B-29 bomb bay doors help?????

That seems like a tall order! I once hinged the main gear doors on a 1/48 P-51 and used nylon thread as the "piston" of the actuator treaded into the wing and attaching to a wire lever which was actually the hinge for the flaps. When the flaps were down the gear doors were up! Flaps up, gears doors open. You could maybe hook the tread to the top turrents and turn them to open and close the bomb bay doors. I might have to try that on my 1/48 B-29 that is a "hanger" queen for some years now awaiting some sort of completion!

You could try model railway point motors.

These are generally quite small and come in two distinct types:

The solenoid type which move a bar side to side:

or the:

Motor, 'Tortoise' type, which are very slow and very contolled, but a bit on the large side.

Failing that try 'Memory wire'.

This is a wire which contracts when a current is passed through it if memory serves me.

Might be ideal for popping up gear doors etc.

Karl