50cc -> 6kW conversion

[charliebruce]

Awesome project! It's cool to see someone else using an RC motor and a CVT.


Last time I saw it done I found it to be a bit too inefficient for my liking. Looks like TONS of fun though!

Id like to convert a scooter with a perm, and a direct gear drive, but it's pretty hard to convert from the CVT...

My initial plan was to have multiple motors (running each motor near its peak efficiency), one say 1kW for cruising, and the 6kW one for accelerating and hills. Couldn't find a way of coupling the motors though, so I ditched the idea. I'll keep you posted on the efficiency aspect (will get idle/loaded current readings and mess with rollers), but I can't see it being much less efficient than, say, a 72v brushed motor, or hub doing the same work, especially when you consider the initial price difference. My criteria for success in this project is 20-mile range at moped speeds in London/at uni without needing to pedal (though I'm still considering a composite/e-bike build next year, will end up being more energy-efficient and no risk of being stranded and out of charge, though it's easier and more popular to steal bikes from uni towns) - anything more demanding than that kind of journey (motorway, luggage/passenger-carrying), and I have some some more... ambitious plans for next year

[spkpn]

maybe there are out of the box gearbox kits for your scooter, maybe check some of the scooter-tuning pages. I, however would try with some more air cooling and more voltage and leave the drivetrain as it is^^

[charliebruce]

You can really see the ratio drop as the brakes are applied. I'm not changing the throttle at all, only braking.



The rollers are pretty badly worn, the last owner would probably never have replaced anything, so they've done 5000+ miles.

8.4g? 16x13 rollers (measured 8.375g, 15.7x12.6 presumably due to wear, so could be 8.5g - no markings to indicate original dimensions/weight).

The heaviest "stock" rollers I could find on ebay/moped shops were 11.6g. Alternatively I could go for a slightly larger-diameter roller (18x13 if it exists), and/or pack them with a lathed steel or brass piece, or maybe a cast pewter bit. If it's at 5k rpm compared to the 8k rpm petrol, I'd ideally want 8.5*(8000/5000)^2=21.8g rollers to match the petrol setup. Obviously the additional torque the motor can put out means that I can push this even further, but as it is, it's still double the weight of the heaviest rollers I could find.

No current readings yet I'm afraid.

[gwhy!]

I think I mentioned it before, but you can buy 16mm roller shells ( stage6 ) , I cut some bar to the correct length to fit inside the shells

[charliebruce]

@gwhy!

Just wondering, what kind of licensing/legal issues have you run into with your moped? I'm in the UK too, just starting to work out what paperwork I'm going to have to do in order to get this thing road-legal again. The aim is to get it MSVAed as a 0cc, low-power moped (tax-free).

Roller shells and brake switches on their way ASAP, sorting bodywork soon as well. I'm leaving it with the secondary ratio unmodified for now. Maybe I'll up it in the future if I want some more fun

[gwhy!]

I never did get mine on the road, but I did try when first had it running then give up, But recently I got chatting to someone who have converted a few electric bikes and he is ex mot inspector and he gave the inside info on how to go about getting it sorted , Apparently you will need first to get it mot'ed and any mot testing station ( this is the tricky bit as its all computerized ) the problem tends to be that many examiners will not mot a converted bike as the info on the system will not correspond to the bike, but if the cc of the bike is entered into the computer as 0cc then the electric menu for mot'ing will be displayed, once you have it moted then you just send the new mot with the logbook of to the dvla to get the logbook changed, its as easy as that, He also said that ( he thinks ) if it was originally reg'ed as a 50cc then no other inspection will be nessersary, as long as the power rating of the motor is not over the legal limit for a 50cc , which is 2.8kw I think. Please let us know how you get on.

[datahar]

@gwhy

is it possible to see any of the arduino set up?

I am doing the exact same thing myself, but can't quite get the motor to act normally under the arduino
not sure if I am doing something wrong or I have set the ESC up wrongly

[gwhy!]

@gwhy

is it possible to see any of the arduino set up?

I am doing the exact same thing myself, but can't quite get the motor to act normally under the arduino
not sure if I am doing something wrong or I have set the ESC up wrongly

Originally I just used a off the shelf servo tester from hb and fitted a hall throttle, then I went and changed the whole setup to a use a e-bike controller and fitted hall sensors to the motor.

[Quajochem]

I know just the set for you!
The best vario you can have is the NYC overdrive 2 vario:
http://www.revolution70.nl/xtc/product_ ... llen-.html
(sorry this is a dutch page..)

Blue clutch springs:
http://www.revolution70.nl/xtc/product_ ... 4takt.html

and possibly an overdrive gearing system:
http://www.revolution70.nl/xtc/product_ ... velg-.html

NCY is the Taiwanese equivalent of Malossi, they make good quality parts!
Just installed that OD2 vario, and it's just sooo smooth and nothing like the unrestricted stock one which has dips and short range. The NCY OD 2 has no dips at all and a very wide range, just buttersmooth!

good luck!

[datahar]

Originally I just used a off the shelf servo tester from hb and fitted a hall throttle, then I went and changed the whole setup to a use a e-bike controller and fitted hall sensors to the motor.

i have a servo tester, my set up is simply 6s1p battery pack going into ESC which is attached to the motor and the servo tester

with the tester set to manual, full throttle sends the esc into program mode, no throttle causes 2 beeps, which I assume is it's read tone
playing with settings I was able to get the motor to spin briefly, but for no more than a second and at a low speed (probably 20% servo tester) then there was a beep as the motor stopped

main goal is to read the results from the throttle and use the arduino to translate to the ESC

is it just a case of getting the right combination? or is there a certain start up procedure so the esc does not hit program mode?

Thanks!

[SamTexas]

This is great.

... I'll keep you posted on the efficiency aspect (will get idle/loaded current readings and mess with rollers), but I can't see it being much less efficient than, say, a 72v brushed motor, or hub doing the same work, ...

Looking forward to seeing those numbers. I'm really interested in knowing how much power/energy is lost going through the CVT.

In the mean time, a few quick questions: How much weight did you save after removing the gas engine? How much does the scooter weight now with and without the battery.

[gwhy!]

Originally I just used a off the shelf servo tester from hb and fitted a hall throttle, then I went and changed the whole setup to a use a e-bike controller and fitted hall sensors to the motor.

i have a servo tester, my set up is simply 6s1p battery pack going into ESC which is attached to the motor and the servo tester

with the tester set to manual, full throttle sends the esc into program mode, no throttle causes 2 beeps, which I assume is it's read tone
playing with settings I was able to get the motor to spin briefly, but for no more than a second and at a low speed (probably 20% servo tester) then there was a beep as the motor stopped

main goal is to read the results from the throttle and use the arduino to translate to the ESC

is it just a case of getting the right combination? or is there a certain start up procedure so the esc does not hit program mode?

Thanks!

there is no phase combination to get correct the motor will either run forward or run backwards no matter on the conbination, the throt must be at min ( are you using the tester in a original state i.e built in pot ? ) until the esc initialises ( the esc I have played with normally beep twice then play a 3 beep tune ) then it should respond to the pot as a throttle as you would expect.

This is great.

... I'll keep you posted on the efficiency aspect (will get idle/loaded current readings and mess with rollers), but I can't see it being much less efficient than, say, a 72v brushed motor, or hub doing the same work, ...

Looking forward to seeing those numbers. I'm really interested in knowing how much power/energy is lost going through the CVT.

In the mean time, a few quick questions: How much weight did you save after removing the gas engine? How much does the scooter weight now with and without the battery.

the main weight saving is from the exhaust system and the flywheel, the original engine casing is still used and the only thing that is removed from the engine is the crank so maybe 1-2kg from the engine ( if its a 2 stroke, a bit more can be removed if its a 4 stroke ), the exhaust weighs about 5kg+ and the flywheel is about another 1-2kg and all the other stuff that can be removed comes to about another 1-2kg, more can be saved if its a water cooled gas scoot. 50cc scoots have a kerb weight of around 80kg but some makes are upto around 110kg, you just add a motor and battery's the motor is about 1kg and what ever the battery weighs 10ah of 48v lipo weighs around 4kg. So it will end up about the same weight after conversion with 20ah worth of battery's. I believe you will never get the same performance from a hub or fixed geared motor of more than 2 or 3 times the current limit than if going through a CVT, a cvt is lossy but more than makes up for it in the long run. My scoot was loosing around 300-400W through the cvt and spinning the rear wheel and a push bike with a 2 stage reduction spinning a 26" wheel looses 70W but im sure this could be improved with a much better motor mount ,and a new belt . My motor wasnt quite straight and cause a fair bit of vibration.

[charliebruce]

@SamTexas
I'm going to be a while getting the current readings I'm afraid, I've got to get through my exams before I can do any major programming/design work. Will keep you updated though/ I suspect that if I can sort my mechanical issue (see below) then it'll be around 100w lost in the CVT (belt vibration, slippage, etc) and a fair bit more in the motor due to the fact that it's running right in the upper end of its RPMs all the time. Not sure though, will definitely be interesting to see.

Weight savings - the exhaust was pretty meaty, about 5kg sounds right. The cylinder, air box, fuel/oil tanks, flywheel/alternator and carburettor are another 5 or so kg, but the batteries are going to be pretty heavy to get a decent range so I'd estimate it'll be around stock weight when finished - I don't have the final pack yet though. I've not finished reassembling and I didn't weigh before starting, so I can't give you any better numbers than that, I'm afraid. I'll make sure that I get the weight when it goes in to get tested, but I don't have access to any decent weighing equipment.

@datahar
I butchered the oil pump to fit a potentiometer (so I could use the original cables and throttle), ran that straight to the Arduino ADC pins and mapped that to a pulsewidth with a simple map() function (I used the range 1000ns - 2000ns but you'll probably find the ESC will only actually operate between the range 1200ns and 1800ns or so - depends on the ESC though, so play around until you get it working smoothly. My ESC didn't run using the writeServo command, only the writeMicroseconds command for some reason, probably relating to the pulsewidth). Every 50ms it checks the pin, maps the value to a pulsewidth, checks the brake cut-out and sends the appropriate pulse to the ESC. Start-up is currently as simple as connecting the batteries through a resistor, listening for the ESC beep, then connecting the high current lead - I'll probably add a safety "twist to max whilst squeezing the brake to arm" feature at some point but for now it works fine.

Current code:



Might use this eventually:



@gwhy!
I noticed a mechanical issue on the drivetrain last weekend whilst playing around with some other bits - the splined shaft holding the variator on had slipped slightly in its bearing (was hammered into place, obviously not well enough) and was not spinning true, which was creating some horrible vibrations and "stalling" the motor/making the ESC lose sync, I'm not sure which. I'm going to see if I can re-align it in-place this weekend, if not I'll have to take the motor out and try it again. A bit of a kick in the teeth since it was working pretty nicely the last 3 times I tried it, but it hopefully shouldn't be too hard to correct.

@quajochem
I'm just going to try the variator rollers for now, if I need more performance later then I'll probably go with a gear-up kit. I'll probably end up using either no springs and changing how the throttle responds at low speed (increase accuracy at low range - exponential throttle map?), or buy the lightest springs I can find. The gear-up kit might well prove useful though, if the variator mod doesn't help enough.

[SamTexas]

@SamTexas
I'm going to be a while getting the current readings I'm afraid, I've got to get through my exams before I can do any major programming/design work...

Thanks for the reply. Good luck on your exams. CS or EE?

[charliebruce]

@SamTexas
I'm going to be a while getting the current readings I'm afraid, I've got to get through my exams before I can do any major programming/design work...

Thanks for the reply. Good luck on your exams. CS or EE?

Neither, I'm still doing A-levels. Will be studying General Eng in 2014 if I get the required grades, but I'm taking a year out to work on some projects first (some of which are EV related, watch this space).

[SamTexas]

Ok, I didn't know you're from England.

[datahar]

Just wondering, what kind of licensing/legal issues have you run into with your moped? I'm in the UK too, just starting to work out what paperwork I'm going to have to do in order to get this thing road-legal again. The aim is to get it MSVAed as a 0cc, low-power moped (tax-free).

I contacted the DVLA and explained what I was intending to do, this is the response I got:

It may help, if I advise at this stage a personal inspection would not be required.

In order for us to update your vehicle record please return the following:

1. Vehicle registration certificate (V5C) with section 7 completed
2. Letter on headed paper from the mechanic or engineer confirming these changes
3. photographic evidence, with the registration number visible on at least one photograph

Arduino wise, I was considering writeSeconds before I got your reply so that will definitely be my plan of attack, is it possible to get the wires from the ESC to the motor the wrong way? As that is how I would describe the motors behaviour. It may be a case of the ESC is simply not powerful enough to handle the motor (I just bought an entry price 150A controller off ebay (sky wing 150A)) as I had a quick play with the writeSeconds, and no real progress, although now I have recreated the same issue with the servo tester (which is stock yes) with the e-throttle and arduino mapping the results to the ESC

I have been starting the set up with the full power of the pack, but you mentioned a low power to start with? Maybe this is something I need to try, as my suspicion is I am simply not arming the damn thing right (fingers crossed)

[charliebruce]

Just wondering, what kind of licensing/legal issues have you run into with your moped? I'm in the UK too, just starting to work out what paperwork I'm going to have to do in order to get this thing road-legal again. The aim is to get it MSVAed as a 0cc, low-power moped (tax-free).

I contacted the DVLA and explained what I was intending to do, this is the response I got:

It may help, if I advise at this stage a personal inspection would not be required.

In order for us to update your vehicle record please return the following:

1. Vehicle registration certificate (V5C) with section 7 completed
2. Letter on headed paper from the mechanic or engineer confirming these changes
3. photographic evidence, with the registration number visible on at least one photograph

Arduino wise, I was considering writeSeconds before I got your reply so that will definitely be my plan of attack, is it possible to get the wires from the ESC to the motor the wrong way? As that is how I would describe the motors behaviour. It may be a case of the ESC is simply not powerful enough to handle the motor (I just bought an entry price 150A controller off ebay (sky wing 150A)) as I had a quick play with the writeSeconds, and no real progress, although now I have recreated the same issue with the servo tester (which is stock yes) with the e-throttle and arduino mapping the results to the ESC

I have been starting the set up with the full power of the pack, but you mentioned a low power to start with? Maybe this is something I need to try, as my suspicion is I am simply not arming the damn thing right (fingers crossed)

Can you post a circuit diagram or decent picture of how you've set it all up/describe the problem you're having?

ESC: 3 phase wires on the output side, they can be attached in any way, and swapping any pair reverses the motor direction. On the input to the ESC, orange - signal, into the digital output pin, as assigned by (Some Servo Object).attach(pinNumber); command. Black - 0v, must also be connected. On an opto-isolated ESC you may also need to send power (5v) to the remaining pin.

Definitely consider using writeMicroseconds - the ESC will expect a decent signal before it'll start. My code maps the throttle to the range 1000-2000us. Does the motor go into braking mode when you attach power? "Low Power" - do you mean the code I wrote so that the bike can't move until the driver is ready? If so that's unrelated. I started testing with 6s LiPo, but I've been using it on 12s with no issues. My ESC is a 160A from hobbyking, anything over 120A should be fine at full power though.

Re legality, I'm speaking to the previous owner but he's probably lost the paperwork. I could reapply for a logbook and then contact the DVLA but the MSVA route gives me a bit more confidence in the safety/sturdiness, and saves me money on the MOT for the first three years. Either way works, I guess.

Mechanically, I've taken my motor out and need to add a spacer in between the main bearing and the motor - that looks like it might have been the root of my mechanical issue (hopefully, it's nothing worse).

[Jeremy Harris]

I've been through the DVLA hoops to get my converted Yamaha RD50 accepted as an EV. It was incredibly frustrating, took literally dozens of letters, and the issue of no less than 4 registration docs before they got things more-or-less right. The level of incompetence at Swansea has to be experienced to be believed - a bigger collection of useless numptys would be hard to find.

In my case I managed to break the rules and get the personal telephone number of a chap at the local DVLA office. He was fantastic, acknowledged that his lords and masters at Swansea were incompetent pillocks and bent over backwards to help. He came around to my place, did his own inspection of the bike, confirmed it would be reclassified as electric (and hence tax-free) and passed the details back to DVLA at Swansea. Despite this, the numpties at Swansea still managed to make errors on the registration, from getting the serial numbers wrong to randomly changing the colour of the bike.

In the end I've just accepted the last of their errors (the docs state that the electric motor is 50cc.................) as I lost the will to live in trying to get them to put things right.

[charliebruce]

I've been through the DVLA hoops to get my converted Yamaha RD50 accepted as an EV. It was incredibly frustrating, took literally dozens of letters, and the issue of no less than 4 registration docs before they got things more-or-less right. The level of incompetence at Swansea has to be experienced to be believed - a bigger collection of useless numptys would be hard to find.

In my case I managed to break the rules and get the personal telephone number of a chap at the local DVLA office. He was fantastic, acknowledged that his lords and masters at Swansea were incompetent pillocks and bent over backwards to help. He came around to my place, did his own inspection of the bike, confirmed it would be reclassified as electric (and hence tax-free) and passed the details back to DVLA at Swansea. Despite this, the numpties at Swansea still managed to make errors on the registration, from getting the serial numbers wrong to randomly changing the colour of the bike.

In the end I've just accepted the last of their errors (the docs state that the electric motor is 50cc.................) as I lost the will to live in trying to get them to put things right.

Sounds like I've got plenty of fun in store for this summer, then

[SamTexas]

I've been through the DVLA hoops to get my converted Yamaha RD50 accepted as an EV...

I'm curious. You converted the RD50 into a legal European ebike (250W, 25kph)? Or to an electric scooter/motorcycle that still needs registration? Either way, did you have a build thread? I would be interested in reading it.

Sorry OP for getting off track.

[gwhy!]

I've been through the DVLA hoops to get my converted Yamaha RD50 accepted as an EV. It was incredibly frustrating, took literally dozens of letters, and the issue of no less than 4 registration docs before they got things more-or-less right. The level of incompetence at Swansea has to be experienced to be believed - a bigger collection of useless numptys would be hard to find.

In my case I managed to break the rules and get the personal telephone number of a chap at the local DVLA office. He was fantastic, acknowledged that his lords and masters at Swansea were incompetent pillocks and bent over backwards to help. He came around to my place, did his own inspection of the bike, confirmed it would be reclassified as electric (and hence tax-free) and passed the details back to DVLA at Swansea. Despite this, the numpties at Swansea still managed to make errors on the registration, from getting the serial numbers wrong to randomly changing the colour of the bike.

In the end I've just accepted the last of their errors (the docs state that the electric motor is 50cc.................) as I lost the will to live in trying to get them to put things right.

Sounds like I've got plenty of fun in store for this summer, then

@JH,
Did you get a mot first before you applied for re-classification ?. The info I was given was from a poster on this forum that have re-reged 2 motorcycles and was a ex-mot inspector. He said that he had no trouble at all getting his bikes re-classed as electric once he had a valid mot that stated that indeed the bike was now electric which can be done at any mot station. I havent tried this myself but I think this would be the way I would try to do it first off as I wrote a letter to the dvla and sent the log book off twice but just received the log book back unchanged with no explanation so I gave up.

[charliebruce]

I've been through the DVLA hoops to get my converted Yamaha RD50 accepted as an EV...

I'm curious. You converted the RD50 into a legal European ebike (250W, 25kph)? Or to an electric scooter/motorcycle that still needs registration? Either way, did you have a build thread? I would be interested in reading it.

Sorry OP for getting off track.

No problem - discussion is always good. The RD50 has no pedals so presumably he means it's now classified as a motorbike/low-power moped, not e-bike.

I'm having a big workshop day tomorrow, and maybe Friday, so will be back with pictures - if anyone wants to see something specific about it, let me know before tomorrow. Then probably a bit of a dry spell for a while, no work on it for a week or two. I'm hoping to sort out my mechanical issue re motor mounting, and stop dirt getting in tomorrow. I'm a bit nervous about the motor mounting issue, but should be able to sort it.

Any advice on the following issues?

Rollers - I bought replacement roller shells, they have about 14mm dia x 12mm height inside - unless I go for a lead slug in the centre and pack the space completely full, I'm not going to hit 21g/roller (which makes up for the 5000 vs 8000 rpm - original weight: 8.4g or so, 8.4g*(8000/5000)^2 = 21.6g to match the original rollers). Am I going to be ok with a steel core (14g), should I buy some lead (will just about hit 21g), or should I just try the rollers with steel and lighten the rear pulley-spring? Or more radically still, if it fails to improve the top speed, just jam the variator at maximum ratio? I'm open to suggestions.

Brake - I don't want to burn the brakes out or have the ESC "jam" at full throttle due to cable/potentiometer issues - is using the brakes as a motor cut-out going to be more trouble than it's worth? The motor braking is noticeable when I tried this out - is motor-braking a moped enough to burn out a cheap ESC if done on a daily basis, or can they take it?

Vibration - Has anyone mounted their motors on rubber mounts to reduce mechanical noise? Last time I ran it, the noise was fairly loud - that's probably due at least in part to my motor mounting but could be improved with some rubber pads? Alternatively, it might have been a warning that something was rubbing/off-centre (which caused the issue I discovered?)?

[Jeremy Harris]

With hindsight I should have got the bike MOT'd first, as you say gwhy, as others have said that this often seems to ease the DVLA problem

For those outside the UK, legally the RD50MX is a moped here in the UK, and doesn't have pedals but does need registration, insurance, road tax, a licence etc. Here's a pic of mine part-completed:

I provided "evidence" to the DVLA to show that because of the battery voltage, motor Kv and overall gear ratio the bike was limited to 30mph so remained a moped, despite having a 6kW motor. My RD50MX was a pre-restriction model, so would do 50 mph plus with it's original engine, despite having a Yamaha plate on the frame saying it'll only do 30 mph. This practice of selling technically illegal mopeds was very widespread here years ago, until the government changed the law and made the manufacturers limit engine power and checked this during Type Approval. The fact that my bike was a pre-power restriction model made life a bit simpler with the DVLA inspection, as I didn't have to provide an accredited test house certificate for the maximum motor power.

[datahar]

Can you post a circuit diagram or decent picture of how you've set it all up/describe the problem you're having?

ESC: 3 phase wires on the output side, they can be attached in any way, and swapping any pair reverses the motor direction. On the input to the ESC, orange - signal, into the digital output pin, as assigned by (Some Servo Object).attach(pinNumber); command. Black - 0v, must also be connected. On an opto-isolated ESC you may also need to send power (5v) to the remaining pin.

Definitely consider using writeMicroseconds - the ESC will expect a decent signal before it'll start. My code maps the throttle to the range 1000-2000us. Does the motor go into braking mode when you attach power? "Low Power" - do you mean the code I wrote so that the bike can't move until the driver is ready? If so that's unrelated. I started testing with 6s LiPo, but I've been using it on 12s with no issues. My ESC is a 160A from hobbyking, anything over 120A should be fine at full power though.

Here is my set up, it is all very basic, I got my throttle to act the same way as the servo tester, so I am happy it is all mapped right now.

the "stalling problem" still exists though

after the what im presuming is the ready beep if I go to full throttle it enters programming mode again, this leads me to believe it has not armed correctly?

I read on another forum someone did not get his to work properly because it didn't have BEC but attaching an external power source to the throttle cable solved that problem for him, so I will try that next