Bridge pin angles

[Ron Nossaman]

> Phil, are you discounting, or unaware of the Wapin system of bridge 
> pinning?  I know Ron is aware of it, though, given his reaction to my 
> raising it in the context of a previous thread about downbearing, I got 
> the sense that he was not favorably disposed towards it, reasons 
> unknown.  

As I've said before, I don't see a need for it, nor do I consider a 
poorly functioning soundboard to be "fixed" by it's application.


>There is some information on their site  
> http://www.wapin.com/science1.htm , though I don't think it's thorough 
> enough to add any insight into understanding exactly what is taking 
> place at the bridge termination.

They don't know, and say so up front. Nothing wrong with that. 
Patent wording tends to be very vague, with the word "believe" 
showing up a whole lot. By necessity the patent needs to be filed 
before the years of field testing and R&D answers, or doesn't answer 
these questions. Plenty of patented items and processes proved not 
to live up to their original concept expectations. Some exceeded them.


> As I see it, you need to decide, from the beginning, whether your 
> inquiry is directed towards understanding the mechanical processes at 
> work, or the more practical aspect of building something that will 
> continue to function for a reasonable length of time.  For the most 
> part, questions of loosening bridge pins and crushing notches and caps 
> are of the latter direction.  

I disagree. I consider these concerns to be inseparable. Trade-offs 
can't be reasonably assessed without considering function, 
production cost, and longevity.


>That an angled bridge pin might be more 
> prone to causing cap damage than a vertical one is helpful to 
> understanding piano forensics, but it doesn't, by itself, explain the 
> possible differences in acoustic properties of between each.

When the acoustic property in question is false beats. I disagree. 
No other acoustic property has been claimed or discussed.


> So, assuming you had adequate down and side bearing, what's changed by 
> slanting the bridge pin? 

Safety factor - insurance. Don't assume anything, but rather do 
everything you reasonably can to make the termination good and long 
lasting.



I did a service call on a new piano a few years back. It was out of 
area, and the local tech was having trouble pinning down the cause 
of a string noise. There was an obnoxious "whang" on a firm blow to 
one particular unison. The local tech and I went out together to see 
what we could find. The downbearing was very slightly negative in 
that section (guess where), not much offset angle, and the speaking 
side bridge pin was very nearly vertical. The other unisons had pins 
angled more in the 15°-20° range, but the problem unison was next to 
a strut. It looked as if the bridge was drilled with the plate in!

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 the above piano had 15°-20° angled front 
bridge pins in that problem unison, the only tonal problem would 
have been the generally nasty distortion at higher attack levels in 
the killer octave that everyone is so used to hearing that they 
don't even notice, and everyone would have been happy. What I'm 
interested in is a standard of offset and pin angle that will 
reliably provide that termination. I'm not particularly interested 
in establishing minimum tolerances, because I don't wish to build to 
minimum tolerance, and these tolerances can't be accurately 
established anyway. There are too many variables.

Ron N