pic: Stripped VexPro gear

[pilleya]

Originally Posted by Mechvet

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

It only really takes one tooth to break or chip to cause all the teeth to be stripped off the gear, as I believe that the shrapnel causes the next tooth to be clogged and break.

Originally Posted by Mechvet

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

Aluminium gears are usually fine, especially 7075 ones. But if you can, it can be good practise to use 4140 for the smallest gears (isn't a huge weight increase for small gears)

With gears that small there is only a small amount of tooth contact, meaning that the forces aren't spread out over a huge area. Something we found with the impacts of stronghold is that it can cause cantilevered gearboxes( CIM's are heavy and have a lot of inertia) to move up and down, which can mean that in gearbox 3rd stages the amount of tooth to tooth contact can be decreased. Also teams are putting much more torque on them than usual, for example if a team normally uses a shifting gearbox with a 11fps low gear on a year with an open field and 4inch or 3.25inch wheels, and then they change to 8inch wheels and a 6fps low gear, then the final stage is experiencing almost 4 times the torque.

Depending on how you are using it, a 4140 Steel gear http://www.andymark.com/product-p/am-2354.htm might be better for your purpose