ATV electric conversion: final part (or not)

This project has been on hold for a while, mainly due to me being incredibly busy with other things. But finally I found time to put this together and test it. But not without one final modification which I a bit dreaded from get go.

The rear sprocket I originally had had 54 teeth, and combined with motor's 11 teeth this gives relatively low down gearing. I feared that this might cause issues getting the ATV moving as motor might not be able to generate enough torque to get moving.

It certainly wasn't powerful enough to move me, even on perfectly flat terrain, but with kid's weight this wasn't too bad an issue (as we tested outside) but I wasn't too happy with it either. This ratio also gave me theoretical maximum speed of 30 km/h, which I deemed a bit too fast for comfort, even if it could not realistically be reached in real world.

So I ordered new chain and rear sprocket, this time with 68 teeth. This dropped max speed to 20-ish km/h (according to my notes, it's been a while since doing the calculations) and gave nice boost to zero-speed torque. It isn't exactly powerhouse still but it should move nicely in slightly uneven terrain too.

Time for test drive!

Well, it worked. For a while. Then, as battery was getting near-empty, kid tried to drive on upward slope on wet-ish mud, overloading the engine and eventually burning it out. So my fears about gear ratio were completely justified, but mitigation with larger rear sprocket was not enough.

Back to the drawing board.