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Check those servo arm screws!

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Check those servo arm screws!

Old 07-23-2013, 08:00 PM
  #26  
byrne1157
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Default RE: Check those servo arm screws!

Sorry about your airplane, but thanks for the tip!! Of course, it's not as expensive as a jet, but I had a problem with my GP Escapade on it's maiden flight, with the same issue. I took off, and didn't get through the first cicuit around the field, and it felt a little "squirrely" to me, so I landed, and taxied in. When I checked it out, I found the right aileron control rod, and servo arm had detatched from the servo. So I got some ca and put a drop on the replacement screw, and the one on the left, then dismounted the wing and took care of the elevator and rudder servos as well. I didn't know about the problem with loctite and plastics, good to know! Thanks again!![8D]
Old 07-24-2013, 12:08 AM
  #27  
Rob2160
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Default RE: Check those servo arm screws!



Sorry for the loss of your beautiful Jet..



From my experience with RC Helicopters which require every single bolt and screw to be loctited...



Metal to Metal use Loctite



Metal to CF or Plastic - use Foam Safe CA glue.



EG   http://www.horizonhobby.com/products...e-7-oz-PAAPT25



For securing the servo arms I would definitely recommend the Foam Safe CA.  Loctite will damage plastic.

Old 07-24-2013, 04:49 AM
  #28  
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Default RE: Check those servo arm screws!

Who sells plans for the tsunami? Short kit?
Old 07-24-2013, 06:52 AM
  #29  
zacharyR
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Default RE: Check those servo arm screws!

I don't understand why a Jet would have issue with servo screw backing out I thought they had a lot less vibration over all in comparison to a large gass engine
Old 07-24-2013, 06:58 AM
  #30  
essyou35
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Default RE: Check those servo arm screws!

Re Loctite: I put the smallest amount I can on the thread of the bolt, and whipe it off so it is only inside the threads just barely. I do this for two reason. One is so it doesnt get on the plastic arms and two, too much loctite will make getting that bolt back out a real PITA. I usually only get it on the first couple threads as well.

I'd be willing to bet it was never on there. It happens!
Old 07-24-2013, 08:15 AM
  #31  
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Default RE: Check those servo arm screws!

If the output shafts are plastic do not use loctite. If they are metal then put a drop on the end of a toothpick and apply to the hole in the shaft. Silicone works fine for the plastic shafts, putting the arms on and off is going to make the holes bigger also. Never had a problem with Dubro arms, has anyone contacted them about the issue? I would rather have a complaint directly from a customer than get bashed on a forum. I have had arms that said they were for a certain brand but never fit right. I wonder if servo manufacturers change their specs and the after market suppliers don't know it. The best solution is inspecting the aircraft before flight always, not much difference than full scale. Sorry you lost one, always sucks no matter the reason and more so when you miss the simple things.
Old 07-24-2013, 09:44 AM
  #32  
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Default RE: Check those servo arm screws!

One problem I have seen in the giant scale gasser side is folks that are using MG Hitec servos and want to get rid of the Phillips head screws are replacing them with 2.5mm hex head bolts, when they are in fact 2.6 MM and will vibrate out.
Old 07-24-2013, 11:21 AM
  #33  
drac1
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Default RE: Check those servo arm screws!


ORIGINAL: Jim Cattanach

I also read that Loctite attacks plastic.
I've used loctite on metal output shafts with plastic arms for years with no problems.
Old 07-24-2013, 01:10 PM
  #34  
Flyfast1
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Default RE: Check those servo arm screws!

I put a dab of silicon glue on top of each of my servo arm screws. It's quick, inexpensive and ensures that the screws will not come out. The glue is easily removed if a servo arm needs to be removed. Works great.

-Ed B.
Old 07-24-2013, 02:02 PM
  #35  
ssautter
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Default RE: Check those servo arm screws!

Yes, liquid threadlock such as Loctite, will attack many plastics....

Use Tamiya threadlock: http://www.tamiyausa.com/product/ite...oduct-id=87004
It is safe, for use on most plastics.

For those of you *****fuse tobuy Tamiya products....you get the crash trophy!
Old 07-24-2013, 02:07 PM
  #36  
ssautter
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Default RE: Check those servo arm screws!



Loctite "425" will also work, but it is actually CA glue: http://www.henkelna.com/product-sear...=8797887234049

Old 07-24-2013, 05:22 PM
  #37  
cubluver
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Default RE: Check those servo arm screws!

In reading all these posts about Loctite, I wonder what type of Loctite people are using. If you go to www.Loctite.com and check out their product listings for thread lock, it appears the only suitable one for this application, (small screws), would be #222 or #222MS The #222 is not mil-spec and the #222MS is mil-spec. If you are using #242, or something similar, it's not the right stuff for this application.
Regards
Old 07-25-2013, 05:41 AM
  #38  
flyinfool1
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Default RE: Check those servo arm screws!


ORIGINAL: ssautter



Loctite "425" will also work, but it is actually CA glue: http://www.henkelna.com/product-sear...=8797887234049

If you read the MSDS sheet, the Loctite 425 is 30-60% CA glue. Straight CA glue will also attack many plastics.
Where I work we were having issues with loctite 242 damaging plastic, changing to the loctite 425 solved the issue.

Different of servo arms are made from different plastics. Some can tolerate loctite some can not. So some people will have no problem with loctite on a servo arm and some will.

Different brands of thread lockers do have different chemical compositions that may or may not be safe on any given plastic.

After my own experimenting, it is my opinion that the black Futaba servo arms and the HD Hitec arms, are loctite 242 and 290 safe. I have not experimented with others.

Old 07-25-2013, 06:56 AM
  #39  
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Default RE: Check those servo arm screws!

It should be noted that if you're using enough thread locker to squeeze out and get onto the arms, you're using too much.

But again, don't use it with nylon or karbonite gears
Old 07-25-2013, 07:09 AM
  #40  
VF84sluggo
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Default RE: Check those servo arm screws!

It sounds like the way to go is to put just a dab on the last few threads, wipe the thread lock into the those threads and thus wipe away any excess thread lock, then carefully insert the screw into the metal spline. This should keep any thread lock from oozing onto a plastic arm, and be enough lock to secure the screw.

At least this is my plan...

Sluggo
Old 07-26-2013, 06:07 AM
  #41  
flyinfool1
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Default RE: Check those servo arm screws!


ORIGINAL: VF84sluggo

It sounds like the way to go is to put just a dab on the last few threads, wipe the thread lock into the those threads and thus wipe away any excess thread lock, then carefully insert the screw into the metal spline. This should keep any thread lock from oozing onto a plastic arm, and be enough lock to secure the screw.

At least this is my plan...

Sluggo
Your close.
The best way to be sure that no threadlocker gets on the plastic arm is to use a toothpic to put a small amount into the hole. This way there is no chance of getting any on the plastic. Putting the thread lock on the screw you always have the chance of wiping some on the sides of the hole while you are inserting the screw thrrough the hole in the plastic.

As mentioned, many people use way to much thread locker on each screw.
Old 07-26-2013, 09:15 AM
  #42  
VF84sluggo
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Default RE: Check those servo arm screws!

^^^^^^ Yes, I like your technique better...thanks!
Old 07-26-2013, 09:27 AM
  #43  
grbaker
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Default RE: Check those servo arm screws!

The best way to be sure that no threadlocker gets on the plastic arm is to use a toothpic to put a small amount into the hole.
Agree.


I've been using this method since the ICDF days. They vibrated everything loose!!
Old 07-30-2013, 12:53 PM
  #44  
ssautter
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Default RE: Check those servo arm screws!

Another option, entirely, is to use an internally-toothed lock washer.
The washer will tighten into the softer plastic servo arm and not dissolve it.

Not so good for aluminum servo arms....

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