Pitting or Peening?

[mhorowit]

I know there is a technique called peening but I"ve never seen it.
My first reaction when the coating was removed from the landing gear was this was pitting, but it was so uniform I thought it might be something else.
Is this peening or pitting? - Mike

[1938BF50]

Re: Pitting or Peening?

Mike,

Great pics!

To me this looks like NASTY pitting/corrosion that has at one time been sandblasted to the clean base metal. I would be VERY suspect of this gear! Your gear looks to me as if it had been acid etched to an extreme. I think if you cross-sectioned your gear thru one of the highly contrasted areas, you would see a substancial reduction of material thickness. It is possible that way back when, the gear were acid etched to remove the "pickling skin" common to the process used to produce tubing. Acid etching was the common removal technique. We use it in our metallurgy lab to define grain boundries of samples in preparation for micro-photgraphy of grain structures.

Shot peening is a cold work process whereby round metal beads are projected at the surface to induce a compressive layer into the surface of the metal in an attempt to reduce or remove microscopic stress risers that can later manifest as fatique cracks. We "peen" a lot of out high end bike frames. The fatique life is in some cases increased 20X or more. Shot peening if done correctly DOES NOT remove any parent material.

[fearofpavement]

Re: Pitting or Peening?

I concur that this is some serious corrosion damage. Before! the gear fails may be the time to weld in some new tubing. You obviously have it all cleaned up and ready to do some needed structural refurbishment. Might need to refill you coffee cup first though. Speaking of which, mine is calling from the kitchen...

[jgerard]

Re: Pitting or Peening?

Sorry, but the tubing is supposed to be smooth. That surface looks like the result of excessive sandblasting with some extremely course media on a rusty tube. Hard for me to tell from those pics. I would go with pitting from rust.

[mhorowit]

Re: Pitting or Peening?

Might need to refill you coffee cup first though. .

Lawnchair and coffee cup getting a workout - Mike

[VictorBravo]

Re: Pitting or Peening?

I vote for pitting too.

My vote also goes for installing a new tube there, as big of a pain in the butt that it may be.

Others here have far more experience than I, but to me it's fairly straightforward since your landing gear is still in one piece...

Get some 3/4 plywood scrap and 2x4 scraps. Build a frame around the landing gear that fits on all the attach points, bolt points, axle, etc. Make this frame so it can bolt together and bolt onto the landing gear, and not have any play or wiggle. This jig can be very low tech, made from wood, Bondo, 5 minute epoxy, etc. All it has to do is holld the gear in alignment while you tack weld it later. If this jig takes more than half a day to make, you went overboard.

Carefully cut the damaged tube out, using a Dremel tool, die-grinder, etc. Cut your new tube to fit, shape it, and put everything back in the jig, then tack weld it.

If the jig survives the tack welding process without too much damage, leave the jig on while you finish weld the gear. You're making a one-time jig that will go into the garbage can afterward, not production tooling.

You can also send the gear to the factory and have them use their jig and their welder, which on something as critical as the landing gear would not be a horrible idea anyway.

[crispy critter]

Re: Pitting or Peening?

Mike,
Sorry to be so blunt but that shit is PIT.Maybe it's not deep enough to cause replacement but it is pitting.

[mhorowit]

Re: Pitting or Peening?

Mike,
Sorry to be so blunt but that shit is PIT.Maybe it's not deep enough to cause replacement but it is pitting.

OK, pitting it is.
So what caused it so uniformly over the gear? The only thing like it I've seen before is a TV antenna mast that's been outdoors for 20-30 years! - Mike

[crispy critter]

Re: Pitting or Peening?

How about a t-craft gear leg wrapped in water soaked fabric....that will also cause it.

[mhorowit]

Re: Pitting or Peening?

How about a t-craft gear leg wrapped in water soaked fabric....that will also cause it.

Or stored in a cardboard box that repeatedly got wet. yep.- Mike

[Guest]

Re: Pitting or Peening?

How about a t-craft gear leg wrapped in water soaked fabric....that will also cause it.

Hi Mike

I think Kevin has got it figured out.

My guess is its pitting on the tube under the fabric that was probably glued or doped on with out first applying a dope proof paint or epoxy paint to protect the primer from the solvents.

So the dope/glue lifted the primer and exposed the metal to water captured under the fabric.

The general pattern of the pitting probably follows the pattern where the fabric would generally be wrapped and glued. Does it?

Dave

[crispy critter]

Re: Pitting or Peening?

Or stored in a cardboard box that repeatedly got wet. yep.- Mike

Mike,
How/why would the gear legs be in a cardboard box getting soaked with water. If that is where you have been keeping them for the last couple months then I don't think that caused your damage.With the amount of pitting I can see in the pics it would have taken a long time to do that.

[1948TCARTDRIVER]

Re: Pitting or Peening?

Stressed steel or aluminum parts that have been peened will usually have a dull sheen to them, if you look at them with a 10x glass they will have tiny dimples similar to a golf ball( depending on shot size). What you have is pitting.

[mhorowit]

Re: Pitting or Peening?

Mike,
How/why would the gear legs be in a cardboard box getting soaked with water. If that is where you have been keeping them for the last couple months then I don't think that caused your damage.With the amount of pitting I can see in the pics it would have taken a long time to do that.

I was thinking that sometime in 88M's checkered past, they had to replace the landing gear; what they found was a landing gear that had been kept in a damp condition and replaced the original gear with the one that had been exposed to moisture.

When I get home, I'll examine the pattern as DAve mentioned; I know that on the bigger diameter tube there is an abrupt line where the pitting stops, so he may be right on the mark - Mike

[mhorowit]

FOLO: Pitting or Peening?

Severe pitting it is per my A&P and the gear is unusable as is. So... it's either find another left gear or start thinking how this one can be repaired. Sure glad I'm enjoying this, otherwise these challanges could be a REAL challange. - Mike