Locktite on rail button screws?

[Bill S]

I'm finishing up my first real mid-power rocket, and have installed two 1010 rail buttons. I am under the impression that it may be better to leave the screws a little loose so that the buttons can turn if they need to. I epoxied the backings inside the body tube.

Two questions:
1) I am thinking of trying some low-grade Locktite (the ones used on scope rings for guns), but am not sure if I ever need to replace the button at some point, the extra torque needed to remove the screw might break free the backing inside the body tube where it isn't easy to get to.

2) If I don't Locktite them, are they likely to unscrew themselves? I could get into the routine of tightening and loosening them a little bit before each launch, but that is an extra thing I can mess up on.

 

[prfesser]

I don't see why the railbuttons need to rotate at all. They're only there to guide the rocket for a few feet. They fit rather loosely into the rail anyway, so the friction is low, and there's little friction anyway between the plastic and the rail. I epoxy the screws to the body tube and tighten snugly.

 

[waltr]

I have both non-rotating and rotating rail buttons.

The HPR adviser in our club recommends rotating rail buttons as we have seen rail buttons that have flats from sliding on the rail. It is a short distance but the speed and pressure can wear one side quickly.

For rotating buttons I use Blue locTite. None have had the screws come loose.

 

[Grog6]

Blue or purple are easy to remove, but wont loosen by themselves.
Red locktite can twist off a 2/56 screw in stainless.

 

[jmasterj]

I don't think you need loctite. There's no rotational force on the buttons given the play in the channel.

 

[DaHabes]

I've never used Loctite. No issues.

 

[g.pitts]

I'm anal-retentive and use BLUE Loctite on the screws for my rail buttons. There's no downside in doing so. As @Grog6 indicated, you want to avoid RED Loctite - it is marketed as permanent, and in our model rockets you can bank on that being the case.

 

[Bill S]

I think I'll try not gluing the buttons on just yet then, and see if they loosen up in actual use. Thanks guys.

 

[OverTheTop]

I have had a screw work loose due to wind across the tie-down straps holding a launch tower for my two-stage half-scale Nike Apache inducing vibrations in the tower. Spotted before any damage was done. Solution was to unrack it and add some CA to it as a temporary fix. So yes, it does happen.

 

[SmurfTacoSupreme]

When I'm using rotating buttons with machine screws like Aeropack RG10A's I use a dab of blue thread lock. I don't necessarily care if they rotate, but I prefer them not too tight (they'll crack) or loose (screw can back out).



For buttons with wood screws (Aeropack RG10B) I back them with 1/4 ply and make the hole so the screw bites nicely and won't go anywhere on its own.

 

[jqavins]

Those are sheet metal screws, not wood screws. OK, I'm a nit-picking smart-ass, but there is actually a point.

Wood screws have that shoulder under the head. If you want your buttons to be able to rotate, wood screws would be the better choice so that the buttons roll on the smooth shoulder.

 

[OverTheTop]

OK, I'm a nit-picking smart-ass, but there is actually a point.

I see what you did there.

 

[kenstarr]

I have always locked them down using machine screws into a pem nut or some type of threaded insert. AND red threadlocker. I hadn't considered free rotating rail buttons until now. Might be a good idea on a 30 pound rocket. There was a member of our club several years ago who would use a K-lath type screw like a Dottie KW81 as the rail button. Management was always worried it would tear up the rails. Not sure of the validity of such a concern but I'd give a mental negative score on craftsmanship and die a little inside when I'd see it! Sorry for the digression. Please do anything but that
Ken

 

[Bill S]

I launched my rocket that had rail buttons twice now. Today was the second flight, and the rear rail button decided to leave the rocket and dissapear upon launch. The front one was fairly loose. I had not Locktited them down, and didn't use a screwdriver to ensure they were tightened down (but not all the way).

I will be Locktiting them from now on.

 

[DaHabes]

I've never used Locktite on my rail button screws and never kept them loose enough to rotate. They won't rotate anyway; they are not that tight in the rail slot. I've never had them come loose, dozens of flights. Just tighten the screw down and fly.

P.S. If I ever need to do airframe repairs and repaint, I want to take the rail buttons off. Red thread locker is overkill. If you feel you need to use it, blue is sufficient.

 

[jmasterj]

I launched my rocket that had rail buttons twice now. Today was the second flight, and the rear rail button decided to leave the rocket and dissapear upon launch. The front one was fairly loose. I had not Locktited them down, and didn't use a screwdriver to ensure they were tightened down (but not all the way).

I will be Locktiting them from now on.

How did it affect the flight?

 

[Hobie1dog]

I wonder if every rocket inspector checks them for tightness?

 

[Bill S]

Not sure. It was only the 2nd flight. The first one, on an F44-4, went up about 200' and then turned right at about 45 degrees. The RSO said he'd seen this kind of thing before, with the Der Red Maxes, particularly the Mega one.

Yesterdays flight, it was windier (8-10mph I guess), and I tried an F67-6. It did turn into the wind a bit, but not as bad as the first launch. To be fair, many of the launches yesterday were turning into the wind a bit, so I can't tell if losing the rail button had any effect at all.

 

[David Schwantz]

Wood screws get a drop of CA to keep them in place. Machine screws get blue loctite. I always leave my buttons to rotate slightly. If you think your mounts on the inside of the airframe may break loose trying to remove a button, then you need better epoxy. See what I did, this is now a glue thread

 

[jmasterj]

The "let them rotate" recommendation applies to the 3-piece buttons. It doesn't apply to the single-piece ones.

 

[Rocketjunkie]

With most rockets, you will have to replace the buttons every few flights. All it takes is a dirty rail, asymmetrical ignition of a cluster, or even the off center (with respect to the buttons) thrust of a large diameter rocket to tear up the buttons. I had to replace the buttons on my 98 mm Deuce every flight, even with simultaneous ignition.

 

[David Schwantz]

see below.

 

[David Schwantz]

Button should always rotate.

 

[jmasterj]

You're saying that's the result of the button not rotating? Or you want to rotate it later so the undamaged side is against the rail?

 

[David Schwantz]

Nope, they get damaged even when they rotate. Just the nature of them.

 

[jmasterj]

Then I'm not sure why they'd need to rotate.

 

[David Schwantz]

They get chewed up less when able to rotate. If the one in the pic was solid, it would have worn through already. They are easy enough to replace, and cheap. But if they last longer cause they spin, I'm good with that.

 

[mh9162013]

My experience is only in LPRs. Given that, any time you screw metal into metal, it's a good idea to use threadlock. But there are different kinds of threadlock where some of the weaker formulations don't require that much additional force to unscrew. But when you unscrew it, it feels like you're removing a screw from solid rubber...at least that's my experience with threadlock.

 

[jqavins]

Wood screws get a drop of CA to keep them in place. Machine screws get blue loctite. I always leave my buttons to rotate slightly. If you think your mounts on the inside of the airframe may break loose trying to remove a button, then you need better epoxy. See what I did, this is now a glue thread

It already was. What's Locktite if not a special purpose glue?

And "blue not red" isn't to avoid stressing the internals. It's because with the size screws that hold rail buttons you'll break the screw or strip the head before red lets go.

 

[karlbaum]

I don't use loc tite but I do leave my buttons loose to spin. Been there learned that. I like wood screws and counter sunk buttons. Occasionally I will use nylock nuts on machine screws for the buttons. Another lesson is to never use the plastic loop on a nose cone. I use a eye bolt and nylock nut.