Re: Custom Two Speed Gearbox
 

Can you please elaborate on how I should go about ensuring that I design the high gear to slip at stall?

Are there formulas/a calculator/white paper that somebody has written describing this phenomenon?

I'm using Blue Nitrile Tread from McMaster. However, I do not know the coefficient of friction.

Thanks

Re: Custom Two Speed Gearbox
 

If you're designing the wheel to slip instead of stall, the force the gearbox can exert on the ground through the wheel should exceed the maximum frictional force that the ground exerts on the wheel. The maximum gearbox force is a function of the motors' torque at stall. The maximum frictional force is a function of normal force (itself a function of weight) and frictional coefficient.

If you're designing the gearbox to always shift into low in case of a failure, you should characterize the possible failures and try to deal with them. This isn't easy for shifting mechanisms that don't return to a home position (e.g. servos) during a malfunction, and is also difficult if you can't walk up to the robot to override a malfunctioning valve (which you can't, at least not during a match). Since redundant actuators and control channels aren't really feasible under most circumstances, taking this design approach will invariably lead you to compromise—but that might be good enough.

John V-Neun wrote one, and has updated it over the years. It's very useful. Others have written similar tools (like this and this), but I haven't tried them.

Probably about 1.0 on carpet (an educated guess). See here for a bit more information.

Re: Custom Two Speed Gearbox
 

Any type of roughtop seems to be more like 1.2 to 1.3. I would try to ere on the side of caution rather than pushing things so definitely use the higher coefficient of friction.