spinet hammer blow

[Dave Nereson]

----- Original Message ----- 
From: "pianolover 88" <pianolover88@hotmail.com>
To: <pianotech@ptg.org>
Sent: Sunday, November 02, 2003 12:04 PM
Subject: Re: spinet hammer blow


> >.. how do you know for sure the felt squares that the
> hammer rest rail are resting on are origional ?.<
> 
> I removed the felt squares from under the hammer rail to exazmine them; they 
> certainly appear original. I have indeed encountered verts where the 
> previous "tech" had "padded" or built-up the rail with felt (sometimes even 
> with what appeared to be a snippet of muting felt!) in order to quickly 
> eliminate lost motion..boy I HATE that!  L A Z Y !!! 

    Building up the hammer rail felt or the rest pads for same will increase, not eliminate lost motion.  Felts or pads added to the rest pads are usually put there to set the blow back to normal after filing hammers, which on very worn hammers can remove 1/8" or more of felt.  Adding these pads of course increases the lost motion and then the capstans have to be turned up, which sometimes also makes the dampers lift too soon, and with the hammers filed, the let-off is now wider, so that has to be re-regulated, and usually the dip and backchecks also.  So those added-to pads are sometimes a sign not of laziness, but of someone's major regulation job.   
    Yes, hammer skiving felt should be used rather than temperament strip - type felt, but some factories use backrail cloth for their hammer rail rest pads, which isn't much denser.  I confess to using temperament strip felt because it's usually the exact size, after filing hammers on an old upright, to bring the blow back up to 1 7/8".  I've never had a problem from the hammer rail "settling" to the point that there's not enough lost motion.  How much is it gonna settle?  1/32", if that?  You can always pound it with a hammer to pre-compress it, just like new key punchings.  Or use hammer skivings.  

 >   Anyway, since my post I 
> have increased blow to within the recommended range as set forth in the 
> actual Wurlitzer service manual for this specific piano, which is "1  5/8"- 
> 1  7/8". Much more power now!

    Thought so.  Glad it worked out!   --David Nereson, RPT