RE sleeve- no the sleeve is SPLIT and partially rolled together and is typically lubricated with a dry lube, and after expansion simply falls out or is easily removed. Look up the ( at least in Boeing ) the term ' coldworking ' and the firm in tukwilla called Fatigue Technology for more details.Fatigue Technology

401 Andover Park E, Tukwila, WA 98188, United States

They are a few blocks from Southcenter. Little known fact - one of the owners- perhaps now deceased was Burke Gibson-


Since the sleeves are NOT reuseable, and since they held some - but not all of the patents on the tooling ( pullers and certain adaptors ) they made- making a boatload of $$$.

And Lou Champoux was really more than a consultant - he was the inventor. :cool:

And to add or forestall the next ' logical' question re splt sleeve. Initially, Lou tried to use a spiral split sleeve due to concerns re a straight axial 'line' in the coldworked hole being a discontinut in the stress pattern. Almost impossible to make. So a straight simple split was tried- then the question was would the location of the axial ' line ' affect the load pattern and fatigue results ? After bucu tests the answer was nope.

By the way a large mandrel ( 1 inch approx ) lubricated with cetyl alchol as I recall has been used/tested to coldwork bolt holes in railroad tracks to improve fatigue life.

That link says the change was FOR the 777 and NOT the 737.

As someone who cut their teeth on Boeing Structures with the B 727 -223 and also a few of years on B-757-200 it is very sad to see what has become of Boeing Airplanes. I also have about 6 years experience on B 737 - 800 Structures. To borrow an expression from a TV Commercial the B 737-800 " Is Not Your Daddy's Boeing". In my OPINION it is an example of Lean MFG Gone Wild. I can tell you that Boeing Airplanes do develop cracks and corrosion in Primary Structure Members over time. What is concerning about this story and my experience with the
B 737 -800 is how early into the service life these Structure members are cracking.The B 727's were much older when we started seeing these kinds of problems. A lot of the problems with the B 737 -800 APPEARS to be Design issues to save weight as compared with the B 727 that was built like a tank. I do not recall issues with the B 727 Pickle Forks but the Wing Rib Chords were cracking on the 727 much later in the life cycle of the Airframe.
Example B 737-800 - In an apparent effort to save weight the Skin and Stingers above the cabin floor line were made in a manner that Boeing had to go back and add Bonded Doublers to the Skin and Stringer Hats. These were added to stop vibrations and buzzing of the Airframe and are called Acoustic Dampeners . We experienced a lot of cracking on the Main Frames where the Lower brackets of the Overhead Bins attach to the Frame. We discovered these on numerous B 737-800 frames in their 1st Heavy C Checks which were relatively low time aircraft. The repair includes stop drilling / routing out the crack - cold working the holes - and installing a doubler. We did not see this on the B 727 and B 757 Generation aircraft this early into the life cycle. All these repairs just add weight back to the aircraft that Boeing seemed to be avoiding in the original design and MFG. .
The first generation B-737 were built like the B 707 and B 727 Airframes : Heavy Duty. Even with the Stringer 10 Skin Lap Corrosion issues they were much better built airframes in my opinion. The Aloha B 737 Proved this in Hawaii.Pictures are available on Goggle Images because this forum will not let me upload pictures.

I think you are on to something here because many of the B737 -800 wings had to be modified on the outer part of the wing structure before the winglets could be installed. Maybe the Wing loading at the Pickle Forks changed due to the installation of winglets.

The Crew and Passengers could be in a real "Pickle" if the pickle fork fails in flight.

OK. I was already familiar with the "burnishing" process.
Your burnishing tool is what I am referring to as a roller reamer.
But I was not familiar with the use of the sleeve, which I now understand, in principle anyway.
Each roller of a roller reamer (burnishing tool) actually pushes a little bow wave of material ahead of it.
The hertzian contact stress so imposed has the potential, in itself to create microcracks, that potential could be obviated by use of the sleeve.
It also explains why the sleeves are not re-used.

I'm still interested to know whether the sleeve material is the same as or similar to the parent metal: harder or softer?

This is going far afield- suggest you take the time to read available catalogs and such from Fatigue technology
generally ( from long ago memory ) sleeves were steel when used in aluminum, and I ** think* heat treated. were there different ones used in steel or in 6AL4V titanium ?- dont think so. Lots of earlier discussion and testing re internal or external sleeve lubrication . But that was 30 to 40 years ago.

My point is/was it is and has been a common technique used world wide for over 40 years in the industry . Why not just drop the detailsm and wait till we find out just where the cracks are-were. BTW- lou champoux was at the desk next to mine for a year or so - and there is much more involved then needs explanation here.

Thanks for the input. As mentioned earlier, I was just interested in the general process, not how it might or might not apply to pickle forks.
I asked again about about the sleeve material because I thought you might know. I'd have settled for an "I don't know".

The correct answer is it depends there are several specialized variations of the process including leaving sleeves in place etc -PLEASE take the time to look up for free and read the basic catalog.

END END END

That seems far more likely than the so far unsubstantiated rumour that the cracks affect only aircraft retrofitted with the SS winglets.

If the latter had been true, the association would have been made by now and we would all know about it.

The link works for me.

"A pickle fork is the part that helps attach a plane's fuselage to its wing structure. It helps manage the stress, torque and aerodynamic forces that bend the connection between the wings and the body of the jet.

Engineers design pickle forks to last the lifetime of the plane, more than 90,000 landings and takeoffs, a term known as "flight cycles" in the aviation industry, without developing cracks. There could be dire results if the pickle fork system on the jet fails in flight."

I doubt that. The mass of the fuselage would be the same with or without winglets. So the load on the pickle forks would not be altered by the addition of winglets or bigger wings or whatever.... Lift = gravity

The bending moment at the pickle forks will vary on any change to the wing length, profile, weight or any other factor.

They transfer loads in all directions not just a fuse mass to wings.

The fuselage does not carry any of the wing bending, only secondary effects from displacement. There is a very heavy structure often called the wing box that keeps the wings together. And yes, L=m*(g+x") added with a small number from horizontal tail.

See color sketch at https://www.pprune.org/showpost.php?...6&postcount=14

Bending moment 216, deformed pickle fork (exaggerated) 218

That is a so called secondary moment that is caused be the displacement of the wing box. It very small in comparison to the primary bending that is carried by the box. The fuselage has to be flexible enough not to carry the loads. It is really a question of relative stiffnesses.

Actually a case of surprise cracks in the pickle forks.

The pickle fork is attached to the wing SPAR which is a primary load carrying member of the wing.

or the center wing box anyway