Cage Through B-Pillar OK?

I am not an engineer.

In the first cage, I don't like how far away that main hoop is from the A-pillar legs, and I don't like how steep of an angle that A-pillar bend is at the windscreen. In a rollover that hits hard near the top of the windscreen, I see that flattening (draw a straight line from hoop to the dash, essentially). An extreme scenario, but with the current design as pictured that's a cavernous space between the main hoop and the A-pillar. That cage DEFINITELY needs an FIA bar, IMHO. Not sure what else it's called, but one that runs from the roof joint of the A-pillar/windscreen node straight down to the A-pillar foot plate. I also would like to see it triangulated from the roof bar at about the B-pillar down to the top doorbar node at the hoop, like in the red car pic by a larger triangle like FIA rally cars.

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But again, I'm not an engineer and am just blabbing based on what I've seen from other cages and my own beliefs of how tubes could behave in impact situations.

The idea to plate the B pillar holes and then weld them to the tube seems like when you do the circumference weld of the middle of the tube where it passes through, aren't you potentially introducing a weak spot for sheer forces (which is essentially what you want the door bar to resist-- the sheer forces from a forced intrusion)? I know in the Prius I caged and while I was researching it (there's a first responders publication from Toyota on the Prius),the B pillar is made of a different steel alloy (more boron??) as is the roof rail area and is supposedly tougher than traditional construction materials and may not react to extrication tools the way they anticipate, and alternative entry points are offered. Anyway, the whole point of that statement is you may not need to worry about the holes in the B pillar if you choose to punch through there.

I have no answers. Just questions to consider. It's all a tradeoff. You and your car's occupants will have to be happy with which way you choose to bias your decision making and cage design.

[made some edits for typos and clarity]

http://forums.24hoursoflemons.com/viewt … 45&p=2

Do you have room to go outside the B pillar?

I'm not sure all inspectors would pass a B pillar with holes in it for the cage. Might depend on how good the cage is. Before you potentially ruin your car you should email teo with your plans.

As for the door bar with the return bend, it's not ideal but depending on its design it may be better than a straight bar impact wise. It likely depends on the design though. I'd love to see some aftermath, testing, or simulation of a return bend door bar. Something I've been wanting to do in solidworks to see what happens.

Definitely clear your plans with John the Tech guy mentioned above...  That said the 4 door E34 my team brought to the Joliet 24HR race had door bars through the B pillar - the car passed tech with no issues.  YMMV of course...

"Ruin your car" lol..... Lemons, remember?

The white car pictured has a sweet cage. Way better than any cage I've seen in Lemons for sure. Having bars through the B like pictured is WAY stronger than the S bend and increases stiffness - to do over I would do it that way. Also, and perhaps as important, it increases the crush zone between you and the cage increasing your survivability.

Have you considered moving the drivers position instead?

I see nothing wrong with cage A I would rather be in cage A at hit 150 MPH then in cage B . The B pillar is not doing much but to keep the door from falling off
Bob

FWIW, I just had to cut my b-pillar in half on a Sentra, and then sorta-reconstruct it, because the nascar bar ran right through it. Of all the things I've cut off of cars over the years, this one would be one of the more tech-friendly, for sure. That said, sawzall advice from me is always questionable.

P.S. Is it just me, or the nascar bars on car #2 are supposed to be the other way around, narrow end towards your feet, so that wide end gives you more seat/elbow space/clearance? That's how I've always done them O:

Here's a crappy picher of ours: