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10-03-2012, 11:02 PM
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Join Date: Jul 2007
Location: Molalla, Oregon
Posts: 955
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Safety Wiring Question
I've done some searching, and not having much luck trying to come up with some help learning more about safety wiring. How did you guys learn all the tricks? I get the basic concept... "righty tighty, lefty loosy" and all that. But here's a specific question.
I just installed my autopilot servos, and there's one bolt on the roll-axis servo in the wing that I don't know how you would safety. Here are some pictures to help explain. This is looking into the wing, where you see the servo in place:
The red arrows in the following picture show the two front bottom bolts. No problem figuring out how I'm going to safety these. I'll just wire them to each other.
Here's the one I'm questioning how it should be done... it's behind the servo, on top. It's a single bolt. There isn't anything nearby to wire to. I hope this photo isn't confusing, I put my inspection mirror in there so you can see the bolt head reflected in the mirror, and a red arrow pointing to it.
Those of you with TruTrak servos, how did you safety this bolt? Or any single bolt, for that matter?
Last edited by BSwayze : 10-07-2012 at 04:21 AM.
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10-04-2012, 03:02 AM
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Join Date: Feb 2008
Location: Dublin, Ireland
Posts: 179
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Drill the bracket?
Hi Bruce,
How about drilling a small hole in the angled bracket under the bolt and running the wire from the bolt through there? Choose the hole location to maintain 'righty tighty'.
I have the same servo mount in stock for my MGL servo but haven't fitted it yet. (Trio Gold servo and mount installed initially - both still for sale - offers?) so I am looking forward to the answers you get.
By the way, there are very good videos on safety wiring on the Homebuilders Hints section of eaa.org
__________________
Loman O'Byrne
RV9 TU. O-320-E2D. Engine hung, working on FWF, Arklow, Ireland
=VAF= dues paid through Dec 2020
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10-04-2012, 04:24 AM
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Join Date: Dec 2004
Location: Gold Hill, NC25
Posts: 2,400
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You would want to safety wire the 2 screws together in the absense of a local location to secure them.
A very simple review of safety wiring is on wiki and your screws are first up on the lesson.
As mentioned, search safety wire on EAA's website and you will find some neat stuff.
__________________
Kahuna
6A, S8 ,
Gold Hill, NC25
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10-04-2012, 04:34 AM
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Join Date: Nov 2005
Location: Asheville, NC
Posts: 2,692
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Safety all three bolts with one wire. There is nothing preventing you from going around the servo with the wire.
Just keep the righty tighty rule in place.
__________________
Bill Pendergrass
ME/AE '82
RV-7A: Flying since April 15, 2012. 850 hrs
YIO-360-M1B, mags, CS, GRT EX and WS H1s & A/P, Navworx
Unpainted, polished....kinda'... Eyeballin' vinyl really hard.
Yeah. The boss got a Silhouette Cameo 4 Xmas 2019.
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10-04-2012, 04:48 AM
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Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
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I agree with Loman..a small hole in the angular bracket will suffice. My Air Tractor counterweight bolts on the elevator have such a hole drilled in the outboard rib and safeteed to them.
Best
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
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10-04-2012, 05:41 AM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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Or go ahead and put a bolt in the other corner and safety to it.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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10-04-2012, 06:27 AM
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Join Date: Aug 2010
Location: Wichita, KS
Posts: 1,958
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How about a lockwasher? Is this bolt absolutely critical to flight controls? What happens if this one bolt loosens in flight? If the answer is not catastrophic, then perhaps the safety wire is simply susbsituting for a lack of another locking mechanism like a locknut. In this case perhaps a star lockwasher is the assurance you need. Not as good as a locknut, of course, if that were an option.
__________________
Kurt W.
RV9A
FLYING!!!
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10-04-2012, 07:26 AM
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Join Date: Dec 2007
Location: Flagstaff, AZ
Posts: 2,653
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Dingdingdingding! Kurt has hit the answer according to TruTrak. The instructions for the roll servo specifically call out "Install either internal lock washer or AN960-10 washer with safety wire". I will safety the two on the bottom of the servo but that one on the top would be a nightmare to safety in that tight space (between two ribs with linkages and stuff in the way), so it will get a lockwasher and a little locktite as extra insurance. And, if that screw were to fail, it would allow the servo to flex slightly in a vertical, longitudinal plane relative to the aircraft, but the z-bracket would still be in place to prevent that, along with the angle bracket and spar web at the forward face of the servo (I'm picturing the installation in service, where the spar is forward, not like it looks with the leading edge down during construction) and most of the loads on the servo will be lateral. An A&P or TruTrak can chime in here but I don't think a failure between inspections is likely or critical.
__________________
Patrick Kelley - Flagstaff, AZ
RV-6A N156PK - Flying too much to paint
RV-10 14MX(reserved) - Fuselage on gear
http://www.mykitlog.com/flion/
EAA Technical Counselor #5357
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10-04-2012, 09:30 AM
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Join Date: Feb 2006
Location: McKinney, TX
Posts: 27
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I had occassion to remove my pitch servo in my RV-7. I originally used socket cap bolts with lock washers and Loctite 262.
It worked well - I won't try to come up with colorful analogies to describe how hard they were to remove, just this: They were very difficult to back out. Use Loctite sparingly. Someone told me there was a permanent and a not so permanent version of Loctite. If so, that's an option. And while I was able to remove the socket bolts, I was fearful I'd strip the hex slot in the socket. Better to use AN3's where it's not likely to create the removal issue.
__________________
Daryle L. Grounds
214-505-8378
daryle.grounds@yahoo.com
McKinney, TX Based @ T31
RV-7, N33DG, IO-360-A1B, Hartzell C/S, Flying since 12/15/12; Swick TCraft under construction
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10-04-2012, 09:48 AM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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RTFM
Quote:
Originally Posted by flion
Dingdingdingding! Kurt has hit the answer according to TruTrak. The instructions for the roll servo specifically call out "Install either internal lock washer or AN960-10 washer with safety wire". I will safety the two on the bottom of the servo but that one on the top would be a nightmare to safety in that tight space (between two ribs with linkages and stuff in the way), so it will get a lockwasher and a little locktite as extra insurance. And, if that screw were to fail, it would allow the servo to flex slightly in a vertical, longitudinal plane relative to the aircraft, but the z-bracket would still be in place to prevent that, along with the angle bracket and spar web at the forward face of the servo (I'm picturing the installation in service, where the spar is forward, not like it looks with the leading edge down during construction) and most of the loads on the servo will be lateral. An A&P or TruTrak can chime in here but I don't think a failure between inspections is likely or critical.
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Once again - RTFM is the correct answer.... 
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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