To head off the "why not use a bigger motor" question, I'm a high school mentor for an FTC (First Tech Challenge) robotics team, with a bit of a soft mechanical / hardware background. They're somewhat limited in what they're allowed to use, motors in particular. Up to 8x 1.5 ft-lb 12v DC motors, max.
This year they came across the problem of needing more lifting power, which gearing could help with, but to get the lift they needed cost a lot of speed, which in a very short (~2 minutes) competition, was a costly trade off when there was a need to go up and down frequently.
Possibilities I've considered (and haven't had time to mess with yet, but I'm trying to research and get input from engineers better than myself..)
- Having two motors directly driving the same gear on the shaft seems like the first obvious answer, but error prone (slipping out of sync and grinding potentially.)
- Two motors driving two separate pulleys on the driven shaft, which should theoretically gain power without the gear jamming issues.
I'm planning on having the kids experiment and test, but as my ME experience is extremely weak, I'm soliciting input.