Opinions on a roll cage

[ScottyP]

I'm looking for a 6 point roll cage and builder planned to put this one in. Does it seem a bit skimpy or will it get the job done if I flip my Bronco on the freeway?

 

[Bferrari]

Looks like it needs some geometry. Remember, strength comes in angles. Add some bracing and you should be fine.

 

[Digger556]

I'm looking for a 6 point roll cage and builder planned to put this one in. Does it seem a bit skimpy or will it get the job done if I flip my Bronco on the freeway?

Yes, that is weak. Triangular routing makes for strong cages.

Look at Federal Motor Vehicle Safety Standard 216 (FMVSS 216) THis is how new vehicles are judged for roll-over crash resistance. There is considerable force placed on the A-pillar during a highway rollover. Upwards of 4x the vehicle weight.

 

[Apogee]

That's a good starting point, but more triangulation would certainly help. I can't tell from the picture, but it looks like 2" tube, whereas others will generally use some combination of 2, 1.75, and 1.5 inch tubing. Wall thickness and material (DOM versus HREW) count for something as well.

As for holding up if you flip on the freeway, is that the level for which you're going to design your EB? Low-speed rollovers are one thing and high-speed rollovers are something completely different. If you really want to avoid ending up on your roof on the freeway, lower your rig's center of gravity and add sway bars and springs/shocks for street use, not off-road, otherwise everything is a compromise.

 

[DC_Gearhead]

Yes, that is weak. Triangular routing makes for strong cages.

Look at Federal Motor Vehicle Safety Standard 216 (FMVSS 216) THis is how new vehicles are judged for roll-over crash resistance. There is considerable force placed on the A-pillar during a highway rollover. Upwards of 4x the vehicle weight.

That roll cage is sweet. Did you build that?

 

[Casey4wd]

Looks like it needs some geometry. Remember, strength comes in angles. Add some bracing and you should be fine.

View attachment 398981

Bferrari - Who built your cage? I like that design.

 

[Bferrari]

Bferrari - Who built your cage? I like that design.

I built it myself. The design was inspired by the cages built by Nickstrix for their custom builds. My goal was to have a cage for safety but I didn't want to feel like I was driving a race car or a rock crawler (nothing wrong with them but wasn't what I am trying to achieve with my build). I was able to get the tubes really tight up front so you don't really realize they are there and it minimalizes the obstruction getting in and out of the vehicle. Here are a few more pics of it. You can see more on my build thread.

 

[marjama]

Digger...did you create the 3D model of the body or download it from somewhere?? Any chance it is something you'd share? That would be super useful...

 

[ScottyP]

That's a good starting point, but more triangulation would certainly help. I can't tell from the picture, but it looks like 2" tube, whereas others will generally use some combination of 2, 1.75, and 1.5 inch tubing. Wall thickness and material (DOM versus HREW) count for something as well.

As for holding up if you flip on the freeway, is that the level for which you're going to design your EB? Low-speed rollovers are one thing and high-speed rollovers are something completely different. If you really want to avoid ending up on your roof on the freeway, lower your rig's center of gravity and add sway bars and springs/shocks for street use, not off-road, otherwise everything is a compromise.

I live in Florida and the majority of cars and trucks Ive seen upside down have been on the freeway so I guess when I picture my role cage doing its thing that's what I picture.

 

[Mountain Ram]

For starters- most any cage is better than none in a roll. With that said- triangulation is important in a reliable cage. My crawler's cage has way more triangulation than my street rig. The street rig is more likely to have a higher speed roll, but my crawler is more likely... OK- will definitely end up on its top at some point (I suck at driving off road- too much stupid pedal!). You can see the differences below. My green street rig is very similar to the cage you posted except I added crossbars for seat mounts and one behind the seats to mounr 5 point harnesses to.

So- what are you going to do with your rig? Mostly street- that cage you showed will be added protection over a single bar or just a hard top. Jeep cages are thin, bolted to the body and not triangulated at all... yet they survive highway rolls...

Don't skimp- buy the best you can afford.

 

[Digger556]

Digger...did you create the 3D model of the body or download it from somewhere?? Any chance it is something you'd share? That would be super useful...

I made it. My build was so extensive, I needed a full Bronco model to understand how everything fit together. (It's still not quite done) Normally I share a lot of my work, but some of the CAD I'm hanging onto due to commercial potential I'm working on. I do have some parts of the model you can download at:
https://grabcad.com/digger-3/projects

That roll cage is sweet. Did you build that?

I did. Wife took the kids to the inlaws, I banged out 50+ hrs of work in 3 and 1/2 days. I'm very happy with the results. Aside from the added safety, the truck as a whole is more rigid. Even steering response is better.

 

[Mountain Ram]

.

My friend- you have talent!! This is really cool!

 

[Digger556]

My friend- you have talent!! This is really cool!

Thank you!

 

[68stang73]

You want to build mor cages there Digger?

 

[sykanr0ng]

You want to build mor cages there Digger?

Wait until you see the plates he made for the front legs.

A full cage with a working glove box and parking brake, without moving them.

 

[gddyap]

Triangulation is good but nodes are important too. Nodes are where the end of tubes meet other tubes and support each other. I'm not sure what all the fit constraints that marjama was designing under but I think these changes would improve the strength of the cage and remove a tube.

 

[68stang73]

Let's see it man

 

[Digger556]

Triangulation is good but nodes are important too. Nodes are where the end of tubes meet other tubes and support each other. I'm not sure what all the fit constraints that marjama was designing under but I think these changes would improve the strength of the cage and remove a tube.

What you are looking at is a preliminary model. If you look at the final version

you can see that I replaced that tube with a plate gusset that is located closer to the "node". That triangle area becomes the whole node and is quite strong according to the CAD FEA analysis. Those C-pillar bars must be angled in slightly to provide strength to the A-pillars since a family cage lacks B-pillar X-bracing. If you look at it from overhead, the bars form an arching "X". The angle of the C-pillar bars is a trade off between rear passenger room and cage strength, but I tested the model is a variety of scenarios and
it should take a 4G hit in the worse case with less than 2" of deflection at the A-pillar. It is a little hard to quantify because force is being dissipated as the cage is deflecting. A lot of crash data shows that the 3.5-4G's experienced, only happens for a fraction of a second. Without crashing the truck(s), it would be impossible to say exactly how it would hold up.

That brings up a good point. This is a family street cage designed to survive a handful of rolls at highway speed through strength and controlled deflection. Most low-speed rock crawling situations are far less demanding. Only full-blown high-speed racing would potentially place greater demands on the cage that would require B-pillar X-bracing, helmets and 5-pt harnesses, but I'm not doing that with the family. ;D

 

[68stang73]

I still want one. How much?????

 

[marjama]

I made it. My build was so extensive, I needed a full Bronco model to understand how everything fit together. (It's still not quite done) Normally I share a lot of my work, but some of the CAD I'm hanging onto due to commercial potential I'm working on. I do have some parts of the model you can download at:
https://grabcad.com/digger-3/projects

I totally understand...I'm sure a lot of work went into making the models! Can you talk about how you built it? Are you using a 3D scanner? Or ???

Thanks!