One of the most important as well as difficult tasks of piano regulation are the dampers. This article explains how to adjust them on an upright, particularly after replacing them.
Before replacing dampers in an upright, you should measure their depth. Some modern replacements are too thick. There are 7/16" and 3/8" deep dampers. If you have an option (some actions don't have enough clearance to give you an option), use the thicker head. Using a thin damper head will weaken the damper springs by decreasing the depression an additional 1/8".
What you are going to have when you get through will be a damper line that lifts evenly from the strings with the damper lift rail and the key. They will operate exactly like a finely adjusted grand.
Once you get all the damper heads cut off the blocks, lay the action horizontally with the damper blocks facing you on the bench and soak the remaining glue off, scraping, warming, whatever you need to do to clean them up. Then do not install your new dampers quite yet. Replace the action first and align the damper head blocks a little better with the strings. Use chalk to mark the bad ones so you can bend their wires with more control when the action is pulled away. Remember too that angled piano strings change the alignment with the bare damper block. So if you can't visualize where the damper will end up on the damper block, have one handy to slip right in there and check it, first before you deflect the damper wire. (Make sure the damper block screws are tight, too, but don't overtighten them.)
Replace the action and start installing the bass dampers first, using the strings to align them on. Work your way up to the treble by doing the same with the treble felt pads. Grand damper felt usually is best. The upright damper felts for treble are too often cheap felt, off-color, stiff, coarse, and backed with a red backing that isn't necessary, but cheaper to make that way. The best treble dampers are just fine felt pads, no backing at all-- but suit yourself.
Be careful about replacement bass dampers, by the way. Some are still constructed at the factory with contact cement. This stuff turns to dust and the damper heads fall off. I reglue each bass damper to its felt mounting pad top and bottom with a PVC-E glue, first.
There are now two things you have to do before the dampers are regulated. First, you have to adjust their pressure on the strings. Second, you have to adjust their lift from the strings. When these two settings are correct, the dampers will all work together.
A properly adjusted damper line, even after being regulated, will not necessarily be aligned perfectly with the damper lever lift when you pull the action out of the piano and try it, because of the different spacing between double strings in the bass. In the treble, unevenness can result from damper heads being tilted vertically, so that even while the damper works, it appears to be ahead or behind the others. Do not let an apparent damper line be too much of an influence while the action is on the bench. And at that time, you should straighten the vertical tilt of any heads. They must be straight up and down despite their sideways angle. Tighten the heads, too. Some may be loose.
First you will need to cut a small wedge of hardwood about 5-6" long, 3/4" wide, and tapering from 0" to about 1/2-5/8" at the widest part. This you will place vertically, thick end up, between the damper lift rail and the whippen molding at the bass end of the action. It is used to gradually raise and lower the damper rail. It is quickly adjusted and stays put.
To start adjusting then, you will press your wedge into place until about 1/3rd to 1/2 of the dampers start back. That means 2/3rds to 1/2 are still contacting their strings. Now if, when you start, no dampers are touching strings, then you will have to first bend all damper wires forward a little on the bench. do that task with the wedge in place so the dampers are in a theoretically straight line. Then begin, back at the piano.
Leaving the wedge in place, replace the action. You may have to bend some action bolts slightly with a hammer and block of wood so that all your bolts align well with the bracket mounting holes. You do not want any bolts dragging their holes as you swing the action on and off the shoulder bolts, rocking it back and forth on the ball end studs in the keybed.
At the place you have chosen to block in your wedge, you will now set your damper heads by bending their wires slightly in the piano, and by rocking the action you are able to reach in and support the damper lever while safely bending its wire with your fingers (usually). If your damper springs were too weak to begin with, a very slightly more deeply adjusted wedge position should allow you to bend the heads in a little deeper, so you can change the percentage of heads contacting, as mentioned above.
Now the idea is to bend each head so accurately that there is a small but equal amount of deflection in each damper head when you rock the action back onto the shoulder bolts each time. This is easier to do than it sounds like, here.
Do it this way: Start with the ones that are already too close and bend them back toward your chest. Get the worse ones FIRST! Progress to the least worst. Then graduate to the ones not touching and bend them forward. The worst ones first, and progress to the least worst. By staring into the row, even the tiniest movement becomes noticeable as you very gently rock the action a little-- just at the point of deflection. In probably 10-20 minutes, even a novice can have this finished on a badly out-of-adjustment action. It's no sweat.
At this point in the regulation, you have now adjusted the damper's depth setting, so first, remove the wedge and see if you like the way they damp. If you didn't get enough depth, go through them again, but this time depress the wedge more. A damper should depress about (roughly) 1/8" on the string. Perfection is hard to attain the first time around if you're new to doing it. Go back through a few times and touch them up.
You have set the depth, so now you will set the lift. With the action still in the piano, reinsert your wedge and as the dampers just barely budge, fine-tune the row so they all barely budge at exactly the same point! Very important, now. Don't compromise and say, "That's better than they have ever been so far, so it's good enough." It's NOT good enough. Do it right! Get them perfect. Doing them this way, you will be able to, and you will then get faster.
Next, replace the wedge at the point that they all just begin to get light in the strings together and remove the action to the bench with the wedge jammed in place right there. Leave you wedge right where it is. Face the action with the dampers toward you, and get your damper spoon adjusting tool handy.
The next step is really a time-saver! Cut a straight stick of wood about 1/2" to 3/4" square and a bit longer than your treble section between action brackets. Clamp this to the action brackets. (Some brackets do not allow good depth adjustment, so bear with me and get the principle involved first, then you can make whatever modifications you have to make later).
You want your hammers to raise about 3/4" before the dampers budge. But that depends on the action and the touch you want. So for now, we'll go that route. Our stick is clamped between a section on the brackets and the hammers touch it about half-way through their travel (or a little less). Start raising the stickers with one finger. When the hammer contacts your stick your finger stops. Slip the spoon bender around the whippen spoon and bend it so that it starts the damper back at the point the hammer touches your stick. There is some deflection in each spoon and they will all spring back, so slightly overbend (GENTLY), and then try it by dropping and raising the sticker a couple of times. The moment you see the hammer touch your stick, the damper head budges. That's perfect. The factory NEVER got them that good! And if you recheck your damper line the next day, you will discover that there are a few that didn't stay adjusted. Fix them.
One last point: Nothing in a piano action is in a perfectly straight line. So the end result is not straight lines! The end result is that each note is fine-tuned and precisely regulated regardless of its neighbors. The overall effect will be perfect regulation. You are dealing here with 88 notes of separate trapeze acts. They will all be approximately the same. The only thing that must be exactly simultaneous is when the dampers all lift off their strings. Keep checking this parameter, because it must be perfect. Just remember, it's a good act when they all take their bow together.
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