William: I do net "component" bearing measurements using the bubble gauge, although I'm open to trying to adapt the Wixey gauge in order to get the feet on the bridge top as a zeroing point. All of the methods, used properly, with a proper understanding of the use of the trigonometry, yield useful and practical results. They all suffer, too, from the drawbacks of non-planar bridge tops (potentially causing false-bearing conditions). But if you understand how to use any of these gauges, how to do the easy math, and as long as the measurement techniques are consistently applied, then any of them will work for new boards (setting proper bearing conditions), or old boards (discovering compromised bearing conditions). I like the net component method because of the zeroing (which takes into account the varying bridge plane), and the separation of the components both for accuracy and for differential adjustment between the front and rear string angles. Paul -----Original Message----- From: William Monroe <pianotech at a440piano.net> To: pianotech at ptg.org Sent: Sun, 23 Nov 2008 12:13 am Subject: Re: [pianotech] Downbearing Got it.? Thanks for clarifying that, Dale. ? Does anyone try to separate the components (front/rear bearing)?in setting up a new board?? In evaluating an existing board/bridge? ? William R. Monroe ? ? Hi Bill ? Well, gently I correct this. Ok, I'm looking for total overall net bearing.?Previously, the simple bearing sticks?were posted here? It is?a small straight block of maple in various lengths and 3/8 ths wide by?3/4 high.?It has a notch cut out as it goes over the bridge to clear the bridge pins. Lay the stick on the speaking length with the notched edge butting up against the pins & the?back end protruding over the bearing point. If there is any string deflection at all there will be a gap between the back end of the bottom of the stick and the touch down resting spot of the rear string segment. Like gapping a spark plug. Capishe? ? To find your bearing angle measure the rear string segment from the front bridge pin to the rear termination point. For example...Say it's 4 inches. To find the downbearing angle multiply 4?inches by .026?and the net distance bearing is?.104 thou., which equates net bearing angle?at?1 & 1/2 degrees. ?If I multiply .017 by 4 inches net distance bearing is .068 or 1 degree. Multiply by 4 by .034 &? it's 2 degrees. Or take any rear length & multiply by. 026 or any of theses specs?to get the degrees of bearing?angle.?My primarily use of the sticks? is when reading net/residual bearing in my own board set ups but I've used them on many pianos new and rebuilt...and some of you didn't even know it! Anyway it's an old method outlined by Nick Gravagne in some of his ancient writings from the last century. LOL. It's a simplistic way or a way to think about or calculate a bearing angle. I find most piano 30 years and older exhibit practically zero net downbearing angle except in the high trebles. What does that tell you. ? I suspect my colleagues probably find similar conditions. The real question is what kind of bearing?is needed to drive your new soundboard set up or?an old one.?As a technician it seems like?I have spent much time trying to detect bearing?by measuring old boards? ?I find it's mostly its a waste of time. It has what it has and if it sounds bad there is something wrong. If it doesn't sound bad something is working. If we are restringing then we obviously need to make a decision about a lot of things. Don't get me wrong, Evaluation has many uses but mainly?I look at ancient pianos that lost bearing & crown long ago. ? Many things work when?it seems they shouldn't and many things don't work well when it seems they should. Any one confused?? I am ? Dale -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech_ptg.org/attachments/20081123/095a055e/attachment.html>
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