[s_forbes]

The material of the gear is not the end-all deciding factor in whether or not it's strong enough for the job. If you stick enough torque on it, you can break anything!

Each stage of gear reduction adds up fast. Whenever we need a gearbox that needs more than 3 stages of spur gear reduction, I start to get a little paranoid. We underdesigned the 3rd stage of our stacking mechanism last year and separated several gears from their teeth when operating it with the braking mechanism engaged.

Always make sure each stage can handle the maximum torque the motor can output, and add however much cushion you think you need. (Then test test test... break it at your shop so you don't have to break it at competition)