To grandpa Jianzhong Wang (1927-2018), veteran of many battles, whose spirit was around during the process, who taught his children and grandchildren to be honest, and hard working.
The aluminum jig in the first picture takes key top height on bottom of the tongue. Top of the tongue shall be the height of underlever. This also means that the thickness of the piece of metal is the keyend travel distance before it pushes up the dampers, usually 1/3 of key dip. Install the homemade adjustable dowel on trap lever under damper tray, adjust its length till most of underlevers just touch top of jig. Then turn capstans up and down to make underlevers the same height, or they all will just sit on top of jig.
The shop owner prefers to regulate the damper wires before gluing on felts. The 8mm thick sticks replicate height of damper felt. The damper wires are new and also too long. Install one damper, check wire length, trim to about 1/8" above center-pin of sostenuto tap. Put the wire in the hole to test. There shall be a little play before wire is bottomed up in the hole. Insert the trimmed wire into a straw, cut straw to the length of wire, use the straw as template for all wires in the same section. Do bass wires and the rest separately since the bass strings are higher, thus damper wires longer.
With a sample damper wire installed, mark where the 2 bends will be. We use the 2 glue lines on the belly for easy adjustment after piano is back to customer's home. Transfer the marks onto wire bending platform.
With the damper wire flat on the platform, the wire should be horizontal. To make it leveled, first bend the little neck upwards with a plyer or damper hook, then bend up or bend down the length of wire right at the crease with a wire bender. Check that the wire is horizontal. Carefully install wire through guide rail, be careful not to push out or foul the bushing.
Gentilly press down the damper head, observe if the wire aligns with its hole on damper post. For this wire, it is to the left, needed to be bent to the right. There are usually two bends on a wire, bottom bend is spacing bend, top bend is squaring bend. Do so at the two lines marked on jig. Check to see if top and bottom of wire are both horizontal. Then check wire position to the hole again. Install wire.
Looks like the damper head on the right needs to move to the left a hair. To space it, bend the neck then crease, make sure the wire is still horizontal when laying on jig, install wire, and check spacing again. Sometimes the wire needs a few degrees of angle from the vertical line shown in bottom-mid picture. The lines marked on jig indicate degrees of wire to the vertical line. Tighten set screws.
When tightening the set screw, the damper wire may twist with it thus damper head twisted, too. Simply twist the wire back with a plyer. Check before moving on to the next damper.
Some damper heads need to clear the plate strut. The wire is bent as picture in the middle to push the damper heads forward. The best way to bend it is to copy the old wire which we've lost. Go slow, maybe do it over and over again, to make sure the bends are right.
The left picture shows when the damper post is not quite vertical. The wire is bend to compensate the post angle. The right picture shows when guide rail hole is off-centered from the factory decades ago. A mini bend is made to clear wire from hitting string when moving up and down.
After one day and a half, all wires are installed. Check for flaws. Take out pitman and drop the tray before gluing on damper felts.
Lay out the damper felt, make sure there are enough pieces for this job. Press thread in tri-cord felt. The thread opens up space between the two teeth for a better damping effect. In another word, the wedges of felt sit better in between strings. Apply felt glue on back of felt, lift damper head, glue on dampers. A mirror is very helpful to check if the felt is glued on centered. The weight of damper head is almost enough as a clamp.
The flat felt is given tapered, longest to the bass, shortest to the treble. At tenor section, tri-cord felt is glued in front of damper head, and flat felt at back. Also use a mirror to monitor the process. Sandbags or rice/bean bags are helpful as downward pressure for a good glue joint.
At treble, the felt both in front and back are flat. Gluing can be down out of piano. Simply glue felt at center of each end of damper head, press down with something like sandbag or rice/bean bag. The damper felt gluing jig was made by Tom Rourk (1955-2021), an Irish piano technician, expert of historical keyboard, who passed away a few years ago.
The damper heads next to the plate strut are shorter at back which require shorter felt. Cut the felt with a very sharp blade and a quick downward blow so the cut surface comes out clean. Dry fit before glue application. If there is not enough space between back edge of damper head and damper wire, glue both pieces in the front part of damper head.
With sandbags on top of damper heads, the glue is left to dry over night. It took two days to finish the fitting and felt gluing at the shop now. At Mason and Hamlin factory in Haverhill, MA, it takes a worker maybe half a day for this job. Hopefully next time, the work speed could be a few hours faster.
Grandpa, thank you for your company. Miss you lots and lots.