Ed sutton wrote: > Could I make or buy a gauge to measure this? [MOI] A couple of things I have tried. The first one is very simple. Hold down the damper pedal and place just enough weight on the key to get a sound out of the note when you release the key. I call this the "noise weight" or NW. You pick up all the junk this way. Friction, BW variations, regulation variations, but it's interesting to play with. If you take NW-DW then you should get rid of a good bit ot the friction and BW variations. A graph of NW-DW, in theory, should be related to the MOI. Funny thing, though. I graphed this for my piano and instead of decreasing nicely across the piano, it went down, then back up, then down again. (I have smooth SWs). I expected a more or less decreasing curve across the piano, albeit with some noise, and this was not what I saw. Instead, it appears that NW-DW and SWR are correlated (my SWR is curved in a similar way). The second thing is a bit more involved, but not too hard. I tried to imitate an arm with rigid finger dropping on the key. So I took a piece of 2x4 about 20" long. Put a pivot in the middle and made a "finger" on one end - a nail, head down with a piece of felt stuck on the head to avoid scratching. I use a smaller block of wood on top that I can slide forward and backward to change the balance. I set it up so that it's level with the finger on the key. Lift it about 5/8" and but a block under the finger. Pull out the block from under the finger and let it fall on the key. Adjust the block on top until you just get a sound, as above. Then measure the distance of the top block from the balance point (i.e. define the point where it balances as zero, and measure how many mm forward you have to move the block to get a sound - I have a scale taped on top). Now the curve is quite different, looks more like what you'd expect, with a nice curve from bass to treble (still noise in it from friction, etc). The block already has speed and a fair amount of momentum before it comes in contact with the key. Somehow the fact that there is an impact and not just a constant force (as from a weight) makes a difference in the type of curve you get. This tool seems to be quite sensitive and numbers correlate well with the touch of the piano. Things like pre- and post-regulation, friction changes, and weight changes are quite readily seen in these graphs. -Mark
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