fatbillybob

Redline Man John and Geo among others is right. We all had some nice threads regarding HANS, HN systems, harness types and full containment seats. John and Geo were right about all of their comments. Other posters were also correct, I’m sorry I cannot remember who those contributors were, John and Geo were the stand outs. I was lucky enough to shake hands with Dr. Hubbard of HANS fame last wekend at a seminar hosted by www.The Racers Shop.com The seminar was presented by Dr. Hubbard regarding HANS and Mr. Morizot president of Stand 21 regarding heat stress in racing. Wow were we lucky to get a double whammy lesson from two big men in autoracing. Dr. H answered all our questions professionally and with data until the group basically tired out. The take away message was similar to some posts here on Rennlist except I heard it from THE MAN Dr. Hubbard himself. Enclosed single seater tubs or Full containment seats connected to the cage not your tin floor, side nets, HANS, 3” shoulder belts, 4 belt dual shoulder belts are his personal choice. MOUNT THE SHOULDER STRAPS EXACTLY AS HANS SAYS is the single most important issue if using HANS! Comments on controversy: 1) Belt slip: It has never happened in a crash. The high level sanctioning bodies have not reported issues with slippage when asked. 118? sanctioning bodies around the world approve HANS, and for some it is the only device allowed, and there are no reported belt slip issues. Therefore HANS does not think this is an issue to re-engineer a problem that does not exist. Reported Belt slip does happen with some drivers just driving around and in each case was remedied by proper shoulder strap mounting. Current HANS lips are there in an attempt to mitigate and make us feel better. In crash tests and real life crashes lips or no lips makes no difference. Finally the crash dummy has different crush characteristics than the body and simulates but does not completely emulate the human body. History is replete with instances of great engineering that failed in real life. It is important to take crash test data and real world data together in formulating a working solution. 2) Belt type: HANS recommend 3” belts as universally available. Some part of a 3” belt is more likely to be on the HANS is his impression. However, the concept of the 2” hybrid provides similar positive crash results with a slight advantage which is within the error of the test beds. Therefore there is no statistical advantage in the 2” belt. There is an advantage in the 4 belt design in that it is easier to control HANS wearer comfort and directional anchoring for differing impacts i.e. up to 20 degree down angle on HANS belt and an additional 60mm +/- 15mm further down on the body belt per FIA. 3) Lateral impacts: HANS is not design to control lateral impacts anymore than your harness system. It is the seat design with full containment/sidenets or enclosed tub that controls your movement laterally. This is the best current way of handling lateral impact. Tested offset 30 degree impacts are proven reduced to safe thresholds with HANS. So the goal is to reduce forward headloads and lateral components are reduced i.e. rotational torques on head by reduction in forward loads and reduction in forward movement by HANS. 4) Device retention/attachment: The HANS theory is based on the premise that the solution is to “control the position of the head relative to the torso” so the HANS is attached to the helmet and nothing else. My impression is that he does not believe it is proper to control the head while tethered to the shoulder straps and hope that the torso stays in position relative to the shoulder straps, i.e. an extra layer of complexity. Therefore, the HANS is not attached to belts. In fact, HANS slippage during the crash loads the tethers before everything locks up which is why there is an acceptable range of tether lengths and why extra short tethers which restrict head movement are of no crash safety value.
Well that’s what I took from the seminar. Standard disclaimers apply. I may or may not have missed some points. I’m not a professional but I think I understand it all better now. So here is another data point for you all. Thanks yous go to The Racer’s Shop the largest WestCoast supplier of HANS and Dr. Hubard. The goal of this thread is informational not to rekindle the HN holywar. Your mileage may vary...

ltc

Thank you for taking the time to post your experience.
I am somewhat confused, so I was hoping you could explain what appears to be conflicting statements:

Belt slip never happens is what I take away from this.

Belt slip occurs during the crash, which has negligible effect on tether length vs head loading.

Hence my confusion......does it slip or does it not slip in a crash?

kary993

I still struggle with the loose tethers concept not mattering in the final calculations. Even the crash tests show quite a variance in preformance based upon the tether tightness. The fact still remains in my estimation that the differential between the torso and the head is based upon the tether tightness regardless of the loading of the seat belts as was pointed out in the recap from the seminar. The tighter the tethers the less head movement resulting in limited visibility while loose yields great visibility and less performance.

smokey

Facts and clear thinking from an expert. Wonderful. Thank you.

924RACR

Thanks for taking the time to write it all up and post it.

Re slippage - I think we're talking at cross-directions here - literally! The HANS does slide BACKWARDS on impact with the belts, relative to the body, from what I've seen/heard, effectively pretensioning the straps. A good thing.

But the slipping sideways off the shoulders is a different thing entirely, different direction, and would concern/irritate me if I had a HANS. I find it somewhat misleading that they state that belts slipping off has not been an issue in crashes, but does happen for some drivers when driving around.

Personally, I tend to drive a bit before I set up for a crash.

Of course, dummies don't wiggle around much on the sled on their way to the impact zone.

Then again, at least there are ways to fix the slippage. I would feel more confidence in Hubbard-Downing if they stood up and admitted that slippage can be an issue, just not for everyone, and here's how to address it - but yes, you do need the straps on the HANS. If they're trying to say that it's not a big deal - well, isn't it important to keep the shoulder straps on the HANS for the impact? Are they implying that the shoulder straps don't even need to be on the HANS for the HANS to be effective?? Doesn't add up, IMO.

Don't get me wrong, I'm not slamming the device - I'm simply not impressed with what they're saying, how they're selling it.

RedlineMan

Tried to post this AM, but JD was doing a backup!

Lew -

I might imagine there are two types of "slippage" at work here, and that this word is not really a good term to describe the second type of movement. In the first case we are talking about the belts not staying upon the HANS yoke. This would have them slipping off. Pretty straight forward.

I would actually be surprised that it had never happened in real world situations. The key point from my own experience and my research is what FBB reiterated; belt angles are THE MOST CRITICAL aspect in making them work properly. One aspect that the manufacturer cannot control, unfortunately.

The second type of "slippage" would better be described otherwise. This point gets to what Kary is questioning, and solves that point nicely. If you look at a still photo of a HANS device within a crash at full system extension, you will note that it seems to have "slipped" back off the shoulders, and may actually be substantially hanging out in thin air behind the driver.

This neat little trick of the HANS staying quite where the driver WAS has the effect of taking the slack out of the tethers quite quickly, and also keeping the head in position relative to the torso (as FBB described), which will travel forward SUBSTANTIALLY due to belt stretch, torso elasticity, and other things. This is probably the least understood aspect of what makes the HANS work. Pretty neat!

If you sit in your car with your HANS installed, and roll your head forward, you might be a little nervous wondering why it would be safe to move so far and remain unrestrained. If you PROPERLY throw your entire body forward into the belts to simulate a real impact, you will immediately see the light, as the dynamic changes noticeably.

ColorChange

Ummm What? The belts will slip during normal driving (but never during crash? You proved that how? Because no one showed high speed video of their body during a crash ... Ummm nobody has that data. Lack of data doesn't mean it didn't happen, though it also doesn't mean it did.), so we put a flap on the end to stop it so you'll feel better, even though you don't need it. And we had belt slippage on a crash dummy but that doesn't count either because the dummy is different than a human chest.

Ummm doubletalk?

gbaker

1. Belts slip off the HANS device, laterally. Not all the time but it is well documented, both on track and in the crash lab.

2. The "slippage" to the rear RedlineMan speaks of is also well documented, and works to the HANS device's advantage, effectively preloading the tethers.

ltc

John,
Thank you for the clarification.

I am still somewhat skeptical as to the 'zero' reported slippage claim from any sancitoning body anywhere in the world, but so be it.

As an engineer who has designed a LOT of different stuff in my career (commercial and military) and have had to 'stand up in front of the class' many times for critical reviews , I am automatically skeptical of someone who stands up and only outlines positives with no negatives. There is a line which is crossed somewhere between science and sales.

I have designed many systems which I thought were 'perfect', only to realize that nature abhores perfection.....in the end, entropy always wins.

ColorChange

ltc: I agree. Nothing is perfect, but to not frankly/honestly discuss your product's strengths and weaknesses, you lose a lot of credibility in my eyes.

Geo

That's pretty much the basic premise behind Murphy's Law.

Give a monkey something that is "monkey-proof" and eventually the monkey will "outsmart" the engineer (being a physical product, software, etc.). That's life.

So back to Murphy....

Anything that can go wrong, will go wrong, and at the worst possible moment.

Nobody is immune.

Geo

That's just joy riding you maniac.

I don't know, I seem to wiggle around a lot.

924RACR

Aaaaack!!! I've been spotted!

LOL!

fatbillybob

I need to clarify some statements. John and 924racer understand what I was saying quite badly. The lateral reported slip is entirely different from the slip or reward relative motion of the HANS in a forward crash. The HANS rearward movement does preload the tethers which is part of how HANS works and why these things are so hard to understand. Think of how elegant this design really is. Compare it to the R3 which is fixed to you vs the HANS that moves on you. Under the same conditions of forward impact I do not know but suspect that the tether length in the R3 is much more critcal than the HANS due to the relative available movement or preloading of the devices if you will.
To Colorchange: this is not double talk but me trying to demonstrate with bullet points of information. So When I talked about belt slip during normal driving I should better state this case as: there are reports of guys with HANS who complain the belts slip off when driving. However, those who bothered to call HANS are instructed in proper HANS/belt mounting and HANS has been able to solve all problems. HANS is very specific. If you are not willing to alter the seatbelt mounts from what you have to what HANS needs then HANS will not work for you. If you want HANS to work then you must follow their instructions.
You say "Because no one showed high speed video of their body during a crash ... Ummm nobody has that data." I do not know if this data exists. But there is crash data recording of significant high level IRL Champ car and F1 crashes and those drivers live to race another day. Which ties into the point about crash dummys. There is no arguement that what happens in vitro and in vivo someitmes are different while we try to simulate the human body with artificial plastic and sensors. I can tell you when I train for a boxing match my heavy bag which simulates the human body losses everytime. When I get into the ring however, the beating heart of the other guy is always a wildcard. You can always train for the SAT and score really high but alot of guys with 800 SATS did not make in in the real world of college. And...I don't have stats for that either but just about everyone who went to college knows at least one gifted highschool student who was a total burnout in college.
"And we had belt slippage on a crash dummy but that doesn't count either because the dummy is different than a human chest". I did not see these crash tests where things slip off... maybe they have. The test beds I have seen are not like our cars. Seats look more like a chair welded to a cage than our seats with bolsters etc... Set-up can alter test results and quite frankly I am not impressed by even rumors of belt slip unless the test are carried out in tub or full containment seat and there is slippage. Then I would have my undies in a bunch. I think to draw real world conclusions you need to at least have a real world simulation and the HANS test with Mercedes in an F1 tub are pretty impressive to this lay person and the source of my quote about proven positive HANS results in 30 degree offset crashes. HANS is trying to achieve very specifc goals and test with a test rig for specific reults. When experiments are concieved we have a hypothesis of desired results. We experiment or test and we get them or we don't. We hope our test rig or simulation is representative of what we are trying to test for in the real world. HANS appears to achieve them and is based on sound biomechanical theory, followed up by succesfull crash testing, follow-up by real world succesful use, and finally, endorsement by significant sanctioning bodies we amateur racers tend to look up to.

My reason for posting was not to stir controvery but provide information as I understand the science directly from Dr. Hubbard and confirms the concepts that John, Geo and I and others have talked about regarding safety as a "system" where full containment and head restraint are cornerstones to safety.


ITC, as Dr. H puts it belt slip is not an issue. Therefore there is no need to engineer a solution for a problem that does not exist. There are no slip reports to sanctioning bodies and HANS has asked. No one has died because the belts slipped. Drivers of properly mounted belts are not reporting slip issues. That is how I understand it. I do not think I have misunderstood Dr. H's comments. HANS is not designed for lateral impacts any more than your seatblets are for lateral impacts. Your seat and sidenets are for lateral impacts and devices such as HANS and seatbelts assist the primary function for full containment seats and sidenets or and enclosed tub. Thus HANS is usefull in say a 30 degree offset forward impact (with resultant lateral forces) to reduce overall movement and the rotational torque placed on the head. Thus HANS is useful in lateral "componants" of impacts rather than a pure lateral impact.

Kary993, I do not quite understand your concept of tether tightness. I did not see the graphs you speak but may have missed that slide. To my knowledge there is no statistically significant difference in a range of tether length due to the action of the HANS in a crash. The rearward movement of the HANS pretensions the tethers (makes them tight) then your belts lock up and you lock the HANS yoke between you and the belts now the HANS action begins. If I understand the ISAAC device it does something similar in that the damper length is not critical within its range due to the action of the ISAAC base rolling on the belts and not locking until you pinch the roller between you and the belts. To me a very similar action. I think that the point you raise may be more of an issue with the R3 that is attached to you in a fixed position. There it would appear that you need to know how far your neck stretches before it breaks and then have a tether shorter than that. I'm not an engineer and have never driven the R3. I do not know why but the R3 on one of Dr. H's slides was specifically not allowed while I believe it passes the SFI 38.1 spec. Is tether length in the R3 an issue?

ColorChange

FBB: I really have no major axe to grind here, and am not enough of an expert to argue heavily. I think the HANS is a good product, with some minor concerns. I think the ISAAC is a good product with some minor concerns. I just want to make sure people separate marketing from science and this sometimes does not happen, and it sounded to me from you description, that the line was being crossed. That's all.