Triumph belt tightening

[mjbarnes]

Unlike the lucky collectors with living rooms full of phonographs, my few machines are in my garage. Well sealed and dry but I let the temperature drop to 5 C (41 F) on a winter's night, then heat it up to 19 C (66 F) during a day I am working there. The humidity must be fluctuating lots. Anyway, I find that the belt on my Triumph gets loose and does not necessarily tighten back up on its own. So I am constantly adjusting the motor downwards from the bedplate. That requires adjusting the stop switch so it does not contact the bedplate. Premium belt material. I have made a few belts of different lengths but still have the problem.

Any suggested fixes? Instead of using the Triumph I am playing records on a VI that does not have a belt.

[Jerry B.]

Your post does not mention if you have a belt tensioner. It's possible to make the perfect or nearly perfect belt and not need a tensioner. Just curious, does your machine have that part and, if so, are you using it?

Jerry B.

[mjbarnes]

I like tensioners. But I don't think any Triumphs have them. Instead, the front motor mount screws up and down, lowering or raising the motor.

[Inigo]

That's the advantage of a tensioner... It eats out the excess of belt when it stretches, or gives more belt when it shrinks, thanks to the spring action and third wheel over a variable belt extra length... A simple and ingenious mechanism.

[Valecnik]

Before installing the belt, did you stretch it between your fingers and then glue the stretched piece into a loop? You need to get that initual elasticity out of the belt or it keeps stretching after installation.

[Wes K]

The Triumph does not have the spring loaded tension idler used in the lesser machines. Instead, the front motor mount had a large thumb nut which is used to raise & lower the motor to adjust belt tension. The belt adjusting range is limited by the hole in the cabinet and the winding crank, and the range you can move the motor before these contact each other.
The belt should be just tight enough so that if you grab hold of the mandrel and hold it from turning while the machine is running the motor almost stops.
Raise the motor up as high as it will go without the winding crank contacting the cabinet before figuring out how long the new belt needs to be.

[mjbarnes]

Thanks for helpful suggestions here, especially on how to judge the right belt tightness.