Question for the A&Ps: welding; reinforce with inner sleeve

[mhorowit]

Folks - 43-13-1B says an inner sleeve can be up to 1/16th inch smaller
in diameter than the ID of the original tubing.

When you slip the inner tube inside the original tube 1/16th turns
into a lot of slop.

Someone suggests making it a tighter fit by slitting the inner sleeve and expanding it to get a tight fit, or taking some of the outer tubing, taking a slice out of it and thereby reducing its diameter.

Does anyone know if this is an approved technique for getting a tight fit?

- Mike

[VictorBravo]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

Just cause the inner sleeve can be sloppy doesn't mean it has to be sloppy. Use the correct diameter sleeve that "telescopes" into the main tube IMHO.

[fearofpavement]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

Splitting an outside tube repair is standard practice. On an internal sleeve I don't believe splitting it would be acceptable without specific authorization from the manufacturer or the FAA. If you split the sleeve you no longer have a "tube" and have weakened it from its original manufactured strength. On the outside sleeve, the split is welded shut, this of course is not possible on an internal sleeve. If someone was a good welder, they may be able to split a tube, adjust its diameter and weld the split closed. I don't see any reason why that wouldn't work but doesn't sound too easy. The weld would have to be ground smooth for it to fit.

43.13-1B figure 4-44 (in my version) shows a landing gear repair using a split streamlined tube to allow use of the same material to form the inside sleeve. There they specify cutting out a kerf on the trailing edge of the tube and then welding it closed and putting that inside the tube to be spliced or repaired. If that is the repair you had in mind, that's the section to check out for acceptable data.

[mhorowit]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

Splitting an outside tube repair is standard practice. On an internal sleeve I don't believe splitting it would be acceptable without specific authorization from the manufacturer or the FAA. If you split the sleeve you no longer have a "tube" and have weakened it from its original manufactured strength. On the outside sleeve, the split is welded shut, this of course is not possible on an internal sleeve. If someone was a good welder, they may be able to split a tube, adjust its diameter and weld the split closed. I don't see any reason why that wouldn't work but doesn't sound too easy. The weld would have to be ground smooth for it to fit.

43.13-1B figure 4-44 (in my version) shows a landing gear repair using a split streamlined tube to allow use of the same material to form the inside sleeve. There they specify cutting out a kerf on the trailing edge of the tube and then welding it closed and putting that inside the tube to be spliced or repaired. If that is the repair you had in mind, that's the section to check out for acceptable data.

Fear - This is a round tube repair. I think we're not going to find the reference I want for splitting an inner tube. But thanks, Mike

[mhorowit]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

Just cause the inner sleeve can be sloppy doesn't mean it has to be sloppy. Use the correct diameter sleeve that "telescopes" into the main tube IMHO.

Wish I could. In this case the next size down with the correct thickness is .007 too large, so I have to go down a second size - Mike

[high time cub]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

Mike,
You can take the next heavier wall thickness tube, say .049 rather than .035 and turn it down on a lathe. However, with practice, you will find that welding with a small gap between surfaces (either a splice or a rosette) easier that with a tight fit.

When you slip the inner tube inside the original tube 1/16th turns
into a lot of slop. - Mike

If centered, the gap is only 1/32" .......Slightly flare the ends of the inner tube with a ball peen hammer.
Jim

[mhorowit]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

Mike,

If centered, the gap is only 1/32" .......Slightly flare the ends of the inner tube with a ball peen hammer.
Jim

I'll try it tonight! Thanks, Mike

[mhorowit]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

I practiced last night.
Almost immediately it became apparent that if I tried to form a puddle in the inner sleeve (aiming the torch thru the 1/8" gap between the two outer pieces of tubing) that too much heat was getting to the outer pieces.

Do I need to be concerned with weld penetration of the inner sleeve? - Mike

[high time cub]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

Do I need to be concerned with weld penetration of the inner sleeve? - Mike

Yes, otherwise the inner tube (or big heat sink) is just going along for the ride.

To get started, heat the entire area first from below.... this reservoir of heat will rise up and help get the inner tube hot.

Use the smallest welding tip that has the ability to heat /puddle the inner sleeve. This tip should be close to its maximum heat output with a neutral flame. If the tip is to large, the wide flame cone will exacerbate the problem.

Practice, practice your torch-welding rod choreography. The puddle management dance of the three parent metals and welding rod is the key.

Don't get discouraged, doing the perfect inner sleeve splice is always a challenge.
Jim

[mhorowit]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

...choreography. Jim

What I"m seeing is I know the basics, but I really could use someone with experience to say "the trick is to hold the torch this way" and that's the choreography. Back to my EAA chapter I guess, unless I can figure it out- Mike

[mhorowit]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

FYI - I spoke with my IA. He rejected the idea of an inner tube made to fit by slotting it along its length.

Back to the drawing board; the practice was good though.

Someone suggested splicing using a larger diameter replacement tube, which I'll look at next - Mike

[Dusty]

Re: Question for the A&Ps: welding; reinforce with inner sleeve

I'm not an A&P, but I do like to break stuff....

What are you trying to accomplish here? An Acceptable repair? The slop won't hurt anything once it's all welded up. Maybe your inner sleeve isn't long enough? I suppose a little slop seems like a lot with a short sleeve?

Don't like listening to tinkly things? Whack it with a hammer until it 'fits'. Same result as above, but you don't have to listen to anything rattle around while you're welding it, and it sometimes makes things a little easier to position..

If you want perfect fits, start with bigger, thicker 4130 stock and turn it down in a lathe until it fits. There is no other acceptable method to resize tubing that I'm aware of.

Not much is simpler than repairing pranged tubing, but don't try to make your own techniques up as you go. 43-13 was published for a reason - the things in there work.