Roll cages, your views

[Ron B]

Another reason I got these was the issue of flammability, and figured I'd need some zip-tying so I already bought a bag from the hardware store (it's a trail-truck so it's always function over form anyway). A good idea about the fabric covers.

I do not have a 5 point harness system in place, just the stock seat belts -- so I was worried about the occasional bump in the road as well as the usual getting in/out head bumps. There's at least 5 inches to the closest bar when I'm sitting (a bar over my head). It's no race truck, it's more of a crawler. I got the cage for protection from a slow rollover. Being a soft top (and a big one) god knows what I might roll onto...and what will come tearing through the fabric (tree stump/branch, boulder).

rb

 

[R_Lefebvre]

5", and a 3 point... could be a problem. I don't think you'd get a concusion, but it'll hurt. I'm talking about bouncing down a trail.

In a rollover, you'll be glad for the rollbar, and the padding.

And don't skimp on the application. You'd be surprised how far the human body can stretch in a collision. You want it down to the dashboard at least. I went right to the floor, that's for leg protection. Hitting a wall at 100mph, or getting hit by a larger vehicle... the cage will bend into your footspace.

Probably less of a consideration in a Hummer than it is in my car, but I would at least pad from the windowline up.

I think that it's a very good idea you're putting the cage in the Hummer. A rollover would not be pretty with a soft top. There's always the risk of hitting your head, but overall, I think it's much safer with the cage.

 

[kellymoe]

I have a older Defender 130 Crewcab and would like a bit more protection but as has been stated i do not want the addes weight.

What are you opinions on a single roll bar, say right behind the front seats?
Another option is a cage of sorts with a roll bar bend the rear seats and another behind the front seats tied together with truss bars. I would like to keep it as light as possible.

What are your thoughts on square tubing cut and welded to shape for a roll cage? I am guessing the welds unless perfect would be the weak point?

As is obvious I am no expert in this area and would have a fab shop build it.

 

[kjp1969]

I have a older Defender 130 Crewcab and would like a bit more protection but as has been stated i do not want the addes weight.

What are you opinions on a single roll bar, say right behind the front seats?
Another option is a cage of sorts with a roll bar bend the rear seats and another behind the front seats tied together with truss bars. I would like to keep it as light as possible.

What are your thoughts on square tubing cut and welded to shape for a roll cage? I am guessing the welds unless perfect would be the weak point?

As is obvious I am no expert in this area and would have a fab shop build it.

I've never seen square tubing for a roll bar, even when cost was no object. I'd guess that its less rigid. If you'd like a local estimate for a custom cage, try John at http://www.betamotorsports.com/ He does great work.

 

[R_Lefebvre]

I have a older Defender 130 Crewcab and would like a bit more protection but as has been stated i do not want the addes weight.

What are you opinions on a single roll bar, say right behind the front seats?
Another option is a cage of sorts with a roll bar bend the rear seats and another behind the front seats tied together with truss bars. I would like to keep it as light as possible.

What are your thoughts on square tubing cut and welded to shape for a roll cage? I am guessing the welds unless perfect would be the weak point?

As is obvious I am no expert in this area and would have a fab shop build it.

You can't do a single hoop, because it will likely just fold over. Some trackday guys do use a single hoop, but it has to be diagonally braced back to some point on the rear lower portion of the car, such as the rear shock towers or floor. You do sometimes see cars like convertible Mustangs with a single hoop, but that is a "style bar" not a "roll bar".

Having two hoops connected together at the top would be better, but it could still "matchbox" on you, I'd think. If you had gussets between the horizontal and vertical members, that would help a lot. Two hoops, braced together at the top, with the rear hoop also having diagonals down to the floor in the back may work.

One other option, is if you could brace your hoops into a suitably strong part of the car, such as the upper seatbelt mounting points on the pillars, that may work too. Still far from ideal, but better than a freestanding hoop.

Square tubing... I don't know ALL the reasons it's not used, but I can think of several. First, square tubing tends to be pretty low quality compared to some of the offerings in round tubing. Also, it's impossible to bend square tubing "out of plane", and difficult to make joints out of plane, as is often required when building a cage. Square tubing is stronger than equivalent round tubing when bent "in plane" but weaker when out of plane. It's also weaker in torsion. With cages, you never really know where the forces are going to hit, so the omnidirectional strength of round tubing is better.

The welds are critical on cages made from any material. Crap welds will give you a crap structure. You need a cage built right, because a bad cage can be worse than no cage.

 

[ntsqd]

I concur with everything Rob said, particularly that about round vs. square when the direction of the roll is unknown.

 

[kellymoe]

I have never seen square, I was just wondering about it and I am not so ignorant as to know you do not bend square tubing. When I said single I should have been more clear about diagonal bracing, I know you need it.

My problem is simply room for a roll bar, inside the cab there really is not much room and a external cage is just not an option. There are a few race shops in town and a few good 4x4 fabricators too, I'll stop by and see what they have to say.

 

[R_Lefebvre]

Ok, well, just trying to be as clear as possible and cover all the bases, not assuming ignorance.

You can bend square tubing, but only in 4 distinct directions. Well, probably do the diagonals with the right tooling. But anyway, yeah.

As for a single hoop with diagonal back braces, absolutely, go for it. Lots of trackday cars do that. The only thing is, it'll render your rear seats useless. In fact... any cage will pretty much render your rear seat useless. Way too much possibility of rear seat passengers hitting their heads on the main hoop. I'm sure there are cases where people do things like that (such as 4 seater sand buggies, etc.) but, it's down to your personal risk threshold.

 

[kellymoe]

Ok, well, just trying to be as clear as possible and cover all the bases, not assuming ignorance.

You can bend square tubing, but only in 4 distinct directions. Well, probably do the diagonals with the right tooling. But anyway, yeah.

As for a single hoop with diagonal back braces, absolutely, go for it. Lots of trackday cars do that. The only thing is, it'll render your rear seats useless. In fact... any cage will pretty much render your rear seat useless. Way too much possibility of rear seat passengers hitting their heads on the main hoop. I'm sure there are cases where people do things like that (such as 4 seater sand buggies, etc.) but, it's down to your personal risk threshold.

Yep, there is not much room in there at all to stuff a hoop or a cage. A cage would probably be more feasable than a hoop but that would add more weight than I would want. Not too many options.

 

[R_Lefebvre]

Do you want to retain the use of the rear seats? If you put a hoop behind the rear seats, I think you'll still get some benefit. Either way, cages take up a lot of interior space. No way around it.

 

[ntsqd]

A really good cage fabricator can bury the tubes inside at least some of the bodywork. That would alleviate some of the space consumption problems, but it won't eliminate them.

Assuming that there is room to do so, a hoop behind the rear seats (buried into the body as much as possible) with a transverse diagonal in it, and a hoop behind the front seats could possibly work.
Depending on how far into the rear door opening the rear seats intrude, it may be possible to put in some shallow fore/aft diagonals. Not the most ideal, but better than nothing.

A good fab guy will have some suggestions, but an Ace can do things that we wouldn't think of. Ace's don't normally come cheap though with the economy what it is I'd expect that you can find an Ace desert fab guy in need of work.

 

[kellymoe]

Thanks for the suggestions I'll be on the lookout for a good fab guy.

 

[dzzz]

I'm curious if just an internal roll bar at the B pillar, with fore-aft bracing at the floor, would help. What I really don't like the tube at the A pillar. With padding it's huge and without padding it a hazard.

 

[R_Lefebvre]

Yes, as long as it's braced back, a single tube at the B pillar will help.