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.
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?
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)...
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 :/
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, 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.
DerStrom, that motor photo I posted has the link directly under it.
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.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.
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.
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
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.
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
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