Does high rpm or torque kill drive train parts?

[Desertprep]

I have read many posts on this forum about how to connect very powerful motors to the rear wheel. Invariably I hear of chains breaking or wearing out quickly, gears getting rounded off, etc. Is it the torque from the motors that causes these problems or is it the speed? or a combination of both?

 

[Solcar]

Speed is more of a concern with noise, although bearings getting over-reved can become a consideration.

Indeed, my crank drive endures heavy force which degrades it (gearbox, chains, sprockets, and mounts stress). On the other hand, I am working on friction drive so that I can get away from those high torques but that means some extra consideration has to be given to high RPMs. The advantage I see for friction drive for me might be that the smallish motors I use have to spin fast anyway, so with the drive right at the outer circumference of the wheel, less gearing down is necessary. It's mainly a matter of getting the thing fabricated since friction drive is rare compared to what it used to be and that means less available premade stuff for piecing together.

 

[Whiplash]

In a word, YES. LOL!

 

[Desertprep]

hmmmmm okkkkkkkk To make the rubber meet the road...if using a motor, tranny and chain setup, I am guessing that the chain, the gears and everything else in the rear of the bike will last longer if the motor speed is geared way down (say, to 8 mph speed) in the reduction unit and then sped up with gears in the rear? I am in search of dependability with this question.

 

[REdiculous]

if using a motor, tranny and chain setup, I am guessing that the chain, the gears and everything else in the rear of the bike will last longer if the motor speed is geared way down (say, to 8 mph speed) in the reduction unit and then sped up with gears in the rear?

There's no reason to gear it down to a really low rpm just to gear it back up.....unless you're driving the crank.

 

[bobc]

My experience (for what it's worth...) is that chains are fine until you go over 4000revs - then they throw out all the lubricant. For that reason I always use belts for the first stage from an RC outrunner now. For me the belts are more expensive & trickier to set up but, done right, they last.

 

[hekdude]

In general, wear is based on contact force (which relates to torque and distance) and number of cycles (which increases with speed). A smaller diameter/number of teeth sprocket will have larger forces and wear quicker.

Metal fatigue is also based on force and number of cycles. So it is a combination of both.