relevance of bridge pin spacing

[pianoguru at cox.net]

Hi Gene et al,

  I routinely vary the front to back spacing of bridge pins to facilitate negotiating the dogleg(s) in the bridge.  I always make certain that the angle of side bearing deflection remains the same, regardless of the front to back distance.  I have brought this up before on this list, and there are those who disagree with this practice.  None of those who would object to this have given me any reason to reconsider this practice, and I am not inclined to engage in a protracted argument about it.  Regardless of where you come down on this issue, there is one other relevant problem to take into account.

If you maintain the same front to back spacing throughout the tenor section, there will inevitable come a point at which the holes you drill for a front pin, will intersect with the hole you drill for the back pin of the next unison, if not directly intersecting, they will come dangerously close.  Clearly, once a pin is driven in the first hole, the intersecting hole will be blocked for the pin to be driven into the intersecting hole.  Anticipating this, the distance front to back can be shortened slightly, approaching the problem area, and lengthened on the opposite side, to insure, by a reasonable margin of error, that no pin will come too close to interference with another.

In some designs, the bridge pins angle is a compound angle.  The front pin angles forward, as well as to the side, while the back pin angles to the rear, as well as to the side (in the opposite direction, of course).  Regardless of the relative merits of this scheme, it further complicates determining where the potential problem of intersecting pins will occur.  

Another way to deal with this is to make the front to back spacing the same throughout the tenor section, use simple side to side angles through most of the tenor section, and compounding the angles slightly, as needed, to avoid intersecting holes.  Personally, when I see this, it appears to me that the designer failed to anticipate this problem, and the production people came up with a "work around" to deal with it.

Frank Emerson