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MMD > Archives > January 1997 > 1997.01.27 > 17Prev  Next


Gulbransen Valves
By Craig Brougher

Bruce Hannover asked about setting Gulbransen valves.  The travel of that
valve is important, Bruce.  If your valve travels too much, then some
notes just won't play when called on for fast repetition, and you will
have too much travel loss during busy sections, so it won't be as fun to
pump -- unless you don't really mind fast heart rates and seeing double
by the time you've finished.

The Gulbransen valve, first of all, has a section of brass tube to seat
on for an inside seat.  Make sure that every one of these is completely
resealed.  They were stuck in there with shellac, and are quite often
loose enough to leak.  Multiply that leakage by 88, and you have a
gusher.

As far as spacers are concerned, blotter paper is a laminate that you can
take apart, edgewise, so you can adjust each valve's travel to be
approximately correct.  Before you glue them down, build a pneumatic
tester, which is just a matching hole pattern in a board of some kind and
a regulated supply.

Set the supply down to 6-8" max., and with a 3-5 foot long test tubing on
the pouch nipple on the tester, operate each pneumatic/valve, holding or
clamping the outside seat lightly.  (In other words, rig up something to
check these out with, or you may be very sorry.  It's a lot more work to
do it over again later.

Setting valves is rather time-consuming but necessary.  The more even
they are set, the better.  However, practically no player piano valves
play well when set to only .031 inch.  I recommend setting them wider --
say, instead of .032, more like .040 to .045 -- not real critical
perhaps, but .031 inch is too narrow, except for a few kinds of valves.

I also suggest that you properly seal the pneumatic leather you used for
valve coverings.  Pouch leather by itself is porous, today, and it will
leak.  It is also more vulnerable to bacterial action and will rot much
faster than the old original stuff unless you seal it correctly.  Then a
little talcum powder (please, not starch), and you'll be ready to go.

The Gulbransen stack, when assembled, should have a combined equivalent
leakage of no more than about 2-3 3/32" holes.  Less is even better.
When you get done with that baby, you'll be wondering why they bothered
putting two pedals on it when all you really need is just one.

Craig Brougher


(Message sent Mon 27 Jan 1997, 16:04:35 GMT, from time zone GMT.)

Key Words in Subject:  Gulbransen, Valves

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