Yep, if your hanging hammers. David I. ----- Original message ----------------------------------------> From: Farrell <mfarrel2@tampabay.rr.com> To: Pianotech <pianotech@ptg.org> Received: Tue, 13 Jul 2004 06:06:52 -0400 Subject: Re: Ancient Backchecks? >Bill Spurlock has an excellent jig for this that takes the guesswork out of >the process. >Terry Farrell >www.farrellpiano.com >----- Original Message ----- >From: "David Ilvedson" <ilvey@sbcglobal.net> >To: <pianotech@ptg.org> >Sent: Monday, July 12, 2004 11:57 PM >Subject: RE: Ancient Backchecks? >> Make sure your hammer tails are the correct shape...circular curve with a >3 inch radius. To understand that shape, use a compass with a 3 inch >radius. Clamp each section and use a drill with a sanding disk. 60 >grit. Look at the shape of the drawing and approximate the curve of the >hammer tails. The friction in hammer checking is the wedging of the >hammer/center pin circle and the balance pin/backcheck circle. A roughed >up backcheck is mostly unnecessary if all else is right. Also the back >check should be as high as the hammer shank at rest. Lower than that will >cause problems. >> >> David I. >> >> ----- Original message ----------------------------------------> >> From: Richard Cromwell <rcromwell1@msn.com> >> To: 'Pianotech' <pianotech@ptg.org> >> Received: Mon, 12 Jul 2004 23:10:20 -0400 >> Subject: Ancient Backchecks? >> >> >> >Greetings List! >> >> >I have a question regarding this absolute nightmare of a piano action >(1927 >> >Chickering - 5'8") I've been fortunate enough to have on my bench for the >> >past few weeks. After countless repairs, I get it back together and >while >> >rough regulating it I find it impossible to get consistent backchecking. >> >> >When the action is on the bench, I can get he hammers to check, a bit >low... >> >but at this point I'll take what I can get. When I duplicate the string >> >height over the hammers with a jig and then play a mezzo forte/fortissimo >> >blow - I get mostly no checking and a lot of double bouncing. The jack >is >> >escaping... so I can only come up with a few reasons why this is >> >happening... >> >> >1. The rep spring is too strong... unfortunate because they are really >> >difficult to get to on this beast. I don't think this is the culprit, or >at >> >least the only one. My guess is... >> >> >2. The fact that the backcheck leather is 80 years old, misshapen and >worn >> >smooth as a baby's bottom where the hammers should be making contact. It >is >> >almost to the point of being spongy in look and consistency. Not leather >> >like at all. This leads me to a few questions... is friction in regards >to >> >backchecking coming more from the wedge like positioning of the hammer >and >> >backcheck when they come into proper contact? Or, is it from the tail >> >rubbing up against the rough surface of the leather? (I know the answer >is >> >probably a combination of both - but what I really want to know is how >> >important is it to have good condition leather on the backchecks? - thus >> >justifying their replacement.) >> >> >3. Also, at some point in this piano's lifetime a well meaning fellow >> >attacked it in an attempt to repair it. I can go on and on about the old >> >botched repairs I've fixed and crooked keytops etc... But I won't. But >> >one thing I will mention is whomever it was put new hammers on the old >> >shanks, could it be possible that they were bored and/or had their tails >> >shaped incorrectly (too short) - thus leading to the checking problems. >> >> >Now if it is determined that the misshapen and ancient backchecks are >indeed >> >the guilty party and we ignore the misshapen hammer tail/improper boring >> >hypothesis... I have never had the pleasure of replacing a set of >> >backchecks, how difficult is it? I removed one as a test and it sure >wasn't >> >easy to get out, I can't imagine it being very easy to get the new ones >back >> >in. There is little information out there on backcheck replacement... so >I >> >turn to you my esteemed colleagues! Please offer up any hints, >experiences, >> >help, aid, sources of information, etc. that you may have to offer. >> >> >Thanks in advance. >> >> >Richard Cromwell >> >Cromwell's Piano Service >> >Detroit-Windsor Chapter >> >_______________________________________________ >> >pianotech list info: https://www.moypiano.com/resources/#archives >> >> _______________________________________________ >> pianotech list info: https://www.moypiano.com/resources/#archives >> >_______________________________________________ >pianotech list info: https://www.moypiano.com/resources/#archives
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