About Checking

[Paul McCloud]

If your hammers are heavier than the old ones, your spring tension is going
to have to be more to lift those hammers.  I'll bet your spring tension is
not what you think it is.  Play a key and see if, after it checks, you can
push the hammer down into the backcheck while holding down the key.  It
should not go very far.  Where does the tail contact the backcheck?  It
should not be so close to the top of the backcheck that it barely grabs on
the tip.  Look at the backchecks from the rear of the keyframe.  Do they
line up with the tails?  Put pressure on a hammer while you press the key
through it's stroke.  Does the tail brush the backcheck on the way up?  It
shouldn't.  Is the buckskin on the backcheck very hard?  Maybe it's time to
renew it.  When the hammer is at letoff, the height of the backcheck should
be just below the hammer tail.  
Just a few thoughts.  Good luck.
Paul McCloud
San Diego



> [Original Message]
> From: William R. Monroe <A440WRMPiano@tm.net>
> To: Pianotech <pianotech@ptg.org>
> Date: 11/08/2004 6:11:59 PM
> Subject: About Checking
>
> Hi List,
>
> I've a small grand that I'm regulating (mine) and I'm struggling with
> checking.  Just finished regulation, and everything works well except
> checking.  Checking is nice and even throughout from a medium blow on up
at
> 15mm.  I've double checked things like:  repetition spring tension -
> definitely not too strong; escapement - jack is clearing knuckle
> sufficiently; backcheck height and angle seem right.  I guess my thoughts
> now lean towards, maybe backchecks are too low?  I can get checking on a
> soft blow by decreasing the checking height from 15mm to about 8 or 9,
but I
> just don't like it that close.  Thoughts? and Thanks.
>
> William R. Monroe
> Madison, WI
> Assoc.
>
>
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