Thread locker on servos? - RC Groups
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Nov 10, 2012, 01:00 AM
Registered User

Thread locker on servos?

I tried googling but the concensus seems to be lacking. Servos are used everywhere and it's hard telling what kind of RC some of the people posting are using.

I put the crashed VWinRC 450 sport back together using a combination of CopterX and Align parts (Even the CopterX parts fit better than VWinRC), unfortunately, while test hovering in my garage, it suddenly flipped over. When i checked, the servo arm was off and the screw was missing. I know i tightened it up the previous day, tho i do admit i was getting a lot of vibrations before i figured out how to do the blade tracking (Spun the heli up on the 2nd floor room while i stood at the stairs so the blades were at eye level). After blade tracking, no more vibrations on spinup but the screw may have loosened at that point already.

I guess part of maintenance is making sure the servo screws were tight in between flights. But do i really need to do that? Or can i just put in threadlocker (Metal gear servos) and be done with it?

Some of the posters said no, tho i noticed most of them are airplane flyers but there were a few helis mixed in as well. Some said no because it'll melt the plastic, making me wonder if the others that said no were also using plastic servos, in which case, the screws would be self tightening anyway. Some of them said that they haven't lost a screw in 10 years of flying, but i'm a 450newbie and i already lost one. The other half that said yes typically just want to secure everything but were also told that adjusting the servos would be difficult (Do you even need to adjust the servo arms after the first setup?). But again, i can't tell what RC they're using.

So how do you guys secure your servos? Do you put thread locker? Superglue? Or just keep a screwdriver handy?

PS: Do you guys also do anything to secure the links? The two sets of Sport FBL linkages i got both were too short for the forward, right servo and i ended up having the threads halfway out. Any risk of them slipping out all the way?
Last edited by Hajile; Nov 10, 2012 at 01:06 AM.
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Nov 10, 2012, 01:20 AM
Registered User
finguz's Avatar
I don't see how it would come out anyway. When the servo is working, the gear, arm, and screw all turn together.
Nov 10, 2012, 02:47 AM
the great Gassif´er
Usually, even with metal gear servo's threadlocker should not be necessary, but most of those servo's have a springlock-washer supplied with them, and maybe you forgot to use that (or lost it, or didn't notice it should be there but wasn't, etc etc)

But to be honest, as the horn normally sits pretty tight on the serated output shaft, and the screw normaly only secures it in place, the screw should not be carrying any load, normal hand-tightening should be more than sufficient, so I guess there is more wrong than only a tracking issue and a lost screw.

Brgds, Bert
Nov 10, 2012, 03:41 AM
Registered User
What's a springlock washer? These are the only things left over that came with the servo. The single arms are on the heli, the middle one is missing a dual arm because the single arm broke on the first crash and i trimmed the dual arm to fit the rear servo. Each servo came with a single arm, a dual arm, two crosses, a disc, and four screws. Nothing that resembles a washer.

I guess all i can do is put the heli back together and hope it doesn't happen again.

Also, these are the linkages that came with the heli

The only way i could get the swash to level using the specs in the manual was to unscrew the link halfway out of their sockets. If i were to tighten that up, the link would be too short and the blade links would then be out of their sockets to level the grips, not to mention the link on the servo on the other side is actually all the way in and would not be any shorter (It actually matched the specs exactly with the threads all the way in), the swash and blade grips would no longer be level. It hasn't pulled out yet, but it's at the back of my mind every time i test hovered it.
Nov 10, 2012, 04:30 AM
the great Gassif´er
Maybe I am using the wrong name, but I refer to these washers that slightly resemble a circular sawblade, with the "teeth" a little bit twisted to grip the screw head.
They are usually supplied with at least the bigger metal gear servo's.

Don't worry about the links being screwed in only half.... they usually grip pretty tight on the threaded rod, and if the rod is halfway up the link, it should be enough.

But if you want, you can use threadlocker sparingly (put a small drop of threadlock on a piece of plastic, and dip only the first round of thread in it)

Brgds, Bert
Nov 10, 2012, 01:32 PM
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finguz's Avatar
The thread locker is for the servo (if any), not the ball link plastic. I'd think you'd already know that at this point, but just to make sure, I don't want you or your heli to get hurt. The first time I read it I thought it was saying to put the thread locker on the links, please no offense Brutus.

Some dfc ball links I have are 45mm long, or 31mm thread to thread. Maybe something like these would work for you.

Here's some spring lock washers, the upper right is similar to what comes on the align servos (for under the screw), the align one is less agressive. That's if my memory serves me, I don't have one out of the heli. They're basically lock washers.
Last edited by finguz; Nov 10, 2012 at 01:42 PM.
Nov 10, 2012, 02:03 PM
the great Gassif´er
No offense taken.... there's always that danger that I am not expressing myself clearly, English is not my mother tongue....

I was referring to the screw that holds the horn on the servo output shaft....
NOT to the ball link (but depending on design, sometimes the balls are fitted with a bolt and a nut to the servo horn, in that case lock the nut with some threadlock)
and certainly not the links to the rods....

Brgds, Bert
Nov 10, 2012, 02:07 PM
Get to the choppa!
RFDelie's Avatar
Brutus is the man, always listen to him. I am not the most experienced one here. But I am a self taught pilot who has crashed alot and built/rebuilt my own heli from scratch so I have learned a lot of lessons the hard way.

My advice: A good rule of thumb, do a preflight check every 2 to 3 flights and check all of your screws for movement. You dont have to re-tighten, infact if you do have threadlocker in there you will break your threadlocker that you previously applied. You just have to check the screw for play. Also visually check the rotor head and make sure your blade holders do not have any extra play (to check the feathering shaft).

I have three types of headlocker. Locktite blue and red, and plastic threadlocker. I use red on my feathering shaft and blue on all metal to metal screws. Then I use the plastic threadlocker for the screws that go into plastic. You dont need alot of it, I usually put a drop on and then blot it off so that the threadlocker is just inside the threads of the screw. On places like the feathering shaft you use a tooth pick and apply the threadlocker to the inside of the shaft (not the screw).

It is unusual for the servo screws to back out, but if your heli has any issues at all that can cause a vibration or wobble any screws can start to back out.

My advice:

-When in doubt use threadlocker
-Don't over apply the threadlocker
-Make sure you do not have any vibration problems
-Perform preflight checks every 2 to 3 flights.

Follow those steps and you will never have a problem like that again.
Nov 10, 2012, 05:38 PM
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finguz's Avatar
RFdelie, you use red on your feathering shaft? I noticed that I had to start cleaning my screws before re-thread locker'ing them back in the shaft. When I do this a lot of stuff comes off, and the screw is clean as a whistle. I just use my shirt or a rag and screw the bolt into the cloth. I also recently started noticing how much oil or grease can get into that hole of the feathering shaft. Blue loctite started failing me until I started obsessively cleaning my screws threads and the part's threads, now it works again, that and I had some binding so that doesn't help.

Brutus: I'm glad you took it so well, I just read it funny and didn't want anyone else to also, especially someone potentially just starting in the hobby coming across this forum. Trust me you know a lot more about this stuff than I do.
Nov 10, 2012, 06:13 PM
Get to the choppa!
RFDelie's Avatar
Ya, I switched to the red, its really not that big of a deal. I can still easily get the screws out. They just don't move on their own. I noticed that the align manual called for it so I figured I would give it a try. My last crash was a bad one. I was practicing my nose in hover on my street and a nasty gust of wind hit me, my heli shot up and over into a power line. I cut the throttle right away (the last thing I wanted to do was chop through a power line) and it fell like a log onto the concrete, among other things I had to replace my head and feathering shaft, along with my main shaft and tail boom. Since I was starting over I decided to try out the red, so far with good results.
Nov 10, 2012, 09:45 PM
Registered User
finguz's Avatar
that sucks about your crash. I got my mcpx stuck in a tree the other day, I got it out though. I was like 'oh crap what now?', I haven't climbed at tree in years, but it wasn't very high up. And while 30's isn't old (maybe to some of you), it's not exactly tree climbing age.
Nov 10, 2012, 10:07 PM
Registered User
Ok, i'm actually still waiting for the feathering shafts before i start repairing the 450, but i checked out the screws again. The precision screwdrivers really wouldn't go any further, but i got one of my larger screwdrivers and applied more pressure while twisting it. It went in a couple more turns before the big screwdriver finally started to slip. Maybe it really is supposed to be this tight? When i screw the frame together, especially the metal parts, when the screw stops, that's as far as you'll go.

The amount of pressure i used on the servo until the screw finally stopped was about the same as when i stripped the hex bolt in the tail boom block (Also waiting for new hex bolts).
Nov 10, 2012, 10:32 PM
Get to the choppa!
RFDelie's Avatar
LOL fin thats funny. When I first got started I crashed my 450 into a bush and as a noob I did not hit my throttle hold and as I was pulling it out I accidentally hit the throttle. It was like a massacre there were pieces of bush everywhere. I am also in my 30's but had to face my wife like a kid going to the principals office. Not my best day.
Nov 11, 2012, 01:10 AM
the great Gassif´er
@ Finguz: Don't worry , I'm aware that sometimes my english is not completely adequate, so if somebody, in whatever way, says he read something else than I intended to say, than I am not the guy to get offended, I'm the guy that needs re-evaluating his language skills....
And you're right: getting somebody on the right track, is way more important than personal feelings So again, don't worry!

About the threadlocking issue: I only use Loktite # 270 which is a medium strength thread locking compound. No other colours or other numbers.

I just vary the amount/clean the bolt depending on the purpose of the bolt.
On the feathering shaft, I clean the bolt and hole, and use the stuff liberally, on other locations I just use a really small amount, and bolts that are not subject to heavy vibrations, I use that stuff the first time, but just put back as they came out afterwards, and judge their resistance while screwing in.
And to give an idea: some of my feathering shafts hold together 6 ft rotors. with big, heavy vibrating gasser engines driving them.
Others hold together 450 sizers, and anything inbetween.

Brgds, Bert
Nov 11, 2012, 03:10 AM
Registered User
finguz's Avatar
Hajile, with your swash links, I was gonna ask if you have equal blade pitch up and down on your stick.

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