robmug

JCP - accelerometer is on the sled...

Interesting comment re the FIA test being a minimum standard. After FIA testing, we put a Cobra Imola (entry level composite seat) on the sled then went for maximum G loading. We managed to hit over 70g and the seat was still perfectly OK.

Re flex: don't forget that some FIA seats are steel constrcuction (eg Cobra Monaco) and as such don't flex. They still have to passd the same FIA test which causes concern, as the rules are very obviously written for a composite seat (eg - seat must not de-laminate).

As above, the flex isn't a design thing, it's just what happens. You could argue that the flex then causes whiplash as it reverts to its original shape (like a spring).

Interestingly, Cobra (with whom I FIA tested) use US Confor foam which is shock-absorbing, unlike normal foam which is more spring-like. This again helps the driver.

Note - I'm not saying that composite FIA seats are better than Aluminium...I have no way of knowing - just giving some info on FIA testing.

FWIW, the FIA randomly post-homologate, where they buy (retail) a FIA seat then test it on their own. This stops manufacturers from producing "test specials", although some manufacturers have, I understand, recently had homologation withdrawn...

robmug

Finally, I agree - it's not the seat breaking that hurts, jor is it what you hit. It's how hard you hit it. At 25g, your 2kg head + helmet weighs 50gh, whicg is a lot for your spine to take. In addition, your internal organs are crushed against your rib cage.

Finally, your brain is compressed (25 times its own weight) against the skull causing bruising, swelling ...not nice.

That's why, in my view, it's not really worth getting seats to pass 50g tests - the key here being the duration of the g loading (50ms). A 50g loading for 50ms would probably kill the driver, irresoective of whether the seat was OK or not.

F1 and Indy drivers do have bigger impacts, but these are peak g loads measured by the car's accelerometers, and for very short durations - unlikely to be passed directly to the driver.

RedlineMan

Hey all;

Good stuff, as has become "our" pattern!

I would offer that it is not only the maximum g-load that a body sees that is important, but the time frame of the onset of that max load. Allowing too much movement in the restraint systems allows KE to build, where as the reduction in movement to a certain level reduces the time frame in which KE will build, and will also soften the onset of max G's.

I think one of the reasons that open wheel drivers are able to withstand such huge impacts is that their confined environment does not ALLOW that much movement.

Regarding the whipping motions that are possible, HANS says that it is this phenomenon that is most dangerous. Their testing and research has shown that the brain (for instance) can actually handle quite a large compression against the inside of the skull without causing permanent damage, as long as it is a linear impact. It is the violent twisting, snapping motion that is BY FAR the most troublesome.

This is another thought that has caused me to feel safer in an alloy seat -vs- my assumption that an FRP (fiber reinforce plastic) seat might spring back.

NASCAR had their heads buried for quite a while, but the recent spate of fatalities has caused them to get seriously involved with some of the leading experts mentioned here to improve safety. If you notice, the NASCAR cockpit has become increasingly similar to the confined cocoon of the open wheeler, and in many respects they are now leading the way in safety, or at least providing the test bed for the experts to make new breakthroughs.

Many of the NASCAR people are now giving voice to the change of thinking that has finally arrived. Through their study they have learned that too much freedom of motion in an accident is BAD, and that keeping the driver from moving too much is actually very important.

Again, it is not the movement so much as slamming into whatever there is proximate that is dangerous. Even when these items are belts, seats, it is the sudden impact that is most dangerous, as this not only creates a very sudden g-load spike, but a change in direction as well. All this has led NASCAR to realize that it is actually safer to keep the driver from moving much at all than to take the chance of slamming into something, belts and seats included.

I must say that this has caused me to rethink my position that all flex is good! It clearly seems not to be the case.

Geo

Yes indeed. Approx 7 or so inches (I'll know after I get my Sparco seat rails tomorrow). But, you are assuming I'm going to install any sort of back break, er, brace. I'm not.

Geo

I noticed that myself recently. Kind of scary.

robmug

RedlineMan - good comments.

I agree re HANS. Again, the FIA testing video footage shows any driver the need for HANS.

..now what's needed is a composite seat that is designed to be used with HANS...

Bill935K3

Hi All.
Please see attached photo of my Kirky Deluxe after a hard crash at Mt Tremblant. (The short version). 145 MPH at brake point turn 7 NO BRAKES, spin car to right ¾ rev. before leaving track. Rough grass kicked car and flew over gravel trap. (shallow tire marks only 10 feet before I hit tire wall) I hit a 12-15 layer thick tire wall. Behind tires there was double ARMCO with dirt backing. Best guesstimates are 110-115 MPH at impact. I hit very square on the passenger side.
As you can see from the photo the seat racked to the right about 4”. The right shoulder restraint was bent away as I went right through it. The right thigh bolster was bent out .
I was using a 5PT harness from Leaf Racewear 3” straps and Hans device with a composite Bieffe Helmet.
I walked away (VERY SLOWLY) I ended up with a very sore stiff neck for about ten days and a permanent dent in my rib cage, near the top/front where the ribs re-curve outward. The soft tissues at the base of my neck were bruised from folding over the Hans and from the Hans being pressed into my neck as it took all the force from the belts. The short Hans tether (1.5” long with 2 d rings) opposite side to the crash was permanently stretched ½ inch. (I wonder how much it it maxed at?) The fully caged tub was junk, it was very interesting to see all the places it compressed and tore in consideration of the very wide impact area and the tire wall cushion.
All and all things worked as planned, but man my upper body was really over in the passenger area at one point. This brought me to conclude if it had been on the other side it would have been much worse. IE hitting padded NASCAR bars etc. Thus see photos of new seat from Ultra shield in Texas. They supply a lot of the world of outlaws. We had to modify the new seat quite a bit due to Hans interference and head restraint built too high. Ultra-shield construction/quality is good but they were not responsive at all to my interference and sight line complaints. Which kind of PO’d me as they I had sent them good measurements to build from.
Any one hazard a G estimate 110 MPH to 0 in about 12 feet (the width of the tire wall)

Bill Chadwick
711 #2 is a 1979 935K3 replica GT-1R

Bill935K3

Can you attache more than one photo to a post?

Bill935K3

final one

robmug

Bill - that's quite some accident you had. Looks like, as you said, everything worked exactly as it should. Sounds like it was a very good idea to wear the Hans...

smokey

Bill: 33.5 G's

RedlineMan

Hey Bill;

Thanks for being (and remaining) our live crash test dummy! Stories like yours make me even more satisfied with my 147HP Monster!!

Ultrashield is making some pretty nice stuff from what I have seen (in pictures). Too bad they were not so nice to deal with.

All in all it looks like the Kirkey performed pretty well, which I'm glad of since I too own one. Interestingly, I just spoke to Doug at Kirkey yesterday about product improvements and he was very receptive. Although I have not seen one yet, I might imagine their new Full Containment model is a nice piece. I know they are absolutely SWAMPED with orders for their new safety equipment.

924RACR

Ow. Glad to hear you made out more or less OK, if bruised...

As a fellow passenger-side-impact survivor, I trust you're going to be adding an interior net to the new car?

JCP911S

Bill... nasty... thanks for sharing... I'd guess that is close to a "worst case" hit for most PCA type situations.... good to know that you could walk away... looks like you decided that head restraints on the seat would have helped...? And you're getting back in a car?... You have big ones...

The FIA test does not appear to test survivability... only strength of the seat... these are two different things... test really ought to test max load on the driver.... i.e. limit G load to some "survivable" threshold... not just integrety... its the driver we don't want to break... not the seat...


The "whip-back" issue is a good one... to the extent that the seat absorbs some amount of KE... and then returns it back to the driver... that doesn't seem to be a best case scenario... what probably makes more sense is controlled deformation.... something aluminum seats would seem to offer...

That said, this is just speculation, or focusing on asking more relevant questions.

As far as containment... interesting info from Simpson on their new Platinum harness product:

"Less Elongation During A Crash Event

7% to 9% for the Platinum Series (Polyester) vs. 13% to 17% with Standard Nylon Belts.All of our testing indicates that earlier loading on the belts positions the driver better for the impact and helps reduce the forces that lead to increased neck tension or whipping."

I'd say the conclusion is that it doesn;t necessarily mean the containment is more rigid.... but that it begins abosorbing KE earlier in the event, and with less body movement.

Geo

Well, it appears that contrary to popular speculation, the HANS actually does provide benefit in a side collision.