Hello piano techs- Before you stop reading, these are not my thoughts. Hold it! Thought I would contribute some published observations about the plate, and even the Baldwin Acu-just hitch pins, without proof-reading, excerpts from "Piano Servicing, Tuning, & Rebuilding; For the Professional, the Student, the Hobbyist," by Arthur A. Reblitz, New York: Vestal Press 1976, pp. 13-15, and add a few comments: "The plate is made of cast iron and is designed to support, with the help of the frame, many tons of string tension. The average medium size piano has about 230 strings, each string having about 160 (72.7 kg) pounds of tension, with the combined pull of all the strings equaling approximately eighteen tons (16,300 kg). The tension in a concert grand is close to thirty tons (27,180 kg)...." Is not the primary function of the plate of the modern piano to withstand string tension? "The hitch pins in Baldwin pianos made after the late 1960's are made of slotted tubular steel and are mounted at a 90 degree angle to the strings. They are called Acu-just [sic] hitch pins, and they allow the height of each string to be adjusted individually for correct down bearing...." Pretty ordinary conclusion. Maybe there is more to the hitch pin. "In any piano, the plate must hold everything together under enormous tension, but at the same time must permit the strings and soundboard to vibrate freely without absorbing and deadening too much vibration. To accomplish this double purpose, a plate is screwed down around its perimeter but does not touch the soundboard anywhere else." It appears Reblitz also observes a potential for the plate to deaden the sound as well. "The pinblock, frame, and soundboard must be aligned precisely to support the plate all the way around without any high or low spots, so nothing is forced to bend when the plate is screwed into the piano. At the same time, the height of the plate over the soundboard must be adjustable, in order to adjust the downbearing of the strings on the bridge for optimum tone quality...." So then pinblock shifting as I formerly explained 4/25/09 under the heading "Nichtgebunden" is a consideration. Still no word on the original "In a grand, the plate is usually supported by wooden dowel pins glued into the rim; their height is adjusted until the plate makes contact with all of them, without rocking. Most piano plates also have one support somewhere in the middle, consisting of a nose bolt passing through an oversize hole in the soundboard. The nose bolt has a shoulder, and a nut screws the plate down to the shoulder. The height of the bolt is usually set so the plate does not bend when the nut is tightened. Some grands have a second nose bolt attached to an iron casting called a bell, under the high treble part of the soundboard. The bell has two functions. By screwing the nose bolt further into the frame, and by tightening the nut, the plate may be pulled down and flexed a little, in order to restore bearing to the high treble after the soundboard gets old and loses some of its crown; also, the hollow casting of the bell supposedly adds brilliance to the high treble notes by sympathetic vibration of the air chamber." It is coincident with observation of Jeff Tanner below that there theoretically is a bell effect of the plate. For my sake I add that the conviction of Reblitz is that not only with pianos with accujust hitch pins, but on grands with a bell, one should consider certain modifications, even plate flexing, to accommodate the slumping crown of an old soundboard to retain downbearing, rather than replacing the soundboard. Why didn't I think of that? - Ben -----Original Message----- From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Jeff Tanner Sent: Friday, May 08, 2009 3:42 PM To: caut at ptg.org Subject: Re: [CAUT] Accujust and grunting fish bait ----- Original Message ----- From: "Don Mannino" <DMannino at kawaius.com> "But an iron plate will not ring very efficiently most of the time......The manner in which iron will transmit vibrations is very different than mud, so the analogy may not really apply." Bells are made of iron, not mud, right? Jeff
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