Re: [Harp-L] Tension Headache




On May 10, 2011, at 1:25 AM, Joe Leone wrote:



On May 9, 2011, at 9:57 PM, Elizabeth Hess wrote:


<snip>

Then I got greedy and tried to get 1 overblow. Put the harp back together, and couldn't get 4, 5, or 6 for nuthin'.

.... Screwed the harp back together, couldn't get them. Backed the interior screws off a bit (Did I have them so tight that I was warping the reed plates?), but no joy. Gapped and embossed too far, backed off, back and forth, stayed in denial and just tried for determination... last couple of days: bupkis.

Just now I disassembled the harp, held it together gently, and didn't I overblow 4, 5, and 6 as just nicely as you please. Put on the

cover plates and then the



binder clips, and lost the overblow on chamber 5. Took the clips back off and got it, again. Can anyone explain what's going on, here, and what the remedy is?

<snip>


Your harp is suffering from ' crooked door frame syndrome'. Let me explain. Please.

But of course! :-)



Imagine that you have just installed a door frame. And you are standing inside facing it. You measured the opening and it was 32 1/8" (the proper amount). But what you DIDN't realize was that within the 4" width of the frame, there was a deviation. The INSIDE of the frame (the edge facing you) was 32 1/8", BUT the edge facing outdoors was only 32 1/16". You wanted the door to be tight. For security reasons. You don't want to leave any room for someone to stick in a shim and jimmy your lock. But when you go to mount the door, it is too tight and won't fit. Why? because the cant of the frame has changed the dimensions that you needed. (Key: doors are oversized anyway with the idea that they will be finish planed).

When you had the binder clips on the ends, you made a belly ever so slight in the plate. Hardly descernible with the naked eye. But there none the less. The clips have a foot pound rating of (I'm guessing) 75 to 80 foot pounds. If you were to apply one to your finger, it would exert as much pressure as if you had your finger under the leg of a loaded chest of drawers.

This explanation is so lucid, even I can understand it.



So, embossing will exascerbate this problem because you were already working with a fairly small dimension. And now, you made it even smaller.
So, visualize looking at the cross section of the reed slots and you will find that even this slight belly in relation to the small reed plate can be extrapolated to the 1/16th" in relation to a full sized door.


Ergo, the slot is now too tight.

EXCEPT that the problem I had when I screwed the harp back together to "normal" tightness was that I couldn't get the blow reeds to choke. (And there's no way to know whether the draw reeds would have sounded the overblow if I *had* been able to get the blow reeds to choke.) Sorry I wasn't more clear on this point the first time.


Sooo..... Maybe I need to emboss just a teensy bit more?


Backing off the pressure will allow the plate to flatten out enough just enough that the deviation disappears and you now are SQUARE in the slot. When I use binder clips, I sometimes put them at the BACK of the plates. And even if they rest on the rivets, that shouldn't make a difference. Now at the high end (where the reeds are short and leave a lot of plate), the clips can take a deeper bite thus spreading the load more evenly.

Hmm. I was putting the binder clips on the whole magilla sandwich, cover plates and all.


The current state of affairs is that I have the reed plates *very* gently screwed together, and the cover plates *very* gently screwed on, and I can get 4 and 6 overblow reliably and 5 with some effort. It kind of violates my sense of ship-shape not to have those screws snug, but I understand that too much of a good thing is a bad thing, and it's the sound that counts.

Of course it's hard to diagnose a hardware problem via written correspondence. I know that I mostly have to do this myself. But your answer has been enormously helpful in identifying the relevant mechanics, so now I have a better idea of what's going on. Thank you very much.

Elizabeth

P.S. I used to think that practicing meant harp-in-mouth time. That's turning out not to be the whole story.

I refer to this as "rigging the sailboat": If you don't enjoy rigging the sailboat as an activity in its own right, then sailing is not the hobby for you.





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