pic: Concentric Shifting Transmission Concept

[gburlison]

Lets first analyze what is going to happen to the gear that is engaged by the pins. Looking at your at your diagram the biggest problem that I can think of would be the binding of the pin when you try to shift gears. Assume that the inner rod is shifted to the right and the pins are engaging the green gear to the red shaft. When a load is placed on the transmission, the pin will be bound very tight. Moving the shift rod to the left will not be enough to disengage the pins from the green gear. I can not imagine springs strong enough to disengage the pins. The transmission will have to be unloaded long enough to unbind the pins so that the springs can then move them.

Next lets analyze what is going to happen to the gear that is not engaged. Once again assume that the shift rod is shifted to the right and the pins are engaging the green gear. The blue gear is turning at a different speed than the red shaft. The springs in the blue gear are pushing down on the red shaft with some force. This will cause some friction and a loss of power. Ever half revolution, the springs will press down on the pin and possibly push it in a little depending on how good you machined the pin. This means that the spring might enter the hole in the red shaft a small amount and will either bind up the transmission or cut off the end of the spring.

Like Kevin has mentioned, the solution to the problem of using pins is to round them off until they are balls,