By Craig Brougher
|The heavy bellows cloth which is used to cover things like pumps and reservoirs has been the source of most of my worries, generally. Some years ago, I stripped some original Duo-Art cloth with acid and dis- covered that the rubber inside, when it has not been torn out of the material, measured about 35 thousandths thick.
I sent a large sample of this to Player Piano Co., who in turn sent it to their cloth company, but for some reason, it was never made. Durrell asked, "How do I specify this cloth to them?" I suggested that he have them analyze it and tell him what he had. At the same time, I suggested that he also ask them to give him a test he could make to assure the company that he had what he ordered, _before_ he gave them the order. I wasn't in on the buying of this stuff.
Coatings thicker than about .015 inch have to be made differently, in a process called "calendaring," or something like that. It is a much more expensive process, and would probably have priced the cloth out of this solar system. However, I have always added cabretta leather punchings to all the folding corners of the cloth and haven't had any more problems with the thinner rubber on rotary pumps.
Without the cabretta, however, a player pump wears its cloth out in about 6 months of steady playing. We're talking _holes_ here -- those you can stick a pencil through. But if the leather is put over those folds when new, (and I just use hot hide glue) after the cloth has been clamped tightly to crease it first, the cloth holds up for at least 18 years and counting.
What causes most pump problems today anyway is the old, unrestored inside flap valves and seats. In 99% of the cases, these were never rebuilt, and so the pump must be completely torn down again. You will notice that inside flap seats usually just zip off with light pressure from a putty knife. They will have completely dry-rotted away. It seems to be an accelerated process. What may have been tough and tight ten years ago is now rotting away to dust.
(Message sent Tue 4 Feb 1997, 15:07:35 GMT, from time zone GMT.)