Front Weight--measurements

[Jon Page]

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At 08:34 AM 07/18/2000 -0400, you wrote:
>At 06:28 PM 07/17/2000 -0700, Richard Brekne wrote:
><snip>
>>Gotta admit.. this stuff is really fascinating. From what I can tell from
>>the stuff included in the Stanwood kit, The Whippen Weight Ratio and the
>>resulting Whippen Balance Weight look ok. Also the Strike Weight looks
>>reasonable. The Balance weight is way of the scale due to really high up and
>>down weights. The Front Weight seems really really low. Increasing FW by 20
>>to 25 grams would bring Balance Weight down to acceptable levels but that
>>alone will not change the Strike Rate Ratio by much which seems a bit on the
>>high side here.

Results of current action modification:

Original action had a shank with a 16.2 knuckle radius and an angled wippen 
cushion.
This action was heavy and had little to no aftertouch (jack was not 
clearing the knuckle sufficiently).

Installed a shank with a17mm knuckle and a straight wippen cushion (Turbo Wip).
Trial regulated a few notes and the aftertouch was the same. I set the 
hammer to half-blow
ran a line from the b/r to the c/p, capstan too far forwards. I placed a 
mark on the cushion where
the line intersected. With the hammer still blocked and the capstan removed 
I also placed a
spacer under the key front to simulate the key's attitude at that key event 
(half-blow). I simply held
a small ruler parallel to the wippen support post and drew a line through 
the mark on the sides of
the wip and keystick. A temporary capstan allowed a trial run, perfect.  I 
set all the capstans to this new line.

The original capstan angle was 10 degrees with an average KR of .48.
New line has capstan angle at 90 degrees with an average KR of .50 and in a 
tighter range. It makes you
wonder how capstans are drilled so haphazardly to begin with. Had this 
'magic line' intersection
resulted in the jack not functioning to my liking, I would have moved the 
capstan fore or aft to where it did
and adjusted the wippen cushion height to accommodate the 'magic line'.

This method has allowed me to specify blow distance, dip, etc, and result 
in a fine regulating piano as
opposed to having to fudge on hammer height or dip to get the action to 
function  properly.
The biggest mistake we make is to assume that everything at a factory was 
performed with absolute accuracy.

My next step is to sample UW/DW and have David calculate a smooth FW spec.

This stuff is so easy.
Jon Page,   piano technician
Harwich Port, Cape Cod, Mass.
mailto:jonpage@mediaone.net
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