gbaker

Mitch,

Thanks. I stand corrected.

ColorChange

Gregg: How much benefit do the dashpots offer in side loads?

gbaker

Tim,

The best estimate is about 50%. This number comes from computer simulations performed by the Wayne State lab. Most lateral crash testing is done on sleds equipped with head surrounds and/or nets, which do not isolate the contribution from the H&N restraint.

Larry Herman

Greg, how difficult is it to move your device from car to car. I'm probably a broken record on this, but as an instructor I spend almost half my time in someone else's car. I can rationalize that in a 3 point harness with the airbags I am better off than with nothing, but in another car with a harness I would like to take a H&N device with me. At the moment the R3 system works anywhere and the Hans is cumbersome but can be relocated with mitigations. What factors have to be considered with yours? Does it just snap onto other belts? What about the shoulder belt pads that everyone (me included) like to run?

ltc

Larry,
Rennlist user "Mark in Denver" posted this a while back:
https://rennlist.com/forums/racing-and-drivers-education-forum/160000-hans-vs-isaac-oh-that-debate-again.html
I believe this would address your question.

Since I move mine from car to car, I have replaced one of the circular pins that attach the device to the belts with a quick disconnect, to make it easier to move to another seat. That might work if you need to use it in instructing.

I use a shaped cotter pin. I was just looking for a picture of one on the 'net and found this "locking cotter pin" which is an improvement over what I use. The ones that I use were purchased at Home Depot and don't have the lock.

http://www.pivotpins.com/catalog/bow_tie.shtml

The tiny circular pins that come with the ISAAC are hard for me to deal with and I invariably dropped them. I haven't had any problems in the 34 track days since I started using the cotter pin. BTW, I just use it on one end.
Mark
__________________
1987 Turbo 944 racer car
1993 Spec Miata racer car (SCCA -- "The 13/13 rule is not in effect")
1991 Miata daily driver
1993 968 (wife's car)

2003 4Runner Tow Vehicle

Geo

Not to be a PITA Gregg, but isn't the second part the very definition of a displacement? Furthermore, isn't the second part proof that the displacement and death can occur at 1g?

It just occurs to this monkey that displacement is still the killer and that in the specific environment of a race car the displacement is caused by sufficient g-force. No?

ltc

Geo,
Think again about the analogy used regarding the "Hangman's Injury". You do not need absolute displacement (far in excess of that allowed by normal skeletal structure) for BSF.

The race car environment complicates this visualization process as you now have to consider kinetic and potential energies, motion in 2 degrees of freedom, etc. Application of Newton's Laws and some math aid in the visualization (but I hate math).

RedlineMan

Mr. Baker;

Thank you very much for weighing in here. I was quite hoping you would. We in the enthusiast community suffer greatly from a dearth of collated information, and your contribution here is a tremendous asset to our forum. Other wise it is up to us to find answers. Your input - while understandably "reserved" - is ever so much appreciated!! You are further to be commended for a delightfully elegant solution. I love it!
----------------------------------------------------------------------------------
My thoughts on the HANS (and other things) are as follows -

- It seems to me that the HANS comes with a bit more length in the straps than they used to. Mine seems much longer than my buddy's who is about 3 years older.

- With a HANS, you learn to hold your head directly over your shoulders. This effectively lengthens the tethers for greater rotational freedom of the head. After learning that little trick, I do not find it an issue. Heck...it promotes good posture!

- I have not found the HANS to significantly raise the level of difficulty in entering/exiting my car, nor does it interfere with my home-made helmet halo when I'm seated. It does require a little more care getting in, but you get used to it.

- I made my decision because I felt the HANS may be the easiest to deal with in more situations. As Larry mentions, we need versatility, both in and out of various cars. I felt the HANS was the best in this regard and have so far not been dissapointed.

- The HANS has had the most testing, both lab and real world. It has been around and has performed very well. I went with a known quantity, even though I was highly intrigued and impressed by the Isaac as a product and a design.

- As someone asked, yes there are space issues involved with using a HANS. Some seat styles or mounting positions can interfere with proper HANS use. I had to carve some of the foam out of the head rest portion of my Kirkey seat cover. Some on this forum have had to go so far as to refabricate their seats.

Larry -

I had not broken into laughter upon contemplating your driving. I had focussed on the intent of your inquirey. However, now that you mention it...

mitch236

The heart uses the SA node to excite the heart which because of its special channels, is able to keep firing without nervous system input. It doesn't need the spinal column at all (and therefore the brain) unlike the reflex circuit you mention with the flame which requires the spinal column but not the brain. Pretty interesting stuff this human body!

JC in NY

On a related subject, can a human head be kept alive apart from the body? Didn't Soviet scientists experiment with this, or was it a bad science fiction movie I saw? I can't distinguish anymore.

ColorChange

Damn Mitch, thanks. Didn't know that, way cool.

gbaker

Larry,

The question has come up from endurance racers and driving schools, so we have been testing a quick release pin for the belt connector. A photo is here (the only one I could find on short notice--it's pretty ugly after compressing):

http://www.isaacdirect.com/images/Pr...ns/BeltPin.JPG

You should check with the folks at Finishline Racing Schools. They use Isaac systems in their school cars and are constantly moving them around between driver and passenger seats.

I would stay away from shoulder pads. They probably will work okay, but we haven't tested with them.

Also (ahem, Lewis ), please don't substitute parts. The pins, for example, are from aerospace suppliers that certify their conformance to particular mil specs. You can't get this quality product from your local hardware store. The QR pins are certified to a double shear strength of 8,000# minimum and are made in the U.S. We've been offered 70% discounts on imported pins that are "really good", according to the salesman. Their offers have been respectfully declined.

ColorChange

Gregg: New pins look nice. Available yet?

gbaker

We've known each other for quite some time now George, and I would never confuse your stirring the grey matter with being a PITA.

Actually, if one were very gently lowered down to the end of the rope while in the noose, it would be 1g just hanging there. And, unless one weighed 900#, one would survive. It's that nasty trap door combined with the rope slack that makes for a bad day.

Exactly, but you skipped a step. Also, we need to keep in mind what is being displaced.

First the missed step. The Gs of deceleration multiplied by the mass yield the force (Sir Isaac's Second Law of Motion). Force applied to anything will yield displacement. So you are correct when you suggest that the injury is associated with displacement, but the displacement is caused by the force.

The hanging example is a good one because all the loads act in one direction, i.e. along the axis of the neck. If the neck is stretched too far, injury occurs. But in order to stretch it you must apply a force. This displacement is very different from that of one's head swinging forward during impact (although about 5-10% of the total load is from centrifugal force). The problem begins when the driver runs out of neck, like the poor guy with the noose when he runs out of rope.

Mark in Denver

Gregg,

I replied in an earlier thread that I had replaced the circular clips at the ends of the pins with an easier to use clip, since I have to move my ISAAC setup from car to car. I had great difficulty handling the circular clips that you supply with the system. Are you telling me that your circular clips are that important? I understand why one would be ill-advised to replace any other parts of the ISAAC system and I wasn't proprosing replacement of the black pin that goes goes under the belt. I'll probably keep using the replacement clips. I won't sue you if they fail, but then again, I've already agreed not to sue you.

BTW, I'm pretty happy with my ISAAC system. However, now that certification is becoming probable in our sanctioning bodies, are you going to try to certify your system?

Thanks,

Mark