Farrell wrote: > Richard wrote: > > "Basically what I do is to pick a SW curve based on the target ratio I want, install FW to fit the FW max table ...." > > How do you relate/figure SW to SWR? I thought target SW should be based on piano tone, and then geometry and FW and whatever adjusted to accomodate the desired SW? Well... yes... but as I said, this is a more or less generic solution that is workable for most actions without getting into to much meat and only a bit of potatoes...light on the gravy as well. But.. and for example...you can pick a SWR of 5.6 and a SW curve to match for a BW spec of 38 that yields the maximum FWs (The chart included in the kit is simply the result of figuring FW's based on these other parameters being ideal.) Both the FW's, and the SW's are easily controlled variables so you can make those fit the equation no problem. Whats left is the whippen weight, leverage, and fricton. Friction you can controll pretty well too. Whippen weight is what it is, basically and doesnt really contribute much to the formula, so you have KR and perhaps the knuckle position to fool with leverage wise. But put it this way..... if you have a FW and a SW and a KR and a WBW and Friction that all fit into place in the formula for a given SWR specification.... well the result is BW. In anycase.. this approach works pretty well and I have never missed by more then a gram or two in BW, or looked at the other way around... I always end up with a SW to SWR relationship that is very close to what I planned ahead of time, and much better then the action was to begin with. SW's are picked for tone yes... and if you need a big set of hammers that makes it neccesary to approach touchweight concerns in a more complete manner then by all means... get Davids resources on the line. But his system is also great for providing an extremely even touchweight. In just every case the hammer mass and front key mass are on very even curves... which essentially evens out the inertia component of the action.... in itself a very valuable asset. > Unfortunately, this piano appears to have new Yamaha hammers on it. But they are not tapered, or arced. Friction in the hammer-shank flanges is all over the place. Is it reasonable to try the water/alchohol thing to shrink-size the bushings before repinning the whole shebang? I wish the hammers and knuckles were more worn, then it would be easy to recommend a new top half of the action. Never tried that trick... Roger swears by it.. I re-pin and apply teflon powder after reaming the bushings a bit. > By installing FW to "fit" the FW max table, are you suggesting that FW should be at or near that maximum value? If so, why? Doesn't "maximum" in this case mean that "at that value or below is fine"? Or not? Thanks. Read above. You can figure on lower FW curves if you are going to install helper springs tho. Hope this helps. > Terry Farrell > > ----- Original Message ----- > From: "Richard Brekne" <richard.brekne@grieg.uib.no> > To: <pianotech@ptg.org> > Sent: Wednesday, May 15, 2002 3:11 AM > Subject: Re: Touchweight Metrology Question -- Richard Brekne RPT, N.P.T.F. Bergen, Norway mailto:rbrekne@broadpark.no http://home.broadpark.no/~rbrekne/ricmain.html
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