martenistic stainless cage?

Vanimal

Vanimal

NAXJA Forum User
Location
escondido, ca
Has anyone used a martensitic stainless steel for cage construction?
It seems to have a lot of similar properties to chromoly, and i know Ford uses it quite a bit. It's also making it's way into higher end mountain bike frames, in place of titanium and chromoly.
I ask because i have a friend who produces heat treated martenistic stainless tubing, and is pretty knowledgable in welding it and whatnot. It should end up lighter and stronger than a DOM cage. i can get the tubing probably cheaper than anything else including probably hrew, or possibly free. these seem like pretty good reasons to give it a shot, so i figured i'd ask if anyone has attempted to use it, or has seen it used before. i'm guessing not due to cost, but worth a shot.
 
While on the subject....What about carbon fiber material? I built a little race car out of the stuff, and it was extremely strong when built. All fittings were epoxied. Price was extraordinary though. $20-30 per foot, lol.
 
this steel has a tensile strength of about 200,000psi (1399MPa) and a yield strength of about 150,000psi (1070MPa) and 34% elongation at break.
 
mako my day said:
While on the subject....What about carbon fiber material? I built a little race car out of the stuff, and it was extremely strong when built. All fittings were epoxied. Price was extraordinary though. $20-30 per foot, lol.
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carbon fiber is strong, however, when it goes, it goes. there is no bending, there is only failure. i'd hate to be on my 3rd roll when the tubing shattered on the second.
 
vetteboy said:
Brittle and no bending...sounds like martensitic stainless to me. :)
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martenistic SS can handle bending far better than carbon fiber. case and point, try putting either one in a jd2 and see what does better :D

i'm planning on building a cage with an external halo much like the team naxja KOH truck. i'm taller, and don't feel like losing head room. my biggest concern is the tight bends on each corner. i'm thinking of just bending everything in an annealed state and heat treating the halo or any other tightly bent sections after bending and welding. i can weld a good bit of it beforehand. the vaccum furnace is pretty huge, it'll all fit in.
As for brittleness, you can fine tune the hardness to help with that a bit i would assume. i cant imagine it being too bad at around 36-39rc.
 
So what section are you planning on using, then?

On top of the difficulties posed by bending anything really thin-walled in a JD2, I'd be worried that anything thinner than .095 is gonna have trouble being in direct contact with rocks. One dent in material like that and your cage turns into a crumple zone. I was denting the hell outta good quality .120 wall DOM; I'd find it hard to believe thinner stuff regardless of how badass it is is gonna hold up much better in that respect.

So even if you get away with .095 wall and save 30 lbs over the entire cage, the high carbon is still gonna present difficulties welding (I know there are ways to do it, and most involve heat-treating the joint in relatively short order after welding, especially if you're going to wind up with internal stresses in the cage members as they pull/push on each other while the structure is being fully welded. And it's one thing to heat treat a whole chassis; how were you planning on heat treating or executing the junctions between the 410 and the rest of the junk steel unibody?).

I mean, to me it looks like you're gonna spend a ton more time on the weld & prep process, using a material that's harder to work with, prone to HAZ brittleness at the welds, prone to denting because of the application...in an effort to save 30-50 lbs.

Guess I just don't see the appeal.
 
the tubing in question is .098 wall.
as for welding, you purge it with argon internally, not a big deal. like i said, i'm dealing with my friend who deals with welding this stuff every single day, and much of that is bicycle frames, where weld strengh and brittleness is very, very important. he's got all the equipment and knowhow. they litterally make the tubing, in house.
as for attaching it to the body, weld it to a thicker plate and weld the plate to the body, and/or bolt it to heavily reinforced areas. i'm not terribly worried about that, i think it's easily doable, and i would probably be doing it a similar way with dOM anyways.
As for the appeal, cost for one thing. little to no rust (external halo), and probably greater chassis rigidity.
 
Right. For the $500 it'd take to do a full DOM cage I'd rather experiment with other areas of the rig and leave the safety stuff to known and proven materials.

To each his own I guess. Still sounds like you might as well make it out of soda cans when it comes to leaning into rocks.
 
vetteboy said:
Still sounds like you might as well make it out of soda cans when it comes to leaning into rocks.
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i definitely diasagree with this, i work with it all the time, the stuff is pretty tough. it holds up on bicycle frames fairly well, very similarly to chromoly. i realize it's not a 4000lb jeep, but they regularly go smashing down rocks with much, much thinner walled smaller diameter tubing. mountain bikes are also designed to flex in certain planes to give a smoother ride, but be rigid enough in other planes to corner and climb well. it's all relative.

i guess a simple test would be bolting a piece to the front of my jeep and ramming it into some rocks :D
 
You should make it out of dana 60 axle tubes, after they've been pressed in. I expect another thread about how to press them back out so they can be reused within the hour.

Vanimal said:
i definitely diasagree with this, i work with it all the time, the stuff is pretty tough. it holds up on bicycle frames fairly well, very similarly to chromoly. i realize it's not a 4000lb jeep, but they regularly go smashing down rocks with much, much thinner walled smaller diameter tubing. mountain bikes are also designed to flex in certain planes to give a smoother ride, but be rigid enough in other planes to corner and climb well. it's all relative.

i guess a simple test would be bolting a piece to the front of my jeep and ramming it into some rocks :D
Click to expand...

There is a difference here. Mountain bikes are built to be strong while bouncing over rocks, cages should be built to be strong while bouncing INTO rocks. As in, the tubing smashing into the rock, not the tubing riding on tires that are smashing into the rock. I think this minor difference may have escaped you.
 
kastein said:
There is a difference here. Mountain bikes are built to be strong while bouncing over rocks, cages should be built to be strong while bouncing INTO rocks. As in, the tubing smashing into the rock, not the tubing riding on tires that are smashing into the rock. I think this minor difference may have escaped you.
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i think you havent been mountain biking.
 
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