V Belt Groove Design - Have I got it right?

[emisnug]

Before I put the dimensions in the CNC and potentially ruin a drum, I'd just like to check and make sure I've got this whole V Belt groove dimension right. I think that I've got it mostly right, but I'm unsure that I have the depth correct.

We're using "B" section belts, which, depending on what site you go to, are either 16.5mm (occasionally 17mm) x 11mm or 21/32'' x 13/32''. You can find these belts here - We're using Bearing Boys as they are on my way home from work and we can just swing by and pick stuff up.

V Belt Groove.PNG

[overkill]

The depth looks too small to me. Also what angle are the cheeks? When a belt is wrapped around a pulley the inside compresses and widens, changing the angle of the sides slightly - you need to compensate for that on smaller diameter pulleys. Here is a great reference page on pulley design: http://www.roymech.co.uk/Useful_Tabl...Vee_belts.html

[emisnug]

I've read through the RoyMech page a few times, and still don't really understand any of it, especially in regards to what the groove should look like and why.

The cheeks are 13.5°, O/D of the drum is 200mm.

[overkill]

All common V belt designs use 40 degree included angle (that is the sum of both side angles). To compensate for the belt deformation pulleys always have a smaller angle; the smaller the pulley, the smaller the angle.

I had a read through the Machinery's Handbook; for a 200mm diameter pulley, you want a 38 deg. included angle and a depth of at least 14.7mm below the top of the belt.

[emisnug]

All common V belt designs use 40 degree included angle (that is the sum of both side angles). To compensate for the belt deformation pulleys always have a smaller angle; the smaller the pulley, the smaller the angle.

I had a read through the Machinery's Handbook; for a 200mm diameter pulley, you want a 38 deg. included angle and a depth of at least 14.7mm below the top of the belt.

I had a read through my ancient copy of American Machinist, got 37.5 deg and 19/32'' depth! I think I've sorted most of it now, and also used a downloaded CAD model of the drive pulley that we're using to make sure.