It will be the engineer who works out the math, the practical physicist who maps out the actions and reactions which the inherent forces will have on various interdependent parts, and finally, the skilled craftsman who will actually build the piano. When someone designs a piano, (let us refer to that person as the architect), he or she will be very exacting in the placement of every component of the piano. I will explain why.Ī technician draws a piano wire across a bridge to demonstrate its path across the bridge. While the definition of down bearing is as I have given it, when a piano rebuilder asks, “What is the down bearing,” he or she is asking what the proper angle should be.
There must be a positive (+) angle on both the front and back bridge pin. From this we learn that there will be force it will be evident in two places on the bridge, and it must be balanced within a certain range of tolerance.
The soundboard (which the bridge is anchored to) may develop an indented curve, the bridge glue might fail, or the bridge might crack. If too much force is at either bridge pin, front or back respectively, the bridge may “roll” towards the greater force. Down bearing must be balanced between the force exerted as the piano wire arrives at the front of the bridge with the force exerted by the wire as it leaves the bridge. Defined, down bearing is the force felt upon the bridge of a piano, caused by the pressure exerted by the piano wire. The perils of poor design can contribute to drastic failure of the piano’s components.
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