Rebuilding Standard Action Valves
By Bob and Sonja Lemon
Roger Waring wrote:
> Suction is poor when playing, and the stacks of both pianos appear
> to be leaky. I don't think it is all due to poor condition gaskets.
> We suspect that the problem may be with the valves but would like a
> more experienced view.
I would suggest bench top testing of the player stack before disassembly, using auxiliary suction. Apply low suction level at 5 to 10 inches and check completely for leakage using burning incense stick. This should be done with the tracker bar completely covered and then with tracker bar uncovered. (Double check on suction pressure between covered and uncovered tracker bar.)
Pass the burning incense stick close to all the gasketed joints and valve caps. If there is a leak, the smoke will be drawn into the leak. If the pneumatics are in very bad shape, this test may not work when they are energized, but would work if the decks are removed and the suction holes taped over.
> The valves that we have are a threaded thin wire stem type, ... a small
> cylindrical wooden button screwed on to the top. This button ...
> makes contact with the pouch.
If the small (action regulating) button makes direct contact with the pouch, the pouch probably will not generate enough force to lift the valve and push the atmospheric side closed. There should be a 3/4 inch fiber disk (approximately) attached to the center of pouch with a small drop of glue. The pouch-to-valve-lifter must be more than the area of the face of the atmospheric side valve to ensure correct seating when pouch is energized.
> The gap between the inside faces of the two fibre discs is
> approximately .06".
This gap is not important as long as proper valve travel is obtained.
> Question 1. The leathers are generally OK on both instruments --
> a simple suck test using the metal seat is quite effective for both
> facings. Should we replace regardless? Is sheepskin OK?
If you press the valve face against the metal disk, it will flatten possible warped facings and cause better seating than obtained during actual operation. In other words, a bad valve can test good if tested improperly. Yes, replace valve facings and disks, if warped. Try to use leather similar to the original.
> Question 2. The small leather punching is not glued to the white
> suede. Should it be? What is its function?
We have pulled 2 different sample valves and both have the small leather or felt punching between the fiber disk and the collar on the stem. This punching acts as a seal and allows some rocking motion of the valve disk. It is not supposed to be glued to anything.
> Question 3. Many of the narrow fibre guides have their bushings
> missing, and thus the wire stem has a lot of play. Would this cause
> serious problems? Is too much play worse than not enough?
Yes, too much play will allow the valve to drop too low on the valve seat causing gap-osis and major leak! Stem guide clearance should be just enough to allow free movement of stem. Replacement fibers are available from Player Piano Company in Kansas. (It will be easier to replace these than to re-bush that tiny hole!)
Proper rebuilding of these valves is a real challenge. Have fun!
Some other areas you might want to check for leakage. The air motor. Remove the suction tube, plug the fitting with the palm of your hand and try to turn the sprocket backwards. If it won't budge, it is air tight. If it is easy to turn, rebuild the air motor.
Also check the tempo governor. This can cause a great deal of trouble also.
Hope this helps. I'm sure others will chime in with more information.
Sonja Lemon
Lemon's Player Piano Service
Sacramento, CA |
(Message sent Sun 23 Feb 1997, 20:57:47 GMT, from time zone GMT-0800.) |
|
|
Mechanical
Music Digest™ Archives
