Changing roller size.

[Jon Page]

At 11:51 AM 09/01/2000 -0400, you wrote:

>In a message dated 9/01/2000 11:13:07 AM, you wrote:
>
><< Ok,  Here we go.  I would like to hear the relationship between
>knuckle size and backchecking defined.
>Thanks,
>Ed Foote>>
>
>Troll!!?? Moi?
>Well this is the first time I have ever been called a Troll. :-)
>
>All other things being equal, (we know they ain't but humor me here) a
>smaller knuckle would  require a higher capstan to get the same hammer
>line,.... but since we only changed the roller/knuckle the key must move
>further to reach letoff and it is this addtional key travel that produces a
>higher catch point for the backcheck. Distance to let off/key movement ratio
>comes into play here.  The change in the roller/knuckle dimension is
>reflected in the distance the key must move. Ergo, egads and gadzooks! there
>is a realtionship between smaller/larger knuckles and backchecks......que?
>   The same thing happens when you change heights of your capstans, i.e.
>hammerline, in that the backcheck catch height changes also.
>
>  If I am totally screwed up here it won't be the first time Ed. :-)
>Jim Bryant (FL)

If the ONLY item which was changed was the knuckle with capstan and l/o - 
drop readjusted,
the backcheck would stay the same. A change in keydip would necessitate the 
need to reset the
backcheck.

If you change the hammer height, the check height remains the same, what 
alters may be its
relative position to hammer height. But its point in space does not chnge.

Lift a hammer, press the key and drop the hammer into check.
Press on the key through letoff and have the hammer check-in.
Same height.  The wippen has no bearing on check-in, keydip does however.

The only thing I can see that a smaller knuckle would do at check-in is to 
allow the
repetition lever to be higher than a larger knuckle at check-in.

More later, off to Weefleet;



Jon Page,   piano technician
Harwich Port, Cape Cod, Mass.
mailto:jonpage@mediaone.net
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