[ Bernt Damm wrote in 160724 MMDigest --

> The manual says 120 to 125 rpm but when I calculate it, based on
> the pulley sizes and 1150 rpm motor, it should be close to 150 rpm.
> Is the manual wrong?

Bernt, I don't think the manual is necessarily wrong, but I think
you are comparing two varieties of the same species.  This is my
personal conjecture, but I think it is a reasonable supposition.
The 15" box pump was developed to be able to "fit" into grand piano
belly frames with a minimum of redesign of the timbering.

Obviously, a 15" pump is going to have a smaller volumetric
"displacement" than a 17" pump.  Since the vacuum demands of the
Duo-Art systems are roughly the same, no matter where you find them,
grand or upright, a good way to boost the "output" of the smaller
pump is to use the same motor and same pulley size, resulting in
a slightly faster rpm of the pump so the cubic inch displacement of
the two is roughly the same.  Differing opinions are welcome.

John Grant