Turning a freewheel around

[NeilP]

I can't get my head around this tonight..too many glasses of red wine, and a guest discussing his plans for a non hub drive folding 'monkeybike' motorbike. Doing this on the cheap..with what he has.



Motor-wise what he has is a small hub motor exactly like this:

Want to drive the original rear wheel front he hub motor..mount the hub motor by its axle to the frame and drive sprocket to sprocket

I already said I am not going to get involved in trying to source a rim, calculate a spoking pattern, cut spokes etc etc etc.It is just not happening..so..the thought came that he could mount the motor in the frame and drive the original motorbike rear wheel via the sprocket on the hub motor..direct to the sprocket on the rear wheel.

Ignoring the gearing issue and what speed it may do for now..also ignoring the sprocket / chain pitch issues.


Now, the issue is the direction of the freewheel..if I just unscrew the freewheel from the hub motor and and flip it and screw it back on..does that change the direction of the 'drive' and freewheel or will if not make ay difference.

I have sat here for an hour or so rotating beer cans against each other trying to visualise it..but to no good..just can't get it this evening.

 

[Rassy]

Neil, it will work in just the opposite direction. If you plan to run the motor in reverse then it will work properly.

On my trike, one option was to run the motor in reverse and wrap the chain over the top of the freewheel, looking at it from the rear sprocket. Instead of running the motor in reverse, I chose to just flip it around, since the motor already had the proper threads on the other side that were meant for a disk brake adapter instead of a freewheel. Then I had to wrap the chain under the freewheel, looking at it from the rear sprocket.

I've run this setup both with standard freewheels and track cogs with no issues.

One reason I choose to flip the motor was because I wasn't sure the phase and hall wires were symmetrical in both directions. A downside to the way I did it is that the wires come out on the same side as the freewheel, which makes it a pain to change freewheels, etc.

EDIT: Hey Neil, I think I got that wrong up above. If you run the motor in reverse, the freewheel would still need to be put on the normal way for a right side drive. I don't even have a wine excuse.

If you run the motor in it's normal direction it will just freewheel if the freewheel is put on the correct way and just unscrew the freewheel if the freewheel is put on backwards. I did think about using a track cog that was somehow permanently affixed to the threads so that the chain could have a normal over the top wrap. I didn't think about flipping a freewheel over so that the freewheel function would still work, but the freewheels threads would still need to be affixed to the hub threads to keep it from unscrewing under power. A lock nut setup like track bike hubs use so they can "brake" with the pedals would prevent the unscrewing.

 

[NeilP]

If it will work, just turning it around, then no need to reverse the motor, as we want it turning in the correct direction.

but these motors to, do have a thread on the other side so turning it around is not a problem if necessary, though can't see what that will achieve

 

[NeilP]

Ah, i see why you talk of running the motor in reverse..you are thinking there was going to be a pedal crank forward of the motor, but no , not in this case..the motor will be as far forward as the chain goes..this is on a folding monkey bike/pit bike motorcycle, replacing the petrol motor with the hub as the drive unit

 

[Rassy]

Okay, I understand the intent. However, the same problem exists, that the freewheel will just want to unscrew. Think track cog instead of freewheel to make it simpler. In fact, since the bike would probably have a freewheel at the rear hub, no freewheel would be needed at the motor. So if the track cog was screwed on and then welded a bit so it couldn't unscrew it should work fine. The downside of course being you couldn't change cog size without grinding off the welds.

 

[NeilP]

No, no freewheel at the rear wheel..remember it is a motorcycle rear wheel not a bicycle one..so it needs the freewheel.

Hell it is a bodge job...i'd find a way to stop it unscrewing ///bloody big hammer and chisel if need be. the way this bloke goes through bikes and odd projects it won't last any way

 

[Thud]

You will need to capture the freewheel to keep it from unscrewing under pressure.

The simple & nearly permeant way is to clean the mating threads & use epoxy at final assembly...when it comes time to remove it, you use heat to break the bond.

A mechanical retainer could also be used if you drill & tap a couple holes to bolt a stop on the end of the anchor stub.
(But i would opt for the epoxy in this senario)

 

[NeilP]

That sounds desperately like proper engineering and not the way the is job seems to be going :lol: