Greg W

I'm balancing the risks of a squashed spine against those of a broken neck, and am looking for some thoughts from experienced folks.

My '05 is setup to fit the Schroth 6-pt harness within their specs. I have a Hard Dog double diagonal w/harness bar and Sparco Evo II Plus seat on Buddy Club sliders. The harness bar is ~12" behind my shoulders with a ~4" drop, right about the max 20 degrees from horizontal that Schroth specifies. However, when I put on a HANS or Defnder device, the shoulder harness is about ~25 degrees from horizontal, a touch steeper then their specs call for. I understand the concern with spinal compression if the downward angle is too steep, but I'm weighing that against risk of neck injury without a HANS in event of a frontal collision. In the future I'll be lowering the seat by mounting it directly to the floor pan, but for right now I'm looking at my current setup for 5-10 HPDE/TT events a year (advanced run groups).

My question: how does the risk of spinal compression from ~25 degree shoulder harness drop compare against risk of neck injury due to not using a HANS-like device? My inclination is to use a HANS-like device despite the ~25 degree angle as it would help mitigate the more common neck injury scenario, but would like your insights and thoughts.

rioyellows2k

Can you compromise and use a Neck Support Collar?

PedalFaster

Manufacturers generally build some tolerance into their recommendations to hedge against user error. I'd be surprised if the difference between 20 degrees and 25 was a big one, but (a) most if not all of the people on this forum aren't qualified to answer you (myself included), and (b) it's unlikely any manufacturer will go on the record approving something that's outside their specified tolerances because of the liability risk.

Have you considered relocating the harness bar on your roll hoop?

Neck support collars don't provide any protection against neck hyperextension, and thus shouldn't be considered an alternative to a head and neck restraint.

Greg W

The Hard Dog harness bar is welded in, so relocating it would be significant work.

I agree with your comment on manufacturers' opinions, they've all got good clear published specs and wouldn't deviate from them for risk of liability. With a seatback angle of ~20 degrees, there's less then a 10% increase in compressive force when comparing 20 and 25 degree harness angles. It then becomes a question of whether that ~10% increase in compression is worth significantly mitigating a basal skull fracture.

The long term answer is to move the seat (or weld on a new harness bar), which I plan on doing (along with other unrelated safety upgrades). I'm trying to enhance my safety in the interim between now and when I move the seat.

Ben-NSI

How does the height of your shoulders compare to the height of the seat back. In many cases the seat back is parallel or even a bit higher than your shoulders and the belts lay on top of the seat. You didn't mention your height but in my case I can't use the holes in the seat and the belts actually lay on top of the shoulder area of the seat. In a case like mine the belts would have to compress your seat to compress your spine, that's no easy feat with a well designed seat and in any case will certainly take SOME of the load off your spine. I'm not saying it's a good idea or not, but it's something to think about. I'm sure you could find someone to fix that harness bar for you for less than $200 though... might be worth saving your neck (literally)

dc_s2k

All of these things run along a continuum. One shouldn't assume that a 20 degree angle is fine and then, bam, at 25 degrees your spine will be compressed. 25 is probably just a little less optimal than 25. All things considered you will be much better off with a HNR than without. Anecdotal evidence, and most research, points to basal skull fracture as a very common cause of death in auto racing. HNRs significantly mitigate that possibility.

I spent a fair amount of time obsessing about this very issue and asked a lot of questions. At the end of the day, you end up doing what everyone that has gone before you does because its the appropriate thing to do. You get a good rollbar, a HNR, a 6 pt harness, and try and make the geometry work as well as you can given that you are using off the shelf (standard) stuff. Eventually you realize that you'll never turn it back into a street car and then you get a custom cage with the right geometry and side nets. Where you can, follow the best practices that are out there. Lower your seat.

Greg W

Ben-NSI, the top of my shoulders line up with the harness bar, allowing the harness a direct path to the bar.

dc s2k, I agree with your thinking, that's the path I'm on. Taking steps (not leaps) to a safer track experience as I get faster and closer to 10/10ths. I'll be trying the other HNR's (may rent per your suggestion in my other HNR post), and will get the one that fits best. I may be instructing next year so an HNR that can be used with 3pt OEM is an advantage. I may have a THill day (with HOD) in a couple weeks and will see about renting the R3 for that day. Harness angle issue will be solved once I mount the seat lower (maybe next year). Thanks for your thoughts...

turbo8765

Are you aware of actual incident involving a compression induced back injury secondary to improperly aligned should harnesses?

Are you aware of any database/group/sanctioning body that keeps track of on track accidents at the amateur level?

bky

I'll go out on a limb here and say there probably isn't much guarantee on any safety equipment preventing injury in a racing application. I think most people are out on their own when it comes to competition gear.

Greg W

Not aware of either.