tapping strings

[Ron Nossaman]

>You may have gone over it... but you have not explained or answered the 
>point that
>Ron T makes in anything close to satisfactorilly. This is one of the big 
>problems
>with the explaination you put forward here.... It doesnt, and hasnt at any
time
>yet dealt with this issue. Nor has it dealt with the condition of positive 
>bearing
>at front where the strings HAVE gotten themselves up the bridge pin a bit.

Yes, I have addressed this in the past, and more than once. It's not
practical to  repeat everything I've ever written on the subject in every
single post. Certainly play will cause wear on the bridge. Isn't the
depression at the edge of the bridge cap deeper on the speaking length side
than on the back? So why is there a depression at all on the back, since
that side doesn't get played? 

Static downbearing of one string at 160 lb tension, net downbearing angle
of 1° is about 2.8 lb. The overall 1° bearing is hopefully split between
front and back of the bridge, so the actual bearing load on each edge won't
even be the full 2.8lbs.  During a dry to wet cycle, the bridge section I
measured changed overall height, getting taller by 0.028". In doing so, it
would push a string installed on it up the bridge pin by 0.009" (measured
difference in pin height above bridge). In a bridge with bridge pins at 20°
slant, offset to produce a 10° stagger offset to the string (at 160lb
tension, producing around 26lb of side pressure against each bridge pin),
it takes something in the neighborhood of 23lb to push that string up each
bridge pin. That's pounds, not psi. At say, 0.5" length from the center of
the bridge to the bridge pin, and with a bridge to string contact surface
of a generous 0.015" wide, that's 0.0075 sq", for an average 3066psi, most
of which is concentrated at the point of resistance (the bridge pin) at the
notch edge. 

Under the circumstances, the load resulting from the downbearing angle
being less than 10% of the overall abuse that bridge cap is suffering at
the notch edge, makes it seem relatively inconsequential to me. 
Ron N