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MMD > Archives > October 1996 > 1996.10.25 > 11Prev  Next


Gulbransen Unit Pneumatics
By John A. Tuttle

Regarding the replacement of the pouches in the "late style"
Gulbransen. I used a modified version of Durell's treatise on the
rebuilding of the "glued" stack (see Player Piano Co.  catalog, pg.151
Step by Step Instructions, No.6).

NOTE: THIS PROCEDURE CAN BE DANGEROUS. STEAM CAN SEVERELY HARM YOU IN A
SINGLE SECOND. PLEASE EXERCISE CAUTION BY WEARING APPROPRIATE
PROTECTION.

First, I clearly marked (where no one could see when the job was done,
where possible) all parts involved.  Then I removed the moveable board.
Next, I used a steam iron (set to cotton setting) and placed a water
saturated (almost dripping) double thickness terry cloth towel between
the iron and the pneumatic board, pressing very hard. The intense steam
heat applied to the board for ten to fifteen seconds was enough to
soften the glue just a little. Then, while still quite hot, I placed
the edge of the pneumatic on a steel bar with an "L" secured to the bar
so I could hold the whole unit straight up with one hand and just the
pneumatic board rested on the metal bar. Previously, I had fashioned a
piece of leftover pin ply stock to the same width as the "valve block"
at the smaller end. Sort of like a big wooden punch. Then, holding the
punch and pneumatic unit up against the "L" bracket with one hand, I
struck it sharply with the hammer in my other hand. About 80% of them
broke relatively clean (no big chunks). A few broke the pneumatic board
and had to be chiseled apart and then new boards were made. A few
cracked the valve block and here again were chiseled apart and then
glued back together.

I also tried sawing the unit apart with a very thin blade.  The problem
I ran into there was consistency. On the long side of the block, the
blade had a tendency to wander or bow leaving an irregularly shaped
contact area. Further, the valve stem had to be shortened (which I
decided later could have been done with thinner felt disks) to account
for the thickness of the blade. I also tried a thicker blade to solve
the wandering problem and then fabricated a gasket of the same
thickness and simply glued and clamped the whole affair back together.
Initially, I really liked the idea of the gasket because it would make
the next rebuilding easier. WRONG. Since the unit was clamped together
to dry, when the clamps were removed there was a minute amount of
leakage that adversely effected the operation of the unit.

That's when I tried using dry heat. I tried an oven set to 175 degrees
(slightly above the glue pot setting) but even after twenty minutes the
glue didn't seem to soften.  At higher settings, the brass valve seat
actually started to contort as the wood expanded inwards. That's when I
tried super fast, super hot and super moist, the extreme opposite.

Eighteen years later and now with a new owner, the unit has only needed
regulation and the major repair of the lower section which developed
severe cracks in the area around the tempo control and cut-out valve.
(I also tightened the pneumatic/valve units. The new gaskets had
compressed somewhat.) Perhaps if I had sealed ALL the wood when I
initially rebuilt the lower section, that problem would not have
occurred. Hind-sight, the almost perfect science.

Why do I remember this job so well? One seldom forgets a serious
nightmare. I remember I got paid $450.00 for rebuilding eighty units.
When I "landed" the job, I figured $5.50+ per unit was a fair price if
I could do each unit in about ten minutes. WRONG! I guess I made about
$9.00/hour on that job. OUCH! It still hurts.

BTW, I also used an iron/wet terry on the valve caps.  After trying dry
heat and breaking three or four on a row, I tried wet terry and it
worked good. I did end up sanding the block to get off all the fibers
of wood from the removed caps but I replaced them (the caps) with the
fiber washers sold by Player Piano Co.

Musically, John A. Tuttle¶
•---------------------------------------------------------------------------
John A Tuttle "Self-Playing Pianos"    E-mail:tuttleja@concentric.net
407 19th Avenue                             908-840-8787 (leave message)
Bricktown, NJ 08724               Rolls:1-800-870-8784 (leave order)
"We Keep Your Music Rolling"  http://www.concentric.net/~tuttleja/
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(Message sent Fri, 25 Oct 1996 20:42:19 -0400 (EDT) , from time zone -0400.)

Key Words in Subject:  Gulbransen, Pneumatics, Unit

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