Repairs, Maintenance & Upgrades > Preamps, Modifications & Upgrades

Slotted Harp Brackets...

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sean:

Here is my solution for buzzing harp brackets.  It keeps the harp brackets from touching the tonebars.




I cut the slots using a 5/16" end mill.  I should have been more precise with this, but I was in a hurry that day.  I just marked approximate endpoints for the slots with a pencil.  I then removed the harp brackets from three pianos and took them over to my dad's machine shop.  I think I tried to get the slots to be 1/4" from the top edge of the brackets, but after installing them I realized that I could have centered them, or I could have actually measured exactly where the center of the tonebar was. In spite of my haphazard preparation, they all came out looking good and working fine.

Note that the slots are not the same length or location on the two brackets.  That is because the tonebar sections that would rub against the bracket are different in each location.

I don't really know how I would attempt to cut the slots without a milling machine.  I guess I could have tried to drill out the endpoints, and then saw between them, but I would never have gotten such clean straight lines.

Even with the slots, the brackets are still stiff and strong.  Cutting the slots exposes fresh unprotected metal that will probably show some rust in a few years, so I wiped a little oil along the slots.  I hope that works well enough.  I thought about painting over the exposed metal with clear nail polish, shellac, or varnish; but I took the lazy way out.

When they are installed in the piano, you don't really notice the slots unless you are up close and looking for them, so it doesn't destroy the vintage appearance of the piano when the harp cover is off (or on, obviously).


Sean


Tim Hodges:
Great work Sean.

I've always thought the mod which Chris did at VV was a good idea, obviously there could be the danger that their particular method may affect the structural integrity of the bracket as it took out a lot more of the material but this method won't.

I definitely want to try this out. 

Chris Carroll:
Looks good, nice and clean- this is something we did about 10 years ago but stopped doing because it was too hard to cut the metal without the proper machinery like you have done. Your cuts look really clean better than what we had done, I bet it works well. These days, we have found that grinding the side of the tone bar is quick and very effective without any adverse effects.

Good job!

David Aubke:

--- Quote from: Chris Carroll on July 27, 2017, 07:08:26 PM ---These days, we have found that grinding the side of the tone bar is quick and very effective without any adverse effects.
--- End quote ---

Do you do anything to protect the metal where you've ground away the plating?

I'm always on the lookout for ways to protect metal when re-plating is not practical.

Ben Bove:
These are really professional solutions, looks great.  For those without the tools, in many cases you can find one of the tonebar screws are bent, and adjust it to move the tonebar to the farthest point away from the bracket.  Often, both neighboring tonebars have a slight bend in one of the screws and you can watch for the tonebar to rotate left-to-right as you adjust it.  The bracket is also a simple 90 degree bend itself, so in many cases a hammer tap will slightly bend the angle of the bracket away from the touching tonebar. 

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