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  #1  
Old 09-16-2017, 06:39 PM
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bkervaski bkervaski is offline
 
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Default Flap Actuator Safety Wire .. ugh

I was so happy to be installing the flap motor tonight .. until I saw the section calling to drill the flap actuator safety wire hole .. any words of encouragement? Advice?
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  #2  
Old 09-16-2017, 07:38 PM
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Default Drilling the hole

Start drilling at 90° from the shaft, enough to keep the bit from sliding, then hold drill at 45° to finish the hole. Pretty easy to do.
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  #3  
Old 09-16-2017, 08:33 PM
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Default

Use a tiny drill bit, just big enough for the wire; easy peasy.
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  #4  
Old 09-17-2017, 05:46 PM
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Thanks guys .. it was trivial .. I over thought it, took about a minute!
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  #5  
Old 10-10-2017, 08:56 AM
slngsht slngsht is offline
 
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This safety wire solution is giving me pause. Dealing with same thing on my -7 build.

The wire doesn't really keep the nut locked. It does keep it from turning freely. Its other function is to keep the thread from completely backing out.

But let's say the nut does become slightly loose. The shaft is now somewhat free to rotate back and forth as you operate the flaps, right? When shaft turns in direction that backs thread out, tension in safety wire is what will stop it from continuing. That's the real purpose, right?

Wouldn't that work harden the wire?

Strange solution to this problem.
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  #6  
Old 10-10-2017, 11:12 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by slngsht View Post
This safety wire solution is giving me pause. Dealing with same thing on my -7 build.

The wire doesn't really keep the nut locked. It does keep it from turning freely. Its other function is to keep the thread from completely backing out.

But let's say the nut does become slightly loose. The shaft is now somewhat free to rotate back and forth as you operate the flaps, right? When shaft turns in direction that backs thread out, tension in safety wire is what will stop it from continuing. That's the real purpose, right?

Wouldn't that work harden the wire?

Strange solution to this problem.
It is called safety wire for a reason. It is not put in place expecting it to do a job. It is there just in case it needs to do a job, and then hopefully only for a short time (Checking this is just one of the many things that should be part of a condition inspection......) If properly assembled and torqued, this rod end should never come loose, but since it is subject to rotation it is appropriate to safety it in some way.
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  #7  
Old 10-10-2017, 12:32 PM
slngsht slngsht is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
It is called safety wire for a reason. It is not put in place expecting it to do a job. It is there just in case it needs to do a job, and then hopefully only for a short time (Checking this is just one of the many things that should be part of a condition inspection......) If properly assembled and torqued, this rod end should never come loose, but since it is subject to rotation it is appropriate to safety it in some way.
Scott, I agree with your points. However, if the nut does work itself loose, the safety wire in this case is actively subject to torque from the operation of the actuator. In other safety wire applications I can think of, safety wire's job is simple to keep the bolt or not from turning - nothing more.
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  #8  
Old 10-10-2017, 01:06 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by slngsht View Post
In other safety wire applications I can think of, safety wire's job is simple to keep the bolt or not from turning - nothing more.
True, but for a bolt to turn against safety wire there also has to be a torque being applied to it (though I admit, not in a cyclic mode).

The actual rotational torque of the actuator is very low (you can easily hold it with two fingers), so the risk of anything happening to the safety wire with even repeated cycles is extremely low.

I am not aware of there ever being a failure of any safety wire, though I am aware of at least a couple instances were the wire kept the assemble together.

It is experimental after all, so builders can do whatever in their mind seems best, but I say that service history proves the safety wire method to be 100% reliable.
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  #9  
Old 10-10-2017, 01:11 PM
slngsht slngsht is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
True, but for a bolt to turn against safety wire there also has to be a torque being applied to it (though I admit, not in a cyclic mode).

The actual rotational torque of the actuator is very low (you can easily hold it with two fingers), so the risk of anything happening to the safety wire with even repeated cycles is extremely low.

I am not aware of there ever being a failure of any safety wire, though I am aware of at least a couple instances were the wire kept the assemble together.

It is experimental after all, so builders can do whatever in their mind seems best, but I say that service history proves the safety wire method to be 100% reliable.
Don't get me wrong - I'm not saying it's unsafe. Just a design exercise for me. Sometimes I go down these rabbit holes

As for amount of load, I did operate the motor last night and the torque is load, but wouldn't the applied torque go up as a function of load on the shaft? I assume source of the free rotation of the actuator is thread friction and that would go up with load.

There have been a few failures involving the safety wire - found this a few minutes ago:
http://www.vansairforce.com/communit...y+wire+fatigue
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  #10  
Old 10-10-2017, 01:27 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by slngsht View Post
Don't get me wrong - I'm not saying it's unsafe. Just a design exercise for me. Sometimes I go down these rabbit holes

As for amount of load, I did operate the motor last night and the torque is load, but wouldn't the applied torque go up as a function of load on the shaft? I assume source of the free rotation of the actuator is thread friction and that would go up with load.

There have been a few failures involving the safety wire - found this a few minutes ago:
http://www.vansairforce.com/communit...y+wire+fatigue
I have never seen that thread. The first thing that comes to mind is wondering how long the rod end had been loose (I know of RV's that have gone for many years without the inspection cover being removed from the flap motor)

I agree that the rotational torque of the actuator probably does increase under tension load from the flap system but I still feel that the prescribed method is adequate.

I shouldn't have to say it, but builders should make sure they torque the jam nut to the proper torque value and then use a safetying method you are comfortable with.
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