"double striking" problem

[Horace Greeley]

Avery,

I got your message twice.  Did you post twice, or is my Eudora acting up
(again).

Thoughts to follow after some rumination.

Horace



At 09:39 AM 2/12/97 -0600, you wrote:
>List,
>
>   I had a problem yesterday with our Hamburg D. One of our piano faculty
>gave a recital last night and had been talking to me about notes "double
>striking" (his term) on very soft playing. It was a VERY soft, but
>noticeable, double strike on some notes (hammers not going into check and
>bouncing back into the string), primarily notes in the middle third of the
>piano.
>   I was able to solve the problem to his satisfaction but I don't *really*
>understand what caused it in the first place so it was pretty much a trial
>and error kind of thing. I just now talked to him on the phone and
>everything worked out very well. He said he felt very comfortable with the
>piano. So, I guess all's well that end's well, but I need to understand
>what causes this type of thing so I can prevent it from happening in the
>future.
>   It's very difficult to explain this problem in words, but here are some
>questions and some things I did to try & solve the problem.
>
>   What really controls how much upward "throw" (I can't think of a better
>term) the hammer does when adjusting the repetition? Is it strictly how high
>the hammer catches on the backcheck? Does the amount of let-off or drop
>affect it also? I know that key dip would also affect where the hammer is
>caught in relation to the strings, of course.
>   The repetition spring tension is what "seemed" to be causing the problem.
>I had to play at least mp to get the hammer to go into check but most
>hammers had very little lift at all. Certainly not strong enough to cause
>any kind of bounce at the top. I even had to increase the tension the
>smallest amount possible to ensure repetition without getting a bounce back
>on very soft playing. I brushed the hammer tails with a suede brush to get
>any residue out the grooves on the tails to try to improve checking.
>   Also the backchecks. They're Hamburg backchecks, about 1-1/2 yrs. old,
>having been replaced when new hammers, shanks and flanges were installed. I
>regulated them as high as possible without getting a rub on the hammer tail
>
>on a hard blow. This also seemed to help some.
>   I even increased the aftertouch a little by raising the hammer line
>slightly, trying to insure that the jack was completely escaping from under
>the knuckle. Yes, I lubed them, too. I did notice that the knuckle leather
>is starting to get slightly loose around the core, so I guess I'll have to
>do that correction as soon as I can put the piano out of commission for a
>bit. Could that looseness have any affect on this?
>   I normally regulate with a very close let-off, especially on our
>performance pianos and have never had a problem. This time, I increased the
>let-off and the drop, very slightly, to see if this would help stop the
>hammers from bouncing back into the strings but I would like to put the
>let-off back at 1/16" without having this problem recur. The bedding was
>also checked.
>
>   Sorry this is so long but I'm trying to give all the information I can
>in hopes someone can explain this to me. I hope I've explained it clearly
>enough for you to understand what I'm talking about. Any comments to help
>me understand the "whys and wherefores" of this problem would be greatly
>appreciated. Thanks.
>
>Avery
>
>_____________________________________
>Avery Todd, RPT
>Moores School of Music
>University of Houston
>713-743-3226
>atodd@uh.edu
>_____________________________________
>
>
>
>
Horace Greeley

"Great ideas have always encountered violent opposition from
	mediocre minds."

		Albert Einstein

Stanford University
email: hgreeley@leland.stanford.edu
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