Crush Box

[Frank]

I had a chat with an official at the aussie comp about crush boxes.

What do you think of this idea?

SAE specifies energy absorption of the crush box.
You crush one, and bring the resulting item and test data. For example:

http://www.uq.edu.au/fsae/Crush_Box_Test_Results.pdf

[Frank]

I had a chat with an official at the aussie comp about crush boxes.

What do you think of this idea?

SAE specifies energy absorption of the crush box.
You crush one, and bring the resulting item and test data. For example:

http://www.uq.edu.au/fsae/Crush_Box_Test_Results.pdf

[Tony K]

We have to do that every year for our safety equivalency report due to our carbon fiber monocoque. Last year we actually brought a tested crush zone to competition and the judges initially didn't like our design, but after showing them the data and test piece, they changed their mind.

[Sparky]

Well we managed to give a practical demonstration of just how well our crush zone worked on the first day of comp. Although I wouldnt recommend destructive testing at comp, can be kind of hard to pull together the resources for repairs.

Thanks must go to Swinburne University for providing us with one of their old crush zones and use of their workshop space.

[James Waltman]

Frank,
You're talking about what the rules call the Impact Attenuator (3.3.6.2) right? I think you have a good idea. However, energy absorption is only one aspect of what the attenuator is supposed to do.

I may have gone a little overboard when I explained some of this stuff before in a different discussion. (http://fsae.com/eve/forums?a=tpc&s=763607348&f=125607348&m=85510167411&r=85510167411#85510167411)If you read through it I won't have to repeat myself here.

Sorry, but your example graph is really bad. Is it from a computer simulation? Could you explain it a little bit about how you came up with it?

[Frank]

it is from a "instron" testing machine www.instron.com (http://www.instron.com)

load (kN) vs displacement (mm)

in your previous post you talk about abtaining 30g rundown,

ours seems a little soft (like a factor of 10) at 10g peak, and 3g rundown

[PatClarke]

Hey Frank, I have a better idea.
How about at the end of the event we have an impact attenuator shootout...Mano e mano, head to head(on) at 30 paces.
We could sell tickets to that!
Pat

[Nate Notta]

... so as it is now the only incentive to have a 'safe' impact attenuator is to avoid criticism from the judges?

[Frank]

seriously though pat,

they should put some more technical guidlines in the rules about this
(guessing)

10000 Joule min absorption

100 g max spike
30 g suggested rundown

[Travis Garrison]

I don't know about 100G spikes, isn't 60G's ~the survivable limit for the average person? Spikes are bad mmmkay....I don't know how well it would work for box style crush zones, but pre-crushing honeycomb should take care of the spikes

I think that really you should have to prove that your car is designed to be survivable from 5-10mph below average enduro speed to 0mph in a head on collision. 40G's, 15G's, whatever...provided your crush box is the right size for your ride down rate.

Seriously, did they let you through with a 3G crush zone? if so some one was asleep on the job...

-Travis