Bridge pin angles

[Ron Nossaman]

>> The point is that we can't assume downbearing, so we angle and offset 
>> pins to provide a positive termination that's largely independent of 
>> bearing.
> 
> 
> If we're a factory cranking out pianos using construction methods that 
> don't guarantee downbearing or using a design that doesn't insure 
> downbearing long term, then we better have lots of insurance. I thought 
> the point of these endless discussions about rib crowned boards, 
> laminated ribs, proper rib size for bearing load applied, etc. was for 
> us as rebuilders to arrive at a point where we're doing what we're 
> claiming the factories are not doing.  Designing and building a board 
> that's structurally adequate for the load applied, insuring that it has 
> the bearing load intended when it leaves the shop, and is going to stay 
> that way long term.  If we're accomplishing this then I don't see that 
> we need the levels of insurance of said factory.

I didn't say that very well. Sure, if we were factories, and talking 
about boards, I agree. As rebuiders, we don't get to put what we 
consider to be our best soundboards in every piano. More often, the 
original board is there, and we have to make the best of what we 
have. Even with a new board, if we aren't allowed to make changes to 
the design, we will very possibly be setting the plate for zero 
bearing on a cantilevered bass bridge. With an original board, we 
can't say what the bearing will be next year, and a sampling of 
posts to this list indicate that the majority of pianos being 
rebuilt are not getting new soundboards, and of those that are, very 
few are getting rib supported boards. So we (collectively) can't 
assume bearing, and the rebuilt pianos I've looked at through the 
years indicate that to be the case.


> Establishing a minimum and building to it are two different things. I'd 
> like to know what the minimums are.  If what is needed for the 
> termination to function properly with a properly set up and properly 
> functioning board is 2 degrees of side bearing and a bridge pin angle of 
> 5 degrees then I don't want to put on 10 degrees of side bearing and a 
> 20 degree pin angle just to be safe, because there are negative 
> consequences for doing so, in the form of poorer rendering and increased 
> bridge cap wear.
> 
> Phil F

If the minimum is 2° offset, and 5° pin angle, and you don't want to 
go to 10° and 20°, what would you chose as a suitable set of angles, 
and why?

Then, by what criteria, and under what variations of available 
materials and climate conditions would you establish these minimums?

Ron N