Automobile starter motor to power bicycle?

[Mr RB]

Yep, and it's not just the weight of the generator and batteries, the generator will be a narrow diameter rotor meant for high RPM.

On a bike that will need lots of gearing, and every bit of gearing is more weight and more energy drag.

This is a technology that has been greatly improved with motors of a size, RPM and torque all suited for electric scooters and bikes running with good efficiencies.

Derstrom, I respect that you wanted to use common local sourced parts etc but I still you should look at these new EV motors, here's one at $39, 300W 24v and comes ready to attach a small chain;
**broken link removed**
https://secure.oatleyelectronics.co...d=665&osCsid=9b1519768b8c2542dae7da67ac2e05e0

The motor is 100mm in diameter. I can't see $39 for the motor as being expensive, it will save you at least $39 in battery cost, and a generator might cost $39 from a wrecker anyway.

 

[DerStrom8]

Derstrom, I respect that you wanted to use common local sourced parts etc but I still you should look at these new EV motors, here's one at $39, 300W 24v and comes ready to attach a small chain;

The motor is 100mm in diameter. I can't see $39 for the motor as being expensive, it will save you at least $39 in battery cost, and a generator might cost $39 from a wrecker anyway.

Hi Mr RB

That motor is very tempting, actually. You say it is 100mm in diameter, which seems like a good size. I might consider buying it if it was $39 solid, but I imagine it would cost at least half again that price for shipping. I am not prepared to pay over $50 for a motor--that is why I was hoping for a very cheap solution. I appreciate the idea, though. Do you have a link to the site? I would appreciate it.

 

[cr0sh]

In any discussion about going el-cheapo on electrifying a bike - one must post this picture:

https://inhabitat.com/crazy-diy-bike-runs-with-electric-drill-and-car-batteries/

Have you ever thought about using an electric drill?

Ok - maybe the above is anything but efficient (or safe...or sane?) - but it does show that where there's a will, there's a way, I suppose. While I was trying to find that picture/article (saw it a while back), I was GIS'ing "electric bike from junk parts" - and finding even more of these strange homebrew contraptions...

TBH, I have such a contraption on hiatus in my shop - so I am somewhat familiar with the urge; mine was going to be a custom recumbent with a 14 inch front wheel (from a child's bike), and a 26 inch rear drive wheel (from an adult bike - both bikes were from yard sales). I chopped both up and rewelded the frames together for a recumbent frame, and added a cheap plastic boat seat from Walmart. I was originally planning on using a 90 volt ball-bearing brushed DC motor w/ a 1/2 inch shaft - it had a lot of torque even at 12 volts (and I was going to run it with a high/low switchable 12/24 volt battery pack); I had a sprocket machined down (face ground) to fit the bicycle chain. I never actually got it put completely together because I was/am seriously doubtful that such a machine could take me the distance from my home to work and back (about 30 miles) on a single charge, given the weight of the bike, the batteries needed, and my fat butt (I weigh over 200 lbs).

Recently I've been giving thought to going with a small bike engine instead - the only issue I seem to be having a problem figuring out how to get around is the fact that all of those engines are gravity fed, and the only spot on my current bike that would be higher than the engine would be directly behind my head (I'm not sure I want a tank of fuel right there). Right not, though, the whole thing is "up in the air" - though with gas prices the way they are, I might just get back to work on it soon again!



BTW - another motor to think about might be a DC motor from a treadmill (I think that might've been the kind of motor I had)...

 

[DerStrom8]

In any discussion about going el-cheapo on electrifying a bike - one must post this picture:

https://inhabitat.com/crazy-diy-bike-runs-with-electric-drill-and-car-batteries/

O.O

Have you ever thought about using an electric drill?

As a matter of fact, that was actually the first type of motor that I considered. I soon found out, though, that all the drill motors I have are not powerful enough, and the ones that would work are the 36v drills, which are rather expensive :/

BTW - another motor to think about might be a DC motor from a treadmill (I think that might've been the kind of motor I had)...

This was also one of the first types of motors I thought of using, but I recently found out they generally run on 130vdc. I have no idea where I could get a 130 volt DC power supply, so that almost instantly eliminates that option

UPDATE: I found someone who is willing to give me an old generator from a VW Super Beetle. All it needs is a set of brushes, which will only cost a few dollars. Definitely worth it, IMO. What do you all think?

 

[cr0sh]

As a matter of fact, that was actually the first type of motor that I considered. I soon found out, though, that all the drill motors I have are not powerful enough, and the ones that would work are the 36v drills, which are rather expensive :/

If you take a closer look at what that person did, the drill was a corded AC machine - so they ran the batteries thru an inverter, then to the drill. It also appears that two motors are used, one for the right front wheel (the drill), and one for the left rear wheel (what it is, I don't know - maybe another drill?). That's one bodged machine!

This was also one of the first types of motors I thought of using, but I recently found out they generally run on 130vdc. I have no idea where I could get a 130 volt DC power supply, so that almost instantly eliminates that option

I found a different treadmill motor that had nearly the same specs as what you've seen - it ran fine on 12 VDC; I'm sure at 24 or 48 VDC it would be even better (which would probably be the upper limit of batteries you could haul anyhow). It had a lot a of torque. Also, both that motor and the one I originally bought were both PM motors - the first one needs new bearings, but it is a b**ch to get back together once apart, because the bolts which hold the end-plates together are made of steel, and pass between the pole gaps of the magnets (!) - and the bolt is only long enough to join the plates, so by the time you pass it to the other end, you are "guiding" it by the head of the bolt, trying to hold it off the magnets while finding the hole to thread into. If anyone here has a good way to make this easier, I'm all ears!

UPDATE: I found someone who is willing to give me an old generator from a VW Super Beetle. All it needs is a set of brushes, which will only cost a few dollars. Definitely worth it, IMO. What do you all think?

I say go for it - even if it doesn't work for the current project, maybe it will work for the next? You might want to have the bearing inspected and replaced while the brushes are being done (maybe even have the commutator resurfaced?); couldn't hurt.

Something I found when I went searching for a sprocket for my bike (the motor had a 1/2" shaft, as I noted before) was that finding a sprocket to fit a 1/2 inch shaft that would also fit bike chain, and have the fewest number of teeth (for highest gear ratio and torque - to move my fat butt, see) - it wasn't to be found. I had to purchase (from Bearing, Belt and Chain - see if a distributor is nearby, they're a great place to get parts), IIRC, a #420 sprocket for 1/2" shaft (it had a setscrew for mounting it), and I took it to a small machine shop here in Phoenix to have it face-ground on a lathe to the width of the bike chain; while such a sprocket has the same pitch as bike chain, it is wider, so I needed to make the sprocket thinner. They did this, and it was on a weekend (and a walk-in), but because of the small size of the project, they gave it to me for free (and told me to bring in a larger order next time - even so, they said for the work, it would've been about $65.00 - but the liked the idea of the project, so talk it up a bit as you shop, you might get a deal). If you have something like this done, make sure they re-chamfer on the teeth on the sprocket, otherwise you might have issues with the chain climbing or binding on it.

 

[Mr RB]

DerStrom, that motor photo I posted has the link directly under it. They are an Australian supplier but I'm sure the motors come from China etc so you can probably source the same motor on Ebay direct, and maybe cheaper.

That bike in post #23 is very cool! I looks like he discovered he couldn't weld to the chromemoly frames, so they are held together with cable ties and sticky tape!Quality vehicle engineering!

Cr0sh, why not make the bike hybrid electric with a tiny 4-stroke RC 'plane engine driving a small DC generator? You can get 0.5hp engines about the size of your fist that should give 250w from the genny, 24v 10 amps or so. Series hybrids can be really fuel efficient as you run the motor/genny at a fixed RPM for peak efficiency and it can charge the batteries autonomously while you shop or work.

 

[KeepItSimpleStupid]

Back in the 60's or so I remember an article bout building an electric bike. It suggested to borrow some parts from a starter and a GENERATOR and turn the generator into a motor.

 

[cr0sh]

Cr0sh, why not make the bike hybrid electric with a tiny 4-stroke RC 'plane engine driving a small DC generator? You can get 0.5hp engines about the size of your fist that should give 250w from the genny, 24v 10 amps or so. Series hybrids can be really fuel efficient as you run the motor/genny at a fixed RPM for peak efficiency and it can charge the batteries autonomously while you shop or work.

That sounds like a good idea, and I plan on doing something like that for a future robot - but I am not sure how well it would work for a bike, at least in my situation - when I get to my work, the only place I can store the bike is inside our office - its a sketchy neighborhood, and I wouldn't want to leave something like that outside. I've been thinking about this some more, though - and I'm waffling back to an EV, but it seems that if I am going to be able to manage it, I'll have to have a very beefy frame and some large SLAs, and in some manner have three packs in rotation; one on the bike, one charging at work, and one charging at home. Something that I've had a question about for a while, though - and have only found conflicting information online - is whether you can charge SLAs using an automobile battery charger? I've read you can't, because they use a different charge curve, and run at 13.8 volts during the charging - and that you shouldn't do this to SLAs? On the other hand, I've seen claims just the opposite...

Anyhow - I don't think the frame I already have is going to be cut out for this sort of thing, but I've been giving thought to a frame made out of steel "gridbeam" (I wish I could find the aluminum equivalent, but I haven't had any luck so far), using one of the DC motors I have, and coupling it thru a right-angle reduction drive I have. Maybe I'll return to this idea when winter rolls around, or I get bored or something...

 

[DerStrom8]

DerStrom, that motor photo I posted has the link directly under it.

Oh, I didn't even see that!
Thank you!

 

[DerStrom8]

Well guys, I'm thinking of just taking off the pedals of my bike to make room for other parts. I guess I'll be powering it just by motor. Otherwise, I wouldn't have room for anything else. Just thought I'd let you all know

 

[crutschow]

The obvious negative with using a car generator (or starter) as a bike motor is that it requires field current, which likely makes it less efficient then a permanent magnet motor, which doesn't. And I would think efficiency is a very (if not the most) important consideration for the motor of a battery operated vehicle.

 

[KJ6EAD]

Instead, I will be welding a sprocket to a sort of "flange" (not the right word, but you get the idea ) on the rear wheel.

The word you were looking for way back on post #11 would be "bracket" I think. That is the extent of my weak contribution to this thread. The efficiency of a bicycle is largely dependent on keeping it light. Once you start adding motors and such, it's not really a bicycle anymore except in the defining characteristic of having two wheels.

 

[DerStrom8]

The word you were looking for way back on post #11 would be "bracket" I think. That is the extent of my weak contribution to this thread. The efficiency of a bicycle is largely dependent on keeping it light. Once you start adding motors and such, it's not really a bicycle anymore except in the defining characteristic of having two wheels.

No, it is not quite a bracket. It is more like a short tube, attached to the side of the rear wheel. However, if I take the pedals off like I suggested, it eliminates the need for another sprocket on the back. I will simply connect the motor to the "pedal" sprockets. This is probably the easiest way to do it, anyway.
I have seen lots of videos of people who have done this sort of thing. I think it will work very well for driving the short distances that I would need it for.
Thank you for your contribution, KJ6EAD

 

[tcmtech]

I don't see a problem with using common old style DC generators as a motor being the field excitation current on most of those is around 1 amp give or take. Just have a relay supply power the constant 12 volts power to it when the throttle is applied and use the PWM circuit to drive the armature windings.

As far as PWM goes a simple 555 IC driving a common 100+ amp IGBT or Mosfet switching device would be plenty sufficient power wise.

Regarding gearing you may likely end up putting the large drive sprocket on the back and the small one on the generator being they run about 10 -20 times faster than what the rear wheel spins at. Pedaling is low RPM high torque. Motor drive is high RPM low torque for the same given power output.

Just a few things to consider.

 

[DerStrom8]

I don't see a problem with using common old style DC generators as a motor being the field excitation current on most of those is around 1 amp give or take. Just have a relay supply power the constant 12 volts power to it when the throttle is applied and use the PWM circuit to drive the armature windings.

As far as PWM goes a simple 555 IC driving a common 100+ amp IGBT or Mosfet switching device would be plenty sufficient power wise.

Regarding gearing you may likely end up putting the large drive sprocket on the back and the small one on the generator being they run about 10 -20 times faster than what the rear wheel spins at. Pedaling is low RPM high torque. Motor drive is high RPM low torque for the same given power output.

Just a few things to consider.

Thanks tcmtech. Those are some good suggestions.

I'm afraid I don't quite understand what you mean when you say to use the PWM to drive the armature windings. Perhaps I should do a little refresher course on the parts of a motor/generator

For PWM, I plan to use a uC. I figured it would be a lot easier, and that way I may be able to add a few extra features, like a speed sensor.

As for the gearing, I have a "stack" of six sprockets from the rear wheel of an old 18-speed bike, so each one is slightly larger than the one before it. I plan to put this on the motor shaft, so that I can figure out which one is the right size. Since I decided to remove the pedals, I will be using those three larger sprockets (my bike is an 18-speed as well) connected directly to the sprockets on the motor.

That is where my idea stands at the moment. Let me know if you have more suggestions

 

[alec_t]

I don't think your existing bike sprocket stack will have a large enough diameter. As pointed out in post #34, the motor will need to spin at 10-20 times the rate of the back wheel, so the back sprocket will have to be 10-20 times the diameter of the motor sprocket.

Alec

 

[tcmtech]

On typical DC generator you will have two lugs to connect to.
One is Stamped 'F' and the other 'A'. 'F' is the field winding and is either tied to the case or the 'A' lug.
The 'A' is the Armature or rotating part. In a motor it would be the rotor power input or you can think of it as the Amps lug too being thats where all the power goes in or out of.

Thats about all there is to an old DC generator and as far as PWM goes it all up to you as to how you plan to implement it. I don't do uC stuff so for me a simple and well proven 555 timer IC based PWM system is more than enough.

 

[DerStrom8]

I don't think your existing bike sprocket stack will have a large enough diameter. As pointed out in post #34, the motor will need to spin at 10-20 times the rate of the back wheel, so the back sprocket will have to be 10-20 times the diameter of the motor sprocket.

Alec

Hello, Alec.
I have pretty much decided to just remove the pedals from my bike, which would leave the 3 large ("stacked") sprockets free. I am thinking of mounting the generator (motor) right above these sprockets and connect them using the chain. I will still have the original chain going from where the pedals were to the rear wheel. I think if I use the smallest sprocket on the "stack" mounted to the shaft of my motor, and run it to the larger sprocket on the "pedal stack", the ratio would be just about right. Essentially, I would have three sets of sprockets, so minor adjustments (moving the chain from one sprocket to the next) wouldn't be a problem.

On typical DC generator you will have two lugs to connect to.
One is Stamped 'F' and the other 'A'. 'F' is the field winding and is either tied to the case or the 'A' lug.
The 'A' is the Armature or rotating part. In a motor it would be the rotor power input or you can think of it as the Amps lug too being thats where all the power goes in or out of.

Thats about all there is to an old DC generator and as far as PWM goes it all up to you as to how you plan to implement it. I don't do uC stuff so for me a simple and well proven 555 timer IC based PWM system is more than enough.

Thanks, tcmtech. That clears up a lot!

I've been thinking more about the PWM and I think you're right. It would be easier and cheaper to just go with a 555 for now. I don't really need any special features--just a throttle.
Thanks for the explanation

 

[alec_t]

I think if I use the smallest sprocket on the "stack" mounted to the shaft of my motor, and run it to the larger sprocket on the "pedal stack", the ratio would be just about right

I don't think so. I'm guessing the smallest sprocket is at least 2" diameter and the largest no more than 8". That gives you a reduction ratio of 4:1 tops. You are likely to need at least 10:1 (probably 20:1), otherwise your motor will be operating under near-stall conditions and be very inefficient.

 

[shortbus=]

Unless I misunderstand you guy's, which is possible, you have the gearing backward.

Large on motor, small on wheel is gives a faster RPM at the wheel. If the large sprocket turns one time the wheel sprocket will turn more times, depending on the ratio.

You want the motor sprocket to be the smaller of the two, to gear down the speed.