[CAUT] Backcheck replacement revisited (was: balancier/wippens report)

[David Skolnik]

Israel -
All the differences you mentioned are big differences when it comes 
to checking.  The length and stiffness of the wire, the durometer of 
the felt and buckskin, the characteristics of the buckskin surface, 
the tension of the buckskin gluing, the profile created by the cut of 
the felt.  Given that I agree with RicB regarding the spring 
(tensioning) function of the checks, I think the "springier" wires 
you mentioned are a big factor.  Too bad you can't send some 
pictures.  While not conclusive, it would be interesting.

Happy holidays

David Skolnik





At 06:20 PM 12/22/2006, you wrote:

>Finally got a chance to closely examine the two backchecks side by 
>side, and to my great surprise found out that the height difference 
>between the two is negligible - 1/2 of a millimeter. The replacement 
>backcheck appears to be longer at first glance because it's body is 
>1/2" longer than the current Steinway backcheck - but the wire is 
>shorter, so the height difference turns out to be negligible (at 
>least as installed in this particular 1999 Steinway D). So, David, 
>you are right - there is something else happening here, because the 
>difference in function was quite striking. The regulation fell into 
>place very easily. I simply duplicated the angle from the old 
>backchecks - and all the backchecks were working fine after one 
>regulation pass. The client noticed the difference right away.
>
>So, what could it be if not the height?
>
>Here are the dimensions (excluding wire):
>
>Current style Steinway: 30 mm tall, 9 mm wide, 12 mm thick at base - 
>tapering to 9 mm at top of moulding
>Old-Style Steinway made by Tokiwa: 42 mm tall, 10.5 mm wide, 12 mm 
>thick (not tapered). I compared it to an old Steinway backcheck on 
>one of the pianos at SFSU - and it is pretty much identical (at 
>least dimensionally).
>
>So, does the greater mass relative to the hammer have an effect? Is 
>the front-to-back tapering on the new style a problem?
>
>There is almost double the thickness of felt on the old-style 
>backcheck (5.5 mm as opposed to 3 mm) and the buckskin is thicker 
>and firmer. There is much less "give" in the felt of the old-style 
>Tokiwa-made backcheck than in the current Steinway backcheck. Is 
>that a factor? (I would think that after 6 years' use the felt would 
>get compress and become firmer - not looser - so age does not appear 
>to be the problem here...)
>
>Also, when I was regulating these replacement backchecks, the wires 
>on them felt "springier" than the originals.
>
>That's all the differences I can think of. It just seems to me that 
>these older-style backchecks are more forgiving - and will function 
>and regulate well over a broader range of tail shapes and backcheck 
>angles than the current style. Just an initial impression... There 
>are two high-quality rebuilders here in the San Francisco Bay area 
>who replace any current-style backchecks in their projects with 
>these old-style Tokiwa ones as a matter of course. The only downside 
>I know of (aside from the cost and the labor) is that sometimes if 
>you don't want the checking too close, you'll have trouble clearing 
>the sostenuto and it may be necessary to cove the mouldings...
>
>So, any speculation as to what makes these backcheks work so much 
>better? Because they do.
>
>Israel Stein
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