This post is part of the Milton Player Piano Series.
When dealing with an underperforming player piano, one of the likely culprits is worn out leather gaskets. There can be dozens of these types of gaskets inside of a player piano action and a small leak in each of them can accumulate to the point where the person pumping the pedals has to pump unreasonably hard or fast in order to compensate. When taking apart the player action and bellows, look for leather gaskets with large cracks, missing pieces, and black edges. These are the gaskets that need to be replaced. Also, you might as well replace any other old gaskets that you come across while you have the system disassembled.
There are a few different materials that can be used to make these gaskets. The best material to use is a fine quality suede calf skin leather, however most hobbyists wont have access to leather that has a consistent enough thickness and compressibility for this job. It is much easier to find and use sheets of neoprene to make new gaskets. Cork is also available, which is more durable than neoprene and easier to shape, but offers less compressibility. For this job, I will be using neoprene from http://www.player-care.com/gaskets.html
Once you have separated the two gasketed pieces, mark the outside edges of the old gasket with an awl, and proceed to scrape the leather gasket off of the board. I use a razor blade to remove the majority of the leather without damaging the wood. Next, sand any remaining leather or glue residue with a sanding block until you are left with bare wood. Gently vacuum any wood or leather dust out of the chambers of the bellows or player action.
Cut four strips of neoprene so that they make a neat rectangle where the old gasket used to be. They must fit tightly together and not allow any air to leak through the seams. The compression of the neoprene will help with this a bit, but try not to rely on it. Make your gasket as tight fitting as you possibly can. Make small pencil marks on the board wherever there is a screw hole, so that you will know where to punch holes in your gasket later.
Once your pieces of neoprene are cut, apply PVC-E glue to the bottoms of them and press them into place on the board. After the glue has dried, do any trimming you need to do with a razor blade, and punch out the screw holes with whatever small metal tube you have around. I used the back end of a small brush.
Push the screws through the board to clean out any glue residue, screw the two boards together, and test out the gasket by listening for any air leaks while the bellows are being worked (or by attaching to a vacuum pump).