Hi Ron, Thanks for the intelligent response (used brain notwithstanding). There are a few things here I had not thought about before. One of the things I have wondered about is bridge pin row spacing (am I saying that right? - the distance from the front bridge pins to the back bridge pins) and how manufacturers decided on that spacing. I thought it was random or perhaps had some Magic Circle-like acoustical reason. But as you point out it's also a way of controlling stagger angle. When recapping bridges I have tended to follow what was there before, while correcting what I considered obvious mistakes. I can see that I have some room for improvement, not that that comes as news to me. Phil --- Phillip Ford Piano Service & Restoration 1777 Yosemite Ave San Francisco, CA 94124 On Thu, 06 Sep 2001 21:49:12 Ron Nossaman wrote: >>I think I'm trying to say the same thing. If the bridge driller actually does >>take into account the pin diameter, string diameter, and pin angle when >>determining pin locations for the stagger angle then having a greater pin >>angle doesn't need to result in greater pin load on the bridge. I was >>assuming that most manufacturers followed the rule of having the hole >>locations in a straight line between agraffe and hitch pin regardless of >>other parameters. If so, then increasing the pin angle will result in more >>pin load on the bridge, which would make cracking more likely, if this is >>a primary cause of cracking, which I believe you're saying is not. Did I >>do any better this time? >> >>Phil > >Hi Phil, >You did fine the other times with the premise that the pins were positioned >in a straight line... etc. I was just slow picking up on the premise. What >can I say, it's a used brain. With the pins positioned on that line, >consider this: #6 pin, #13 wire, 15.4mm spread between pin rows = 10° >stagger. That same 10° stagger with the pins along that same line will >result with #7 pins and #15 wire at 17.4mm - #8 pins and #17.5 wire at >19.6mm - #9 pins and #19 wire at 22mm - and #10 pins with #20.5 wire at >26mm. These figures are with vertical pins, so the row spacings would be >somewhat wider if the insistence was that the pins remain on the line and >still produce a 10° stagger angle. As you can see, we can either adjust the >row spacing (if there's room on the bridge), or adjust the offset of the >pins from that direct line, to accommodate the various pin and wire >diameters, our choice of pin inclination angles, and the limitations of the >bridge top surface we have to fit the whole mess onto. Limiting the choices >to what we can get with the pins in that straight line between hitch and >agraffe will mean deciding between pin angles and stagger angles as a >priority somewhere in the scale. Both will likely be compromised at some >point as a result, which isn't necessary if we're allowed to simply deviate >from that straight line placement to make the other stuff fall where we >want it. I think that straight line thing came about as a no fault, no >argument, no thought, guaranteed way to get *some* side bearing on the pins >of a replacement bridge or cap without having to figure out the math in the >days before computers and spreadsheets. It works well enough if you don't >insist on applying logic and standards requiring some sort of annoying >uniformity of angles and such. > >Incidentally, the difference in stagger angle from 5° difference in pin >angle isn't a lot with the pins in similarly located holes. Probably not >even visible side by each. > >As for the load abuse on the cap from excessive pin angles, the more the >angle, the greater the leverage on the surface of the cap, and the less the >amount of wood on the side of the pin opposite the string pressure to back >up and support the pin. It's got to be a factor in longevity, but I have >absolutely no quantifying data. The theoretical idea is to find the balance >between solid termination and bridge cap material abuse that provides the >best balance between performance and longevity, subjective and actual. >Stagger angle increases escalate material loads at a higher rate than pin >angle increases, so I'd assign the first priority there, with the second >priority being termination quality by pin angle. > >Until someone (might be you) comes up with a better bridge string >termination system, we're stuck with trying to understand how the current >one works and to try to make the best of what we have to work with. The >hard part of that seems to be forgetting what we've been taught to assume >about the silly thing, and assessing what we have to work with based on >what we see rather than what we "know". > >Good evening. > >Ron N > Get 250 color business cards for FREE! http://businesscards.lycos.com/vp/fastpath/
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