Author Topic: Lowering aluminum harp supports  (Read 1149 times)

Offline 5077

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Lowering aluminum harp supports
« on: March 30, 2018, 12:39:20 PM »
Hello all,

I am in the process of a refurb of my '77/'78 Mk I Stage which includes, among other things, installing new hammer tips.  In an attempt to get the sound I'm looking for, I switched from the graduated tips that it came with to square tips from Vintage Vibe.  I figured this would change the escapement, and of course, it has.

I predicted that the escapement would be too tight in the bass, and probably no change in the treble (as the square tip kit has wrapped wood core tips in the top octave or so, like the graduated tip set).  After measuring, the bass was indeed too tight, but the treble was actually too wide.  I've put some shims on the bass side (a 1/32" and a 1/16"), but I want to lower the harp on the treble side.  As many of you probably already know, my era of Rhodes has aluminum harp supports; these supports have about an 1/8" of what looks like MDF glued on top.  I assume this exists to do what I want to do to it:  shave it in order to lower the harp.

My question is: what's the best way to remove this MDF material evenly and accurately?  I think of sanding, but I'm worried about not getting a level, consistent surface.  Should I use a hand plane?  I'm less experienced with that, but it seems like it would produce a more level surface.  Should I try a different method?

Offline sean

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Re: Lowering aluminum harp supports
« Reply #1 on: March 30, 2018, 01:45:12 PM »
You have some options:

#1:  You could have installed thin little shims underneath the hammer tips to give them the correct height.  You can do this if the wrapped tips are notably shorter than their neighbors, or to even out the escapement from section to section.

#2:  You can crank down on the tonebar mounting screws to compress the springs a little bit more, and lower the escapement.

#3:  You can modify the shims on the harp supports.  If you need to do this, I would recommend removing the wood strip entirely, and making a new shim.  I think I would try to knock it free, or pry it up with a chisel.  You will have to scrape the glue and remaining sawdust off the top of the harp support. 

If it really fights you, I guess you could remove the whole harp support from the piano, and soak it in the bathtub overnight.  The wood strip seems to dissolve and stick to the harp frame in areas that show water damage (so you might try spilling beer on it).

You can make new shims out of any non-metallic material.  I have had good success with plain old "poster board" - cardboard. 
https://ep-forum.com/smf/index.php?topic=9335.msg51062#msg51062

Don't set the harp frame directly on the aluminum harp support, because over the years the galvanic corrosion would adhere the metals together.  The galvanic corrosion is to blame for the screws usually having a bit of brown rust and white zinc crud.  A thin shim will prevent the layers from getting stuck.  (Dry storage helps too.)

Sean


Offline pnoboy

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Re: Lowering aluminum harp supports
« Reply #2 on: April 01, 2018, 01:00:20 PM »
I took of the shims on my piano.  They're glued quite tightly.  I used a wood chisel to get most of the wood off, and then mineral spirits and/or acetone to soften the glue, and then applied a putty knife to scrape off the softened glue.  It was a bit of a job, but it turned out well.