Nottingham spacedeck motor - driving me crazy

Are you changing the position of the belt to go to 33 1/3? Really it would be impossible for the table to only spin at one RPM as the pully has two different diameters, the smaller one for 33 1/3 and the larger one for 45 rpm. When moving the belt on the motor pulley, change it's position on the platter to keep things even.

Many thanks. I know it sounds impossible, but I initially thought it might have been due to different tension in the belt between the two speeds. Now, however I believe its the actual motor. Reason being, if I remove the belt, the motor will spin BUT on second attempt it does not. If I then move the motor slightly up or down i can get it to spin once or twice but then not again until I move it slightly up or down again. By doing this, with the belt connected, i can eventually get the platter to spin at 45. BUT no matter what I do it will not spin at 33.
Do you know where I could obtain a new motor, or is there some maintenance I could perform on the motor. Thanks again.

The most insane solution!!!! I replaced the belt with a piece of string and the table now works perfectly!!!!!!!! I guess the problem was the belt!!!!

As you may know, that motor is never "off". The push you give to the platter seems to engage some sort of clutch to then drive the platter properly. My guess is that there is some critical loss of torque for some reason, such that the motor cannot get going up to mechanical advantage needed for 33 rpm, but it is probably barely OK to get going using the 45 rpm part of the pulley. To test that, you might try starting it at 45 and then flick the drive belt down to the 33 pulley, see if it can then stabilize at that speed.

There's no clutch in the Spacedeck's motor. It's a simple AC synchronous motor, intentionally too weak to start the mass of the platter from a stop. The Spacedeck's designer, the late Tom Fletcher, argued that the motor's real job is just to keep the platter rotating. He believed that motors powerful enough to put the platter in motion were therefore oversized for their real job and vibrated too much. I vaguely recall experiencing the original poster's problem once. As I recall the issue is really that the motor (which is on a separate chassis or pod) has moved slightly closer to the platter, reducing the belt tension and causing it to slip on the pulley. Replacing the silicon belt with a string fixed the symptom because the string has greater "traction" than the OEM belt. My suggestion is to clean the belt with some cold water and dish soap, put it back in place, and move the motor away from the platter a small distance.