Took the gear off yesterday so I could paint it and lo and behold found the outer brackets both are starting to deterioate with the granular corrosion the left more than the right but both. They've been this way for a while and will go quite a while longer, but I need to line up R&R them.

Pponk has the brackets and I intend to buy them from them or have whatever shop I use aquire them,
http://www.pponk.com/HTML%20PAGES/outbo ... acket.html , What I'm looking for is a shop or a recomendation to a shop that has experience in doing this kind of a repair with references and will do them in a timely manner. (that means get on it and get it done)

Surely there has been others that have had to have gear boxes repaired lurking or active on the BCP site.
PM me if you've got some input. I'm in so cal and willing to fly it to where ever and leave it, within reason.
Thanks Russ

Sorry to hear that Russ. This thread might be of use: www.backcountrypilot.org/forum/viewtopi ... 21&t=12119

ya i saw that thread a while back, thanks. I think he did that repair himself?
I reread it hopefully I don't have as much hidden damage [-o<

I bet Beegle's in Greeley, CO would be your best bet.

It's pretty funny the way Pponk pick on intergranular corrosion.
I mean the basics are accurate; yes, every material can suffer from some corrosion mechanisim and some have a dominant one (in this case oxidation travelling between the grains), some materials can suffer from many at once.
Cold rolled alloy (presumably of the same grade?) might remove the predominant mechanisim and flaking effect produced by the grains being aligned in the extrusion process, but they will still corrode - quite likely at a similar rate, it will just look different at the end... (but it won't flake, probably stress-corrosion cracks - maybe harder to see the corrosion? Is that good or bad?) Sounds like sales talk to me.
The fact that the existing gear boxes have lasted 40-60 years before reaching their lifetime is pretty good - you'd want to expect the same from any replacement parts.

I quote 12 man hours per side to replace the outers individually, or 20 hours to do both outers together. It can be done quickly if a little imagination is used. Of course this doesn't allow for any other defects found during replacement...

[quote="onefitty"]I quote 12 man hours per side to replace the outers individually, or 20 hours to do both outers together. It can be done quickly if a little imagination is used. Of course this doesn't allow for any other defects found during replacement...[/quote]


Ok you come here n do it or do i have to come to you, what's your shop labor rate :) And this can't be due to stress right Matt #-o. Wether Pponk has a legit sales pitch or not their part is $1100 cheaper than the next best online price I've seen so far. The left side gear box on my 56 is subject to exhaust gases but the right side has bigger cracks.

I took mine to beegles last summer and had both outboard brackets replaced. If you have one bad, you can pretty much figure the other is too. They were very responsive, costs about 6700 for them to do the whole thing. Worst part is nothing is visibly different but I know the gear is good.

Try Alan Quackenbush at California City. He has a shop just south of the runway, about halfway between the transient ramp and the west end of the runway. He may or may not give you an attractive bid that you like, but he's close and there may be some value in that you could keep an eye on his progress easily without too much of a road trip.

[quote="EZFlap"]Try Alan Quackenbush at California City. He has a shop just south of the runway, about halfway between the transient ramp and the west end of the runway. He may or may not give you an attractive bid that you like, but he's close and there may be some value in that you could keep an eye on his progress easily without too much of a road trip.[/quote]


I looked at him when I had the STOL kit put on he wanted full price but couldn't sign it off, not an IA.

Glidergeek wrote:

onefitty wrote:I quote 12 man hours per side to replace the outers individually, or 20 hours to do both outers together. It can be done quickly if a little imagination is used. Of course this doesn't allow for any other defects found during replacement...

Ok you come here n do it or do i have to come to you, what's your shop labor rate And this can't be due to stress right Matt . Wether Pponk has a legit sales pitch or not their part is $1100 cheaper than the next best online price I've seen so far. The left side gear box on my 56 is subject to exhaust gases but the right side has bigger cracks.

I'll pack my gear now and book a business class flight over to the US! The pponk fittings are top quality so it's a no brainer really. Just make sure the shop uses a minimal amount of Cherry rivets and preps all the holes well. I also install any cherries with PRC, stops them working loose

onefitty wrote:

Glidergeek wrote:

onefitty wrote:I quote 12 man hours per side to replace the outers individually, or 20 hours to do both outers together. It can be done quickly if a little imagination is used. Of course this doesn't allow for any other defects found during replacement...

Ok you come here n do it or do i have to come to you, what's your shop labor rate And this can't be due to stress right Matt . Wether Pponk has a legit sales pitch or not their part is $1100 cheaper than the next best online price I've seen so far. The left side gear box on my 56 is subject to exhaust gases but the right side has bigger cracks.

I'll pack my gear now and book a business class flight over to the US! The pponk fittings are top quality so it's a no brainer really. Just make sure the shop uses a minimal amount of Cherry rivets and preps all the holes well. I also install any cherries with PRC, stops them working loose

What's PRC?

Tom

PRC=Evil Black Sealant, which even smells like it is from hell PRC stands for "Pretty Rancid Crap."

A recent study about inter-granular corrosion seems it may be a bit more insidious than many thought. It turns out that many of the components that have been exhibiting this came from a specific time period of manufacture (of the raw metal itself) in the 60/early 70's. It is looking like it was more an issue of the alloying process than anything else. Inter-granular corrosion is the formation of corrosion cells between adjoining metal crystal boundaries. The difference in composition makes for an electrochemical potential across the boundary. The result is it forms a little battery (I am an expert on Electrochemical reactions, took that class twice, fist time I finished with a better understanding of the female's legs across the isle than the calculus involved. However when I re-took it, the professor the second time around felt we should concentrate on reactions, not calculus and no legs worth observing in the class).

So these little batteries get involved in facilitating the insertion of an oxygen atom into a marriage with the Aluminum, which so very badly wants to have one (one of the most plentiful molecules in the Earth's crust is Al-O2). The downside of aluminum getting one, it gets fat, a side effect of most marriages. As these crystals put on the pounds, they cause planar fractures that grow to the nasty lesions on your aircraft. As they grow, they allow a bit of moisture in, greatly accelerating the reaction.

If you are ever around Russian aircraft, they get it so bad around rivet heads, it looks like bullet exit holes. Even their props get it. Of course they don't fly old airplanes, so it isn't a problem. They use crappy, but cheap alloys, that they make thicker to offset its poor strength. But the bad production makes sense when you look at two identical components, lets say Twin Otter flap hangers. A high strength, machined, heat treated component. One will last forever and its mate on the other side of the aircraft will flake way to death. It is always the worst with parts that are worked and then heat treated. Heat treatment relaxes the stress and cause the crystals (grains) to relax stress between themselves. With an unfortunate side effect of promoting this condition.

Thanks dogpilot, even though this is the internet, it sounds like you know what you're talking about. I'm wondering if having ACF-50 all over my gear box area of my 1954 with original parts since 1988 has been good for intergranular corrosion control or is it not a problem for parts made in 1954. So far, things look good there.

Besides from the extensive electrochem study, the Navy, the worlds foremost experts on corrosion (except on the LCS), sent me to an entire multi-week course on corrosion, causes and treatment & prevention, kind of snooze fest/endurex, but I learned a thing or two.

As Dogpilot said. PRC is a polysulfide sealant used for gooping up fuel tanks. It's by far the best product for assembling following repairs. Keeps moisture out, stops corrosion and best of all stops rivets and skins from working loose

I've bought new parts from Cessna that have intergranular corrosion off the shelf. Unfortunately it's the type of material and manufacturing process that causes it. Seems most common in their various forgings from the late 60's/70's. Main gear fittings, 300/400 series wing attach fittings, early 210 spar carry-thru's....

At the moment I'm changing aileron and flap hangars on a 1998 Gippsaero GA200, these things are made from 0.250" plate and blown out like weetbix. So it's not only the older aircraft having these problems

Thanks all can anybody recomend a shop on the west coast that can fix? That has done this type of work for them? Come on fess up to your ground loops.

Perhaps PPONK themselves can recommend a shop that they have worked with, since they sell more gearbox parts than anyone?

Maybe Del-Air?

Great idea... I think old Harry has a fuselage jig for Cessnas, and has indeed done major structural repair on this type aircraft.