[EricH]

Originally Posted by Joe G.

Set things up so that your gearbox behaves like a single speed gearbox through one of the ball shift gears, and bolt the other gear to the shifter's frame.

Or set a third gear in contact with both the gear you don't want to use and the gear it connects to. That'll stop motion on that side for sure. (Ever see a gear try to rotate two ways at once?)

If you have a linear force along the inner shaft, you might bend something, but I doubt you'll break it via torsion. Might get a little bit of bending, though that shouldn't be too bad of an issue.

Probably a better way to handle braking is to have something rigged--servo or pneumatic cylinder or electric solenoid--such that when the brake is activated, a pin is shot through a hole in some solid frame member, through a hole in a gear or other rotary part, and through a hole in a solid frame member immediately opposite. Now, that might be a little more complex than just locking the gearbox, but I think it might address the concerns about the pin in the ball shifter.