Originally Posted by turbo1889

At least those are the ways I know of to do it via a roller drive chain (I'm not even counting those cheap nasty sprockets that just bolt to the spokes where they cross on the left side found in the cheap junk gas motor kits that are a good way to mess up a rear wheel fast).

There is also the possibility of doing a friction roller drive that torque pivots into the rear wheel when engaged but that isn't the best option for a hill climber helper ONLY motor set-up because of the high torque levels at low speed that are usually involved. Same goes for putting the set-up on the front wheel, unless you have an incredibly beefy front fork the torque loads of a low speed but strong deeply geared down set-up are just too high.