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Wed Apr 29, 2009 8:13 pm

He had a load of .095 DOM dropped off today. The old roof was .095 EWT.
Are you saying this is stronger than the hoop design going side to side? Having one piece front to back, one each side, and then just connect with straight pieces across?

Wed Apr 29, 2009 8:51 pm

I'm no expert but I would think 1 piece bars going from front to the rear along each side of the compartment area would be stronger, someone chime in who knows this stuff. It looks like your friend smashed his frame in the one direction a berrin is probably weakest, pushing the windshield hoop backwards.

Wed Apr 29, 2009 9:46 pm

I think you need to look at what kind of driving your going to do. I bet that car would have held up in a roll over like on flat ground or small hill.

Wed Apr 29, 2009 10:13 pm

there are a lot of ways to built A pillar bars and Halos. even sanctioned racing bodies like SCCA accept a wide number of designs in the area. so leg style, halo or A pillar hoop. in this case (like Caromin said) a leg type or a Halo would probably hold up the best. i mean the A pillar hoop design obviously didn't work out.

umm im going to go into dick mode here for a second :lol:

is your friend honestly going to put the same material in place of the old? seriously? DOM or not the issue was not the seam failing it was the tubing. it was a mix of design and inadequate wall thickness DOM is not going to change a whole lot.

but if its what he has lets work with it. . . .

Wed Apr 29, 2009 10:47 pm

ok here's my proposal.

if your friend is going to be working with .095 1.5" then we have to go a little bit over kill.

for starters see if its going to be feasible to lower the roof at all, it looked like a pretty tight fit but the shorter we can get those bars the better. see if you can maybe drop the seats down.

secondly as proposed a A pillar leg would probably work out better in this case.

remember to keep everything you can in plane, you dont want anything sticking out thats not going to transfer load in a compressive manner or provide any amount of leverage on the cage.

IE like this.

when you have your roof bars that far in you provide a leverage point that will allow the cage to fold it instead of transferring load through the cage. same goes for bent roof braces, they allow for easier access to the car but they are notoriously weak.

as for the triangulation that was missing in the frame, we need to stick it in a few areas. for starters you want to fab up a SINGLE rear hoop, i dont know whats up with that dual tube deal but it certainly looked a little "backwoods" to me. kind of like a bolt in chrome roll bar for a truck :wink:
brace the rear hoop from the corners, and make sure the braces are in line with the roof bars (load transfer is key) and make sure that the braces go as far back as possible. to ensure that if any load is transferred to the B pillar hoop the stress on the braces will not be leverage loads, but compressive.

the halo should be fully cross braced with a X. corner to corner. also make sure that you get them fully in the corner and no off on one bar or another, smack dab in the middle. same goes for the B pillar, full X corner to corner. now the problem with this brace is that you might not be able to go all the way down to the torsion housing and you will have to settle for tieing it into where the upper frame rail and the B pillar hoop meet.

now here is what you REALLy need to do to avoid another cage collapse like this one.

the A pillar leg brace is going to be a pain, it will make it harder to get in and out of the rail but its the piece that will keep the roof up. its the piece that will really prevent the lay back like before. you could have had all the bracing in the world in the B pillar hoop and the roof with no A pillar brace and you would have gotten a very similar out come from the roll over.

Thu Apr 30, 2009 9:02 am

It looks to me kind of like the welds at the windshield hoop failed. look at the roof bars everyone is claiming failed due to being bent not straight. if this was the case they would be warped and bent back. they look fine. I think the welds may have given where it joind the hoop. a gusset there may have helped abit, and a heavier guage on the windshield loop due to the inherent weakness of a windshield loop RLAP mentioned.

Thu Apr 30, 2009 9:39 am

RLAP's cage design works, except the second downtube needs to be supported on the other side down to the frame. The x-braces in the roof and rear hoop are nice.

I would also add some triangles to the upper corners of the windshield frame, as well as some uprights behind the driver since its a 4 seater and the distance between the A and C pillars is pretty long. Make sure that any bars that can possibly come into contact with ANY occupants' head are covered in SFI foam padding.

Make sure to build the windshield frame large enough so that the overhead bars don't need to be bent.

The main hoop should be one continuous piece with no more than 4 bends going from left to right. The forward hoops should go straight out from there down to the front of the car, with a cross brace between them to make the top of the windshield.

Lastly:

WEAR AN EFFIN' HELMET MAN! There is NO reason ANYONE driving a vehicle at speed for recreational purposes should NOT be wearing a helmet, especially with all of those unpadded bars near your head. NONE! I wear a helmet driving 3 minutes down wash road to get a camp pass. Takes seconds to put on and will literally save your noodle.

Fusername: if you look at the pictures before and after, you'll see the roof bars are now almost straight. This is what allowed the windshield frame to collapse so much. After they became straight, they stopped allowing the windshield frame to collapse because the roof bars would need to start stretching for the windshield frame to move any farther away. It's really easy to bend tubing, but its really hard to stretch it.

BTW, read the roll cage section of this:

http://www.nasaproracing.com/rules/ccr.pdf

Thu Apr 30, 2009 11:47 am

Also gussets help connections from wanting to rotate during failure.

like the two on the back of my car I still neet to add more to the front to keep the windshield from folding back like that.

By kbwakesk8 at 2008-12-01

I built a cage for my neighbor ranger We put in a back seet. His brother rolled 4 times down a hill with his wife and 3 kids. I gusseted all the corners like the picture above and every one was ok. It was only .095 wall. cage didn't bend.

I used alot of sprint car desighn in my cages.

Thu Apr 30, 2009 11:56 am

here are a few solid works stress tests of various intersection points with gussets.

Thu Apr 30, 2009 12:25 pm

HILLAHOLIC wrote: He had a load of .095 DOM dropped off today. The old roof was .095 EWT.
Are you saying this is stronger than the hoop design going side to side? Having one piece front to back, one each side, and then just connect with straight pieces across?

Man after walking away from this one, I would take the .095 back and build with .120!.......

Dale

Thu Apr 30, 2009 12:49 pm

.120 all that way.

Thu Apr 30, 2009 1:23 pm

fusername wrote: It looks to me kind of like the welds at the windshield hoop failed. look at the roof bars everyone is claiming failed due to being bent not straight. if this was the case they would be warped and bent back. they look fine. I think the welds may have given where it joind the hoop. a gusset there may have helped abit, and a heavier guage on the windshield loop due to the inherent weakness of a windshield loop RLAP mentioned.

No welds failed. The roof was bent into the steering wheel and we had to hacksaw it and bend it up so we could drive the buggy back to camp.

Thu Apr 30, 2009 3:36 pm

Yeah I'd sacrifice the weight and go with .120 also

Thu Apr 30, 2009 4:06 pm

There is also no lateral strength with the windshield. If you look closely, the windshield went laterally. That can be fixed with some 45 degree pipes or plates at the bottom of the windshield. Because of the curve at the top, I don't think it will help much. The "X" in the roof will help the top of the windshield area from folding. The force will be pushed to the opposite side and most will be dispersed.

Thu Apr 30, 2009 7:21 pm

are there any photos from the side after the roll over? all the ones here are after you hacksawed it, something I didn't notice at first I thought the roof had gone that far down on the roll, was shocked he walked away.

still nothing to laugh at.

Thu Apr 30, 2009 8:11 pm

fusername wrote: are there any photos from the side after the roll over? all the ones here are after you hacksawed it, something I didn't notice at first I thought the roof had gone that far down on the roll, was shocked he walked away.

still nothing to laugh at.

Sorry that’s all I took. Now I wish I would have taken more angles but at the time we were just trying to get stuff done, get back to camp and check on Bill.

This is before we cut it. This was about 5-10min after the roll.

We broke his high lift trying to bend it off the steering wheel. We actually cut about 2' out on the driver side just so we could steer it. If you look closely you can see the front hoop cuts. It was actually lower than this before we cut and bent it as much as we could.

Thu Apr 30, 2009 8:13 pm

i am not a cage builder. i go by what i hear and see. i raided runslikeapenguin's photo gallery and found this car. you see it has V bracing in the windshield, the diagonal coming from the A post goes all the way down to the pan and i have seen runslikeapenguin critique a baja cage that the roof had been removed. i remember him saying that the B post needed to be behind the drivers seat on convertibles because there is no roof to help. my .02. this is a very powerful car and woodsbuggy guys take their cars to the extreme sometimes. woodsbuggy technology is different but simular to the technology the guys in the sand use. i bet you alot of woodsbuggy guys as well as sanddudes are looking over there rides to prevent this from happening to them. i have seen woodsbuggys flip over backwards on videos. they start them up again and try the hill again.

you might say this is a extreme racing machine, but driving straight up the side of a mountain/hill in a hotrod rail is pretty extreme.

Thu Apr 30, 2009 9:08 pm

Holy snikes! You've got me worried now with my Berrien Sandfox 4 frame. Mine looks like it woud be pretty vulnerable too.

Oh ya, And the fat guy with his shirt off. Tell him to cover up, that's freakin gross. I have to go and throw up now.

Thu Apr 30, 2009 9:22 pm

riNR wrote: Holy snikes! You've got me worried now with my Berrien Sandfox 4 frame. Mine looks like it woud be pretty vulnerable too.

Oh ya, And the fat guy with his shirt off. Tell him to cover up, that's freakin gross. I have to go and throw up now.

Watch it now. The guy with his shirt off is my friend Dave (DVS1). He took his shirt off to try to stop Bills head from bleeding.

Thu Apr 30, 2009 9:36 pm

HILLAHOLIC wrote: riNR wrote: Holy snikes! You've got me worried now with my Berrien Sandfox 4 frame. Mine looks like it woud be pretty vulnerable too.

Oh ya, And the fat guy with his shirt off. Tell him to cover up, that's freakin gross. I have to go and throw up now.

Watch it now. The guy with his shirt off is my friend Dave (DVS1). He took his shirt off to try to stop Bills head from bleeding.

was his head bleeding before the crash? :?