HoneyComb Attenuator - Dangerous?

[SpdRcr]

We have tested a couple different IA's. Aluminum honeycomb was one of the IA's we tested. It passed, but this was in an ideal situation; not an off axis crash.

We feel the aluminum honey comb would be basically useless in any real life crash.

What are your thoughts on this? And if you do use the aluminum honeycomb, do you feel this is almost like a loophole in the requirements to allow you to run the lightest possible IA?

We like to keep safety in mind for our program, so we may accept the extra 2 pounds for our other IA.

[Kyle Walther]

why do you feel that the honey comb is useless in a real life crash?

[Landreneau]

Pretty much the IA is only good for a head on impact. Any other situation it will most likely just shear off.

[Erich Ohlde]

not trying to dis on the competition, cause I think it is awesome that we are supposed to think about safety, but how many autocross cars have head on impacts? We use titanium core for our IA, haven't tested any off axis energy absorbtion tho.

[SpdRcr]

From my intuition after handling the aluminum honey comb, it would be basically useless in any collision that wasn't perfectly head on with a flat surface.

It would puncture and shear very easily.

While our competition, and AutoX in general, doesn't involve collisions, shit does happen...

Just wanted to hear some other thoughts and opinions. Thanks.

[Kyle Walther]

in real life what are the objects you would most likely hit on an autocross course.
curb: too low for most peoples placement of the IA.
Light pole: relatively flat or round but the IA would have a good surface to push against.
other formula cars: few flat surfaces any IA would not fair to well unless a flat surface is contained within the IA to equalize pressure.
other cars: to high, mostly avoid these.

if you draw up a light pole which is the one i'm most afraid of, and imagine an off axis crash the IA will only be impacted partially before it deflects the car which is better than a head on. So if your IA can deflect the car enough to avoid a head on with a light pole then be happy it just tears off your suspension. which when you think about it is your side IA. So if they are really worried about off axis then they should have more requirements for a-arm anti intrusion.

thats my 2 cents anyway

[Alexandre D.]

The danger is the zone between head on and enough angle to slide.
Honeycombs are HIGHLY dependent of orientation. We've tried a unidirectional carbon fiber structure last year. The specific crush strength was nuts... But as soon as the load was not applied directly in the fiber direction, catastrophic failure would occur. I guess that metal honeycomb is less prone to this kind of failure.

Aluminum foam is a good solution. A bit heavier than honeycomb(around .6-1 lbs) but very isotropic.

[Kyle Walther]

If you design the shape of the IA correctly you should be able to minimize the zone where this occurs. And yes you can not just use "unidirectional"� honeycomb without something to redirect the force either towards your crush material or away from your vehicle. There are a variety of Al. honeycombs out there than just the plain "unidirectional" kind. Obviously no mater what crush material you use it has to be a good design in order to work correctly.

[NetKev92]

In one way, this is deadly serious, but in another it's very ironic and funny. You can add all the crash protection that you want to any side of the car you want. It will add weight. Most teams probably won't do it.

The contest rules are blatant in their intent. They are meant to keep the cars moving slow in most cases. Passes are monitored and governed to prevent close combat type maneuvers. The light pole, hay bale, or spin-out accidents at modest speed are your biggest risks. In a spin, the car should lose speed quickly so the odds of high speed impact on the sides are low. I'm with the other posters here in that I'd be most afraid of the lightpole or other fixed objects taken head-on with highest acceleration from speed to zero.

Me, I'm all about crush zones. I'm adding un-necessary weight to my personal project because a streetgoing car may need to worry about side impacts:
http://www.cardomain.com/ride/2276782