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02-13-2009, 09:24 AM
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Join Date: Mar 2005
Location: SE Florida
Posts: 1,499
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More than one way to skin a cat
Quote:
Originally Posted by mburch
Okay, so now I'm scared to drill a hole in my stick. But, I still need a way to get wires out. As somebody asked in the other thread, how is this done on Van's demonstrator airplanes?
mcb
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Mat,
Another solution would be to run the wiring harness externally along the outside of the control stick. McMaster-Carr and MSC sell nice spring steel clips for this purpose. The clips are shaped like a C, with a bulge (for the harness) in the middle of the C. Two or three clips (or other securing methods) will keep the harness in place.
Charlie Kuss
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02-13-2009, 09:25 AM
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Join Date: Feb 2005
Location: N Mn
Posts: 299
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Just to see
I tested a 3/4 x .035 section of moly I had handy, drilled 7/16 hole. Stuck it in a vice, Hole 1" high and pulled-- Did fail at the hole!( ripped) Just started to bend at 100 lbs on my crude pull scale and failed at about 120 lbs pulling 12" from the hole. 1" would do a little better.
It would be good to have all of Van's different sticks types for distructive testing.
__________________
Frank Karasti
Hibbing, Mn
RV-9A
Flying--------->-
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02-13-2009, 09:41 AM
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Join Date: Jul 2005
Posts: 1,347
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I'm guessing that Pat Tuckey is glad his stick didn't bend or break:
http://www.vansairforce.com/communit...hlight=trutrak
I wonder if Pat has any holes drilled in his stick, and if so, how large are they and where are they located?
__________________
Mike W
Venice, FL
RV-6A. Mattituck TMX O-360, FP, GRT Sport EFIS, L3 Lynx NGT-9000
N164WM
N184WM reserved (RV-8)....finishing kit in progress. Titan IOX-370
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02-13-2009, 09:54 AM
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Join Date: Aug 2005
Location: OKC, OK
Posts: 687
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Tested!
Quote:
Originally Posted by FrankK90989
I tested a 3/4 x .035 section of moly I had handy, drilled 7/16 hole. Stuck it in a vice, Hole 1" high and pulled-- Did fail at the hole!( ripped) Just started to bend at 100 lbs on my crude pull scale and failed at about 120 lbs pulling 12" from the hole. 1" would do a little better.
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Frank, nice job. Your test does validate the actual failure mode of the tube. The 120 pound failure load is interesting also.
I want to make sure VAF readers here don't take this result to be the gospel. The real stick tube assembly is loaded and supported differently (not like a tube in a vise) and is a 1" OD tube. This does show how relatively easily a steel tube with a hole in it can fail in bending.
The most important thing Frank's test shows is the failure mode was what I feared would be the "worst case". The wall of the hole began to rip, which then lead to rapid buckling of the tube.
__________________
?The important thing in aeroplanes is that they shall be speedy.?
- Baron Manfred von Richthofen
RV8 under construction
RV4 - Sold
United B777 FO, Chicago
Aero Engineer
RV8
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02-13-2009, 10:42 AM
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VAF Moderator / Line Boy
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Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,256
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Test, Test, Test!
I love the fact that someone did a test! Too often these days, we engineers tend to rely on analysis alone to "solve" problems. In the old days, before sophisticated analysis tools, guys just did testing! I was thinking that I might have an old RV-8 stick that I didn't use sitting in my box, and that I should rig up a test - then I came back to this thread and found Frank had beaten me to the idea. If I get the chance, I'll look to see if I still have a"test article" and see if I can rig one up.
Analysis confirmed by testing is golden - this is a GREAT effort all!
Paul
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
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02-13-2009, 11:31 AM
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Join Date: Aug 2005
Location: OKC, OK
Posts: 687
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Dittos Paul...
Sure would be good to test the real article.
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02-13-2009, 12:13 PM
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Join Date: Nov 2007
Location: Reno, NV
Posts: 2,125
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After catching up on this thread, I took a look at a pic from when I installed my AP roll servo. This is the left stick in a bought-flying '98 -6. Please forgive the dust and my runny nut creep indicators...cleaned it up since snapping the pic!
The hole (which was there before and I re-used when installing a new stick grips) is drilled very close (in my estimation) to the pivot point, which is discussed in the warning referred to above, so this has my attention! Just has a snap bushing in it to protect the wires.
Not sure if the design has changed or if side-by-sides have a different design, but it looks like the attachment for the cross tube, with its fore-aft weld and the triangular gusset would provide some strength to prevent bending and failure at the hole. Just wanted to ask the brain trust for an opinion on that, as I don't want to assume that's the case, and I certainly don't want to have the stick fail there in the event of a lock up!
Thoughts? Look OK, or should I suck it up and weld the washer? Don't want to mess up the nearby welds either, though not sure that would be an issue. Another thought would be, if there is room, to weld a vertical gusset on the back of the stick (sorta like the ones that are on the rudder pedal vertical attach points). Sort of like this (bad drawing, but shows the concept...and this is not an engineering fix recommendation...not qualified to do that...but rather question of applicability to this situation):
Just trying to make sure all is well, and thanks for the great info here!
(Hey Dan, OT here, but note I followed your advice and inserted the long bolt to the servo rod with the bolt's shank in the control stick hole where the force is applied...learned a good one from ya there!  )
Cheers, Bob
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02-13-2009, 12:23 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Bob, hard to tell from the photo, but it looks like the stick is double walled at the position you drilled.
In addition, the pivot point is pretty well reinforced by that gusset plate.
Looks pretty strong compared to the modeling Bill did.
How is the snow doing???
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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02-13-2009, 12:29 PM
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Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,251
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Quote:
Originally Posted by chaskuss
Mat,
Another solution would be to run the wiring harness externally along the outside of the control stick. McMaster-Carr and MSC sell nice spring steel clips for this purpose. The clips are shaped like a C, with a bulge (for the harness) in the middle of the C. Two or three clips (or other securing methods) will keep the harness in place.
Charlie Kuss
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Doctor, it hurts when I do this! So stop doing it! It's perfectly acceptable to run the cable externally to the stick secured in this fashion. Put it on the leading edge of the stick and you will barely notice it. If you don't want the C-clips, wrap the stick and cable with cloth tape (like you get at the bike shop).
Greatly simplifies installation as well. The grip, cable and connector can be wired externally then fitted to the stick later on.
Thanks Charlie!
__________________
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V e r n. ====
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RV-9A complete
Harmon Rocket complete
S-21 wings complete
Victoria, BC (Summer)
Chandler, Az (Winter)
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02-13-2009, 12:49 PM
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Join Date: Jan 2006
Location: Tucson, AZ
Posts: 818
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Hole location?
This is a very interesting thread.
As a mechanical design engineer I use finite element analysis (FEA) as a guide. Testing is the ultimate decision factor for me.
When pulling out of that steep dive just after you released that 500 lb bomb puts quite a load on the stick so we need to be careful
I my opinion the aileron loading on the stick is much less, so why not put the hole on the side of the stick?????
That is where I am putting mine.
Your mileage may vary.......
Paul
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