[CAUT] Subservience, was CAF

[Jeff Tanner]

I PREFER that spring tension is strong enough that rise is all the way to 
the top, but that with more firmly pinned bushings.  The spring needs to 
have enough strength at the top of the rise to hold the hammer up. It 
doesn't much matter how fast it is at the bottom if it won't hold the hammer 
up high enough to reset the jack.
Jeff

----- Original Message ----- 
From: "Richard Brekne" <ricb at pianostemmer.no>
To: <caut at ptg.org>
Sent: Sunday, August 23, 2009 3:35 PM
Subject: Re: [CAUT] Subservience, was CAF


> Hi Mark...
>
> I think we can all agree that reasonably close cushions is a good thing, 
> regardless of how we look at this CAF thing.  As to the variance of 
> opinion about CAF... I am wondering just how much of that is rooted in 
> just how much key kickback each of us find acceptable.  I know techs for 
> example who will have none whatsoever. These usually are also techs who 
> like a very very slow rise from check to drop when setting rep spring 
> tension.  This kind of set up is in my experience a recipe for sluggish 
> repetition, and coupled with a long distance down to the cushion from the 
> shank I can see where one could get into CAF problems.
>
> For myself... I like pinning on the jack and rep lever to be fairly tight, 
> allowing for a strong spring when the rep spring is set to the <<immediate 
> rise>> from check to drop. Just short of a hop I guess you could say.... 
> This can definitely be felt in the key.... if you feel for it... but I've 
> never yet heard a single pianist comment anything that went in the 
> direction of key kickback... so I don't see it as an issue..... and yes, I 
> do keep my ears open for comments that go in that direction.
>
> Anyways... such a set  up is going to repeat period. Good high checking, 
> 15-12 mm or as close as the back check / tail will allow without dragging 
> on a fff blow... minimal aftertouch seen from the perspective of total 
> jack travel...  rep lever correct to jack top height.... all the basic 
> regulation bits in place... and I just dont see the cushion being needed 
> for anything but a system stress reliever for very hard play...
>
> Thats my take anyways....
>
> Cheers
> RicB
>
>
>    Thanks Ric,
>
>    A number of years ago I was working through this on a C-3 action at
>    the Banff Centre; Repetitions failing the "wink" test was the
>    problem, re-pinning them turned out to be the solution.
>
>    I was bothered by having to repin these centers to 8 or 10 grams,
>    when we had a service bulletin posted over the re-pinning bench that
>    clearly suggested they be 4-5 grams.
>
>    So, my good friend and colleague Denis Brassard asked me why we
>    treat this center like the centers within the action? After all,
>    their range of motion and dynamic operation is really quite different.
>
>    That got me thinking about it in a different way.
>
>    So now we re-pin repetition centers quite routinely, and without
>    very much religion... i.e.: often pushing out the original pin with
>    the next over sized, and a quick friction test.
>
>    I'm happy doing this, and ever since have yet to encounter a CAF
>    situation that addressing hammer/whippen centers and spring
>    arc/tension won't solve.
>    Or, in your words... "CCJUNMWYDTWRF is something I just dont run into."
>
>    best,
>    Mark C.
>
>    PS I confess to changing rebound cushions more than once for
>    appearance sake alone, but also believe they should be very close to
>    the hammer shank at rest.
>
>
>
>