50cc auto scooter conversion to electric (with video)

[Jay64]

I don't think I worded my question clearly enough. I know why the original crank was used and milled down. But the crank was cut in half at the connecting rod (I don't know if it was technically in the exact middle or not, but pretty close), and then welded back together. I was wondering why this was done. Did it have to be done to remove the connecting rod? Or was it cut just to extend it? The reason I am asking is because thinking of welding the crank back together it is hard to keep it straight while re-welding it back together with the heat flex and stuff. I was thinking that if it was just for extension, then a longer coupler could be used when connecting the motor to the crank. But like I have mentioned before, I haven't done any work on small scooter motors, so I don't know if the connecting rod is somehow permanently attached to the crank and needs to be cut out.

[vanilla ice]

I'm not sure about the reasoning in this particular case, but I do know on two strokes the con rods do not unbolt. They are one piece. You need to press apart the crankshaft to replace/remove them. PITA.

[gwhy!]

I'm not sure about the reasoning in this particular case, but I do know on two strokes the con rods do not unbolt. They are one piece. You need to press apart the crankshaft to replace/remove them. PITA.

Yes this was the reason, The con-rod needs to be cut out/off, If I was to do this again I may try leaving the crank in one piece but Im not sure how balanced it will be with out the con-rod ( hope this makes sense ) the only piece of the crank that is needed is the splined part that the variator slides onto this is why I extended that piece of the crank so it would run in the main bearings. You cant just weld the 2 halves back together because it will be about 30mm to short.

No updates as yet on the scoot, because rain has stopped play , But on a plus side I have ordered some more batterys and also I have been putting some finishing touches to my battery chargers ( making them a bit safer ) also added some cooling fans.

[gwhy!]

update:
I managed to get some time to play with the scoot today after work (no rain). Well I am very happy with the setup I have at present 12g rollers and the clutch springs were stretched a little and now engages nice at around 2k motor rpm. I still have the problem with the saggy bats but it all works well even with the battery's not performing very well. The acceleration is comparable with my son in-laws unrestricted nrg upto 25-30mph the good thing is that it gets upto this speed with ease and basically stops accelerating at that speed which tells me that without the nearly 20v drop from the battery's the scoot will keep accelerating upto the top speed of around 50-55mph. The standard drive belt that is on the scoot is a cheapo one and is very stiff compared to a performance belt so I may invest in a performance belt and this should also improve the efficiency. And it still never peaked over 2.5kw so I am made up with it so far

[gwhy!]

I have just been looking back at all the scoots I have worked on/owned or ridden. And I think the ideal auto scoot for this would be the honda sky50. Its has larger wheels (16") and it is very light dry weight 70kg.

honda sky 50 SGX50.jpg

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[gwhy!]

Now I have my lipo battery charger all setup nice, with balancing I was able to charge and balance the cheapo lipos that I have so they now perform slightly better, only 10v drop instead of nearly 20 ( they are still rubbish for pulling high c's , but much better than before ) Im still waiting for my new lipos to arrive which will improve things even more. Anyway the scoot runs upto 30-35mph and have run it up all the hills I have access to with no real signs of losing any speed and also pulls away on the hills ok ( without the 10v drop its going to be a top speed of around 40mph ). I was working on the battery voltage stright off the charger ( 50v ) for the initial calulations of max speed which would be around 50mph , This setup would suit 60-70v working voltage perfect with a 170kv motor and top speed will be around 60mph and never really pull no more than 3-3.5kw with a standard drive train for a 50cc scoot. I am going to fit hall sensors to the motor in the scoot so I can use my sensored controller which will give me the option to run a higher voltage. On a negative note my throttle interface have gone pop ( well i hope it is and not my rc esc ). So until I have either fitted hall sensors to the motor or fixed the throttle interface/rc esc I will be unable to do any more testing for the time being . The cheap lipo's that I have where bought off of ebay and were sposed to be 4000mah 15c ( 20c burst )22.2v and although they can not supply the c rating the 4000mah is spot on and I think for anyone that don't need massive c 's these were a very good buy I paid £100.00 ukp delivered for a 44v 8AH battery this was about a year ago but the c rating is more like 5 ( 10 burst ).

edit:
I removed my throttle interface from the enclosure and fitted the esc to a motor on the bench and it worked so I put it all back together and re-tried back on the scoot and it works ... now what was that all about ( dont you hate it when that happens ).

[gwhy!]

Update:
I was fed up with the sensorless controller Pissing me about so I have now fitted hall sensors to to motor and now driving the motor with a 12fet sensored controller.

convert to halls.jpg

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Its not the tidiest mount in the world but it does the job. I know running halls on these little motors was a improvement rather than using a sensorless controller but this has really highlighted that difference in performance yet the setup pulls the same amount of current and delivers the same amount of wattage but the difference is amazing the motor just get upto speed so much quicker. Im looking forward to getting my additional batterys and this will leave my options open, I want to see how good It can be on only 44v pulling only 2.5kw and then when im board with that I can up the voltage which will up the top end speed and not loose any low end performance ... good times .

[vanilla ice]

Nice one on the sensors! Any chance you can give step by step details and macro pics on the job?

[gwhy!]

Nice one on the sensors! Any chance you can give step by step details and macro pics on the job?

Thanks,
There is a thread on here that goes into depth about fitting halls to out runners There are a few different ways to achieve this http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=15686 there is a lot of good info in there. I posted a template for hall spaceing and also some artwork for a hall sensor pcb.

Update:
I just could not resist putting my e-bike good batterys onto the scoot ( the cheapo lipo's I have are what I use for messing around with ) .... Feck in hell wooooooo must get a vid for you guys !!!.... 45MPH as predicted ( kv of the motor limited ) peak wattage have gone up but only to 3.5kw !! ( the drive belt is right on the edge, you can smell it slipping when gunning it ) acceleration is amazing, standing starts are a bit un-nervy feels like it can loop out if not carefull, it will blow away my son inlaws unrestricted nrg away. Well what can I say.. Video will have to be done. And I still got more batterys coming to up the voltage 60MPH will be easy with 3.5kw .... I wonder what it will do if I let all the power from this motor drive the cvt . The big question is now, how efficient is it...

[vanilla ice]

Ah thanks, missed that thread. The old yamaha 50cc scooter in my drive way is calling my visa card.. must resist!

[gwhy!]

Ah thanks, missed that thread. The old yamaha 50cc scooter in my drive way is calling my visa card.. must resist!

no worries, Do not resist !!!! If you are going to give in to temptation then I would recommend getting a motor with a much higher kv ( it will take a lot of the guess work out of sorting the gearing ) look for some thing around 200 -250kv, http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=7710&Product_Name=TGY_AerodriveXp_160_SK_Series_63-64_230Kv_/_3150W would be a good choice but just a tad underpowered ( but it still wont dissapoint ) unless you are thinking of running a higher voltage than 44v , My guess is that the stock gearing on your yam will be taller than on my skp so with the same motor setup as I have it should do 50 .

[Thud]

That sounds fantastic gwhy.
I am working on getting halls mounted to my turnigys this weekend. & I Ihave no worrys that the motor will push my little speedway build to competitive levels with the gassers at an upcoming race meet. (50cc motored bikes)
I have totaly enjoyed watching this build progress. & it is great news that this transmision style works for electrics at this level.
Another internet beer is in order here!

looking forward to a video.

[gwhy!]

Small update:
I haven't had chance to get out to do a more descriptive video, but my son came round and I got him to have a go on it. Its not the best video in the world but it is something. I am away for a few days now so no more vids till I come back. My Lad was a bit warry of just gunning up the driveway, he couldnt get over how much the thing pulled from a stand still he also said it felt like it could loop out.

[spdas]

Aloha, and great work on the crankshaft attachment to the motor. I was wondering how you were going to do it! I may start a build myself if i get some spare time. For higher top speed I would be looking at getting a set of gears for the Diff, (Maybe a 7:1) .... that is what is needed for a gas 'ped if you need to get out of the 55-60 mph range and into the 80+ range.
Also a larger diameter Variator and driven face like a Kitaco, maybe as well as the heaviest weights. Try a slightly longer and wider belt so the belt does not go all the way down on the variator boss. (Machine the variator and driven face to close really tight) and with the wider/longer belt your belt should climb all the way out past the variator BEFORE you run out of pulley on the clutch side.) I am not sure what diameter weights you have (yamaha size?) if so, try Honda as they are a bit larger diameter and will close the variator halves closer without falling out. Also using an FRP ramp will help hold steady rpms vs pulley openings. Do you have a moped breaker nearby that would have an assortment of bits? In the southeast, (Maidstone?) try Chris at Scooters-r-us.

Francis

[ryan_lirui]

I've been thinking a lot about this cvt set up of yours gwy and I was thinking what might be a big help to you is if you change up the type of throttle you're using. As far I as I know, you're using a speed based throttle, which is good for a sort of direct drive set up like most electric bikes, but might not be ideal for your application.

My interpretation of a cvt in a normal ICE engine application is that it juggles the ratio on the pulleys to always keep the motor in the optimum rpm range of your motor. When engine rpm increases, ideally those rollers fan out to adjust the pulley to a ratio that is best suited for the motor at that point in its rpm range. As a driver, you scale the amount of power you want to put through the system with the motor and the CVT translates that into wheel speed.

Currently what you're doing is a bit counter-intuitive, you're adjusting the rpm range of your motor directly and then letting the pulleys juggle around faster or slower according to the amount of rpm your motor's running at. This is probably why you're pulling less current than you did before using a CVT when you try to accelerate. What I think would be ideal is if you use a current-based throttle so that you're directly adjusting how much power you want to put through the system and the CVT be used at its greatest potential.

This way, you could optimize your set up so that you can focus more on a higher top speed and not worry as much about getting it to engage properly at lower rpm because you'll be able to crank the throttle and get full amperage out of the motor to get it up to speed.

Fechter's Current-Based Throttle: viewtopic.php?f=2&t=78&hilit=current+based+throttle

I'm not claiming to be the expert, but please give it some thought. If someone can spot the error in my logic here then please do so.

[gwhy!]

Aloha, and great work on the crankshaft attachment to the motor. I was wondering how you were going to do it! I may start a build myself if i get some spare time. For higher top speed I would be looking at getting a set of gears for the Diff, (Maybe a 7:1) .... that is what is needed for a gas 'ped if you need to get out of the 55-60 mph range and into the 80+ range.
Also a larger diameter Variator and driven face like a Kitaco, maybe as well as the heaviest weights. Try a slightly longer and wider belt so the belt does not go all the way down on the variator boss. (Machine the variator and driven face to close really tight) and with the wider/longer belt your belt should climb all the way out past the variator BEFORE you run out of pulley on the clutch side.) I am not sure what diameter weights you have (yamaha size?) if so, try Honda as they are a bit larger diameter and will close the variator halves closer without falling out. Also using an FRP ramp will help hold steady rpms vs pulley openings. Do you have a moped breaker nearby that would have an assortment of bits? In the southeast, (Maidstone?) try Chris at Scooters-r-us.

Francis

Thanks spdas,
The gearing at the back wheel would be the logical way increase the top end speed but first I what to see how far it can be pushed with stock, there are a few options to play with I am only running it on 44v at the moment so I can up the voltage but this would involve replacing my fets in my speed controller they are only rated at 75v and I think to make it viable it would be nice to try it on 88v ( which should nearly double the speed ) or I can gear up the motor to the crank with a 1:2 ratio this will also nearly double the speed. The motor is not being pushed hard at all so it has a lot more to give. I would be a bit concerned about upping the voltage due to there is a slight vibration through the crank because the motor is not 100% inline with it and the whole thing may just vibrate it self apart if run at 16krpm that is also if the controller will still work upto those rpm levels. running a gear up to the crank may also have vibration problems but at least I will not have to mod my speed controller. The belt is worn and if replaced may add another 5mph also the variator face is quite grooved so if this was replaced this may add yet another 5mph but I didnt want to start spending to much money on it. If I can get hold of a gear set for the back wheel cheap enough this is begining to look like a much better way forward now . I may have to checkout Scooters-r-us thanks for the heads up. I have no way of machining the driven face so this is not a option. The rollers are 19x15.5 and weighted to 17.5g and It still feels like it can push even a heavier roller but needs "road testing to be sure". Well there is quite a few things to think about. The bottom end performance is really good and I think can be improved some more but now I need to concentrate on top end

I've been thinking a lot about this cvt set up of yours gwy and I was thinking what might be a big help to you is if you change up the type of throttle you're using. As far I as I know, you're using a speed based throttle, which is good for a sort of direct drive set up like most electric bikes, but might not be ideal for your application.

My interpretation of a cvt in a normal ICE engine application is that it juggles the ratio on the pulleys to always keep the motor in the optimum rpm range of your motor. When engine rpm increases, ideally those rollers fan out to adjust the pulley to a ratio that is best suited for the motor at that point in its rpm range. As a driver, you scale the amount of power you want to put through the system with the motor and the CVT translates that into wheel speed.

Currently what you're doing is a bit counter-intuitive, you're adjusting the rpm range of your motor directly and then letting the pulleys juggle around faster or slower according to the amount of rpm your motor's running at. This is probably why you're pulling less current than you did before using a CVT when you try to accelerate. What I think would be ideal is if you use a current-based throttle so that you're directly adjusting how much power you want to put through the system and the CVT be used at its greatest potential.

This way, you could optimize your set up so that you can focus more on a higher top speed and not worry as much about getting it to engage properly at lower rpm because you'll be able to crank the throttle and get full amperage out of the motor to get it up to speed.

Fechter's Current-Based Throttle: http://endless-sphere.com/forums/viewto ... d+throttle

I'm not claiming to be the expert, but please give it some thought. If someone can spot the error in my logic here then please do so.

I think you may be right if looking at it to gain max efficiency this may be quite a neat way of doing it and will take the guess work out of finding the sweet spot for the throttle once upto your desired speed. I will give it some thought, but at the moment I need more top end , once I achieve my target speed of 60mph+ with the motor that I have Which is more than doable I will start looking into making it more efficient.

[maydaverave]

a 150 cc scoot doesn't weigh much more or cost much more than a 50 cc scoot and it is built and geared for higher speeds.

[vanilla ice]

In my experience looking for cheap old scooters, it is way easier to find the small ones. Hardly ever see the big ones for cheap. I can see how its smarter to go big if you're paying more for a new or late model used one though.

[dbaker]

Great job on the scoot, Gwhy?! I can see now where you are using your external sensors. 60MPH!

Dave

[Thud]

gwhy,
Are you using your 6fet controllers on this?
(I am sooo anticipating my bike with that motor & this thread has been 100% encouragment)
I am totaly impressed with this builds success.

[maydaverave]

With the cheap prices of rc products and used scoots with some skill and hardwork it is possible to make one cool little toy. Thanks for the inovation

[maydaverave]

In my experience looking for cheap old scooters, it is way easier to find the small ones. Hardly ever see the big ones for cheap. I can see how its smarter to go big if you're paying more for a new or late model used one though.

150 cc scoots usually don't cost that much more, the only real reason to buy a 50cc scoot instead of a 150 cc scoot is in most places a different license isn't required. There is a big jump in price and weight from 150cc to 250cc though. Many times the only real difference between a 50cc model and 150cc model is bore and gearing.

[gwhy!]

a 150 cc scoot doesn't weigh much more or cost much more than a 50 cc scoot and it is built and geared for higher speeds.

Yes I think it may save a bit of money in the long run if you are looking for high end performace to go for a slightly bigger cc scoot.

Great job on the scoot, Gwhy?! I can see now where you are using your external sensors. 60MPH!

Dave

Thanks Dave,
The halls work a treat . 60MPH+ easy , just down to bottle , I have rode these little 50cc scoots in the past just beyond 60+ for normal road use but it all starts to get a bit scary, but with a little nip and tuck of the frame geo they can start to feel very stable again upto around 90 .

gwhy,
Are you using your 6fet controllers on this?
(I am sooo anticipating my bike with that motor & this thread has been 100% encouragment)
I am totaly impressed with this builds success.

This is the 12fet controller with STANDARD fets but with beefed up tracks and current limited to 70A!!, The controller works well but do get hot so needs to be nursed a little ( I will be rehousing and also some form of forced cooling ) Its the cooling that Im finding is the limiting factor for these controllers ( and this is defo down to the enclosure design ). The 6 fet will have no problems pushing the scoot at 70A all day long if I wanted it to ( it has up rated fets installed + better cooling).
I'm Hopeing that the efficency numbers works out now as this can and will open up a big new area in performance/speed on any type of ev ( I wonder how compact a cvt can be made )
I hope your build kicks some butt with the motor/controller combo, its all good stuff and I'm pleased that my bit of playing has given you some encouragement with your venture ( but I think you were already on the case )

[katou]

Since it is working so well now, could you time it from zero to 60? I think that most here would be familiar with the common times and what they feel like, it would really help me understand the performance level.

I love reading about this project. If you ever take it apart to tune/repair it, it would make a great picture essay.

It's got me looking at scooters very differently...


Katou

[gwhy!]

Update:
I have made a decision about the top speed thing. At the moment I am going to concentrate on using the stock gearing, I had a look at the current gear set fitted in the scoot and they are pressed type ( primary to secondary ) and as I have not got access to a 15ton press this will be the last thing to play with but I have priced up a gear up kit and it looks like I can get one at a reasonable price when I go down that route.

scooter gears.jpg

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I will also only be using the 44v for the time being ( I may up it to 60v'ish later ). The plan is to replace the belt with a new slightly longer one as spdas has already suggested , this then should give me my 50-55mph on a fully charged set of batterys ( 48v). Then it should not be to stressfull for the crank and motor ( vibration thing ) just to up the voltage a tad to around 60-65v ( fully charged )to get me to that 60mph+.

Since it is working so well now, could you time it from zero to 60? I think that most here would be familiar with the common times and what they feel like, it would really help me understand the performance level.

I love reading about this project. If you ever take it apart to tune/repair it, it would make a great picture essay.

It's got me looking at scooters very differently...


Katou

I will do a timed 0-30mph and also a timed 0-max mph when I get the chance ( may even offer my son inlaw to have a bit of a sprint race which will be good for comparison as he has a de-restricted 50cc scoot that he thinks is fast )
Scoots are great fun, very easy to work on and ride very well ( not like the old days ). I just wish more people will cut them some slack.