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What happens to roof rack cargo in rollovers?

guido666

guido666

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I see lots of cool safari racks on rigs (carrying lots of stuff like gas cans). In a rollover do the racks survive? Do the gas cans burst?
 
I'm pretty sure that gas cans aren't made of aircraft black box material. Best bet is "don't roll over." Have a good day...
 
But they are full of (uncompressable) liquid. They either don't do much, or burst.

I'm asking for some experience here. I could sit around and say "I'm pretty sure..." all day long, but someone has seen it happen.
 
A combustable is going to be no more different on the top and like on a bumper or inside a vehicle in a crash/rollover. If your worried about it, just don't carry the gas cans up there.
 
Okay. Didn't mean to offend you but the number of variables involved in a roll over ,in the sand, on rocks, pavement, 5 mph, 75 mph,,, just to name a few. Take it easy.
 
personally, I wouldn't put a gas can outside of some tubular protection like that. Depends on the type of wheelin/rig though... there are plenty of terrains where rollovers are highly unlikely. I like driving trails... so my gas cans will stay somewhere safe.

j
 
guido666 said:
I see lots of cool safari racks on rigs (carrying lots of stuff like gas cans). In a rollover do the racks survive? Do the gas cans burst?
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I carry alot of stuff on my roof rack when we go out. I don't drive a rock buggy and I am mindful of that. Also, my Suburban has a 40 gallon tank and I have never carried extra gas. If I did, I would try to put it in a less vulnerable place than the roof. With a loaded roofrack, you do in effect, raise your center of gravity so you should keep that in mind when you choose obsticles to drive over. Thankfully I have no real world experience in rolling with a roofrack, but it would be an ugly "garage sale" I am certain that the gas cans would burst.
 
No offense taken, I'm just saying that I'm not looking for theories. I'm an engineer and am paid to come up with theories. Experience often gives better understanding, so I'm looking for someone's story, picture, friend's rig, etc. Like "My friend rolled slow and it smashed the rack, ripped off the rain gutters, but the can only had a dent." Someone has seen something.
 
THink of it this way, anything on top of a 5,000 pound truck in a rollover is not going to be in perfect shape when its all said and done.

Even if you use DOM/Chromo tubing, its still the highest point on the truck and if the truck flops on its lid fast or slow, it better be able to support that wieght if you want it to survive. Most don't think that far and a lot would depend on you attachment points. Rain gutters are not going to support the truck. Then again if you built it heavy enough and attached it to the fiberglass top it might just push though.

I'd say anything on top is at risk in a rollover, home made or shop built. I personally would not carry much heavy stuff up in one anyway as it just increases your center of gravity that much more. Put the heavy stuff low as possible and if you run a roof rack carry the light stuff, Camping gear, tents, sleeping bags that kind of stuff.

Anyway you slice it, if you have a rack and you roll its toast.
 
guido666 said:
No offense taken, I'm just saying that I'm not looking for theories. I'm an engineer and am paid to come up with theories.
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Most engineers I have known/seen don't come up with theories... they apply what other people have already come up with. Scientists on the other hand... :)

j
 
Shouldn't take an engineer to figure out what would happen to an aluminum, seamed construction gas can when a 5000lb truck rolls over on it, never mind a CK5 forum full of lackies! :rolleyes:
 
fireplug said:
Shouldn't take an engineer to figure out what would happen to an aluminum, seamed construction gas can when a 5000lb truck rolls over on it, never mind a CK5 forum full of lackies! :rolleyes:
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If the interior surface area is say 500 square inches (an honest estimate) there is only 5 PSI on the can, which shouldn't come close to bursting it (same 5000 truck). A 2 litre pop bottle bursts at 90 PSI! So it should survive a good flop, even one that would crush the rack I bet. That's why I'm asking, I've never seen this stuff destroyed, but I'm sure someone has.
 
For normal trailriding it's rather rare to have somebody roll hard enough to end up on the roof. I've personally seen lot's of "flops" on the trail, but all of those just resulted in the vehicle laying over on it's side.

With that said, keep in mind that the vehicle will have some momentum and bouncing going on if the roll is hard enough to put it all the way on the roof. Under this situation you have more to worry about then just the 5,000 lb. force when the truck comes crushing down onto the roof. It's also will be far from an evenly distributed load on the gas can. Also keep in mind that the fluid (gas) is not stored under pressure and the can will not be 100% full so there is the chance that the can will start crushing slightly, and thus weakening the structure, before the "uncompressible liquid" starts playing a role in the overall strength of the can.
 
I still can't seem to get across that I understand all this. I'm not sure if this is my downfall or the shortsight of those who reply. I can't take into account everything, so I am specifically looking for someone that has seen something like this happen, and I would like to hear the story, or even see a picture. We can all debate what would happen, and talk theory all day, but a firsthand story would clear up a lot of speculation very quickly.
 
Get one of the cans and lay it under the truck on a concrete surface (driveway) place a floor jack on top of the can and procede to jack up the truck by the t-case crossmember.
Go slow and watch the can buckle from the weight.
After the can has been crushed remove and pick up what is left for a inspection.
Just think that in a roll over the can is going to see around 100% more force since the truck will be a moving object and it is alot unlikely that the can is going to land on a flat surface that would distribute the force evenly liek a floor jack did.
 
Actually I already did this, kindof. I filled an old one with water, and ran it over several times. No permanent damage. Why do you think I'm asking? Once again, I said I already understand this. And actually the can will take more like 10,000% of the force in a serious rollover (100 x 100%), so I am completely aware that at some point it will burst. I just want to see some pics or hear a real story.
 
guido666 said:
Actually I already did this, kindof. I filled an old one with water, and ran it over several times.
Click to expand...

Well, you say you understand what is going on but then post something like this. Running over something with the soft, deformable tires that only puts about 1/4 the total weight of the vehicle on the can at one time is no comparison to the entire vehicle crushing down on a can with steel structures pushing down on it.

In any case, why don't you fill a can with water, lay it on the ground, and then hit it a few times with a sledgehammer.........probably a more indicative test to what would happen to it.
 
I am still trying to figure out why you still dont understand this. Its a can made out of pretty thin steel.
Of course its going to crush.:rolleyes:

If I can back my truck up to a rock and bend 2x4x1/4" rec. steel then the can would crush like a pancake.

jeez put this to rest.:rolleyes:
 
im not sure wat would happen to the can but im guessing under enough pressure it will get destoryed. Personaly i wound put a gas can on roof i would put it on a bumper mount similar to a jeep if anyone here crushes cars they should take one of water and crush it see how much force it takes to crush it and post it for us to see or send it to mythbusters lol
thats my opinion
 
Even first hand stories are not going to give you an answer as every situation is different. What kind of surface was rolled onto and what angle and weight of vehicle and how the weight was distributed.

I agree that the tire test will just show if a tire can do some damage. If you put the whole weight of the vehicle onto the can can right in the middle it would crush. layering it on slowly, it would last longer.

So maybe you could clarify your question with a controlled scenerio. Such as, stock blazer rolling over to the roof onto a flat piece of concrete at x speed.

I think you will get stories where they survived and where they didnt survive.

Even storied of where they are used in the military might give you a better idea. I'm sure they have have given those cans the Gorrilla Test.
 
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