Richard, Thanks for your post. I will archive your post and look it in more detail when I do the next action set up. I'm currently manufacturing gear for building RC laminated panel sound boards with a vacuum press so I'm rather occupied on this at present. I read most of the posts even though I'm not always contributing to each discussion. Best, Ron O. >My problem with the method you give below Ron is that it doesnt >correspond to the >hammer shank ratio taken by weight measurements... and it should. > >There is more then one way of measuring the ratio of a lever to be sure, but >regardless of the method the result simply has to be the same... or >you have an >arguement with Archimedes and his law of levers. I dont find that >measureing down >to the knuckle/jack contact and up to the hammer center top both >from the flange >center pin does that. > >The weight measurement of R and whatever results from measuring the distance >between fulcrum, force, and lifting points has to be the same >because d1 * W1 = >d2 * W2. > >I find that measureing along the shank yeilds the same result on >average as the >Stanwood method of finding ratio yeilds. Both as the hammer shank >ratio isolated >from the rest of the action, and as a part of the whole. This lack >of consistancy >with the weight ratio, along with the differeing ratios for bass and treble >hammers, leads me to believe that it is better to measure along the shank...ie >centerpin to hammer moulding center / centerpin to knuckle core center. > >Cheers! > >RicB > > >Overs Pianos wrote: > >> By the way Richard, a couple of weeks ago when I wasn't paying >> attention, you mentioned some difficulties you were having using the >> hammer/key ratio formula we use. Your comment about the bass hammers >> verses the treble hammers is correct however. The ratio for the bass >> hammers will be a little higher than the treble sections (all other >> things being equal), since the greater boring distance of the bass >> hammers will result in a longer diagonal length from the hammer >> centre to the hammer strike point. However, you will find that most >> modern action installations in which the hammer core is set 130 mm >> from the centre pin will typically have between 138 to 140 to the >> striking point of the treble hammers. I tend to use this a standard >> when calculating the hammer/key ratio. You mentioned in your post >> about the hammer shank ratio being around 7.6:1 if you are measuring >> a 130 mm shank with a 17 mm roller slot. However, the important two >> hammer lever measurements will be the diagonal length from the hammer >> centre to the hammer strike point and the diagonal length to the >> roller jack contact point. If you look at these figures you will get >> typically around 138 to the strike point, and around 20 to 22 mm to >> the roller contact point. This will result in a ratio for these two >> length of around 7.0. At the end of this process, no matter which way >> you measure the ratio, we are all primarily interested in how many mm >> the hammer strike point moves for each mm of key dip. An examination > > of blow distance and dip alone will tell us nothing, since the let > > off and after touch consumes key dip for its execution. > > > > Ron O. >> -- > >-- >Richard Brekne >RPT, N.P.T.F. >UiB, Bergen, Norway >mailto:rbrekne@broadpark.no >http://home.broadpark.no/~rbrekne/ricmain.html > > >_______________________________________________ >pianotech list info: https://www.moypiano.com/resources/#archives -- _______________________ OVERS PIANOS - SYDNEY Grand Piano Manufacturers Web: http://overspianos.com.au mailto:info@overspianos.com.au _______________________
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