I need to make rather large pulleys (140-200mm) for standard 10 mm V-belt.

Grove is to be 9.7mm wide on the top and 11mm deep as theory and published projects are saying.

What are correct grove angles?

What I have found that tor a small pulley (up to ~3 inches) correct grove angle is 32 deg and for larger pulleys it is 38 deg.

I understand it, as it seems logical that due to larger contact area of big pulley frictional force per unit of contact area does not need to be so high because total contact area is larger.

I am aware that many people are making pulleys with 30 deg angle, regardless of size.

So what is correct angle for large pulleys?

38 deg or perhaps less?

Thanks for all your comments. I will go for 36 deg., not exactly what industrial art calls for larger diameters (38 deg) but more than usually modellers are doing (30 – 32deg).

Reasoning is that pulley will be used quite a lot but because it is going to be made of aluminium, then this angle will be a little bit steeper to accomodate for wear.

Martin

@oldvelo,

I think, I misunderstood you.

Do you mean belts like those used for example in washing machines?