I have a Steinway vertical in my care which appears to have been very
thoroughly restored, except for the six laminated, riveted leather pump
belts. Two of the belts have given up, and the rest are soon
to follow.  I would like an opinion or two on replacement materials.  I
have read Mr. Brougher's excellent and thorough post in the archives,
but would like some further information from the experienced souls on
this list.

I don't know how many variations there are on this pump, but
here are the details of the one in question.  It has two V-belts from
the motor to the countershaft, and four from the countershaft to the
pump, on machined ferrous pulleys, all in good condition, and a
wood-faced idler, also in good shape, except for a generous buildup of
waxy belt dressing and leather bits.  They all appear to be very close
to 4L/A V-belt profile.  I have read concerns about stiffness and noise
from modern composite belting in certain applications, but when I
removed the old leather and ran the pump with just ONE modern belt on
each position, the pump seemed whisper-quiet -- much quieter than
before, according to the customer, with no slippage.

My options are:

1.  Find original-style replacements.  Not available, and I suspect the
friction/strength/stretch characteristics of this type of belt aren't
the best.

2.  Replace all belts with the grade of composite V-belt I had tried.
When using modern materials, is it necessary to run all six belts?  Or
desirable?  Does overkill merely contribute to noise and friction?  The
original pulleys will be kept.  Which belts would you omit?

3.  Replace some or all with urethane V-belts.  Pros: Quiet and
resilient.  Cons (three): Smallest pulley slightly under recommended
diameter, even for the softer of the two formulas; need to splice myself
or custom order; the one rated for smaller pulleys is orange.

Also, is the wooden idler necessary or desirable when running a material
which has a lower stretch/higher friction than leather?  My "test" belt
was a little smaller than the original, so I tested it with the idler
set clear of the belt, and it grabbed very well.

Any thoughts would be appreciated.

Sincerely,
David V. Anderson, RP
Waukesha, WI