Bridge pin angles

[Phillip Ford]

>Hi Phil
>
>A couple things might be good to keep in mind whilst all these more 
>abstract numbers scenarios are being tossed around.

Just basic trig.  Nothing too abstract.

>Bridge pin angle is something that has been experiemented with by 
>manufacturers through the years.  The present standards are more a 
>result of experience with what actually works then a reliance on 
>what in theory should work.

That's probably true.  But you do see variation (just as you do in 
the front termination angle, which you mention later).  We know that 
some pianos have excessive front termination angle which causes its 
own problems.  Perhaps excessive side bearing and bridge pin angles 
are creating their own set of problems in the form of additional 
bridge cap crushing.

>  And of primary concern has been holding a strong contact to the 
>bridge in the face of even the strongest levels of play.
>....
>One other thought... since you are interested in the numbers 
>perspective.  Amoung the factors exerting a significant force 
>upwards is that 1500 psi the bridge cap can take, which I assume 
>increases with each tiny micron of compression in the wood.  With 
>that at a maximum, the net force needed to break whatever friction 
>levels at the pins is quite a bit lower yes ...?

Well no, actually, if some of the numbers that I threw around are 
correct.  That was the reason for questioning in the first place 
whether we really need the 'traditional' levels of side bearing and 
bridge pin angle for a properly built piano, or if they're only there 
to be 'safe' for pianos without adequate downbearing.

>   Strings vibrating, soundboard vibrating, pins themselves 
>vibrating,  all pretty violently seen from perspective of that exact 
>termination point.
>For doubters... find an old beater and shave off about 2 mm of 
>bridge cap, and replace with same thickness brass... carefully 
>fitting around the front bridge pins to yeild the same termination 
>profile as a new wooden cap. Re-string the spot and subject it to 
>some concentrated use conditions for a half a year... bang on the 
>string...vary the humidity over time.... etc etc.
>
>Cheers
>RicB

And if we do that what will we see?  Have you done this?

Phil Ford