Backchecking problem

[Jim Coleman, Sr.]

Hi Tom:

There are two things which come to mind. 1. Balancier flange resistance.
2. hammer tail length.

If you should take the rep spring loose and find that the flange 
resistance is like 20 grams (I have actually found this) the spring has
to be set so high to overcome this that even though you get a slow rise of 
the hammer after releasing from check, it is just too much tension to let
the hammers stay in check.

How much distance is there between the top of the backcheck and the bottom
of the hammer tail when the hammer is controlled by the drop screw? More
than a 1/4" would create a problem with checking.

Too wide an arc on the shape of the hammer tail could be a problem, but
that usually just prevents you from getting close checking and is probably
not related to your specific problem here.

Jim Coleman, Sr.

On Fri, 12 Jun 1998, Thomas D. Seay, III wrote:

> Dear list,
> 
> I am stumped with the backchecks on this piano. The piano is an early 80s
> S&S L with new Premium blue hammers on Renner shanks & flanges and
> re-leathered original backchecks. I have CLOSELY regulated key height, dip,
> let-off and drop, spring tension, and all the other usual suspects. The
> problem is that the hammers absolutely refuse to check when the note is
> played at the level of forte or less. They just bounce between the
> backcheck and the string. The angle of the backchecks is good and they
> check high enough, but I just can't seem to get them to work in the piano.
> The problem is particularly bad in the bass and tenor, where the hammers
> are larger.
> 
> The problem may be in the balancier. When I push the balanciers down, there
> seems to be much more spring resistance than normal although the hammer
> rise is not particularly fast. The original wippens have been rebuilt and
> repinned, so I'm pretty sure that it is a not pinning problem. The slots
> are clean and the springs have been cleaned and polished.
> 
> I'm pretty much at my wit's end and if I don't get this resolved soon, I'm
> going to have to take a hostage. Any and all help will be gratefully
> appreciated.
> 
> Many thanks.
> 
> Tom
> 
> Tom Seay
> Piano Tech Office
> School of Music
> The University of Texas at Austin
> t.seay@mail.utexas.edu
> 
> 
> 
>