The linkage was very bent and the servo gears stripped when I bought the tank but I don't know if that is evidence of self destruction or because the barrel is the obvious point by which to lift the turret - something to bear in mind with any recoil system
I've just picked up a suitable servo so will be able to rebuild it once that arrives. Until I get it fitted I don't know what the stroke will be - does anyone know the correct stroke for a 75mm Sherman
To replicate the dual speed of the recoil, I will be using a PIC microcontroller to step the servo as quickly as possible on the shot but ease it back for the return. I know this is quite simple in theory but I have yet to see how the system behaves in practice
Adrian.
) use a two-spring approach. The gun would be controlled with a flip switch. When flipping the switch in one direction, the gun would be "loaded". That is, the main spring would be pre-tensioned with a reasonably powerful electric motor. Flipping the switch to the other direction would "fire" the gun by releasing the main spring and sending the gun backwards with great speed. At the rear turning point, the main spring would be disconnected from the gun and the much softer return spring would return it to the original position. All this moderated by a gas damper (like in the kitchen drawers mentioned previously) with an appropriate stiffness. Maybe like those used for station wagon rear lifting doors. It'll be a fun project! 
