1890s WNG Action Geometry

[David Love]

Is that a Stanwood 4.9 ratio?   If so, I think that's a bit low and you
might compromise the regulation some.  Remember that as you move the capstan
forward on the key you also benefit from the move away from the flange in
the 2nd class wippen lever.  I don't like to get a ratio lower than 5.5
(Stanwood) which should allow you a fair amount of leeway with hammers and
front weights to achieve something between 36 and 40 BW.  My usual target is
37.  If you calculate the ratio via linear measurements, the number will be
bit lower than with Stanwood measurements.  

 

Otherwise, capstan movements are pretty common on action I work on.
Relocating or changing the height of wippen heels is not uncommon either.

 

David Love

 


Farrell wrote:




Phil Bondi and I dove into an 1890s WNG action from a 6' 4" Knabe today to
try and straighten out some basic action geometry. We haven't got all the
kinks worked out yet, but we seem to be getting there. With only a large
capstan move and removal of a couple leads, we went from an action ratio of
over 6.0 down to 4.9. DWs went from 60+ to 50 and less (I know, too light)
and BW in the 36 to 40g range. We have a lot of work to do yet, but it seems
the capstan move described below has gotten us into the right ball park
anyway. 

 

Most notable was a very large capstan move that we will likely keep (unless
someone so kindly informs us of a potential problem the change might
induce). The photo below shows the original capstan in the background. The
forward key had its capstan moved 10mm forward and 11mm lower. The middle
key had its capstan moved 13mm forward and 12mm lower. The second photo
shows the modified wippen heel. These lower positions put the capstan right
on the magic line at half blow. The capstan/wippen heel interface went from
a traveling, grinding, sliding affair and a note with 17g friction to a
perfectly interfacing union with no apparent sliding and a note with 9g
friction. We were amazed at the improvement in friction and interface
movement. 

 

This strikes me as a rather drastic capstan move. Has anyone else run across
an action that needed such a large capstan move? As our action ratio is down
to 4.9 and key ratio is down around 4.8 with the 10mm forward capstan
migration, we may move it back just a few millimeters. But still it seems
large. Is there some hidden pitfall I'm not seeing? Comments? 

 

Terry Farrell 

 



 

 



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