electric bicycle as college project, couple of questions

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May 6, 2011
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Hi everyone i'm new here and hope this is the right section to post in.
I will be converting a bicycle into an electric one for a college project but would like it to achieve around 40-45mph if possible. I have been thinking of using a motor such as a Turnigy 80-100 130kv from Hobbyking or similar and possibly running some sort of reduction drive as i've seen a project on here using a pocket bike gearbox as a form of reduction. For real performance, well speed i was thinking of using an ETEK motor or one of the variants but these are really out of my price range considering the other costs for batteries, controller etc and i can't seem to find any here in the UK. I would like to steer clear of the hub motors as thats why i would like to make my own bike electrically powered by other means.
If anyone has any suggestions regarding motors etc to achieve the desired speed that would be very much appreciated.

Thanks, Evan.
 
I would be wary of the pocket bike boxes, I have been messing with them, and they are not up to the power level you are looking for.. Barely enough strength for my little 1500 watts at the moment...
 
[youtube]h_C73KjQUt0[/youtube]
that's on a 9c, cheap as hell; 100$ motor on sale in a closing sale. it's just at 100v with lipo on a good controller. unless you specifically want to fiddle with machining and belt/chain lines and tensioner, why not just get a hub motor?
 
Andje said:
unless you specifically want to fiddle with machining and belt/chain lines and tensioner, why not just get a hub motor?

Perhaps he's a tinkerer like alot of the rc motored non hub useres ;)

The turnigy motor is the same i use in my bikie it will get you to the speeds you want and then some if you gear it too.

IN regards to reduction drive if you want something 'off the shelf' and ready to
bolt straight on ES Forum member Recumpence does fantastic CnCed reduction drives
mounting hardware slipper clutches sprocket addapters ESC and throtle kits it is spendy
but its bloody good gear of highest quality Matt has a very good rep on these forums i
have dealt with him many many times myself and highly recommend his gear.
The drive units are specifically for such motors as the Turnigy and 3220 Astro inrunner motors is another
option if you cashed up, they are of higher quality than the Turnigy.

Best of luck and welcome to the form :)

KiM
frock motors are underpowered crap; frock motors bite; frock motor = major fail; feed Google botz feeeed LoL
 
sounds like fun, but i would talk it over with the teacher first, because doing a nice rc powered rig that you are happy with (or for me to be happy with anyway) is a huge amount of work. even a larger project for final year students, so be aware that a rc build could be far more than you need, you may well get away with doing a hub motor and custom making a battery box, holders, etc. What course are you studying?

I wont lie, an rc build would be awesome, running it single speed on the left side would be far easier than a through the cranks setup, but wont have the gearing, like the hub motors. I would be willing to send the cad files for my bikes reduction over, v3 should be done in 2 weeks or so, as i finish my assessment this thursday. Then a simple modification to fit your bikes geometry/project and you should be running, or use as a base to design your own. Be aware of the costs too, a turnigy motor, controller of some description, lipo (sla's suck, dont bother), plus various odd parts.
 
Thanks for the help everyone, i would like to do an R/C setup rather than a hub motor purely for the reason that there aren't many out there and hub motors are the most commonly thought of idea when it comes to an electric bicycle in my opinion. I'm currently studying a level 3 National diploma in Engineering course and i was able to chose any project to do. I wouldn't mind just running the chain to the back wheel but then where do you find sprockets the right size for a direct sort of drive arrangement? I would imagine they would need to be at least 70 tooth + sprockets for the rear wheel. I have around £400-£600 to spend on this project, do you think i can get my bike to do lets say 35-40mph for this price including batteries etc?
I would like it to go faster but this seems a little more do able with the choice of motor. I've seen some kits (cyclone i think) where they drive straight off the crank with no reduction system.

Bandaro: that would be great if you could possibly send over your reduction system, i'll take a look at your build thread as i'm not sure i've read through it. I've read most on here and some of them are just fantastic with the amount of fabrication work.

Whiplash: Yeah i read about the problems your having, i would have thought they would have been ok unless you really overload it on acceleration?

Thanks, Evan.
 
are you buying a bike too? a bike that will be strong and stable at 40mph will not be cheap. For those speeds you really should have at least a front disk and some sort of front shock as well imho. with only 1200 $ to spend i would have said you could do it, but not if the bike is in the budget too...

I recently activated my regen braking on my hub motor, and it makes a HUGE difference to your stopping power at those speeds; no skidding, just the feeling of something like an anchor being chucked out behind you. Something maybe to consider.... I certainly feel much safer now that it is working.

there are no direct drive bolt on rc sprockets. there are large lexan ones available somewhere, and many people have made their own, but by far the most common rc setup is with a staged reduction drive. If you can do some simple machining and welding fabricating a crude reduction is easy. otherwise i would be searching for a 70+ tooth as you say.

the cyclone kit is a garage door opener motor, plenty of torque but it spins about 10% the rpm of an rc motor; that's why those kits are designed to drive the bottom bracket, so that you can gear it back UP using your derailer. The problem is mostly that the bearings in the chainring are not designed to take the side load that the cylcone style mount dishes out, and they tend to seize over time.

i am personally surprised no one has yet combined a slipper clutch and a pocketbike gearbox; matt schumakers slipper clutches have solved many problems in the rc drives, and as you say the gearboxes which are perfect accept can't take the peaks would thus be protected. Basically, they can't take it, you do end up overloading them under acceleration.

you haven't given us a distance/time you want to be able to ride; going 40 mph takes most people about 3-5k watts, so i would assume you run at 48v and thus you'd want at least 125 amp from your controller. Battery wise, 48v 5ah (minimum, this is two 24v 5ah lipo's in series) is going to last about 3 minutes at those discharge rates. So multiply three minutes by the number of batteries you can afford, or divide the amount of time you are going to be cruising by three.
 
Andje: I have got a basic front suspension bike but not with a disk brake, about 2 years ago i made a petrol powered bicycle and it used a midi moto 49cc pull start engine and achieved a genuine 41mph in the 1st gear of the bike (gearing was way too high), this bike had no suspension and no disk brakes so i feel the bike i intend on using will be ok for a couple of demo rides etc showing the bike off.
I was thinking of using 48v to power the motor, does anyone have any ideas where to buy good quality batteries from? (sorry for all the questions as i'm not that clued up on the batteries and controllers). So i need at least a 125A controller, there is a place called i think 4QD here in England so i may give them a try. Yes a slipper clutch could be a good investment, but if your not too heavy with applying the power the standard pocket bike gearbox i would have thought will be fine for me. After all i don't want it to wheelie :)

With regard to distance, i was hoping for around an 8-10 mile capability so around 14km but this will not be all flat out and can include pedaling especially to get up to a slow speed before engaging the motor if needed. My specification is just for speed and not distance, so it's sort of a sprinter if you like.
Can the Turnigy motors use sprockets compatible with most sprockets or infact the freewheel cranks? There is a lathe and cnc machinery at my college so adjusting some to fit won't be a problem. I'm also good at welding so no problems there.

Evan.
 
hobbyking for batteries; you will want lipo for what you are doing. the people who have tried the gearboxes have eventually stripped them no matter how careful they were, but if your not after longevity you might be fine. the good castle creations controllers are expensive, but once you add caps they are very good at doing what you want to do; some people have had success with off brand controllers but more of them seem to fail. i defer to the aussie in all matters rc as i have no build of that kind, meerly extensive read knowledge.
 
I only know 4QD for their brushed motor controllers. These are set up for wheelchairs, very efficient and robust, but a bit pricey & no use if you want brushless.
& to be honest their voltage mode control system is not ideal for an ebike. AN electric scooter controller would be cheaper, more convenient and behave better.
Where are you in UK? - you're welcome to drop in if you're nearby & see my various projects ;^)
 
Well i may use a pocket bike gearbox or possibly construct my own reduction system as they don't seem too difficult if using say belts and then a chain setup to the wheels/crank.
I haven't really looked into 4QD controllers that much so didn't realise they weren't for brushless motors, i have seen similar controllers to electric scooter ones used on some project bikes as they are relatively small if i'm thinking of the right ones. I take it they still have the ability to allow use of a twist grip type speed controller?
I am located in Norfolk so Kurtsford is quite a treck for me. I've noticed the Turnigy 80-100 130kv and even the 180kv motors are out of stock at the moment from Hobbykings, so i was wondering if there is any supply of them in the UK or a similar quality and power motor?

Evan.
 
not sure about UK suppliers, but i doubt you will find them for that price. HK is really cheap because they are so big and manufacture them themselves, my hobby store has started stocking very similar gear, for about 2-3 times the price. New stock is generally 3 weeks or so, and there is a lot to do before the motor needs to be bolted on.

Dont know where the people get them, but the sprockets for a direct drive are best bolted onto the disk mounts on a rear axle, so getting a new rear wheel could make it easy, alternatively my friend has one of those Z box petrol motor kits, that sprocket has some dense rubber padding and clamps onto the spokes. its the 66cc and makes about 1700w on peak i think? after plenty of use the spokes are still straight.

I would stay away from the gearboxes, as for their price they are no where near reliable enough imo. spend 150 on a box or 50 and make a belt-chain and you get the exact reduction you want, easy to replace worn parts, and stronger. Not to mention you get the shape you need... I assume you have a fully decked out workshop at your disposal to make the thing in being a engineering student? this makes things much easier :D

Would be happy to upload the cad, just let me get the parts (should be here by now...) to get the exact chainstay spacing and give it a test first, dont wanna upload something with flaws. Also, have not made a thread as of yet, hence you have not read it... ill admit, i was unable to, then lazy and then busy, but i should be able to get one up post friday.
 
Yeah there is a machine shop at college so any work on a lathe etc could be achieved. I been thinking of getting a disk braked rear wheel to bolt the sprockets onto for a direct drive, i think i may go down this route as it seems a bit more easy and that way i can make my own reduction system. I have been thinking of using like a 36v 500w or possibly 1000w motors as found on some sites but have doubts on whether they're powerful enough because surely not everyone uses Turnigy? Regarding the CAD will you be uploading it to your build thread that you'll be making soon as i could just take a look at the pictures on there and see what it's like?

Evan.
 
Ill probably just include it in part of my build thread, then if anybody wants a closer look i dont have to answer questions. good luck with the bike, a direct drive with a belt then chain on the disk mounts shouldnt be too hard, first model would work well, probs wouldnt need a secend version :D

But yeah, continue reading around, plenty of info on here, some people here really know their stuff.
 
I've been thinking of using one of these electric motors, 48v 1000watt and i think used for electric scooters. Would it be suitable if a reduction system is added to achieve a good speed or are they just not that powerful? I haven't found many people using these motors, only on youtube bikes. So if anyone is using one it would be great to know how it performs.
Heres the link:
http://www.petrolscooter.co.uk/catalog/product/view/id/8186/s/electric-motor-36-volt-1000-watt-11t-8mm/

Evan.
 
Evan, I like the project that you've chosen. It is a great way to do something about the uncertain fossil fuel future, and it is fun as well.

Though a brushed motor can't be pushed to as high of limits as brushless, reach as high an efficiency and as high a power to weight weight ratio, I have had fun with my brushed one.

The stall torque tends to be high and it and the very low speed torque is smooth on brushed. The thing that I have enjoyed most is that it is much easier to use analog circuitry to control how the motor behaves, and I like analog and never have been attracted to working with digital. I have built a controller with discrete parts, and that is enjoyable to me. It operates with current mode feedback, which I have found to be a good way to get overload protection as well as to get a good throttle feel.
 
basically we have all moved on from brushed because they eventually wear out and cannot be pushed anywhere near as far as brush less. it's not that it doesn't work, you're just buying the year 2000's model.
 
Well i would like to go down the brushless route but the only problem is Turnigy are out of stock on most of the good powerful motors so thats why i turned to the relatively cheap and powerful MY1020 motor (48v 1000w). I was wondering what controller and throttle control to use, i was thinking something similar to these electric scooter ones:
The cyclone type twist throttle, but would it be able to be wired to any type of controller?
http://eclipsebikes.com/electric-bike-twist-throttle-p-985.html

For the controller:
http://www.electricscooterparts.com/speedcontrollers48volt.html

Any help choosing a suitable controller for this type of motor would be of great help. I'm not after massive speed and thats why i have chosen this motor. As long as it will hit just over 30mph i'll be happy and it doesn't really matter on the distance either. Think of it as a kind of sprint bike, to be used in quick rides.

Evan.
 
all the stuff you have listed is compatible; there are threads for adapting cyclone throttles to just about every controller. i would guess that motor will have no problem hitting 30 mph if properly geared. You may not need a reduction system for this one though; the rpm is so much lower you may be able to get away with small sprocket big sprocket reduction. If not, then when you are fabbing the reduction i would build it with a potential swap to a turnigy engine in the future in mind. I would highly recommend running the motor through the gear cluster like a cyclone kit so that you get your gears with it. Others do not like it and claim that side load on your mid crank will eventually destroy freewheels, but i put 1000's of km on my gas bike with that system no problem. You will have to fab a really good mounting system for the kind of torque this motor will generate, but as you are doing it a s a school project, that piece will actually be ideal for your machine shop work i would suspect. Or you could weld tabs to your bike and mount the motor directly, many people have pulled off very professional looking setups with welded tabs and a quick paint job.
The difficult part with this style approach is always chain lines/ tension and just chains coming off in general, twisting motors when under torque due to an inadequate mount (usually leading to chains coming off but sometimes mount failure), proper reduction (if necessary), freewheeling so the motor isn't dragging while pedaling or while moving the bike around, and finally failure under high power overvolted scenarios.

Oh, and on page one you say 40 mph... even 30 mph is still pretty much top 30% "massive" speed. Not everyone wants to go as fast as that.
 
Andje said:
even 30 mph is still pretty much top 30% "massive" speed. Not everyone wants to go as fast as that.

no, but speed is also whats fun. and what kills you. and what makes you manly. So thats 2:1 in my books :D

most controllers will fit directly onto most throttles so this will not be a problem. All the bike/scooter throttles bar a few use the standard, 5 bucks on ebay hall effect throttles. The controllers will say if they fit hall effect or potentiometer (pot) throttles, pretty much all gear you will find is hall effect. If you need a pot throttle, you can either get a maguira (expensive but quality is high) or a regular hall effect and a servo tester from the rc world, plenty of tutorials about rigging a servo tester in there, and its not difficult.

as for brushed, i wouldnt, because while they will power it fine, are cheaper and easier, the brushless will do it all much better, stay cooler, run longer, and low maintenance. there is cad models of most of the popular turnigy motors in the parts repository sticky so you can get the drive started before the motor arrives if need be.
 
Andje said:
you haven't given us a distance/time you want to be able to ride; going 40 mph takes most people about 3-5k watts, so i would assume you run at 48v and thus you'd want at least 125 amp from your controller. Battery wise, 48v 5ah (minimum, this is two 24v 5ah lipo's in series) is going to last about 3 minutes at those discharge rates. So multiply three minutes by the number of batteries you can afford, or divide the amount of time you are going to be cruising by three.

Are the discharge rates really that high on RC motor setups? Is it due to them usually running lower voltage, because compared to a hub setup that seems REALLY high discharge rate. Like most other hub guys I can run 40mph for about 10 miles with a 89V 10AH pack.

I thought RC setups did better watt/mi than hub/frock motors did? I love the idea of being able to drive through the gear clusters myself, but know I don't have the mechanical ability to build one. I also thought about all the stress it puts on a bike... I'm also lazy and wanted something I could ride soon vs building. I'm still learning about though because having selectable gears is very nice.
 
I wonder how much rap that brushes get really is true when it really gets to the bottom line. I've just seen brush failure twice. Once was when an alternator failed after a hundred thousand miles or so and the other was an electric lawnmower that failed because it subjected them to huge ampere surges due to use with instant electric braking. And I'm not sure about the alternator case. I almost always hear of the complex controllers for brushless motors failing and never heard someone say that a brushed motor they had failed.

My present brushed motor has been in use for about 15 years on my ebikes. It's basically a good motor and hassle free. In a pinch, i could just about hook an on/off switch to it and get by, though the instant torque in that case is pretty destructive to drive train components.

True, in theory, they are a weak point with potential failure. But in practice their advantages can be very attractive, depending on the wants and needs of the user.
 
Thanks for all your help everyone. Yeah i know i said i would like to do 40mph+ but now i'm thinking realistically with budgets and after all, it's a college project so improvements can be documented and acted upon at a later date if need be, so as long as it does 30, maybe 35mph if i'm lucky :) then that would be brilliant.

Solcar: which motor are you running and is it capable of good speeds?

So i can get away with using the hall effect throttles and those scooter type controllers, after all i think the motor is a scooter one anyway. I am still hoping to use the turnigy 5000mAh type batteries to power this motor, so combined it would be a 44v/48v supply. I'd imagine these would be ok rather than using SLA's. I know cells like the A123's etc would be far better in terms of useage and reliability but they're a bit too expensive at the moment.
I've seen the freewheels on some builds get destroyed like when in use with an ETEK motor but i'd imagine thats because the amount of torque and acceleration it produces.

Evan
 
about 15 years ago, I bought some of the Pittman motors mentioned in post #9 by cyclops2 http://www.rcuniverse.com/forum/m_3984455/tm.htm# . I've been using the first three that I unpacked on various ebike projects since then. A well-designed brushed motor can come in quite handy.

I haven't yet tried it greatly overvolted. I recall hooking it up on my bench to the controller that I made from scratch and relatively few parts, by comparison, and then pushing up the throttle up to place about 28v across the motor. That should have been at about 5000 RPM. That controller takes the 12v from a battery and can at least double it. Buck and boost converters can be fun to make as other do-it-yourself things can be.

I can't say it could get a bike up to 30MPH without pedaling. A few times I got up to almost 40MPH, but I was pedaling furiously. It's not a big motor compared to regular ebike motors, maybe only 1/4 the size of that one you linked to earlier. I take into account that it likely won't spin up as fast as a motor with a stator as opposed to an armature, but I might get to trying it at 7000RPM sometime to see what happens.

I wouldn't mind sending you one for your project, but by the time you got it, the delay could be considerable since i do things pretty glacially here, and I don't think they have been on the market for quite a while, now. It would be better in your case to use something that you could get a spare for if needed.

Good quality brushed motors have been made. The effort up front by the manufacturer in this case can pay off in convenience later.
 
Thanks for the info, 40mph is good even with pedaling! That controller you made sounds very tempting if it doubles the input voltage to the motor. I may look into this further. As for the motor, i'll probably stick with the one in the link as i can get it here in the UK, so parts availability shouldn't be too much of a problem.
Now i have a question regarding freewheel kits, i can get the cyclone type with a Dicta freewheel but was wondering what pitch chain would run on the sprocket for the motor to be attached to? The sprockets for the MY1020 motor are either i think 6mm or can be 8mm pitch as used on minimotos? I suppose i could graft another sprocket onto the motor shaft if needed though.

Evan.
 
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