Sunday, March 11, 2012

Broken Sustain Pedal Pivot

A customer indicated recently at a service call that her pedal was not functioning properly.  What for us a piano technician might seem like a simple repair often will seem completely confusing to you the customer.  While I will describe and show you the point of breakage with this particular pedal I will not suggest you attempt to tackle a problem like this on your own if your piano has the same features.

How do I know?

Cracked Fulcrum block
Internal Pedal Levers

If you look at the 2 pictures above you will see the inside of the piano under the keys and piano action.  This design while not common was used in the 1910-1930's or so.  To know if your piano is like this do the following:

  • Lay on your back under your piano with your shoulder to either side of the piano's pedals
  • Looking at the bottom of your piano do you see any levers or rods that are screwed to the bottom?
  • If you were to remove the pedals and legs would the bottom of the keyed (under the keys) be flat?
If the underside of the piano is flat your pedal levers are "inside" the piano.  

To assist this customer with their non-functioning pedal I removed the key slip, fall board & cheek blocks.  This allowed me access to remove the action from the piano and set to the side. Remember when removing any grand piano action to not press any keys as you slide the action out of the piano.  if you disregard this warning you are going to break a hammer or a hammer shank requiring a visit from a technician with the proper replacement part!  

Once the piano action has been removed you can see the mechanism for the pedals, and if you push the pedals can see what is happening inside and likely you will find the problem.  But as each manufacturer has had different designs it is difficult to tell you exactly how to proceed.

For the most logical approach, follow the links starting from the pedal itself up to the moving lever inside the piano.  You will likely find the problem.  In this piano.... a broken fulcrum.  The fulcrum gives the lever a fixed point to turn or pivot from.  When the pivot is broken the lever will no longer work as intended. 

For this customer I glued the crack before I began the tuning, clamping the workpiece together as the glue had some time to set.  After the tuning I replaced the now repaired piece with instructions that it was possible and even likely the piece would break again.

I took measurements of the original block so that if this piece cracks again I will be able to manufacture a part without an additional service call to the customer to remove the original piece.  When a part is manufacturer I will create 2 or more lengths of this block to use in the future should this problem occur again.

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