Hammer Weight vrs Friction

[Dave Swartz]

Jon,

I'm glad you posted these numbers for the "B".  I have had several "B's"
with very similar results.  Unfortunately, a 58 dw for some players is way
too high, but due to the problems of these actions there are only the
alternatives in which you posted.  My last two "B's" feel spongy and I'm
just not happy with them.  The key element here (using the 17mm shank) is
the key ratio.  A 0.53 is a higher number than optimum.  I think a 0.49
would be much better eliminating the use of yet more key lead....which can
only result in increased sluggishness.  The Strike Weight Ratio at 6.15 is a
vast improvement and maybe your action feels pretty good.  I'm mystified
though when you get around a 6.1 or 6.3 SWR and the action still feels yucky.  

David's (Stanwood) chart depicting medium range numbers I think are a little
high.  Using the Strike Wt. Smart Chart, I've found in just about every
action that the hammers need thinning down to the lower numbers on the
chart, respective to the "range"...otherwise the action is still too heavy
and not nearly responsive.  Bob Marinelli was telling me of his use of the
West Systems epoxy, filling the capstan holes and moving the caps enough to
still catch the whippen heel (without the whole shabang of cutting them and
regluing).  

I've moved capstans before and cut whip heels on some bizzare actions for
Ampico players when retrofitting.  I guess consistently the "B's" need the
most work....I'm thinking of getting that action back in the shop and
improving the cap line...then should be able to remove some lead.

Just another note:  I've had an impossible time getting consistent SWR's
throughout the keyboard...many factors cause this change (felt variation,
pinning, etc...from note to note), but I don't get too hung up on it...use
it as a "National Average" so to speak.

To sum up:  I think if the key ratio is above 0.50, acceptable end results
are more difficult to acheive than if it were lower.  


Comments???

Dave Swartz, RPT
dms2000@majesticpiano.com


At 11:37 AM 10/18/98 -0400, you wrote:
>These figures are from a S&S B.
>This, of course is just one scenario, your mileage may vary.
>
>Touch Weight dropped by 10gr with the removal of 1.2gr SW
>
>The Friction difference is negligable because a judgement call
>was made while surveying and in the second line, 24 UW or
>59 DW could have been decided on, there is a degree of
>fudge-factor. So the difference is not considered significant.
>
>#	UW	DW	SW	FW	KR	BW	F		SR
>16 	34 	68 	11.9 	32.8 	0.53 	51 	17.0 		6.33 
>16 	25 	58 	10.7 	32.8 	0.53 	41.5 	16.5 		6.15 
>
>To make the DW decrease, one or more of the following:
>- more weight removed from the hammer
>- more weight added to the front of the key
>- ease friction (DW decreases, UW increases)
>- change leverage
>
>On this piano:
>- SW is in the lower quarter of the 'med. range',
>  not a whole lot can be further removed.
>- key is already loaded with lead, no more room
>- the friction is fine for this note (F will not change BW)
>- the KR is good (although uneven) and the action regulates well
>
>My advise from this point was to install wippens with assist springs.
>That way, lead could be removed from the front of the key and the
>spring would compensate thus creating a 'lower mass' action.
>At that time I would target a BW of 38; I like an UW over 20gr for
>repetition purposes, so since F =16      38BW - 16F = 22UW.
>The notes below C16 will have a F a few gr. higher so this will
>keep those UW's up as well.
>The SR will drop again with the assistance of the spring.
>
>The customer is considering this further refinement and in the
>mean time is enjoying a lighter touch and may decide to keep 
>things as they are. 
>
>Just another 'rebuild' salavation, tomorrow a M&H rebuilt
>'truck-like action' to make controllable.
>
>Keep 'em comin'
>
>
>
>Jon Page
>Harwich Port, Cape Cod, Mass. (jpage@capecod.net)
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>