wow, that sound's like such a great idea! i've been wondering about that, it actually sounds a bit simpler than i figured it would be lol

In my opinion the best way to wire this would be to have the magnet engage while the throttle is pressed. This would make the most sense because the coil could be wired derectly to the motor leads. The only problem that I see is the magnet may have negative effects on the motor. As close as it would have to be to the can may weaken the magnets in the little bugger.

Off you go...

U could make ur own coil from the thin wire, and either wire it in paralell to the motor, or put the coil in series with the motor lead.

But the resistance might rob the motor power.

Or use a transistor to switch on the coil when forward is engaged. May need an additional cell.

There would need to be a spring that would keep the gear from meshing with the other gears. Dont forget that there needs to be a peice of steel for the coil to pull on to bring in the gear. Now I'm wishing I hadn't cut up my last clone chass for my plane project.