Hi! Fred.
It's not the 4130 steel torque tube that's elongating , its the stainless
16gauge thick bush part of the TP12's. Go get your skis out and enjoy
yourself.!
Regards
Bob H G-PTAG
-----Original Message-----
From: owner-europa@post.aviators.net
Subject: Re: Tailplanes
> PLUS operational forces and 'G' forces and impact momentum etc. when it
hits
> the bump stop.
> Regards
> Bob H G-PTAG
As far as operational G-forces, I did a simple test for fun (it's
snowing).
I drilled .063" wall, 4130, telescoping pipe, 1-1/4" O.D. for worse
case than the TP4 torque tube. I drilled neat holes for a long AN-4
bolt, but intentionally with some play in the ass'y so "elongation"
stress will concentrate more so than a correctly tight fit. Installed
in a vise, not real tight, because the bolt ends can just jam in the
jaws. Using a big pipe wrench on the inner pipe and full body weight,
I applied a calculated (actual lever arm) 160 foot-pounds of torque.
Very slight increase in play, I think. Remeasured the holes with the
digital caliper, and worst I can read is .001" elongation, which
calculates to about 1/32" more play at stabilator trailing edge.
Under microscopic inspection, no bolt damage beyond shining of the
cad, and the only visible change to holes is removal of drill marks by
over a ton of compression.
Using a spring-scale, I measured the torque multiplication, control
stick vs. TP4, and it looks about two. But it doesn't matter, as the
equivalent of this test is a 80# pull on the stick. Level, 60-deg.
bank turn is 2G (same trim), and how much tug on Europa stick is
that? So normal-flight stick pressures shouldn't elongate the holes,
even if TP-12 is less than .063" (TP4 is). Similarly, torque applied
by the mass balance weight, such as a real whack in turbulence, may
through inertia give the pins in the torque tube a whack. I wonder if
it could be anything close to the above test, w/o noticing it in the
control stick or bending the balance arm. I still suspect other
culprits.
I don't know if this wuz a proper test, but could have been!
Regards,
Fred F.
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