time lost. Putting lots of torque through a motor at a inneffecient rpm = heat, and lets see how it works before we assume anything. Is this going to be the optimal solution probably not, is this and easy fun expiriment yes it is.

[swbluto]

The performance gains with a gear box for an electric motor are less than for an ICE because an electric motor maintains torque and efficiency much better across the RPM range... I'm pretty sure you don't know more than companies that make electric motorcycles (neither do I, obviously).

Indeed. First, consider that torque at 0 rpm sucks for an gas engine. Than consider an "equivalent" electric motor - it's starting torque is more than 10 times more. That fact alone points to the fact that electric motors have much less to gain from a gearbox than gas engines.

Also, depending on your time to shift and your power system, the overall acceleration might actually be greater if you don't shift during acceleration since you lose time to accelerate during shifting. Ever wonder why Tesla went straight from 2 gears to a single gear? Yes, reliability problems, true, but eventually they improved overall acceleration from 0-60.

Cvts don't shift, so no time lost. Putting lots of torque through a motor at a inneffecient rpm = heat, and lets see how it works before we assume anything. Is this going to be the optimal solution probably not, is this and easy fun expiriment yes it is.

Oh, well CVTs might have better acceleration within their torque envelope, yes. The only thing that I'd be "concerned about" would be the added inefficiency of CVTs. It's no big deal for ICE engines, but it's a range killer with electrics.

[gwhy!]

Well I still haven't received the main bearings yet ( It may be to do with all this nonsense about volcano's erupting or something ) But I have a good feeling that they may come tomorrow.

Thanks to the few ( you know who you are ) for the encouragement to go through with this. It is very much a fun cheap project to hopefully answer some of the questions that have been brought up. The motor/speed controller and battery's I have already and the scoot was a cheap non-runner that can be stripped and sold in parts to get the cost back of the scoot if its not worth continuing.

I am still amazed about these small motors and what they can do but you can look at it this way, a small 50cc auto scoot is about 3.25kw peak output and even with this small output with a carefully tuned transmission can out accelerate most ( not all ) cars/motorbikes upto 30mph and can eventually reach a speed of about 55-60mph. Is there any scooter/motorcycle size/weight e-bike can do this with such a small wattage output ? If it can be done without a transmission then why hasn't it

[Martin A]

I've been thinking along the same lines. Looking to convert an Italjet. Will be following this with interest as I like the idea of a quiet scooter to waft around the country lanes without frightening the wildlife.