2013 NASCAR roll cage

[DanStokes]

Bill makes a good point. The mass to be decelerated and the location of that mass makes a huge difference. Also, the distance over which that deceleration occurs matters greatly, so adding even an inch or two to the crush zone helps. Many have pointed out that even lower speed crashes result in greater body damage than in older cars, which is true. The manufacturers now allow the car to fold up over a greater distance to reduce the shock load on the occupants.

Dan

[Bill McGuire]

g is a potentially misleading indicator of crash impact force. You could rig up a load cell and beat on an anvil with a hammer and record some amazing g numbers, but your forearm doesn't shatter. The tremendous reported g numbers from F1 and IndyCar crash data recorders are sorta like that.

The tiny metal ball inside an accelerometer can decelerate at these fantastic rates, but the human body doesn't. The belts stretch, the torso distends, the neck snaps, etc etc etc. Survivability is provided by allowing the occupant to ride down the impact over a time/distance. We're looking at the entire crash pulse over a period of milliseconds, not just the initial spike.

One interesting thing about NASCAR is historically, you kinda have two different cars in the same package. When a car goes in rear end first, you have this huge, beautiful crush volume and a nice long, gentle crash pulse. A front-first impact could be a different matter.

[Bill McGuire]

LSR now requires either a funny car style cage or a full containment seat so the driver's head stays inside no matter what, along with a HANS to keep the head from snapping fore and aft. Surprised that the NASCAR cage doesn't have that but maybe the seat is full containment. The windshield (Earnhart) bar and the diagonal brace to keep the cage from folding sideways are great ideas. Not opposed but I'm not sure I get the double halo bar - more explanation, please.

Dan

I presume 360 degree visibility is a consideration, which would be a definite handicap with an FC-style cage.

Naturally, HANS is mandatory in NASCAR.

Upside down in the Big One at Daytona or Talladega, the car is essentially leading with its halo bar.

If you have questions you would like to pose to NASCAR engineers and fabricators directly, you can post them at MCG. There are a few looking in.

[SuperBuickGuy]

so my rememberer isn't working so well

here's the wiki on g-force survivability
Horizontal axis g-force

The human body is better at surviving g-forces that are perpendicular to the spine. In general when the acceleration is forwards (subject essentially lying on their back, colloquially known as "eyeballs in"[13]) a much higher tolerance is shown than when the acceleration is backwards (lying on their front, "eyeballs out") since blood vessels in the retina appear more sensitive in the latter direction.
Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes without loss of consciousness or apparent long-term harm.[14] The record for peak experimental horizontal g-force tolerance is held by acceleration pioneer John Stapp, in a series of rocket sled deceleration experiments culminating in a late 1954 test in which he was clocked in a little over a second from a land speed of Mach 0.9. He survived a peak "eyeballs-out" force of 46.2 times the force of gravity, and more than 25 g for 1.1 sec, proving that the human body is capable of this. Stapp lived another 45 years to age 89, but suffered lifelong damage to his vision from this last test

and googling says that the highest survived is 179.8 times the force of gravity.

[chevy3100truck]

Cool

I wonder if they'll ever change the rules so the cars will go faster - specifically, a body can only decellerate at 19g (IIRC), so making the cage so it appears unscathed isn't the entire story, there would need to be specifically designed structure that keeps the body from decellerating faster then is survivable.

to put my question another way, your organs can move in your body, and, with testing done in the 50s, we've learned the maximum speed a body can stop and still survive (all of this done with rocket sleds in New Mexico). I'm wondering when that knowledge will be applied so that racecars can go faster, with the same level of survivability that the drivers have today.

They changed the way the front clips on the cars were built in the late 90's to collapse more to help with crashes, not sure if they've done anything since. Nascar (and F1) have recorded impacts with 100g plus figures on crashes, no idea the exact number translated to the driver (ie. the measuring device is solidly mounted, the driver will move a bit - hopefully not much)

[DanStokes]

LSR now requires either a funny car style cage or a full containment seat so the driver's head stays inside no matter what, along with a HANS to keep the head from snapping fore and aft. Surprised that the NASCAR cage doesn't have that but maybe the seat is full containment. The windshield (Earnhart) bar and the diagonal brace to keep the cage from folding sideways are great ideas. Not opposed but I'm not sure I get the double halo bar - more explanation, please.

Dan

[SuperBuickGuy]

Cool

I wonder if they'll ever change the rules so the cars will go faster - specifically, a body can only decellerate at 19g (IIRC), so making the cage so it appears unscathed isn't the entire story, there would need to be specifically designed structure that keeps the body from decellerating faster then is survivable.

to put my question another way, your organs can move in your body, and, with testing done in the 50s, we've learned the maximum speed a body can stop and still survive (all of this done with rocket sleds in New Mexico). I'm wondering when that knowledge will be applied so that racecars can go faster, with the same level of survivability that the drivers have today.

[Barry Donovan]

playing with injection... I coulda guessed some resonance bars.

the cages have been strong for decades as mentioned.

I like steel added in anything..the good enough days are challenged with intricate pulse width driven crystal clocks...if they only treated the tortured carb cars like that. damn.

[Bill McGuire]

Here's a little story with nice, clear photos showing the rules-mandated changes to the NASCAR roll cage for 2013.

MCG exclusive! 2013 NASCAR roll cage | Mac's Motor City Garage

The idea was this might be a decent item to generate thought and discussion about roll cage design, materials, and fabrication, not necessarily for NASCAR but anything using the same general construction.