---------------------- multipart/alternative attachment Del, Richard and list, >(Original question) Is there an optimum amount of counterbearing? > >(Reply from Ron O) Yes. > >(Del replied) No. There is no optimum amount of counterbearing . . >angle. The optimum string deflection angle is a function of the >duplex length and the frequency of the speaking length. While this may be true if considering different materials, when using hardened bars, to avoid premature wire failure the counter bearing angle must not exceed 15 degrees. >In general, shorter duplex lengths do not require as great a string >deflection angle to effectively and efficiently cut off the speaking length. >Longer duplex lengths require greater string deflection angles to >effectively cut off the speaking length. It is these longer duplex lengths >that cause trouble. They invite the transfer of energy from the speaking >length of the string into the duplex length. Once there, this energy causes >no end of problems and generates no end of exotic solutions to quiet it >down. Agreed. "It is these longer duplex lengths that cause trouble" should be imprinted on all designer's foreheads before commencing any new project. >(Original question) Is there a recommended way of building it up in >the capo section >when dealing with a cast duplex as in a Steinway? > >(Ron O replied) We have done it, but its far too long a job. Better >to cut off the > > bars with an angle grinder and put them where they should have been > > placed at the time of manufacture. > >(Del F replied) Ditto. > >We both shorten the duplex string length and increase the string deflection >angle by replacing the counterbearing bars. We shorten, detune and set the deflection angle to 12 - 15 degrees, making a new set of bars which are tapered in height, shaped, hardened and electroless nickel plated to prevent corrosion (1040 carbon steel is particularly prone to corrosion if not coated). >But we have not found it necessary to harden all of these various parts -- >certainly not the counterbearing bars. If the back counterbearing bar is >reasonably close to the right place and is reasonably close to the right >height, i.e., keeping the duplex reasonably short and the string deflection >angle reasonably high, the hardness of the material does not seem to matter >all that much. For the counterbearing bars we simply use either half-round >or half-oval extruded brass. Usually half-oval. > >If hardness is an issue with a particular piano it will be at the string >termination Certainly the Capo bar will be more critical than the duplex. Yamaha harden their capo but leave the duplex bars soft. However, we have found that it is possible to improve the tone further by addressing the duplex bar also. >and my solution of choice is to grind off the V-bar and replace >it with a silicon bronze casting. The patterns are not particularly >difficult to make, the castings are not all that expensive and they can >easily be placed to correct for wandering strike points. It would also allow the rebuilder the opportunity of correcting any strike ratio problems which may have been introduced through poor pattern making at the time of manufacture. >They are easily >shaped if needed and -- depending on the exact alloy -- can approach the >hardness of mild steel while retaining the lubricity of brass. For pianos in commercial service (and tuned perhaps 4-5 times per week), say an auditorium which is used daily for broadcasts or major recording projects, the 'easily shaped' part is perhaps a bit of a worry. If it is easy for the technician to shape the capo bar, it follows that it must also be easy for the piano wire the cut the capo bar to shreds, doing its 'cheese cutter' thing. We have experienced this many times with pianos in frequently tuned situations. Our early rebuilds got reshaped bars which were unhardened - some of these pianos have been restrung since, so I am speaking from experience. Regarding lubricity, our bar-hardened rebuilt pianos have retained their easy rendering abilities, when compared to a standard as cast bar. When the wire cuts into a non-hardened bar, the bar tends to 'grab' the wire to the detriment of string rendering. >I have designed these into several new pianos, though I don't know of any >that are still using them -- the manufacturers seem to prefer struggling >with improperly shaped and placed (but traditional) V-bars cast with the >plate. Many manufacturers simply 'don't give a damn'. Furthermore, they don't usually seek feedback from technicians 'out the in field'. After all, technicians don't know anything do they? I would suggest that if manufacturers would go to the trouble of seeking the odd 'in the field' opinion, they might be surprised to find that there are a few thinkers 'out there' who may indeed have useful information, which might well help them to build better pianos. But why would anyone want to do that? Most makers prefer to stick their head in the sand, building their pianos just the same way as that famous maker they keep hearing about. >Or, more frequently, they seem to prefer simply ignoring the myriad >problems associated with improperly shaped and placed cast-in V-bars. And, >of course, they do cost a bit more and they do introduce an additional step >in the plate preparation process. What do you expect for $25,000 to $50,000? >Clear, clean trebles? Don't be silly! > > >(Original question) What are the downsides to building up the >counterbearing, if any? > >(Ron O replied) Time to do the job. Greater risk of string fatigue >and breakage. > >(Del F) Yes, and it's that second one that bothers me about the practice of >hardening things around string deflection points. Especially at the V-bar. >Every company I'm aware of that has produced pianos with hardened V-bars has >come to regret the practice, though not all have admitted so. The warranty >costs of replacing all those broken strings can be considerable. 1) This is a most important point which I have raised previously also. While I come from the 'hard bar' school of tone building, I must admit that pianos with hardened bars will not tolerate technicians who insist on swinging wildly from the tuning lever while setting the pin. Good hammer technique is absolutely critical for the long term survival of piano wire when bearing against hard counter bearing bars. 2) While the wire may survive for a longer period when using softer counter bearing bars, how long does the tone quality survive in a high use situation? 3) We do not warrant piano wire in any of our pianos. This is not an admission of problems associated with hardened bars (we've been hardening bars since 1994). Our rebuilt pianos generally give around six years of high use service (ie. with frequent tunings - say four or five times per week) before the first wire breaks, and by that time its due for restringing anyhow. We do not warrant piano wire because we know that there are technicians with appalling hammer technique. We will not be held accountable for the incompetence of another piano technician. Therefore, we do not, and will not cover piano wire under warranty. In conclusion, it looks as though the jury remains well and truly out on the subject of front duplexes. We are still experimenting with variations on a theme. Some answers may begin to appear in Reno? Regards to all, Ron O -- _________________________ Website: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au _________________________ ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/67/b0/cd/cb/attachment.htm ---------------------- multipart/alternative attachment--
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