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Step Two:
Clevis Links
and Ball Links
I want to deal
with aileron linkages to start with. The goal here is to
have a "friction free" connection that has no slop. The old
method of connecting a Dubro clevis to a plastic twist-on
horn tab works well. However, we're dealing with a plane
that produces vibration. We're dealing with a model that we
plan to fly a lot. And we want it to handle flight #50
as well as it handled flight #5.
The older style
linkage is just as good on day #1 as the more costly BB
linkage stuff. It’s on day #50 that you'll see the
holes start to wear. The clevis pin can wear and break in
cold weather. The worst case is you lose your model.
Best case is the model doesn’t fly as well as it can without
the linkage slop. I ran such linkages for years and was
always fighting them to keep things tight.
You may even get
sick of fixing the problem so you convince yourself it can
go another 5 flights without repair. Then you fool yourself
in actually believing the slop isn't hurting anything. I
did that. I thought I wasn't good enough to feel the
differences. I wasn't being very critical of my model's
performance. A side benefit of improving your flying skills
is the ability to recognize when the model just isn't right.
Of course, if you've never flown one that's properly
adjusted, you have no point of reference.
I'd be willing to
bet money that 95% of the pattern models out there today can
be improved. Life is so much easier when we take care of
the problems.
This belief is
one reason I use MK Ball Bearing clevis links. These things
are bullet proof. I put over 3000 flights on one model —
all with the original pushrods and clevis links. They were
just as tight on flight #3000 as they had been on flight #1.
So I'm sold. They're not cheap but they're worth the extra
to me. Not having to change out clevis links means one less
thing to maintain on the model. I don’t spend time
re-trimming the model. I don’t spend time in the shop (and
not flying) installing new clevises. I don’t worry about a
linkage failure that will cost me the plane.
I use the MKD0810
(2mm). I use this with the Central Hobbies 2mm Titanium
Pushrod Ends. They work great. The pin of the clevis is
actually a 2mm bolt and I stick a hex nut on the backside
for safety. You can use whatever you like, but I haven't
found anything else as smooth or durable as the MK clevis
links.
Next is the
connection on the servo side. I choose ball links, the kind
with a bolt through the pivot ball. There are tons of
sources for these things. Hangar 9 makes some, Dubro, and
others. I started using the NMP Dual Axis Rod Ends because
they're super light and easy to use. They will rotate with
the servo, and also pivot up and down to a certain degree as
the linkage moves. Central Hobbies sells these things as
DARE (Dual Axis Rod Ends). I use the 2mm version with
titanium pushrod ends.
Again, I use the
Dual Axis Rod Ends because there's zero maintenance on them.
It’s a "put on and forget it" type of item. They don’t wear
out.
Next: Geometry of Pattern Plane
Linkage
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