correct belt tension

[Casar66]

hi there,

I had to change the alternator and now I wondering if the description in the manual means with cold or warm engine. I did it when the engine was cold and when it becomes warm the tension was higher,  the way was reduced by half approximately.

here the manuals text:

 

Checking

1. Check that the belt is capable of approximately *to

1 in (19'1 to 25'4 mm) deflection at the mid- point

of its longest run.

[Waldi]

Interesting the tension increases when warm, I would have suspected the other way.

I did it cold. The lower the tension, the better for the bearings, so don’t overdo it, the depression depends on the force, so subjective.

Waldi

[Casar66]

Yeah, not just the bearings. I am worrying about the waterpump as well.

[Waldi]

Yes, these have bearings too, and a mechanical seal.

Waldi

[Casar66]

But what is corecct, 1 inch with cold or warm engine?

[Mike C]

I use about 3/4 inch deflection, engine cold. My belt appears to loosen as it gets hot. I had the car serviced once at a garage that was not used to old V belt drives - they tightened the belt up like it was a modern flat belt and destroyed the alternator bearings in less than 1000 miles, the water pump went soon after but that might have been caused by age.

[Casar66]

Ok, then i did right. But why get my belt shorter when the engine gets warm? 

[Mike C]

Thinking about it my belts may only  feel looser when they're hot . If you're experiencing a tighter belt when hot it could be that the centrelines of the components supporting the pulleys- block, brackets etc.- expand when they get hot and tighten the belts. Maybe that's why I generally first experience a squealing belt with a cold engine?

That said most  manufacturers say to  check & set the belt tension with a cold engine.

 

 

 

[Sapphire72]

Not too tight that it would damage the bearings, but tight enough so that it won't slip. 

This would be at normal operating temperature of the engine.

With the engine off & gearbox in neutral, you should be able to grasp & pull the belt so that you can turn the crankshaft clockwise without slippage.

[Z320]

Very interesting about a belt or chain drive with two sprockets / pulleys is a product from a German company,

a slack "roll-ring" between both pulleys for a smooth run and "automatic" tension

 

Edited April 11, 2020 by Z320

[Z320]

I asked them years ago to use this as a tensior for our timing chain,

but I got a "sorry, no". I thought that would be a good idea....

[DaveR]

The figure given by Triumph was 3/4 to 1"  (19mm to 25mm) for the small 4 cylinder and the six cylinder engines. This would have been with a cold engine.

The problem used to be where a piece of wood was used between the block and generator to tighten the belt.

Dave