Hi Fred, Another good subject. I've a memory of some famous pianist saying the soul of the piano was in the sustain pedal... Horowitz? Measuring Damper up and down weight allows for calculation of Damper Friction weight which will point you in the direction of any problems with damper flange friction and guide rail friction. The Damper BW will also show inconsistencies.. Whenever I install new damper actions I measure Damper Under Lever weight by tipping the lever on a roller bearing and resting the front of the lever on the digital scale. I also measure the weight of the damper felt/head/wire and add it to the underlever weight and graph it out to look for bumps in the scale which I smooth out by adding weight to the damper heads. The break area is often a trouble spot. Lot's of variations in damper weights between/within manufacturers/makes. It's another area of refinement... it all adds up to enhancing the magic. I use a roller bearings on the pivot and damper end of my 1:1 jig. Regards, David Stanwood > In an earlier post in the friction thread, I described a >device I had imagined to measure the weight of the damper as felt >at the key. I had a little time to spare between access to rooms, >and put one together. I think it took me all of ten minutes. A base >about 1x4x8", a "balance rail" scrap of 1/2" plywood, a lever about >2' long, 1/2 x 3/4" (I think scrap from a strip used to hold >hammers in place during shipping), a couple pedal brackets, a >standard .146" balance pin. I glued a little scrap of wood on one >end of the lever as a platform for weights - not really necessary, >but nice - and then drilled a hole in the lever at the balance >point. A couple drywall screws to hold the brackets, driven in with >an electric screwdriver. > It works very nicely. I tried it out just to see what I'd >find, and a couple things jumped out at me. First, there is quite a >bit of force needed to push trichord dampers out of the strings - >as much a 5 gm. Even when trimmed nicely and precisely to the >bottom of the strings there is a significant amount, though the >difference between well- trimmed and not trimmed is noticeable, also >between well-trimmed and just shy of well-trimmed (0.5 mm below the >string line). On the concert instrument, where I have taken a fair >amount of trouble to have the dampers well-regulated in all ways, I >found a range from about 20 gm to over 30 gm top to bottom, and >some zigzagging along the way in the 5 gm range. On a B that I had >replaced action parts and damper felts on, but had only slapped the >dampers in and regulated them for lift and to be sure they damped >(fine-tuning put off until time allowed), I found much larger >zigzags, 10 gms from one to its neighbor in a quick sampling. I >suspect a lot of it had to do with some wires leaning on bushings, >others not, but won't know until I have time to look more carefully. > Bottom line, I think this is a good thing to look at, a >significant element in the touch of a grand. > > > >PC100011.JPG > > > >PC100015.JPG > > > >PC100017.JPG > > > > >Regards, >Fred Sturm >University of New Mexico >fssturm at unm.edu > > > > > > > In an earlier post in the friction thread, I described a >device I had imagined to measure the weight of the damper as felt at >the key. I had a little time to spare between access to rooms, and >put one together. I think it took me all of ten minutes. A base >about 1x4x8", a "balance rail" scrap of 1/2" plywood, a lever about >2' long, 1/2 x 3/4" (I think scrap from a strip used to hold hammers >in place during shipping), a couple pedal brackets, a standard .146" >balance pin. I glued a little scrap of wood on one end of the lever >as a platform for weights - not really necessary, but nice - and >then drilled a hole in the lever at the balance point. A couple >drywall screws to hold the brackets, driven in with an electric >screwdriver. > It works very nicely. I tried it out just to see what I'd >find, and a couple things jumped out at me. First, there is quite a >bit of force needed to push trichord dampers out of the strings - as >much a 5 gm. Even when trimmed nicely and precisely to the bottom of >the strings there is a significant amount, though the difference >between well-trimmed and not trimmed is noticeable, also between >well-trimmed and just shy of well-trimmed (0.5 mm below the string >line). On the concert instrument, where I have taken a fair amount >of trouble to have the dampers well-regulated in all ways, I found a >range from about 20 gm to over 30 gm top to bottom, and some >zigzagging along the way in the 5 gm range. On a B that I had >replaced action parts and damper felts on, but had only slapped the >dampers in and regulated them for lift and to be sure they damped >(fine-tuning put off until time allowed), I found much larger >zigzags, 10 gms from one to its neighbor in a quick sampling. I >suspect a lot of it had to do with some wires leaning on bushings, >others not, but won't know until I have time to look more carefully. > Bottom line, I think this is a good thing to look at, a >significant element in the touch of a grand. > > > >PC100011.JPG > > > > > >PC100015.JPG > > > > > >PC100017.JPG > > > > > > >Regards, >Fred Sturm >University of New Mexico ><mailto:fssturm at unm.edu>fssturm at unm.edu
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