Refinishing Spring Gear legs

[T. C. Downey]

It was done on all gear legs when they were new,

What is your reference?

I have refinished well over 20 sets of gear legs, and never seen the tell tail signs of shot peening on any of them.

[c170b53]

It's a manufacturing process and repair process and probably hard to pick out where the process has been applied, just using your eyes. Again, in high strength steel if you really want to know if there's trouble, NDT the piece.

[bagarre]

5-5A CORROSION CONTROL ON LANDING GEAR SPRINGS.
a. General
(1) The main landing gear springs are made from high strength steel that is shot peened on
the lower surface to increase the fatigue life of the part.
(2) The shot peened layer is between 0.010 and 0.020 inch thick.
(3) If the protective layer of paint is chipped, scratched, or worn away, the steel may corrode
(rust).
NOTE: Corrosion pits that extend past the shot peen layer of the gear spring will cause a
significant decrease in the fatigue life of the spring.

That speaks to the manufacturing process. So what they are saying is that if you make a repair to the underside of the leg, you need to re-peen the surface.

[T. C. Downey]

It's a manufacturing process and repair process and probably hard to pick out where the process has been applied, just using your eyes. Again, in high strength steel if you really want to know if there's trouble, NDT the piece.

In order to do any good, Shot peening must move the molecules of the metal by denting the surface, It is very obvious when it is done. .010"- .020" is the depth of the dent each ball hitting the surface makes. I've done this process many many times while I was in the NAVY working fleet repair stations. you adjust the air pressure to achieve the speed of the ball to produce the depth of dent you desire.
Shot peening is a surface work harding process. that is all it is.

[c170b53]

Possibly obvious to some, but it wasn't obvious when I did my gear and I know I would have to use eye enhancements. Was it obvious on the many gear sets you've done Tom?
I posted the 3M material earlier in this thread for the curious to understand the meaning of the repair specification quoted by George. Although I may not have the extensive experience of others, I did work in the only shop capable of overhauling 747 gear in North America and I did carry out flap peening but never, have I been involved in shot peening.
The afternoon shift at that shop was, amazingly also capable of stripping, carrying out mag particle and refinishing 170 lady legs! and a certain Norton 850. Sadly I wasn't there long but my efforts paled in comparison to others who managed to put through more than one antique car.

[GAHorn]

It was done on all gear legs when they were new,

What is your reference?

I have refinished well over 20 sets of gear legs, and never seen the tell tail signs of shot peening on any of them.

The better question is: What is YOUR reference for maintaining Cessna's gearlegs in accordance with their instructions? (Cessna Aircraft, who provided the instructions/reference.) A repairman is required by regulation to be knowledgeable of mfr's instructions for continued airworthiness and to have those references available when performing such work. What reference were you using when you refinished those 20 sets of gear legs?

[T. C. Downey]

It was done on all gear legs when they were new,

What is your reference?

I have refinished well over 20 sets of gear legs, and never seen the tell tail signs of shot peening on any of them.

The better question is: What is YOUR reference for maintaining Cessna's gearlegs in accordance with their instructions? (Cessna Aircraft, who provided the instructions/reference.) A repairman is required by regulation to be knowledgeable of mfr's instructions for continued airworthiness and to have those references available when performing such work. What reference were you using when you refinished those 20 sets of gear legs?

As you well know there is no specific maintenance manual for the 170, so we use other methods acceptable to the administrator.

I usually send them to ASCO processing, they are a certified repair station that can strip, NDI, and rebow, stress relieve, and bake to eliminate hydrogen embrittlement, as required. They send them back to me as clem as a new penny, And I have never seen any showing they have been shot peened.

[c170b53]

Well these posts almost make me feel the need to refinish a set to see whaa-ss-up ! Emphasis on almost of course! I refinished mine maybe 12 years ago and at that time I had used Alum. Oxide wet blast (total overkill) to prep the surfaces. I would have thought that the peened area would have had a smoother surface but I didn't pick it up visually, so Bruce care to solve this for us?

[Bruce Fenstermacher]

NO Jim I don't care to solve this. After all this don't use chemical stripper, use chemical stripper, don't use mechanized sanding, no it's OK to use a belt sander, the underside surface is shoot peened and you can see it, no you can't see it but you won't remove it (though how would you know if you can't see it).

I'm not touching my gear legs.

They haven't snapped in 60 years and there's a good chance they won't snap in the time I own them if I don't touch them.

[T. C. Downey]

If you really want the gear legs cleaned for new paint, you could send them in for shot peening, I'm certain there will be no paint on them when they return.

[c170b53]

Well you can see it with a 10X and its actually a requirement after peening to ensure the treated area (although it should be) is uniform (no missed spots).
As for hydrogen embrittlement, well caustic substances can cause this issue in high strength steel, doesn't mean it will but it increases the probability.
If you use power tools you might want to think about heat generation with respect to any metal your working on. I know we had to remove Cratex wheels from our workplace because knowledgeable personnel knew they where generating heat but did not realize the amount of heat which unfortunately was damaging metal. To be fair, initially they used cratex sticks to remove defects (ie gouge in a skin) and would work the repair by hand. Cratex wheels driven by air tools air came along and increased production but introduced the heat generation problem.
I think the DIY could get by with portable media blaster and rattle cans and although possibly its not ideal not to do a full lookie- see, its better than wondering. Bruce how am I doing in dissuading you from putting this off, further?

[bagarre]

Or just get rid of the gear legs all together and put the thing on floats

[hilltop170]

I usually send them to ASCO processing, they are a certified repair station that can strip, NDI, and rebow, stress relieve, and bake to eliminate hydrogen embrittlement, as required. They send them back to me as clem as a new penny, And I have never seen any showing they have been shot peened.

Tom-
Would you please post the contact info for ASCO? I have never heard of them.
Thanks!

[mike roe]

And ask if they shot peen the Cessna gear legs.
Mike

[johneeb]

Richard, I wondered the same as you and found the link listed below ASKO is certainly a very complete metal treating business.

http://www.askogroup.com/companies/asko ... efault.htm