action analyses

[Richard Brekne]

Ron, Ron, and Bill.

Well after reading Ron N's reply to this buisness about the jack moveing a
bit backwards at the beginning of the key stroke, and reading Ron O's
aggreement I simply had to take a closer look at this, and I found what
perhaps is the reason for my observation seemingly pointing in the oposite
direction.

Thinking twice and thrice about Ron N's reasoning.... this made sense..

What I did was to remove the whippen spring from the jack, and place it
beside the jack so the tension was still on the repetition lever. Then I
removed the adjustment button so the jack was free to move in as much as it
wanted to with no influence from the whippen spring either. Then I started
setting the spread in both obviously wide and narrow positions to see what
happened. For each spread setting I reset hammer distance to string,
re-alligned the jack to the knuckle core, and I marked a line on the
repetition lever extending the "start position" of the jacks back side so I
could see clearly whatever movement would take place.

What I found was there was no noticable difference. In all cases the jack
moved backwards about 2 and a half mm before stopping backwards movement.
There it stayed until the jack tender came into play.

I tried adding a spring between the back of the jack and the spoon, and the
same results. The spring was equally compressed as best I could tell.
(Tried to set the initial spring tension equally...but it was a bit crude)

OK... I was wrong thought I...grin.. But then after reinstalling everything
as it should be and rechecking the two spreads again.... there it was.. No
backwards movement with a wide spread.. and a very small but easily
noticable amount with a narrow spread.

However !!.. :)  if you pressed the jack backwards to begin with (narrow
spread) then there was no backwards movement. That meant the something was
preventing the jack (with narrow spread) from getting fully back into its
rest position. This is where Ron N's thinking comes in... but in reverse.
With the narrow spread, and because of the same kind of reasoning Ron had
for thinking the backwards movement of the jack would get worse, the jack
was being prevented from comming full in to rest position. With a wide
spread the jack could very easily slip fully into rest position and then
the felt was alread compressed enough to prevent it from moveing any
farther backwards in this first part of keystroke.

So... thats what I think is happening.. thats what it looked like.. and it
makes sense...grin.. I think anyways.
--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway