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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
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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 Sat 26 Oct 1996, 00:42:19 GMT, from time zone GMT-0400.)

Key Words in Subject:  Gulbransen, Pneumatics, Unit

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