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Securing servo screws

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Old 03-09-2014, 11:17 AM
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mustangman177
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Default Securing servo screws

The servo screws on the Hitec servos i'm using are vibrating loose, and in one, came out all together. The engine is a ryobi 31, so vibration is present. Would medium strength thread lock be good here to secure the small screws into the horn ?

Thanks

Cary

* EDIT: Did a search on this and found out that Locktite will attack plastic servo horns. Instead use CA to secure the screw to the spine.

Last edited by mustangman177; 03-09-2014 at 11:34 AM.
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Old 03-09-2014, 11:42 AM
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TLH101
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I used to put a dab of silicone over the top of the screw. Easy to remove when needed. Fly electric now, so I don't have vibration issues anymore.
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Old 03-09-2014, 11:46 AM
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mustangman177
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Thanks TLH.

Do have silicon RTV. Will use this
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Old 03-09-2014, 12:01 PM
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Hi!
You first put a small amount of thin Ca glue in the screw hole, then you screw the in the screw!
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Old 03-09-2014, 07:15 PM
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jester_s1
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And how do you get it back out?

Are we talking about metal gear servos or plastic geared servos? I've never heard of screws vibrating out of plastic gears before since the holes are so tight anyway. A thin piece of teflon tape would probably tighten it up though and would still be removable. For metal gear servos, put a drop of medium threadlocker in the hole, not on the screw. That will let you lock the screw in place without any worry of damaging the control horn.
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Old 03-10-2014, 02:47 AM
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Steve Percifield
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Most Hitec servos with metal gears have a small star type lock washer with the control horn screw. You may have lost it. I had the same issue a few years ago and Hitec did recommend a very small dab of blue thread locker. But I came to prefer a surface mount application of silicon or a dab of hot glue. Much easier to remove when you need to.
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Old 03-10-2014, 03:29 AM
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You definitely don't want to use thread locker on non metal gear servos.
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Old 03-10-2014, 05:35 AM
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mustangman177
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Thanks for the advice. I too have never had this issue. The engine is a Ryobi 31, so vibration is definitely a problem. I still am using the star type metal lock washers. Have applied the RTV silicon to the screw threads. Will check screws after the next flight.

Cary
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Old 03-11-2014, 01:35 PM
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CafeenMan
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I had the same thing happen on mini metal gear servos on a .15 size plane. It could fly 3-channels easily. One time the plane landed with both aileron pushrods hanging straight down from the ailerons with the servo horns attached. Star washers resolved the problem but the next step would have been a very small droplet of blue loctite.
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Old 03-12-2014, 06:04 AM
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jester_s1
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I don't see why anyone is resistant to use loctite on metal gear servos. That's exactly the sort of application the stuff is made for. It won't make it hard to get the servo horn off again when you need to. It only provides enough adhesion to keep screws from vibrating loose on their own.
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Old 03-12-2014, 06:24 AM
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Exactly!

Clean the threads, and put a small dab of blue (medium strength) on and its perfect
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Old 03-13-2014, 03:06 AM
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+2, been using the blue on my servo screws for years.

Bob

Last edited by sensei; 03-13-2014 at 03:11 AM.
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Old 03-13-2014, 04:17 AM
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Loctite is the way to go on metal geared servos when using metal arms. Even though you apply the loctite to the threaded hole only some vapor will get to the plastic arm and you might have an issue. The first thing to do though is to get rid of the crappy screw that comes with the servos and order up some 2.6mm socket head screws. With the better screws you can get the screw tighter and then if using metal arms apply loctite, if using plastic arms then stake the screw with RTV.
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Old 03-13-2014, 04:41 AM
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Yes, McMaster Carr has M2.6x8 screws to replace the crappy Phillips head screws and you can buy them by the 100 for a few bux
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Old 03-13-2014, 04:52 AM
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Rodney
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It is not advisable to use silicon RTV anywhere near electronic assemblies as the fumes are very corrosive. They do make a special formula for use in electronics but it is quite expensive.
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Old 03-13-2014, 06:24 AM
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Rodney, I think the EPA may have fixed that for us. I build lots of class 3 electronic assemblies that use a fair amount of RTV. But to err on the safe side, a drop of Goop would work too.
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Old 03-13-2014, 11:58 AM
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Originally Posted by Rodney View Post
It is not advisable to use silicon RTV anywhere near electronic assemblies as the fumes are very corrosive. They do make a special formula for use in electronics but it is quite expensive.
The fumes you speak of are an ammonia cure silicone and the one you want to use around electronics is the neutral cure, it's odorless.

Bob
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Old 03-14-2014, 07:49 AM
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OldScaleGuy
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Purple for me, for almost everything rc related that is metal to metal.
http://www.amazon.com/Loctite-Streng.../dp/B006GOL5CQ
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Old 03-14-2014, 08:14 AM
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Hi!
I thought we were talking of the four wooden screws holding the servo to the wooden tray...not the 2,6mm screw securing the servo arm.
I have never in my 40 years flying R/C had a servo arm screw comming loose! Just tightening it!!!!
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Old 03-14-2014, 08:54 AM
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mustangman177
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Originally Posted by jaka View Post
Hi!
I thought we were talking of the four wooden screws holding the servo to the wooden tray...not the 2,6mm screw securing the servo arm.
I have never in my 40 years flying R/C had a servo arm screw comming loose! Just tightening it!!!!
Yes, I am referring to the 2.6 mm screw securing the servo arm. Never had trouble with nitro engines vibrating loose, just this gas engine. Do have a OS BGX-3500 that shakes at idle though.

Thanks for all the replys.
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Old 03-14-2014, 08:57 AM
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It is a very good idea to reduce risk and secure metal geared servo arms while using gasoline engines. Glow engines,,,, not so critical.
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Old 03-15-2014, 06:28 AM
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jester_s1
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Oh yeah, then you were right Jaka. A drop of thin CA in a wood hole does wonders for keeping the screw where it belongs. It swells the threads a little and hardens up the wood so the screw won't ever come out until you are ready for it to.
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