Replace a weld on landing gear strut?

[mhorowit]

Attached shows what I've observed is a classical splice on a landing gear down tube. My IA has expressed less than wild enthusiasm with the splice and I've suggested that because of heating concerns I remove the outer piece and replace it with a piece an inch longer at both ends.

I don't have my Dillsburg catalog (largest supplier of steel tubing operating out of a chicken farm); so I'm looking at Aircraft Spruce and don't see streamlined tubing in my dimensions, so I'm thinking perhaps I"m measuring the tubing incorrectly. Major and minor dimensions ARE simply the largest dimensions along both axis, correct? I read my current strut size as 1.52x.74x.05. - MikeH

[Darren Lucke]

Re: Replace a weld on landing gear strut?

Yep, that's a lovely looking splice - it's a wonder what some people trust.

[Guest]

Re: Replace a weld on landing gear strut?

Attached shows what I've observed is a classical splice on a landing gear down tube. My IA has expressed less than wild enthusiasm with the splice and I've suggested that because of heating concerns I remove the outer piece and replace it with a piece an inch longer at both ends.

I don't have my Dillsburg catalog (largest supplier of steel tubing operating out of a chicken farm); so I'm looking at Aircraft Spruce and don't see streamlined tubing in my dimensions, so I'm thinking perhaps I"m measuring the tubing incorrectly. Major and minor dimensions ARE simply the largest dimensions along both axis, correct? I read my current strut size as 1.52x.74x.05. - MikeH

Hi Mike,

You are measuring it right.

Measure the original tube then add twice the wall thickness and to each dimension and look for a tube a skeech bigger than that size.

Since old wall was .050, probably .049 then then add .10.

You could use thicker wall tubing.

I assume the size you wrote about was the original size so I came up with 1.62 x .85.

Can't find it in UNIVAIR or anything close. BTW they make their own and may have weird sizes.

Looked in the chicken farm tubing company catalog they have 1.685 x .714 x .049 for about $18 per foot price may be old, Wicks has it too.

Wicks and chicken farm tubing company have 2.023 x .857 x .049 - perhaps use this cut 1/4" off the trailing edge and form fo fit.

I have some 1.8 x 1.07 (I think have to check Sunday)

Its not an exact science, find a size that's close and make it fit.

Streamline tube sizes seem to come and go.

Dave

[mhorowit]

Re: Replace a weld on landing gear strut?

Hi Mike,

You are measuring it right.

Measure the original tube then add twice the wall thickness and to each dimension and look for a tube a skeech bigger than that size.

Since old wall was .050, probably .049 then then add .10.

You could use thicker wall tubing.

I assume the size you wrote about was the original size so I came up with 1.62 x .85.

Can't find it in UNIVAIR or anything close. BTW they make their own and may have weird sizes.

Looked in the chicken farm tubing company catalog they have 1.685 x .714 x .049 for about $18 per foot price may be old, Wicks has it too.

Wicks and chicken farm tubing company have 2.023 x .857 x .049 - perhaps use this cut 1/4" off the trailing edge and form fo fit.

I have some 1.8 x 1.07 (I think have to check Sunday)

Its not an exact science, find a size that's close and make it fit.

Streamline tube sizes seem to come and go.

Dave

Thanks Dave - just the info I was looking for - MikeH

PS - I liked the idea of putting a reinforcing 'sock' at the end of a worrisome strut; of course one would need to be concerned with the integrity of the 'end plate' and I wonder how the FAA would determine if that repair were acceptable. - MikeH

[Hank Jarrett]

Re: Replace a weld on landing gear strut?

Be careful with the "sock". Done properly it will outlast the original. Done wrong you could intoduce a stress concentration and cause an early failure.
Hank

[mhorowit]

Re: Replace a weld on landing gear strut?

It's a good thing to save old parts.

I cut out the lower section of the landing gear strut and plan on replacing that section with a section out of an otherwise dead landing gear. internal sleeve and external splice.

The bushing is slightly deformed and the bolt won't fit. Can I simply ream that hole to the correct size, or must I replace the bushing? - MikeH

[Guest]

Re: Replace a weld on landing gear strut?

Be careful with the "sock". Done properly it will outlast the original. Done wrong you could intoduce a stress concentration and cause an early failure.
Hank

What is the "sock" ?

[mhorowit]

Re: Replace a weld on landing gear strut?

What is the "sock" ?

The reinforcement of the strut covering the lower ~12". possibly looks like a "bobby sox". Of course you could paint it any color you wanted - MikeH

[Howard Wilson]

Re: Replace a weld on landing gear strut?

Argyle would be nice.
Why is the bushing deformed? From the inside or the outside?

[Guest]

Re: Replace a weld on landing gear strut?

Be careful with the "sock". Done properly it will outlast the original. Done wrong you could intoduce a stress concentration and cause an early failure.
Hank

Hi Hank,

I am not following, can you eloborate?

I don't get what your pinting out. This is not a challange. I just don't get it.

The "sock" threw me. I guess I get that now.

Thanks, Dave

[Hank Jarrett]

Re: Replace a weld on landing gear strut?

Not a problem, I don't take it as a challenge, I just didn’t explain that well. The "sock" is just a doubler wrapped around the damaged tube (usually it is a telescoping section with the same inside size and shape as the original parts outside). It is a great way to fix a damaged tube (but is usually UGLY as sin). The problem is if you shape the ends of the doubler wrong, the loads build up at the edge of the splice and can overload the original tube. If you look at the instructions from the FAA on doing tube repairs, they specify angling the ends of the doubler tube so the load flows "slowly" over the splice and doesn't build up right at the edge.
I'm not the greatest teacher for this kind of thing and there are a lot of good texts on it or your A&P or IA can show you. I have a nice set of “support struts” in the barn with big sock patches on them I saved and will use to hold my wings while I get mine NDIed.
Hank

[Guest]

Re: Replace a weld on landing gear strut?

Not a problem, I don't take it as a challenge, I just didn’t explain that well. The "sock" is just a doubler wrapped around the damaged tube (usually it is a telescoping section with the same inside size and shape as the original parts outside). It is a great way to fix a damaged tube (but is usually UGLY as sin). The problem is if you shape the ends of the doubler wrong, the loads build up at the edge of the splice and can overload the original tube. If you look at the instructions from the FAA on doing tube repairs, they specify angling the ends of the doubler tube so the load flows "slowly" over the splice and doesn't build up right at the edge.
I'm not the greatest teacher for this kind of thing and there are a lot of good texts on it or your A&P or IA can show you. I have a nice set of “support struts” in the barn with big sock patches on them I saved and will use to hold my wings while I get mine NDIed.
Hank

Thanks Hank,

Now I follow what you were saying.

Agree, the ends need taper as you say so that there is a gradual change in the cross section and area moment of intertia so there are no abrupt stress changes.

Its the approved way. I just never imagined any other way so I was thinking you were in to some new "exotic" effect.

Thanks for the clarification.

I have repaired some lift struts with that scheme and it does stick out like a sore thumb as you say. It is a lot cheaper and sometimes the only choice when new parts are not availible. Adds weight too.

I am and A&P/IA but was not sure what you were describing.

Thanks again, Dave.

[mhorowit]

Is this the wrong splice?

Attached shows what I've observed is a classical splice on a landing gear down tube. MikeH

Wait a second.
There is a section in 43.13 dedicated to landing gear repair (para 4-102). In that paragraph is a sub-section describing repairs to Streamlined Tube in which is stated "repair landing gears made of streamlined tubing by either one of the methods shown in Fig 4-42, Fig 4-44, or Fig 4-45.

The picture I attached shows an external splice similar to what is used in splicing ROUND tubing ( Figure 4-38).

Now, I'm too new at this to boldly announce that original splice was incorrect, but as I read the book I don't see provision for an external splice on a streamlined part of the landing gear.

Assuming I'm missing something, could someone talk to this apparent descrepancy? Thanks, MikeH

[Guest]

Re: Is this the wrong splice?

Wait a second.
There is a section in 43.13 dedicated to landing gear repair (para 4-102). In that paragraph is a sub-section describing repairs to Streamlined Tube in which is stated "repair landing gears made of streamlined tubing by either one of the methods shown in Fig 4-42, Fig 4-44, or Fig 4-45.

The picture I attached shows an external splice similar to what is used in splicing ROUND tubing ( Figure 4-38).

Now, I'm too new at this to boldly announce that original splice was incorrect, but as I read the book I don't see provision for an external splice on a streamlined part of the landing gear.

Assuming I'm missing something, could someone talk to this apparent descrepancy? Thanks, MikeH

Good point, look at figure 4-43 though it says "... and other members".

I think its a mistake in the AC. The FAA guy is supposed to call me tomorrow. I want that answer too.

Dave

[tawadc95]

Re: Replace a weld on landing gear strut?

I would not take it back to the same guy who welded the one in the pic for you, kind of scary looking as cold as the weld looks and no bevel on the edges of the splice.