Hello Graeme
I am not flying my XS mono yet (A-265 picked up April 2003). When building
I mounted my gear on a fixture and was able to study and fool with till I
was satisfied I fully understood it's operation.
First off you said you measured the over center, how did you measure it?
First off you need to make sure that the rubber spring block is compressed
to proper dimension. The more you tighten, the more overcentre you will
see. If for some reason the gap becomes less than called out for, you will
start ooching towards undercentre. I used a thin straight edge resting on
the edge of 3 pins that are the same diameter. The top pin is the pivot
pin that attaches to LG08s, the bottom pin is LG04, and the middle pin is
a little tricky, I made an insert that fits in the middle of LG08 tube
with a pin protruding the same size as the prior 2 mentioned. Now I have 3
points and can measure overcentre.
To my horror, 1 side was under centre and the other just bout neutral! I
ground down stops to where there was just a tad over 1/16" overcentre. You
need to be very careful you don't over do this as it will begin to put
much stress on UCMF. I forget the exact number that Andy said, but perhaps
1/8" was the limit.
The top of stop was gone when I achieved 1/16" on 1 side and the other
side was paper thin. What I did was grind down to 1/8" overcentre, and
inserted with Redux/Flox a pretty hard and stiff piece of polyurethane I
got from McMaster Carr, and pinned it after cure with a bolt. The
overcentre is just a tad over 1/16" on the polyurethane. Andy gave my
kluge a thumbs up.
Please don't overlook the connection between LG08P and the retraction
lever. I was careful to ream these 3 holes and scuff sand and Redux this
joint, and installed the mod that reinforces this connection as well. If
this joint has any movement when the lever is in the down and locked
position, it may not be ramming and jamming the LG08s against the UCMF
stops.
I also made a spring return for the down stop lock where it is very
positive in keeping it where you want it.
Once all was assembled on aircraft, the stops were not hitting absolute
the same time. Splitting hairs here, but I put a piece or 2 of some
Stainless Steel tape as a shim. You can get small pieces of that tape from
Lockwood Aviation, they sell it as prop lead edge tape, or
www.mcmaster.com sells it by the roll.
Hope this helps.
Ron Parigoris
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