Stepped Vee Pulley query

[robgraham]

When you measure a stepped Vee Pulley, is it the outside diameter that defines the size, or wha?

And is the speed ratio calculated from the relative diameters - or, again, what ?

Thanks

Rob

[robgraham]

When you measure a stepped Vee Pulley, is it the outside diameter that defines the size, or wha?

And is the speed ratio calculated from the relative diameters - or, again, what ?

Thanks

Rob

[R]

[Dave Osborne]

No, there is an "effective diameter" called the PCD or pitch circle diameter, which is always smaller than the overall diameter.

Speed ratio is calculated from the ratio of the PCDs.

Also, you should be aware that there are Vee belts (size A, B and C) and wedge belts (type Z, SPZ, SPZX), and you need to get the right type/size for your pulley.

[Rob G]

Thanks guys - I'll be able to progress from that. Rob