Checks cause hammer bounce ?

[RicB]

Hi David, thanks for bringing up so many other points.

Hammer flange and action frame screws are all tight for sure,  tho I 
have not looked for play in the rail dowels which I suppose is an 
obvious enough place to look so I will next week.  The symptom appears 
in all bass notes, but lessens a bit at the end glide bolt and at the 
one at the tenor/bass break.  But the entire tenor/treble section makes 
not a move no matter how hard I hit a key.

Back rail is checked by using a long thin screwdriver down through the 
strings and action and thubbing on it with the palm of my hand listening 
for any sound at all.  I would imagine any force on the back rail in 
this kind of problem would be downwards so I was looking for downwards 
motion.  I check dags, usually by dusting a little teflon powder on the 
area where the back rail contacts them, insert the action and run the 
shift pedal a couple times, and then look at the rail.

I dont take off the the top action to do usual bedding work exactly 
because of the chance that frame distortion can change everything and 
render whatever bedding work I do redundant. 

Its an older  Hamburg D.  Serial 398XXX.  I will also make sure of the 
woods used since you asked on my next visit to it.  And I will measure 
the amount of crown with a straight edge as you mention. Tho I do have 
the bolts set to minimum pressure, which at least helped the rest of the 
action quite a bit and lessened the problem in the bass. It also allowed 
me to get reasonable blowdistance/keydip figures.... but thats another 
story :)

Cheers and thanks for the thoughts.
RicB


>     Ric -
>     I'm just trying to fill in with whatever seems not to have been 
>     mentioned, even if it seems something too obvious to bother with:
>     Check solder joints of action rails
>     All hammer flange and action frame screws are truly tight?
>     Any play in the rail dowels?
>     Does symptom appear equally from playing any bass note? ie, less with 
>     notes proximate to glides?
>
>     Since it's not clear exactly how you've gone about testing, some of 
>     the following may be redundant.
>     You said you do all the bedding with the action frame on, but I would 
>     look at the back rail stripped down.  Could the dags in back have 
>     anything to do with it?  Is there any frame distortion when you 
>     reinstall the top action?
>     You said it was an older D.  How old?  New York or Hamburg?  Is the 
>     key frame oak? How much "crown" is there between balance rail and 
>     straight edge running from front rail to back?  Measure under cross 
>     members.  (sorry, my key frame terminology is deficient).
>
>     Can you (with some help) put pressure on the back rail while you are 
>     playing notes?
>     Wedge the hammerflange rail
>     Wedge between pinblock and tops of balance pins
>
>     My biggest concern in all of this is that Andre's response might be 
>     the most correct.  Let's solve this thing, for Andre.
>
>     David Skolnik