Notes from presentation by Tom Gideon, GM Race Satefy Eng.
Here's my recap from the presentation I attended last night.
I just attended, last night, a presentation by Tom Gideon, a GM Race Safety Engineer, to our local road racing group, Waterford Hills Road Racing. Tom is one of those guys who is working regularly with crash-testing the latest gear at Delphi and Wayne State. He has worked on crash safety for all the GM race projects, notably (for us) the C5R, CTS-V, and Cavalier Drag car, as well as of course NASCAR and IRL. The presentation he gave was a version of what he presents to the pro drivers, and was, for me, essentially a recap of safety info presented by Dr. John Melvin in 2000 to the Detrot SCCA Region, with the latest updates in crash safety.
It was extremely timely, given all the discussions going on here and elsewhere online about H+N devices, side impact protection, and the like. He actually focused more on lateral and oblique impact protection, as I was hoping; the head-on impact is fairly well understood now and protected against, not to mention the least likely kind of impact to be experienced in our type of racing (IMO).
To recap on the straight-line stuff, you need (for best protection) a 6- or 7-point harness (properly secured, of course), H+N restraint (of which the HANS is the best for this impact, according to their data and tests - note at this point that I have an ISAAC, not a HANS), and the proper SFI padding on cage bars (though this comes into play more on lateral hits). The 5-pt harness is NFG - no good - compared to the 6- and 7-point; the added movement allowed more than doubles chest compression, from an average of 20mm (with a 6-pt) to about 50mm avg with a 5-point. This is about 2 inches. This also happens to be where the sternum will break. The solution to preventing the sternum breaking is the 6-point harness, not the sternum strap. Actually, in their tests, the sternum strap shows potential to injure the neck. Don't go there, kids!
The ISAAC apparently suffers from the same limitations as the Hutchens, D-Cel, et al in the full frontal impact; where the force is applied from is less-than-optimal, reducing the effectiveness of the device. The HANS, because of the collar, is applying force from a much better direction, and this is why it is more effective. To put numbers to it, the threshold for basal skull fracture or other injury is 4000N (tensile force on the neck). The HANS reduces this to 2000N in their benchmark frontal impact test (sorry, don't remember for sure the numbers, but I think that was 40G, 35mph). By contrast, the ISAAC, Hutchens, etc all apparently end up at around 3000N - enough to save you, but less effective. But the HANS does have its limitations - in lateral. It only contributes in a 45 degree angle; beyond this angle of impact, it will not help control head motion. This was why I selected to go with the ISAAC; again, while not as effective in straight-line, it appears to (based on analysis of design and my personal experiences) provide support and motion control in all up to 90 degree impacts. More on my personal testing of the ISAAC later.
For lateral impact, it was VERY clear that the BEST thing you can do, the most important step - was not to buy the $2000 seat! It was to buy the $75 NASCAR interior side impact net and mount it properly! It catches the shoulders and head and controls motion to the other side of the car (to make it PC for anyone driving a RHD car . The window net and cage provide the same protection on the outer side (LHS) of the driver. Even in the case of a very fancy seat, the net is necessary to back up the support of the seat. The net he had there, to show, happens to be the same one I just bought, from BSR Racing ($75 as mentioned), and that is what they test with. He had numerous test videos shown (from the sled, along with one actual in-car from a hit by Johnny Benstead) showing performance with and without the net. Even with a HANS, as mentioned, in a lateral or 45deg hit, the test dummy is bouncing or coming close to bouncing off the cage bars, and the motion of the dummy is very poorly controlled (really, not at all). Even the fanciest aluminum seats are less than 100% effective without the net. Here's the BSR webpage:
http://www.bsrproducts.com/homepage.cfm
The net, to speak of its installation, straps to the members of the main hoop of the cage to position it vertically to catch the shoulder and helmet. It should be positioned next to the shoulder, and continue straight forward to the dash bar. There is a quick release up by the dash bar, and a ratchet will tension it as required. Since my cage is a little less complete than a NASCAR car, I will need to call BSR back and clarify some fine points on installation. However, their tests have shown that even without a perfect installation, it's better than nothing. Just like a H+N device - something's better than nothing, even if it's not the very best.
But it was clear that the 100% solution was to also have a seat that will provide some degree of shoulder support, to help, in combination with the net, to support and control the driver laterally. I did ask him, specifically, if these big bad aluminum stock car seats were necessary to get all the lateral protection, and much to my surprise he did say NO. Basically any decent sort of seat with some form of support in the shoulders, when backed up with a right-hand-side net, was OK, though I still get the impression that the more stout construction and design of these aluminum seats with shoulder and head supports are still just a bit better than some of the really light-duty composite seats with very minimal shoulder support. However, if choosing between shoulder and head support, clearly the shoulder must be stopped before the head - or you get compression loading of the neck, instead of tension loads! Restraining the shoulders is the key.
Back to the padding - it's been expressed well before, but again, anywhere your helmet can hit MUST have the SFI-approved padding - the stuff that's hard. The pipe insulation stuff doesn't cut it, and can split or send you rebounding. Neither is a desireable result. This tends to be an issue more in lateral than longitudinal hits.
As to my personal experiences; as mentioned, I have an ISAAC device, which I started wearing last year. No issues with head movement, time to connect/disconnect, etc. I also crash-tested it in a lateral impact last year. I went sideways into the armco at maybe 60mph (in my 924). The back hatch was blown out, the right rear fender caved in, and the rim and right rear trailing arm bent - the hit was also slightly rearward, as I was going backwards and hit the wall that was driver's side left when normally driving on the track with the right side of the car. For my protection, I had only 6-point belts, a bottom of the line Kirkey Economy seat, and my ISAAC. My head bounced off the petty bar (unpadded) and cracked the helmet (Bell M3). I felt a little woozy, had a little tunnel vision shortly after, but oxygen cleared that out. I had mild headaches for the week following, and that was it. No other injuries. I'm glad I had the ISAAC, for the lateral support it gave (verified later by ISAAC LLC as I sent it in to them for evaluation). I also did a lot of stupid things, and got really lucky and got away with all of them! Cheap seat, unpadded bars on the cage, no interior lateral support, and driving hard on an untested chassis going for a last-lap pass. The seat will be upgraded or replaced, the petty bar is coming out (not worth the hazard), the interior net goes in, SFI padding for everything else, and I will never tell myself (while on track) - the motor's blown, you're not racing this car again this weekend, you've got nothing to lose by trying for the pass! Boy was I wrong - you can always demolish your car and put yourself in the hospital!
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Vaughan Scott
Detroit Region #280052
'79 924 #77 ITA/GTS1
www.vaughanscott.com
