----- Original Message ----- From: "Ron Overs" <sec@overspianos.com.au> To: <pianotech@ptg.org> Sent: September 08, 2001 7:00 PM Subject: Re: Killer Octave > Sorry about the poor nomenclature of the previous post, it should have read; > > . . . . . While on the topic of the killer zone, I suspect that the > 'tone bell' of Steinway pianos might indeed be a 'tone dissipator'. > If you check the location of the connection bolt from 'bell' to > plate, you will notice that it connects adjacent to the so called > 'killer' zone, or should we say 'killed' zone. Just last week I > crawled under a D to feel the movement at the bell connection bolt > under heavy playing (try it - you'll be amazed). The next D I rebuild > (if it ever happens again) will likely get another beam and set bolt > in place of that suspect device. I'm not suggesting that the problem > is the 'bell' alone, but I suspect it is contributing. It would be > interesting to compare the Yamaha CFs with and without the tone bell. > Gosh its good to see marketing dictating design as usual isn't it? ------------------------------------------------------ Instead of removing the bell you might try leaving it in place and adding a wood brace--i.e., another belly-brace--between the inside treble curve and the bellyrail. If you don't like how much the bolt vibrates you might try threading the hole in the plate and installing a larger (fully-threaded--in fact, you may have to thread the bolt yourself) bolt in place of the original. Then you can also put a nut on top of the bell and another on the bottom making the connection somewhat more solid. The bell does really serve a somewhat useful function, though it's not the one S&S has been telling us about. And, no. It has nothing to do with the Magic Circle of Sound. The bell, along with the coupling bolt, mass-couples the plate to the inner rim. Taking the bolt out--you can do this even with the piano tuned to pitch, it's not structural--allows the plate to move in response to the energy in the string backscale and in most pianos will result in a reduction in sustain time. How much energy loss--hence, how much of a loss of sustain time--there is in the plate at this point depends apparently on the precise characteristics of the individual plate--it's thickness, and certain mechanical characteristics dependent on the pouring and cooling rate of the casting, etc.--but there is a measurable amount of vibration in that area that is damped by the bell and coupling bolt. Del Delwin D Fandrich Piano Designer & Builder Hoquiam, Washington USA E.mail: pianobuilders@olynet.com Web Site: www.pianobuilders.com
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