Model Forum / General / Models / July 2006

Don't know, I'm afraid. But unless someone else knows better, I'd use
the same measurement as the belt : i.e. if you measure the belt's
outside length, then use the top of the groove.

For what it's worth, I have a Picador pulley marked by the manufacturer
as 12" which is 12" across the _outer_ diameter. And I don't think the
bottom of the groove should be important, as the belt isn't supposed
to touch there.

-adrian

Mike,
The pulley should be measured at its pitch diameter not the OD.
Most quality pulleys will measure slightly "oversize" if you measure the
OD.

As a general guide pitch diameter is worked out as follows.

Z section belts - OD (mm) minus 5.5 mm
A section belts - OD (mm) minus 7.5 mm
B section belts - OD (mm) minus 9 mm

This information is taken from a handbook I have that originally came
from Fenners belt manufacturers in Hull.

Using these figures it should be possible to work out the total length
of belt you need using one of the numerous calculators available on the
net providing you know the centre distance of the pulleys.

Regards,