JKOwners Forum banner

1 - 20 of 50 Posts

·
Registered
Joined
·
2,580 Posts
Discussion Starter #1
In planning my new 2-dr build - a LCG, light-as-possible, long travel beast....a gaping hole in JK product options became apparent.

Roll cage = good. Weight = bad. GenRight and Nemesis = good with that aluminum stuff.

When contemplating a roll cage, the first thing that came to mind was the weight of welding a bunch of DOM into my factory cage. Then came the though that all of that weight was also at the highest point on the Jeep. I've seen people create ridiculous roll cages on JKs that must weigh a ton.

So what a lightweight JK build needs is a simple, solid, bolt-on (obviously) sport roll cage made from aluminum. No one else that dabbles in aluminum for JKs to the extent GenRight and Nemesis do. So get after it and build that already, would ya? We're waitin' over here. :beer:
 

·
Registered
Joined
·
2,261 Posts
How well would the aluminum hold up in the result of a rollover?
 

·
Registered
Joined
·
2,580 Posts
Discussion Starter #3
7075 T6 aluminum has higher tensile and yield strength than steel. The strength-to-weight ratio is also four times higher. Even 6061 is no slouch. The factory cage would be the weak link in an aluminum sport cage setup.
 

·
Registered
Joined
·
2,261 Posts
7075 T6 aluminum has higher tensile and yield strength than steel. The strength-to-weight ratio is also four times higher. Even 6061 is no slouch. The factory cage would be the weak link in an aluminum sport cage setup.
Well that's good to know. Thanks for the info!
 

·
Registered
Joined
·
3,070 Posts
Why not a chromoly tubed cage like they use in racecars and drag cars?
 

·
Registered
Joined
·
2,580 Posts
Discussion Starter #7
Couple of points...

Cost -
I really don't think it would cost that much more. GenRight and Nemesis already make aluminum fenders that will cost you about the same as steel fenders from other vendors. With GenRight the increase in cost for aluminum over steel is modest. The real difference is in materials cost and production velocity (MIG vs TIG, etc).

Why not Cr-Mo -
Racing vehicles, drag cars etc are built around a tube frame to begin with, so the cage is a fully supported structural element. There is no inherent weak link in these designs and they are designed to provide protection in incredibly nasty high-speed wrecks.

JKs are very different. The cage doesn't tie into the frame (become structural) unless you do some serious cutting and fab. So when you add to the factory cage, you're strengthening it but also really just moving the weakest point somewhere else in the cage. It's never going to be a fully integrated structural component. Also, you're likely to roll slowly, and a few rotations at best, when wheeling. What you need is more protection, not the ultimate protection like race cars. What I'm saying is that a full CrMo cage attached to the JK factory cage is overkill for our needs....and weighs too much.
 

·
Registered
Joined
·
428 Posts
7075 is generally considered to be unweldable, so I don't know if there'd be any practical way to make a roll cage out of it unless it was bolted together.
 

·
Premium Member
Joined
·
251 Posts
7075 is generally considered to be unweldable, so I don't know if there'd be any practical way to make a roll cage out of it unless it was bolted together.
x2 And even then any flanges would have to be machined into/out which would be $$$$$$.

Also, aluminum is more likely to fracture when it fails. Not what you want in a cage.
 

·
Registered
Joined
·
440 Posts
There's no way to bend 7075 in roll cage radius..besides weld it together..also you would need a very very expensive die to do this with 6061....
 

·
Registered
Joined
·
13,230 Posts
7075 T6 aluminum has higher tensile and yield strength than steel. The strength-to-weight ratio is also four times higher. Even 6061 is no slouch. The factory cage would be the weak link in an aluminum sport cage setup.
Chromoly would be a much more practical material.

I can't think of any motorsport that uses aluminum driver cell structures. To me, that 7075 can probably take a hit...but the 2nd...3rd...4th, may be a different story.

Sorry, but I think you'll be very alone on this debate. CrMo is what you actually want.
 

·
Registered
Joined
·
2,580 Posts
Discussion Starter #13
Might be true that the logistics are too much. Really, 6061 would be plenty. But I still think it's a great idea. I don't care about fracturing, as the goal is not to roll in the first place, and if the cage does its job only once the cost to replace it is cheap insurance to me. And I don't think the race care comparisons are relevant, since spilling while crawling a ledge is nothing like bouncing off of asphalt or a wall at a buck-twenty. They are just very different applications. I may be hare-brained about it, but apparently also hare-brained enough to stubbornly think it's a great idea. :beer:
 

·
Registered
Joined
·
1,283 Posts
Technically you can't bend aluminum and keep the same strength characteristics it had before hand especially 7075. Like others have said it is also very difficult to weld. The best case scenario with an aluminum cage would be to use straight pieces and machine all the junctions.

Your best bet would be Cr-Mo.
 

·
Registered
Joined
·
11,064 Posts
Might be true that the logistics are too much. Really, 6061 would be plenty. But I still think it's a great idea. I don't care about fracturing, as the goal is not to roll in the first place, and if the cage does its job only once the cost to replace it is cheap insurance...
To me fracture equals impailment. I think I'd rather be crushed...

Seriously how much does a steel cage weigh? We have either a cloth or plastic roof, there should a little room there for lcog without making it top heavy.
 

·
Registered
Joined
·
92 Posts
Here is the President of GR's input on pursuing an aluminum cage (from Tony Pellegrino directly). Bottom line is that an aluminum cage wouldn't be an option from GR.

Although aluminum has been made for dune buggy frames, from a GenRight perspective this is not the area to sacrifice strength for weight. With this in mind, the new 2" roll cage going into the "Terremoto" build is steel and only weighs 260lbs.

Additional feedback for the aluminum cage is that the 6061 grade would require a lot of special handling for fabrication in order to maintain the strength characteristics which would make the cost significantly higher than a steel cage. As far as the 7075 aluminum, it can't be bent or welded and still maintain the integrity of the material.
 

·
Premium Member
Joined
·
5,696 Posts
Yeah as cool as the aluminum cage sounds, it just doesn't make any sense from any standpoint other than weight. Utilizing the cage as a disposable item also seems sort of pointless too so why bother.

Hopefully the new GR cage going into the "Terremoto" build will prove to be another alternative and maybe even a better option than some of the others out there since it's going into a custom one off build. One thing I have been personally struggling with in most of the designs is the encroachment into the driver and passenger space when going with a bolt-in type sport cage. I'm sure many have the same feeling that I do but you simply don't have a lot of options unless you really want to tear into the dash and custom fit everything which I keep leaning toward...

With any luck GR will have something very nice for us to look at real soon!
 

·
Registered
Joined
·
2,580 Posts
Discussion Starter #19
Damn, you guys have crushed my dreams. Oh well. I suppose just a few strategically placed steel reinforcements to the factory cage are probably good enough though not ideal. I have to admit the bit about the Terremoto cage being 'only' 260 lbs made me chuckle a bit. The 3.6 is definitely more motor than the 3.8, but I once removed 320 lbs of Hard Rock bumpers from my old 3.8 2-dr.....that alone made it feel like an entirely different vehicle and transformed the personality of the rig on and off road. That's why I'm such a bitch about weight.

At any rate I appreciate the feedback from everyone, and thanks for playing. :beer:
 

·
Registered
Joined
·
2,708 Posts
Here Lies Badger
He's dead
but his rig was light
Godspeed Badger​
 
1 - 20 of 50 Posts
Top