Roll cage half laterals...

So I have noticed something in the past couple years on a few builds, >2 bends on half laterals.

I first noticed it on Derik's BMW but also saw it being done on another build the other day.





Here's Jason's car that I saw it being done on...
http://2.bp.blogspot.com/-iTeRuHSmu94/UoAsFX-z9mI/AAAAAAAAF0Q/VTygVfyR0s4/s1600/DSCN0634.JPG


I suppose it doesn't say that you can't have multiple bends in the half laterals in FIA 253 or NRS rules and it does allow for a tighter fit to be possible. There's something I don't like about it though I can't quite figure out what it is...
Thoughts?

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Grant Hughes



Edited 1 time(s). Last edit at 11/11/2013 01:37PM by NoCoast.

Another thing I keep seeing, mostly out of Jackson Rally and Northern California is this configuration for W/S upper. Again, something I don't like about it but have never been able to articulate. Aside from being outside of FIA 253 that is...
http://i28.photobucket.com/albums/c228/Baker1120/Sunroofpatch.jpg

http://i198.photobucket.com/albums/aa15/Jackson-Rally/Dave%20Foreman/PICT0573-1.jpg

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Grant Hughes



Edited 1 time(s). Last edit at 11/11/2013 01:42PM by NoCoast.

Edit: Are you talking about a 2 degree bend? I think i see?



Edited 1 time(s). Last edit at 11/11/2013 02:08PM by czwalga.

Greater than two bends. There is a slight bend before the a-pillar downturn.

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Grant Hughes

Quote
NoCoast
Another thing I keep seeing, mostly out of Jackson Rally and Northern California is this configuration for W/S upper. Again, something I don't like about it but have never been able to articulate. Aside from being outside of FIA 253 that is...
http://i28.photobucket.com/albums/c228/Baker1120/Sunroofpatch.jpg

What part of FIA 253 do you think that's violating?

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Self-righteous douche canoe

Quote
hoche

Quote
NoCoast
Another thing I keep seeing, mostly out of Jackson Rally and Northern California is this configuration for W/S upper. Again, something I don't like about it but have never been able to articulate. Aside from being outside of FIA 253 that is...
http://i28.photobucket.com/albums/c228/Baker1120/Sunroofpatch.jpg

What part of FIA 253 do you think that's violating?

Not so much violating, but a bit outside intent. Not that my opinion matters...

8.2.8 Transverse member :
Near-transverse single piece tube joining the upper parts of the lateral half-rollbars or of the lateral rollbars

8.3.1
In order to build the safety cage, the connections of the transverse
members to the lateral rollbars, the connections of the longitudinal
members to the front and main rollbars, as well as the connection
of a semi-lateral rollbar to the main rollbar must be situated at the
roof level.

It's never been clear if the FIA rules allow bars that are not listed in the "Optional Members" section either.

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Grant Hughes

We use the FIA template as a minimum. Extra can be added as long as it makes sense and is not obviously a danger, such as a bar contacting a helmet needlessly.

Small adjustments on the 1/2 laterals are nearly mandatory in reality. We need helmet room and there has to be a way to get from the door opening over to the main hoop.

Sorry, my question may've come across a little more aggro than I intended. It was just a query as to what you were looking at, not a "Defend yourself, monkeyboy!" sort of thing.

I consider that windscreen bracing to be transverse with extra bracing in the corners, and don't have a problem with it.




I do sometimes wish that people would stop "getting creative" with their cages and would just follow the damn pictures. I mean, they're right THERE. And then I get over it and go back to just asking people to *please* call for a chat before they start bendin', cuttin', and weldin'.

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Self-righteous douche canoe

I don't care for the windshield bars and they are not near lateral as the FIA requires. Seems like it is putting a lot of welded area right over the drivers face and un-gusseted junctions.

Quote
hoche
Sorry, my question may've come across a little more aggro than I intended. It was just a query as to what you were looking at, not a "Defend yourself, monkeyboy!" sort of thing.

I consider that windscreen bracing to be transverse with extra bracing in the corners, and don't have a problem with it.

I do sometimes wish that people would stop "getting creative" with their cages and would just follow the damn pictures. I mean, they're right THERE. And then I get over it and go back to just asking people to *please* call for a chat before they start bendin', cuttin', and weldin'.

I didn't think it was aggro and was very precise.
I don't have a problem with it either, except when some Subaru guy asks me to do it, which I won't. I am a non-deviator from FIA 253.

I was more interested in what people think of the multiple bends at the top of the a-pillar.

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Grant Hughes

It seems like those extra little adjustment bends to half-laterals help fit quite a bit, allowing bars to actually contact the A-pilars, and dirrectly connected half lateral/ A pillar should add a good bit of strength and deffinitely benefit the visability out the front. As long as they are less than a few degrees, I cannot see them comprimising the cage.


As we are checking the rule with a fine toothed comb, I thought the A-pillar bar was supposed to be a single continuous bar... might have been an old rule set as I cant find it now.
http://i198.photobucket.com/albums/aa15/Jackson-Rally/Dave%20Foreman/PICT0573-1.jpg

The a-pillar bar will continue down to the cage foot. Commonly done in two piece with gussets where it intersects the door bar.

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Grant Hughes

Grant, I consider those "kinks" (not bends) and required to make the cage fit tight. You really need to have one at the end of the half lateral where it attaches to the main hoop or it won't line up. Just a kink to bring it away from the roof a bit to connect up to the bend in the main hoop.
I also use a kink along the A-pillar to make the bar fit up tight to it. That way you can just stitch the cage right to the A-pillar, like in the photo of Derik's car above. That's stronger than having a huge gap, even with a gusset in it plus you can still see out the whole windshield.

Grant,

Quite seriously, referring to the first pix posted, those small degree bends have no significant effect on the strength of the tube or of the cage, either in overall strength or localized impact strength. Any effect that they might ever have is 'way down in the noise' of the impact stress that the cage has to deal with. Particularly in the A-pillar area nowadays, with the A pillar support tubes, there is ton of redundancy in strength members and mutual bracing of those parts.

Similarly, small bends in the top of the main hoop, windshield header bar, and the half laterals over the door openings are inconsequential. The tubing wall thickness is essentially unchanged in such small bends. And we tend to use tubing sizes with quite adequatae safety margins in these shop built (non-engineered) cage rule sets.

For the 2nd set of pix (Jackson), I see why you're thinking what you are thinking, but my only complaint is that the braces by the helmets are joining the half lateral too far forward and might compromise helmet clearance. I would have them shortened by some inches. Having them join so far forward on the half leteral is not necessary for these braces to fully perform their main function. (Limit roof area collpase to forward of the the helmet area.)

The overall design of that whole forward half-lateral and transverse member area does all that is needed and does it quite well: support the header tube (it does the is the least best of any of the required functions that I can see), transfer forces across the WS area from one side to the other, and provide a good anchor point for the roof bracing to further assist that transfer of force. It is well braced and has the benefit of using a tubular gusset (reeeeeally good and strong, far better than a standard gusset) and is still easy to weld and inspect. It has most of the good attributes of a halo hoop with proper tubular gusset and gusset angle, and ends up with a better approach angle of the A pillar tube to that corner than many halos.

But, hey, it is good to be thinking about and questioning such things.

Regards, Mark B.

If tubular braces were so good, don't you think we would see them used and required more places? There are some smrat people who suggest that the transfer all ones to one area--where they are....rather than distribute loads over much more area....but what do I know? Only been watching progressive development of 50 years of the best ideas of very strong and light tube structures...aside from that I don't know shit.

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John Vanlandingham
Sleezattle, WA, USA

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