How to secure steel clevises
 

Hi all,

I was encouraged to change out the plastic clevises on my recently completed GP Ultimate Bipe. So I bought a pack of the DuBro clevises. My question is how do I secure them? They came with shrink tubing which I tried to shrink over the exposed threads of the rod and the base of the clevis, but it didn't shrink enough. I can't use shrink on the actual clevis part since I do need to open it to separate the wings. Do I need to use silicone tubing like on the plastic ones? The steel clevises on the used Cap I bought have nuts behind them but that doesn't make sense to me since the clevis can't turn anyway. What do you all do? Thanks!

How to secure steel clevises
 

The shrink tube that came with the clevises works like silicone tubing. It's a lock for the clevis, not a way to keep things from turning. If you have steel clevises on both ends of a steel control rod, and they both thread, then you will have to use a nut on one side to lock it.

How to secure steel clevises
 

Deadeye is right. The clevises won't turn, but the rod in between will. Lock `em down!

How to secure steel clevises
 

I'm curious. What's the problem with nylon clevises on a small model? Say... 40 size. The loads are not high, they resist fatique well, the rods are held tightly by the nylon thread so won't vibrate loose (assuming a threaded clevis a both ends - not a good setup).

How to secure steel clevises
 

Ok, since none of mine have two clevises, I won't need the nuts. I'll just use the shrink to secure the clevis. I assume the use of the shrink is because it won't cut as easily as silicone tubing?

How to secure steel clevises
 

"I won't need nuts."

For an ultimate bipe, you'd better have some nuts handy when you decide to wring it out.


I use nuts on all clevises, even single ones because vibration can work the clevis down the thread. The clevises and the rods are cheap and not to tight tolerance, so the play there worked one out on a plane I was flying. Fortunately, the alignment was good, so I could trim it down and the rod still pushed the clevis when I flared it for a hurried landing.

Good luck,

How to secure steel clevises
 

If you have a rod threaded on both ends you had best solder one on ! Never trust a nut by the metal clevis to keep the rod from turning! The metal clevis that is adjustable should always be locked by a nut after adjusting to keep vibration from wearing out the rod & clevis threads! If you have never done this on your planes they are living on borrowed time! On control surface connections use some kind of a locking device. Always try to eliminate a trouble before it happens , MURPHY`S LAW always wins if you don`t stay ahead of it! >>>>>big max 1935

How to secure steel clevises
 

As far as I'm concerned, there IS no problem. Unless the clevises are really cheap looking, I always use what's provided. If the kit comes from a reputable MFG like GP, Sig, Goldberg etc., the nylon clevises have always held up (even in 120 size planes - my GP Super Skybolt for example)

How to secure steel clevises
 

MinnFlyer: MURPHY`S gonna getcha! Best be on guard or you will get bit! He has got me so many times I can`t count. Years back he left a long screw driver in my rear pocket just before I got into my new Mercury convertible!! He always wins!
>>>>>>>>>>big max 1935>>>>>>>>>>>

How to secure steel clevises
 

How exactly do Nylon clevis fail? My guess is that the nylon pin shears under high load. But I think the control horn would rip out of the surface before that happened, or the servo gear would strip. The rod-thread engagement is tight and will have very even distribution of stress, so that doesn't seem like a problem. Does the material break down over time? Perhaps it is affected by UV light - but I'd expect the manufacturers to take care of something that basic.

The steel clevis I've seen (Sullivan 2-56) have loose fitting threads compared to nylon, so those might fail either at the rod-thread engagement due to concentrated stress or thread wear, if used with mild steel push rods. The pin could fatigue and snap off at the weld. Since fatique is a progessive failure, it might happen before the horn pulls out, or servo gear strips, and seem to "come out of nowhere".

The keepers don't seem to be an issue in either case since both require pre-flight checks to ensure they are engaged properly. Maybe the fuel tubing on the nylon clevises should be replaced occasionally??? So it seems that only prudence and maintenance that will save you there.

The only clevis failure I've read about around here is someone who put a 2-56 clevis on a metric (2mm?) push rod. But that's not Murphy's law at work.

I'm asking purely out of curiosity.

How to secure steel clevises
 

After 20 years never had a nylon clevis break, ok well when the rest of the plane got broken sometimes they would break, but they were never the cause.

"MURPHY`S LAW always wins if you don`t stay ahead of it! >>>>>big max 1935"

Murphy's Law- Anything that can go wrong will.

There is no avoiding Murphy, No matter how much care and preparation is used. He'll get you.

How to secure steel clevises
 

I have always thought that when you look at a new nylon clevis they are already set in the open position & I didn`t like that in case keeper sleeve broke. The first ones I used were not "snap" ones. The real old ones were steel & I used to get them from a buddy in our local typewriter shop, had a pin on one side & a V end on other . Had to lock them with fuel line & that was clear neoprene ,a little tough. When Sullivan came out with theirs I switched every thing over & then when the Gold one came out I switched again. Like the little keeper on the pin, figure if the pin comes off clevis side the pin will still hold it in on the other. Have tried new Du Bro one ,but rather large. If you do buy theirs buy the 2-56 & drill it out some for the 4-40 rods, that way you will need to keep only one size, OK? Besides most of my planes are IMAA type & they frown on nylon!Enough rattling on by an old fud >>>>>>>>big max 1935>>>>>>>>

How to secure steel clevises
 

I use nylon clevis's on almost everything. The few items that don't get nylon clevis's have Radio South style connectors instead. They are nylon as well. They have never failed, nor shown any sign at all of fatigue. I've never even had one fail in a HARD crash. Best of all, I never have to worry about any metal on metal induced radio problems or having to solder them together.

I like nylon and they like me.

Nuf said and just my .02.

John

How to secure steel clevises
 

I'm going to change out some plastic clevis's on a 5 yr old I have-they look a bit bowed or splayed(too many adjustments!) Why wouldn't a bit of fuel tubing secure them just right? I agree with those that say plastic work fine-gotta admit the metal look so much more like the right stuff....if there is a z-bend on the other end there is no way in heck anything turns loose.

Be Careful of what's in the Box...
 

Nylon clevis that came with my Tiger Stick failed in flight. Lost elevator control and that was all she wrote. The clevis looked ok but next time will use better. Live and learn the hard way. Pete

How to secure steel clevises
 

Fuel tubing is my retainer of choice and what GP includes with both their nylon and metal clevis's.

If you are going to use metal clevis's, be sure you use a jam nut to eliminate any play in the threads.

John

How to secure steel clevises
 

Rocketman612, Were you able to tell how the clevis failed?

How to secure steel clevises
 

I examined a Sullivan connector and there is no welded pin .. as I thought off the top of my head. It is held in using a little press fit ring. That'd be stronger.

I can't really see why either of them would fail on a small model.

Post Mortum
 

Jim,
The clevis was properly setup with a piece of glow tubing on to keep it closed. The plane was in level flight at full throttle ( TT46 with a MAS 10x6 prop) I pulled back on the stick and it was gone :mad: The pin broke off!! Won't use them again. Pete

How to secure steel clevises
 

Well, nothing beats hard data. Thanks.

Re: Post Mortum
 

Just curious, but what material was the control horn made of? Nylon, wood, or metal?

John

How to secure steel clevises
 

A good nylon clevis is as reliable if not more so than the metal ones. Now, you can find some cheap plastic (not nylon) clevises that are not to great. Under normal use, a metal pin will wear out faster than the nylon one will. Regardless of which type you use, be sure there is no missalignment between the horn and the clevis as that will cause probems for either type. That is why, on some installations, a good ball joint outperforms and outlasts the clevis and always has less slop.

How to secure steel clevises
 

Not so! I used to use the ones that came in the kit. One day on final, the vibration over time caused the plastic thread to let go and the clevis slipped right off the end of the rod. I would not use plastic clevises on anything but the throttle on a power plane of any size. Why loose an expensive plane over a 50 cent piece of plastic. I have seen too many let go.

How to secure steel clevises
 

A proper fitting nylong clevis will be very tight on the pushrod end. So tight that the pushrod will cut the threads into the clevis and will nearly require the use of pliers to adjust. In this case, vibration will have no affect unless you are using too small of hardware for the job at hand.

One area where people make mistakes is to replace the clevis's in a kit, or ARF, which was produced overseas, with their favorite brand while continueing to use the metal pushrods that were supplied. The pushrods in many cases are 2mm, which is smaller than 2X56. This will lead to seperation problems, usually in flight. The hardware must be matched to other hardware as well as to the job at hand.

John

How to secure steel clevises
 

The Tiger Stick comes with a plastic clevis. I just got a bad one I guess, but like I said not again. Pete