John Hartman wrote to Tom Saye: >I may be presumptuous but it sound like you have a friction problem. High >up weight and low down weight usually means excessive friction. Subtract >the up from the down and divide by 2. Friction should be lower than 18 in >the bass and gradually lessening to 12 in the high treble. The capstan is >usually the last thing to consider if you have a friction problem. Check >the key easing first. The fraction of the frictional touchweight,(the average of upWt and downWt) due to key pin/bushing friction becomes excessive when it is above 3 grams. I highly recommend direct measurement of key pin/bushing friction if there is any doubt as to its value. The traditional visual tests can be unreliable. Here is a method: 1. Place key frame with keys on the bench. 2. Place temporary lead weights on top of the backside of the key to be measured. 3. Arrange the weights so that the key has a certain upweight, say 20 grams. 4. Measure the downweight and write it down on a sheet of paper. Be sure to put on the paper what the numbers are in case you want to refer to them later. 5. Add the downweight to the upweight and divide by two. 6. If the answer is more than three then your key pin/bushing friction is excessive. Track down and fix the source of friction. Dry teflon lube is extremely effective in reducing the friction coefficiant of the bushing cloth fibers. A report of your findings in regards to samples this actions friction fractions, including overall frictional touchweight, hammer and wippen flange friction, as well as key pin/bushing friction, would be instructive and helpful in beginning to discuss the possible sources of your touchweight problem. David C. Stanwood
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