So I agreed to re-string the church's Baldwin model E. No block, no bridgework, no action work, no improvements beyond new strings and pins. Okay fine. I take the strings off and find:
One of the bent brass duplexes has collapsed, cracked down the middle. The originals are 3/32" brass bent at a 45 degree angle. I'm thinking; (always a risky thing with me) "where do I find 3/32" brass flat stock and someone with a press brake?". Then it occurs to me that the original failed so why would I duplicate it? I imagine a couple of different ways I can fabricate an alternative out of brass and off to the local Alro metal shop I go. The staff there resisted the urge to laugh at the piano guy and showed me over to the scrap area. There I picked out $4 worth of brass flat and rod stock, odd lengths, sold by the pound. On the way back to the counter A shelf of co polymer scrap caught my eye. Acetyl co polymer is very similar to Dupont Delrin a trademarked Acetyl homopolymer which is slightly harder (+- 10%) and slightly stronger (+- 10%) and is used by Ed McMorrow in his patented duplex system and has also been written about in this forum by Jim Ialeggio. I picked up a 1/2" by 6" by 10" long piece for $3.25.
Once back at the shop I took the wood blade off the band saw and put on the metal cutting blade. I was about to start cutting the brass stock when I looked at co polymer and decided to cut the softer material first.
One day I hope to have the time and a client with the money to buy a license to do a Fully Tuned Duplex Scale. When that day comes I don't want it to be the first time I've tried to work with an Acetyl material. So off we go. Having a band saw fence makes this sort of cut a lot easier. After the rough cut I cleaned up the profile with a sanding block I made with a 3/16" profile and some emery cloth.
I then used the 180 grit emery cloth and some 400 grit cloth to remove all the saw marks.and came up with
A very close approximation of the original.
After I cut the individual pieces to length I took one of the waste pieces to the workbench. There I took a piece of music wire and laid it across the co polymer and smacked it with a hammer to see how it would respond to high pressure. There was an indentation in the co polymer to be sure but it was less than the indentation left in the brass duplex by the original string.
In summation the Acetyl co polymer material proved to be a low cost highly effective solution to what had threatened to be a costly and time consuming side track in an otherwise pedestrian repair. I want to thank Mr. McMorrow and Mr. Ialeggio for their posts about using Acetyl materials in duplex systems. Their posts allowed me to think outside the scrap metal box while working on this one.
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Karl Roeder
Pompano Beach FL
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