50cc auto scooter conversion to electric (with video)

[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.

[vanilla ice]

out accelerate most ( not all ) cars/motorbikes upto 30mph and can eventually reach a speed of about 55-60mph.

And get 80 to 100mpg while doing so. After reviewing the low rpm ends of a few electric motor sim charts I aint too worried about cvt inefficiency on this thing.

[swbluto]

out accelerate most ( not all ) cars/motorbikes upto 30mph and can eventually reach a speed of about 55-60mph.

And get 80 to 100mpg while doing so. After reviewing the low rpm ends of a few electric motor sim charts I aint too worried about cvt inefficiency on this thing.

You're thinking that the low-end RPM of motors is inefficient, right? That usually only occurs at "heavy loads" which shouldn't happen in real life if you gear it appropriately. Otherwise, lower speed on the flats would be obtained by partial throttle which the motor is far more efficient at. However, you get controller losses with partial throttle but my last calculations suggest that controller losses are somewhere around 30 watts - No big deal for 1000 watt loads - that's about a 3% loss. It might be as high as 5%.

[gwhy!]

out accelerate most ( not all ) cars/motorbikes upto 30mph and can eventually reach a speed of about 55-60mph.

And get 80 to 100mpg while doing so. After reviewing the low rpm ends of a few electric motor sim charts I aint too worried about cvt inefficiency on this thing.

You're thinking that the low-end RPM of motors is inefficient, right? That usually only occurs at "heavy loads" which shouldn't happen in real life if you gear it appropriately. Otherwise, lower speed on the flats would be obtained by partial throttle which the motor is far more efficient at. However, you get controller losses with partial throttle but my last calculations suggest that controller losses are somewhere around 30 watts - No big deal for 1000 watt loads - that's about a 3% loss. It might be as high as 5%.

When (if) I have this up and running what would be some good tests for working out the efficiency, What would people want to know ?.

[vanilla ice]

I'd be interested to see power use comparisons with the cvt locked out if that is possible. Low rpm is exactly where the heaviest loads usually happen. And on a scooter in the city, it repeatedly happens, block after block.

[gwhy!]

I forgot to put a pic up of the motor mount.... Hear it is

motor mount and crank.jpg

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motor mount and crank2.jpg

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I'd be interested to see power use comparisons with the cvt locked out if that is possible. Low rpm is exactly where the heaviest loads usually happen. And on a scooter in the city, it repeatedly happens, block after block.

I think this will be do'able.

swbluto: In your opinion the motor that I am planning to try this with what do you think the most efficient operation is going to be before the drive should kick in : the motor draws about 6A unloaded on 48v ( I will double check this when I get the chance ). With a cvt/clutch it is possible to spin the motor up long before it starts driving anything or do you think it should start driving the transmission instantly. We got to give it our best shot here so will there be any advantage spinning it up to a certain speed first ?

[gwhy!]

Bearings have arrived.

replacement main bearings.jpg

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These bearings are 3 mm wider than the originals But this was not a problem, The main bearings would have to be replaced due to no oil will be reaching them so sealed mains was in order.

I fitted the modded crank in to the crank casing and this was the outcome:

step7.jpg

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So far so good, no binding and runs smooth, tomorrow I need to make the spacers to mount the motor to the stator side of the crank casing.

[maydaverave]

Thats really cool. Can't wait to see it in action.

[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).

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.

No I have no problem with the original builder using the gearbox, it seems smart and easy, I was responding to the person that said "I wonder why all of these electric motorcycle builders haven't figured this out yet"

[gwhy!]

I had some time to spin the motor up with a rc sensorless esc and no load on the motor it takes 5.96A @ 44v ( I still think this is really poor compared to the other motors that I have ) anyway, it seems from what other people have said about this motor that is about right. I'm hoping with hall sensors fitted this can be improved but Im not holding my breath.

The bad news is with the motor connected and powered up just through the crank the motor draws 15A @44v so there is a tight spot some where and Im hoping that it is only the motor mount needs a bit of adjustment, worst case it could be the crank is not true ( this may have been the result of having to rework the crank to take the additioal 3mm off for the wider main bearings ), if this is the case Im a bit stuck at the moment as of a way to quick fix it. I may have to remove the crank and rework it on the lathe which is something I would like to avoid if I can. But I think I am still on track to have the transmission all up and running by this coming weekend, fingers crossed.

1day goes by
update:
I took the crank out And stuck it back in the lathe in work and got some else to check it and it was slightly out and now its as good as its gonna get unless I start again. The crank runs a lot smother now but I think the motor mount may still need a bit of tweeking also, I havent re-fitted the motor yet I had a few other things I needed to do ( totally unrelated ) tomorrow I will re-fit the motor and adjust the motor mount hopfully I can get the crank current down to a decent level, then we are all systems go for testing

[el_walto]

I'm excited to see how this build will turn out.

[maydaverave]

Not as easy as it first sounded Hopefully you get this straightened out and it will be the hardest part.

[gwhy!]

Not as easy as it first sounded Hopefully you get this straightened out and it will be the hardest part.

Your not wrong , If I still cant get it to a decent current level with the motor connected directly to the crank tomorrow I have a plan B which is put a sprocket on the crank and mount the motor where the cylinder head was and run a 1:1 chain to the crank. I know this in it self will be lossey and a bit more noise but it will prob be the easiest way to make it more efficient just to see if it will work.

[maydaverave]

Maybe you could just run a fixed pulley upfront and just use the variable pulley on the clutch. It might give you more mounting and shaft options.

[maydaverave]

never mind that wouldn't work without the variator to pick up belt slack. Could you just leave the tranny cover off, mount the pulley directly on to the shaft, mount the motor on the outside and run it in reverse. These might be really stupid ideas but just throwing them out there.

[Thud]

gwhy,
Great thread & build. you beat me to this(only differance is I am using a manual tranny ala' frankG)

quote:

I had some time to spin the motor up with a rc sensorless esc and no load on the motor it takes 5.96A @ 44v ( I still think this is really poor compared to the other motors that I have ) anyway, it seems from what other people have said about this motor that is about right. I'm hoping with hall sensors fitted this can be improved but Im not holding my breath.

I am dangerously close to setting up a motor with external halls, Just need to design a bomb proof mount for the external halls. (my bikes all get jumped, & slammed occasionaly) I await your report regarding the no-load conditions especialy regarding this motor. (I have one & another from bubba to re-wind soon).
It seems this particular motor is showing a higher fail rate than others(?) I wonder if it is some dimentional harmonic flaw? (cart in front of horse there)

I like what you have acomplished so far, Having set up a few CVT clutches for snowmobile drag racing I need to ask, does your smaller clutch have replaceable weights & springs to "tune" the launch rpm?
Awaiting next installment.