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pwsk
Apr 4, 2002, 9:59 PM
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Hello guys and gals,
I've had my trad gear for a bit more than 2 years now, and I've noticed a small amount of rust forming at the points of contact between the cam blades and axles of my ACD's. Is this a serious problem and can it be treated? I've not noticed any oxidation problems on the wires/cables of my passive protection, but is it possible that they may also have been affected?
Thanks for reading and helping!
L.O.D
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dustinap
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Apr 4, 2002, 10:06 PM
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Gear rusting seems quite strange to me, unless you do lots of sea side trad climbing??? I have old chouinard 'biners that were kept in a garage for 10 years that are fine.
Are you sure it's rust? sorry this was no help at all, but I find it quite strange gear that new would rust. It maybe the way your are storing it, or where you are climbing though. You may want to try some metolius cam lube, and they also make a cam cleaner. I'm not sure if this would help or not?
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rrrADAM
Apr 4, 2002, 10:09 PM
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Are you sure this is "rust" ???
Lobes... Aluminum doesn't rust, it will oxidize and make aluminum oxide (the plack stuff that gets all over your hands from the rope), but that shouldn't effect it's integrity.
Axle... 300 series Stainless is resistant to rust.
rrrADAM
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lemon_boy
Apr 4, 2002, 10:31 PM
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yeah, i think i know what you are talking about. a while back i noticed some rust on a couple of tcu's. the rust was in the area where the cable meets the axle housing. i was kind of bummed because i live in a dry state and there really wasn't much of a reason that they should be rusting. at first i tried white gas (as per macnamara's climbing article) and it didn't help. then i talked to a couple metallurgists at work and they recommended coca-cola! so, i tried it. i would soak them for about an hour and then scrub with a wire brush. it worked really well, and instead of trying to figure out what to do with the white gas, i just had a rum and coke.
good luck!
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rrrADAM
Apr 4, 2002, 10:58 PM
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redzit, I mean um, slowdraw...
"stress harden" ???
What the hell is that ??? I am familiar with many diverent failure mechanisms due to my job, and have never heard of that one. I have heard of embrittlement, but this is mainly caused by corrosive oy Hydrogen rich environments. (i.e. Hydrogen Embrittlement)
You are correct about 400 series Statinless being less corrosion resistant.
rrrADAM
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apollodorus
Apr 4, 2002, 11:11 PM
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WC says they use a "single Nickel Chrome Molybdenum" axle. This is neither a 300 or 400 series stainless steel. It is more like a 4340 steel, the same stuff used for BD Lost Arrow and Angle pitons.
Spray silicone lube on the axle areas and work the lobes to distribute it. This will help to repel moisture.
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redzit
Apr 5, 2002, 2:52 AM
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Adam, Don't you dare ever do that again. i'm insulted.....jks jks.
i'm just jokeing around.
who did you figure it out dude. i was tring so hard to keep it from surfacing.
by the way, my dad is a mechine nut case, anything he wants to make he can make. if he was to make a cam, he do it and make it lighter and better.
for enlightning definisions of the terms he uses, do A)buy a dictionary specializing in such fields. these would be for university students so fallow one around till you know where to get them.
or B) get an enginering friend who can explain all this to you
I highly recomend B evem though CERTAIN ones can be a pian as to how they tell you.
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miagi
Apr 5, 2002, 7:04 AM
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why did you change your name RZ?
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pwsk
Apr 5, 2002, 7:09 AM
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Thank you for the info people
I'll check again to make absolutely sure that it is rust, but I'll also have some people of the MCSA have a look at it and hear what they have to say. Otherwise it sounds as if some sort of moisture repelling lubricant may be the answer - I gues just keep it away from the slings though.
L.O.D
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apollodorus
Apr 5, 2002, 7:23 AM
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Strain hardening occurs when a material exceeds its elastic limit and takes a permanent set. The material's elastic limit is raised in the region, at the expense of ductility. If you reverse the loading repeatedly, you eventually make the material brittle enough that it can no longer deform plastically and it breaks (coat-hanger effect).
Fatigue cracking is usually the result of surface imperfections opening up into cracks after many cycles of loading, like 10,000 plus.
Hydrogen embrittlement is a problem for welded joints only, unless the steel foundry has really crappy process control.
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rrrADAM
Apr 5, 2002, 11:18 AM
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RZ... Check my profile, as I work closely with both engineers and metalurgists, and have done so for almost 14 years. I usually collect the raw data for them to make their calculations. (i.e. Hardness, Exact Alloy Compositions, Pre & Post Failure Inspections, etc...)
I just talked with 5 engineers, 3 structural and 2 metalurgical, this morning...
The only things that can change the hardness of an alloy while it's in service are Temperature, Working(introduces heat), and Hydrogen. (Note - Hydrogen is the most detrimental of these three.)
The failure mechanism described in the above "coathanger analogy" is simple fatigue cracking caused by Work Hardening the material. Working (cycling) the metal creates heat, which changes the cube latice structure of the surface of the metal making it harder and therefore more brittle. (Note - The forces required to do this are extreme, and the forces on a cam never even get close.) Once the metal fatigue cracks at the grain boundary of the alloy, this creates a "stress riser" which allows the metal to quickly fail. [A stress riser can be anologous(sp?) to: Paper is pretty strong when pulled in tension. But once you introduce the tiniest tear transverse to the tension, it will quickly fail from that point.]
So it would appear that all 3 of us were close to being on the same page, it comes down to nomenclature.
Apollo... Hydrogen Embrittlement is not only limmited to weldments as Hydrogen easily migrates through steel since the atom is so small. If it collects in one area within the steel it can even cause laminations as well as effecting the hardness of the steel. Hydrogen is what starts IGSCC (Intra Granular Stress Corrosion Cracking). Fatigue cracking associated with this is the most common failure mechanism in Hydrogen rich environments. (i.e. In Nuclear Power plants, the heat produced from the core and radiolisis actually seperates water molecules into it's constituant gases. This free hydrogen is of great concern, as it causes the above described problems.)
rrrADAM
[ This Message was edited by: rrradam on 2002-04-05 12:04 ]
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pwsk
Apr 5, 2002, 2:08 PM
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So what you guys are saying, is that such a small amount of surface rust will not cause the units to fail at a lower force than it is marked with. Al I need to do is brush off the rust(if that is what it is) and treat the ACD's with some lubricant and all will be well?
Thanks again
L.O.D
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cedk
Apr 5, 2002, 2:40 PM
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After reading this thread I still trust cams.
But I am a little more nervous about nuclear power plants.
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