My BJ73 with FRP top does not have the typical interior factory roll bar. I like the wrap around exterior cage bars going from bumpers to roof rack etc..., but I'm realizing that is alot of work/time when a simple roll bar would suffice. My concern is getting crushed in a low speed roll over. Or short roll down a hill. (not end over end for 200 feet, or high speed anything). Not interested in a full cage just a single loop above or slightly behind the drivers seat. Would prefer small diameter thicker pipe to larger diameter thin pipe. Thinking about being unobtrusive. Anyone have a knowledgeable answer or experienced advice in a good size? to completely wing it I would think 2" diameter pipe with 1/4 or 3/8 wall. 4-5" square plates bolted to the floor.
What wall thickness/ pipe size for a single loop rollbar? (1 Viewer)
- Thread starter robmobile73
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FishTacos
Full Globetard
2" DOM tubing with 0.120 wall is pretty standard. A little thicker wall is better, perhaps, but bending it becomes more of a challenge.
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Absolutely do not do a single hoop. That’s a death trap.
I have seen many a death trap roll cage and that’s a cage.
Triangles not squares. Do not build any kind of roll cage out of squares. No single hoops, I do t even recommended double hoops with some triangle gussets.
It’s your life which obviously you are concerned with but the factory roll bar will take more than a death trap.
I do agree, they need better roll over protection than stock but only a proper roll cage. Any way you slice it that will be somewhat obtrusive.
Cheers
I have seen many a death trap roll cage and that’s a cage.
Triangles not squares. Do not build any kind of roll cage out of squares. No single hoops, I do t even recommended double hoops with some triangle gussets.
It’s your life which obviously you are concerned with but the factory roll bar will take more than a death trap.
I do agree, they need better roll over protection than stock but only a proper roll cage. Any way you slice it that will be somewhat obtrusive.
Cheers
- Thread starter
- #4
I would feel OK for what I intend to do If I had a factory steel hard top and nothing else, but I don't. I have a FRP top and the factory roll bar you normally see is not present. In this situation I feel if my vehicle tipped over the top may snap and completely collapse where a steel hard top would bend and crush a bit, but not straight up collapse. Tipping over less than 10mph should not be a life ending experience.
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Your are right 10mph no biggie. Can you guarantee that is all it will ever be? Sure what you have in mind will handle 10mph flop. Will it handle 30mph or 50mph?
I rolled an 80-series at 35mph 2 3/4xs. The Cruiser saved our lives but had it gone over that last 1/4 or more, walking away may not have been possible. It was crushed like a can.
You can not predict what may happen. Deer, elk, black ice, drunk driver, who knows? Get it done right so you will live through any of those.
Triangulation man, do that and it will be strong as can be, that is of course if you don’t build it out of pvc or exhaust pipe!
Cheers
I rolled an 80-series at 35mph 2 3/4xs. The Cruiser saved our lives but had it gone over that last 1/4 or more, walking away may not have been possible. It was crushed like a can.
You can not predict what may happen. Deer, elk, black ice, drunk driver, who knows? Get it done right so you will live through any of those.
Triangulation man, do that and it will be strong as can be, that is of course if you don’t build it out of pvc or exhaust pipe!
Cheers
2fpower
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Without it braced front to rear though, how strong is it? Or is it braced front to rear, I can’t tell.
Cheers
Anything you want to keep from crushing you must be supported front to rear as well as side to side, in triangulated fashion.
Also, where the roll bar attaches must be supported or it will just push it through the floor, or act like a punch and punch cut it's way through in the event of a rollover.
Use ROUND plates to bolt to the floor. They do not have points to start like a can opener.
Use a plate on top and bottom of the floor pan, make them different diameters, by about 1/2" diameter. This will prevent bolt rip-through. The difference diameters will reduce the possibility of punch-through.
It is always best to support directly to a frame mounted body point if possible. Otherwise, make a separate piece to attach to the frame below the body. The body will crush and collapse. The frame will be the structural point to attach to.
Yes, there's a whole science dedicated to doing this, however, there also becomes a point where it ends up being unusable due to the interference.
Don't forget to keep the tubes well away from the head of the occupants, or the impact of the noggin on the tube inside can have serious detrimental effects. If you have a ROPS, you MUST have and use restraint systems or they will act as a guillotine. Can still do that with limbs unless you have a net.
Also, where the roll bar attaches must be supported or it will just push it through the floor, or act like a punch and punch cut it's way through in the event of a rollover.
Use ROUND plates to bolt to the floor. They do not have points to start like a can opener.
Use a plate on top and bottom of the floor pan, make them different diameters, by about 1/2" diameter. This will prevent bolt rip-through. The difference diameters will reduce the possibility of punch-through.
It is always best to support directly to a frame mounted body point if possible. Otherwise, make a separate piece to attach to the frame below the body. The body will crush and collapse. The frame will be the structural point to attach to.
Yes, there's a whole science dedicated to doing this, however, there also becomes a point where it ends up being unusable due to the interference.
Don't forget to keep the tubes well away from the head of the occupants, or the impact of the noggin on the tube inside can have serious detrimental effects. If you have a ROPS, you MUST have and use restraint systems or they will act as a guillotine. Can still do that with limbs unless you have a net.
FJBen
SILVER Star
Don’t count on a steel roof saving you more. It’s all about physics and where and how forces are exerted. Triangulation is the best as been stated.
here is my FJ55 I “rolled” years ago. Under 30mph and landed in snow. More like a flip to the top corner which put some major forces on it. I took my seatbelt off 1 minute before I rolled. If I would have had it on, I Probabaly wouldnt be here. Dove/flung down into the foot area. That said I always wear my seatbelt.
The factory add on “cage” was basically just for seatbelts is my understanding and possibly some regulations, however it is better than not having one.
@jfrench has a nice cage in his bj74 that would be great to follow what he did as I believe he didn’t have a factory cage either. I’m contemplating doing what he did as well for more protection.
here is my FJ55 I “rolled” years ago. Under 30mph and landed in snow. More like a flip to the top corner which put some major forces on it. I took my seatbelt off 1 minute before I rolled. If I would have had it on, I Probabaly wouldnt be here. Dove/flung down into the foot area. That said I always wear my seatbelt.
The factory add on “cage” was basically just for seatbelts is my understanding and possibly some regulations, however it is better than not having one.
@jfrench has a nice cage in his bj74 that would be great to follow what he did as I believe he didn’t have a factory cage either. I’m contemplating doing what he did as well for more protection.
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- #10
Thank you all for your advice. I'm seeing 2" .120 as the minimum for a properly designed and triangular braced low speed roll bar or medium speed cage. Without standard triangle tube bracing I would compensate to some extend with .25 wall and .25 plate gussets as long as not too obtrusive with perhaps a large backing plate under the body where it is less obtrusive. Perhaps bolt the backing plate through the sheet metal braces, or weld another body mount and a bolt the backer to the frame with rubber between.
bilt4me- You said "If you have a ROPS, you MUST have and use restraint systems or they will act as a guillotine. " What is a ROPS? I have no Idea what you're talking about here.?
bilt4me- You said "If you have a ROPS, you MUST have and use restraint systems or they will act as a guillotine. " What is a ROPS? I have no Idea what you're talking about here.?
FJBen
SILVER Star
A nicely built cage that still works with hard top.
ROPS = roll over protection system.
ROPS = roll over protection system.
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- #12
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- #13
Nice rig! that's alot of steel around a highly customized rig. I'd like to do the external cage type system 3 loops of 2" from the frame railes and around the body with a rock slider in between with perhaps 1.5" between over the wheel wells. It's just that it's overkill for what I want to do and I want something soon as opposed to doing without until I'm ready for the full deal.
2fpower
SILVER Star
Yes, it is attached to DOM going down the roof and attaches to the A pillar and a cross bar across the top of the windshield.
Builds - Father, Son, and the Unholy UTE
Got 90% of the main hoop welded in. My plan is to close it in next then come back and finish the roll cage.
forum.ih8mud.com
This pic shows the welded sections before they pushed forward in the pockets to meet up with the A pillar.
pistonpete
SILVER Star
Yeah steel roofs don't do much. This is why I have a roll cage in my 40... Broke my neck on this one !
Not a Cruiser, but....
Not a Cruiser, but....
For your reference, post #22:
Internal Rollcage pics?
1/2 way there in that it has some triangular cross bracing. I'd also add some diagonal stays going down the sides from above the seats to the tops of the wheel arches. Clint That was the initial plan, but it takes up so much usable storage space, in luie of the rear stays I am eventually...
forum.ih8mud.com
And thanks, @FJBen
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- #17
Thankyou, his cage looks nice. I"m going to do something before I wheel anything hilly where I might roll.
WarDamnEagle
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As others have more or less said, I think installing nothing is better than installing a hoop with no forward or rear angular bracing. You don't necessarily need a full cage but you should at least replicate something similar to an FJ40 roll bar with 4 points of contact to the tub/frame. Otherwise I think it's just a heavy guillotine awaiting a victim.
