Dr Who time expander

This unit turned out to be a real troublesome. I have worked hours with it and I’m now convinced that I can’t do anything about the problem.

This is the elevation mechanism. It consists of a support bracket in which the main bracket slides up and down. The movement is controlled by a rotating cam disc. In this picture it is elevated a bit past its top position. The two brackets are joined together by four rollers, two in the top fixed at the support bracket and two rollers at the bottom of the main bracket. While the main bracket is in the down or mid position it is stable but in the top position where the upper and lower rollers are near each other the main bracket gets unstable. I first tried to add an adjustable stop for the top position of the main bracket, it’s the rubber in the top left in the picture. The thought was that it should prevent the main bracket from tilting to the left. It didn’t work, the tilting occurs just before the main bracket reaches its top position. Without the stop it tilts and stays in that position, with the stop it tilts and then it is brought back in the horizontal position, it looked worse with the stop than without it so I removed it. It is possible to adjust the width of the support bracket a little bit by an adjustment plate at the backside of the mechanism. If it is widened a bit it firms the rollers and the main bracket gets more stable in the top position. This worked good for a while but suddenly the mechanism jammed and this caused the gearbox to break, the soldering of the gear at the outgoing axle broke. Luckily it happened while I still had the game at the workshop. A friend of mine who works at a mechanic workshop helped me to solder the gear back on the axle using silver solder. After this I adjusted the support bracket back to the original position and gave up. If anyone has a solution for this problem, please let me know.

The gear and axle before and after repair