pic: Stripped VexPro gear

[TheModMaster8]

Originally Posted by Mechvet

We blew every tooth off of two of the VexPro 14tooth 3/8 hex gears.

Turns out aluminum gears just aren't quite rated to the level of impact we were subjecting them to.

those gears are made out of 7075 Aluminum which is as strong as many types of steel, thats one impressive feet lol

[Mechvet]

Originally Posted by TheModMaster8

those gears are made out of 7075 Aluminum which is as strong as many types of steel, thats one impressive feet lol

"Strong" is a rather non-precise word for material descriptions.

Steel and 7075 may have similar load capability and shear strength, but when it comes to a sudden impact (ie a 145lb robot at ~12fps slamming into a barrier), the more brittle aluminum gear doesn't stand a chance.

[pilleya]

Originally Posted by TheModMaster8

those gears are made out of 7075 Aluminum which is as strong as many types of steel, thats one impressive feet lol

In comparison with 4140( normal steel gear material) it has a higher yield strength, but a lower ultimate tensile strength. It also has a much lower %elongation. The percentage elongation means that it can't bend and deform as much before it fails

http://www.wcproducts.net/how-to-gears/

[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)