While many people talk about suitable replacement materials, they seldom if ever discuss why Aeolian started the practice in the first place. Fact is, almost all player manufacturers have always glued the pneumatics directly to the deck board. So why did Aeolian institute this change? While there is no written evidence to support the following opinion, it is widely held by a number of master rebuilders. The reason they don't talk about it centers around the fact that there is NO written evidence.
Those of us who have rebuilt numerous Aeolian stacks have noted that the fact that the striker pneumatics are NOT rigidly mounted to the deck boards gives the 'strike' a more human touch. To understand this difference between conventional mounting and non-rigid mounting, one has to understand a little bit about the power curve of a bellow.
A bellow develops its maximum power at Time Zero. In other words, from the moment the bellow starts closing, its power starts decreasing. That being the case, the striker pushes on the piano action with its greatest amount of force the instant it starts moving. That action is 'non-human'. Imagine, if you will, that you have your finger resting on a key. Then you press down on the key as fast as you can. From Time Zero, your finger starts moving faster as the key goes from the full up position to the full down position. In fact, it reaches maximum velocity just before the bottom of the key strikes the front rail felt. So, you begin to see the stark difference between the way a bellow strikes a note as compared to the way a human strikes a note.
Aeolian realized this difference when they started making the reproducing player action. In fact, they had difficulty getting notes to sound softly because of the operating characteristics of a bellow. So, they introduced an 'error' of sorts. By placing a thin piece of leather between the pneumatic and the deck board, the bellow moved away from the deck board a tiny amount as soon is it made contact with the action of the piano. The leather became a sort of 'shock absorber' and it reduced the amount of 'attack' by just enough to give the action a more human touch.
No doubt, Aeolian experimented with varying thicknesses of leather before settling on the 0.010" thickness of tan pneumatic leather they ended up using. Speculation is that anything thinner didn't have much of an effect, and anything thicker became problematic at high vacuum levels -when the pneumatics strike the keys with FFFF force.
That's why I suggest a tan pneumatic leather that isn't too 'spongy' or supple. Judging by the leather I've seen in the Aeolian stacks, it wasn't a high grade product in terms of its suppleness. In other words, it wouldn't have worked very well for pouches. Explaining this difference in quality is rather difficult to put into words. One has to have a general feel for the difference. That's why I always hand select my tan pneumatic leather at the supply house. While this is much more time consuming, I'm certain that the leather I'm buying will serve its intended purpose perfectly.
So, to answer your question, would Felpro gasket paper work? I'm certain it will serve the purpose of creating an air-tight seal between the striker and the deck board, but I'm not so certain it has the same properties as tan pneumatic leather. In fact, I'm inclined to believe that it would create a rigid bond between the pneumatic and the deck board, completely defeating the purpose of the leather.
BTW, the claim made by some that Aeolian used the leather so it would be easier to remove the bellows when it became time to replace the cloth is nonsense. In fact, the cloth Aeolian used was far superior to anything else on the market except for the formula that was used by Lauter in their Lauter-Humana player. In my personal Lauter-Humana player piano, the cloth on the strikers is still "supple". It has not dried out, and it's now 93 years old. So the notion that Aeolian would go to all the extra expense of adding the leather because they were concerned about future generations of rebuilders is not logical. And back when player pianos were being build in mass, every thing they did was extremely logical.
John A Tuttle Player-Care.com
Portions of this email will undoubtedly be used in the creation of another web page at Player-Care.
On 3/6/2010 2:59 PM, Kirk and Judy wrote: Thanks John, you have been very helpful as always.
It seems I read on MMD that you could use Felpro gasket paper for this. Have you ever seen this done with good results? Or do you think I should stick to acquiring some leather?
John A Tuttle wrote: Hi Kirk,
I just checked my stock of leather and I do not have the piece I thought I might have. I must have sold it....
The problem in this situation is that you don't really want expensive tan pneumatic leather. It's just not necessary... But where to buy lesser quality tan pneumatic leather is a problem. What you really want is a skin that's not really supple. You want one that's a little stiff, and the only company that sold a lesser quality leather was Player Piano Co, in Wichita, KS. Since the owner died in Dec 2008, the people who bought what was left of the company don't have a good grasp of what they do and don't have in stock. And, talking to them about the quality of leather is a waste of time because they don't have a clue. So, that leaves you with the other major supplies like the Leather Supply House and Columbia Organ Leathers. Both of them have web sites. You can compare prices there...
Sorry I couldn't be more helpful.
On 3/6/2010 10:56 AM, Kirk and Judy wrote: Great! Thanks Let me know ... you still have my card info right?
John A Tuttle wrote: Hi Kirk,
Hide glue for the rubberized cloth.
Actually, I might have a piece of tan pneumatic leather that's perfect for the pneumatics gaskets. I'll have to check and get back to you..
On 3/5/2010 9:04 PM, Kirk and Judy wrote: Hello John, I'm still inching my way along ... 1 pouch board done...that dishing tool I bought from you works GREAT!
I was looking ahead through my supplies and realized I have forgotten the thin leather for the gaskets under the striker pneumatics. Do you carry this? If so I need enough for the strikers and some extra for reassembly of the pouch board & valve board.
Glad to see your shoulder is getting better.
P.S. Did they (Aeolian) use hide glue to glue the rubberized cloth on the chest? The cloth I peeled off looks like old contact cement although I can't be sure and I can't seem to find the answer in Reblitzs' book or anywhere else.
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