I've been busy putting a book project to bed but have had a little time to work on the ratchet mechanism mentioned in the previous post. I'm currently aiming at making a robot with simulated unwinding clockwork key. Possibly the robot will be doing squats and arm raises, not sure yet. 

One thing I do know though is that I want the key in the centre of the back not the side of the box. This involves rotating the mechanism through ninety degrees. I also want to keep the shaft end without the key hidden inside the body.

Here's what I have come up with.

I've also inverted the ratchet tiles. The key turns when the strap is pulled rather than when it is pushed. It is easy to bend the strap when it is pushed but when it is pulled it is quite strong and sturdy. By reversing the direction of the ratchet I've taken advantage of this strength.

Here's the inside view. Plenty of room at the sides to add an arm raising mechanism is that is the direction I decide to go.