BSwayze

BSwayze

Well Known Member
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:

P1050369%20(Small).JPG


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.

P1050330%20(Small).JPG


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.

P1050331%20(Small).JPG


Those of you with TruTrak servos, how did you safety this bolt? Or any single bolt, for that matter?
 
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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
 
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.
 
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.
 
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
 
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.
 
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.
 
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.
 
RTFM

flion said:
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.
Click to expand...

Once again - RTFM is the correct answer....:D
 
The Dynon servo mounts look identical to the TTrak. I drilled a small hole in the lower bracket and tied to that.

servo_mount.jpg
 
Is it possible to drill the thread out and put a bolt with nyloc AN 365 and 910 washer right through the servo box? I have the same problem and was looking at that as an easy solution.
 
Thank you, ALL, for some great input! I can see that there are a number of good options here.

flion said:
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". <edit>
Click to expand...

Patrick, you're quoting from some instructions that I don't seem to have. Where is this set of instructions you're referring to? I bought my brackets from TruTrak and I have printed drawings, but no references are there to any hardware, or the instructions you quote.

Bruce, thanks for the link to the video. Excellent!
 
BSwayze said:
Patrick, you're quoting from some instructions that I don't seem to have. Where is this set of instructions you're referring to?
Click to expand...

TruTrak has manuals and specific installation instructions online. There's a small link at the bottom of the website that is easy to overlook. It's easy to overlook, so here is the link: http://www.trutrakflightsystems.com/docs.html and you'll find RV installations listed to the right. Not all the installations are as detailed as the RV-10 roll servo (the pitch servo instructions are a picture without measurements even, for example) but you can find threads on here dealing with issues and TruTrak does participate here. I've also found their support to be quite good.
 
I safety wire all three heads together, but I did it with the servo on the bench. I then installed it into the wing. This was a long time ago, before they were even telling you to use drilled bolts. I haven't seen the newer instructions, but they sound better:D Boy, I'm starting to sound like one of the old-timers....Yikes:eek:
 
Maybe something different ...

I think I remember the hole being threaded all the way through the servo. On my 7, I just got a machine screw(s) (#10 as I remember it) that was fully threaded and ran it all the way through with a lock nut on the back. Maybe I ran a tap through it, that was several years ago but it is bolted and "nutted" on my airplane.

Bill S
7a Ark
 
Hornet2008 said:
Is it possible to drill the thread out and put a bolt with nyloc AN 365 and 910 washer right through the servo box? I have the same problem and was looking at that as an easy solution.
Click to expand...

Well, after looking at a number of ways to safety this bolt, this is exactly what I ended up doing. Getting into the tight space between the wing ribs, working through this small opening with my big hands proved to be difficult enough. Let alone trying to work with my safety wire pliers, on the back side of this servo. So I took the servo out and ran a #12 reamer all the way through this hole, and simply installed an AN3-12A bolt, 910 washer and locknut. I checked for any clearance issues with the pushrod that will go on here, and there's no problem. Now I'll safety the two bolts on the bottom-front in the regular way to finish this.

Thanks again for all the help. I found those excellent videos on EAA's site, and Joe, thanks for the document! I'm saving it for future reference.

P1060010%20(Small).JPG
 
Loctite

BTW, red loctite is very strong, blue is the medium hold. There is also a Stud and Bearing mount that is forever. Gene
 
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