F1M VP spring question

From: Tapio Linkosalo <tapio.linkosalo_at_iki.fi>
Date: Fri, 07 Sep 2012 07:39:08 +0300

So, in order to reset my new VP for F1M, I had a spring winding session
yesterday. The original spring was something like 7 turns of 0.3mm
(0.012") around a 1.5mm (0.06") mandrel, but this seemed to be too soft.
The pitch only started to reduce halfway into the flight, and then went
to bottom setting rapidly.

Looking at Bill's notes, I changed to 0.4mm (0.016") wire and 3 turns
around the same mandrel. However, this seemed way too stiff, with
practically no pre-tension I got the change to happen at reasonable
torque, but then the VP did not go to bottom stop at all but was left
hovering inbetween the stops. No good, too hard a spring. So eventually
I went back to the thinner wire and a thinner (1.2mm, 0.047") mandrel.
At 3 turns and 90 degrees pre-tension this seemed to work better.
Tomorrows trimming session will show if this spring is any harder than
the old one.

A question, however. I seemed to have hard times bending the spring so
that it did not flip sideways. The old one with more turns took better
support from the shaft tube, but the new was so flat that it did not
support, and often it turned to the side. I tried bending the bottom
with a slot that goes around the cross bar so that it would support
there from flipping, but it was not too successful. Making a deeper hole
in the adjustment screw gave better support. But is there something in
the spring geometry that I have not realized, something that would make
it inherently stable instead of unstable, locations of the support point
for instance?



-Tapio-
Received on Thu Sep 06 2012 - 21:39:08 CEST