[CAUT] S & S D rest cushions

[David Love]

Actually, the type of blow (one type anyway) where you have the problem is
on a hard fast repetition where the key remains depressed as the hammer
rebounds and thus the jack is fully pressed up against the stop.  If the key
is released and depressed again when the hammer is in its over rotated
position downward, the jack will not be able to get back under the knuckle
and will jam up on the proximal side of the knuckle.  At the same time the
back check will come forward and lock onto the hammer creating a
"catastrophic failure".  This may not happen on every type of repetition but
it can happen and argues for keeping that gap minimized.  

David Love
www.davidlovepianos.com


-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Richard Brekne
Sent: Sunday, August 16, 2009 3:26 AM
To: caut at ptg.org
Subject: Re: [CAUT] S & S D rest cushions

I have to side in (tentatively) with Jeff on this one.  If the rep 
spring is correctly tensioned, the action centers and key bushings at 
correct (appropriate)  friction and the action otherwise regulated 
correctly...  hammer rest cushions do little if anything to affect repetion.

Indeed... the only way the cushion could get into this picture is on a 
blow where the shank actually does bounce off the cushion... which I 
think as Fred mentioned puts us in the Staccato. But on that kind of 
blow everything is released and there is no reason for the jack to jam 
if the afore mentioned conditions are in order. Very fast single key 
repetition doesn't really get into Staccato per sé... and I am unsure as 
to whether or not the rest cushion is actually contacted by the shank in 
those very fast single key trills. It would seem like an awfully long 
way for the hammer to have to travel back and forth should that be the 
case tho.

This said... I wouldn't go so far as to say we shouldn't need the rest 
cushion. It does keep the rebounding hammer from over stressing other 
parts of the system by preventing excessive downward travel.  But I am 
unconvinced it really gets into repetition issues so much.  In any case 
I have never had a rep problem I couldn't resolve by addressing friction 
and regulation issues alone.

Cheers
RicB