As I see it, with a closed face pinblock, the plate in the pinblock area is acting as a beam - a Z section beam if you will (like an I beam with a couple of pieces of flange missing). The plate flange against which the pinblock bears is one flange (or cap) of the Z and the upstanding flange at the front end of the plate (along the stretcher) is the other flange (or cap) of the Z with the portion of the plate over the pinblock acting as the web of the Z beam. The presence of this web allows the entire section to work as one beam. If this web is not there (as in an open face pinblock) the two flanges work independently as separate beams. The bending stiffness of these two independent beams is substantially less than the bending stiffness of the entire section working as one beam. In practice, on an open face pinblock, the flange against which the pinblock bears will be the only flange working (resisting bending) with the front flange in effect doing nothing. So, there should be less deflection of the pinblock in the direction of the string load with a closed face pinblock than with an open face pinblock. What effect this has on the tone and on tuning stability would probably depend on just how massive the pinblock and plate structure of the open face pinblock in question are. I can imagine it could have an affect on power, as some of the string energy would be used in flexing the pinblock and plate. Phil --- Phillip Ford Piano Service & Restoration 1777 Yosemite Ave San Francisco, CA 94124 On Mon, 13 Aug 2001 07:28:29 larudee wrote: >List, > >Does anyone have any ideas about why so few manufacturers use open face pin >blocks? Cost is a major factor, of course. Leo Duricic of Bechstein says that it >takes a master craftsman 11 hours to fit a block in an open face plate vs. 3 for >the closed face. However, precision robotic manufacturing techniques such as those >used by Yamaha and others should be capable of greatly narrowing that difference. > >Leo also says that the closed type produces more power, which is why their concert >size instruments recently switched to that design. I don't buy that. Bechstein >invariably uses agraffes in the entire scale with open face blocks but is now using >a capo bar with the closed blocks in their concert instruments. I think that this >a more likely factor in power production. Bosendorfer, which pairs open face >blocks with a capo bar, agrees. > >Are there any other performance or design considerations that might lead >manufacturers away from open face blocks? > >Paul Larudee > > Get 250 color business cards for FREE! http://businesscards.lycos.com/vp/fastpath/
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