Larry Herman

George, don't you think that point is moot? If you have to replace your helmet and belts when you have a big impact (provided you didn't write off the car ), don't you think that you would have to replace the seat as well? How could you be sure that it maintained it's structural integrity?

ltc

There was a lightly used HANS (one or two events) a few months back in the Classifieds, asking price was $700. It sold rather quickly.

ltc

George,
The PCA appears to have a different take (a bit confusing to read):
http://www.pca.org/pca/clubrace/docs/pca_rules_2005.pdf

25. All cars will be equipped with a seat back brace except as provided in Safety Rule 26 below. Said device will mount securely to the roll cage/bar and will rest firmly against the back of the seat. The portion that contacts the seat will be a minimum of twelve (12) square inches and larger is suggested.
The seat construction must be compatible with the seat back brace and not pose a hazard to the driver. The seat back brace for composite seats must have a minimum of thirty (30) square inches contacting the seat back, and must have 0.5” to 2” of high density foam padding between the brace
and the seat back. The seat back brace cannot be bolted to a composite seat.

26. If the seat is within 3” of the firewall, a seat back brace is not needed but the area between the seat and firewall should be padded with high density foam. A seat back brace is not required in cars equipped with a current FIA approved seat and seat mount. Installation of a new FIA approved seat
requires concurrent installation of a new seat mount and new seat rails, if seat rails are used. The seat mount and seat rails must be sold by the seat manufacturer for installation with the specific seat selected. The chassis mounting points for the seat must be reinforced and in good condition. The
seat must be replaced after 5 years from the date of manufacture if not used with a seat back brace.

BTW, the high density foam also has a Snell certification #....45.2 IIRC. Similar to 45.1 rollbar padding.

TD in DC

Larry,

I think that he is worried about the seat deforming during the accident (e.g., squeezing you like a taco) and remaining deformed after the accident (e.g., keeping you squeezed like a taco). I have heard conflicting advice about the Kirkey aluminum seat I just bought, with some telling me that they would only consider fiberglass for this reason.

I am sure he will correct me if my assumption regarding his intent is incorrect.

TD

adrial

Anybody have any pictures of the Isaac Link (their new, cheap device)?

Geo

Think about the slo-mo videos of crash tests and how much the belts stretch and the driver comes out of the seat. I don't want to come partially out of the seat, have it deform, and have to fit back into it on rebound. It's not a matter of reusing the seat. it's a matter of my body getting back into it on recoil.

Geo

I don't see the conflict with what I wrote.

Geo

You're very close. But it's more about coming partially out of the seat as the belts stretch and popping back into a seat that no longer has the proper shape. I don't care about being wrapped up like a taco. Aluminum would be easy enough to bend to get out.

And for anyone who doesn't believe you can come partially out of your seat (mostly to the sides), you need to look at a lot of crash tests and read first-hand accounts. It's quite possible.

Sanjeevan

TD, I had the same thought last night and started a seperate thread (not to hijack yours), it seems to me that even on linear G's the dampers work better and certainly is better for lateral G loads (No studies to prove this either), the only thing that's preventing me from placing an order right now is the lack of certification. I am concerned about slippage and lack of lateral support with Hans, R3 will not slip but may get in the way with that back piece and has no lateral support. Once we exhaust all inputs here I'll be making my decision, so eagerly reading through every input here...thanks.

RedlineMan

Todd;

The basic difference in the HANS/Isaac Link, and the Isaac "hydraulic" is that the former do allow a set range of motion before activation. In theory, they are designed to take up before a dangerous level of head exention is attained. The Full Isaac system reduces head travel very quickly, and therefore by reducing the time frame of unrestricted travel, theorectially offers an advantage in reduced overall head/neck loads. Whether the loads attained by the "semi-active" strap devices (the fast stop at the end of the tether) are low enough to be considered "safe" falls pray to many variables, but suffice it to say that they reduce these stresses to an accepted level, far more than having nothing.

The HANS is indeed quite dependant on good system architecture. The layout of belt angles and such is rather specific, and therefore can be rather diffcult to properly render in anything less than a full blown track car. The Isaac does seem to offer a distinct advantage here. I STILL am not quite able to get past my ambivalence towards exactly HOW the Isaac utilizes the belts, but I feel it does indeed offer distinct advantages in versatility.

To those looking at Kirkey road race seats, I would advise against it. Sorry Todd! Unless they have changed very recently - which I am unaware of - they have one key fault that makes them difficult if not impossible to install correctly. They only offer a 20 degree layback design for their road race seats, and in my experience this simply does not work. If you tip the seat back to get a good base angle for torso retention, and proper headroom, you can't reach the wheel. If you tip it up to reach the wheel, you lose headroom and the seat base goes horizontal (dangerous!). I have had no luck using these seats in sedans, in their standard form.

Too bad, because I bought an RR Deluxe for myself before I found this out. I spent many hours hacking away at my car trying to configure the thing. It was a disaster. I could reach the wheel, but only by fabricating a 2" extended hub! I had to cut out all the stock floor bracing and redo it to lower the seat. I had enough headroom (barely), but the seat base was FLAT. I found myself not being able to see out of the rear mirror... when I realized I was sliding out of the seat!!!!

I offered to drive up and help Kirkey solve this problem, but they did not take me up on it even though they said they had no road race expertise. I solved the problem by cutting my seat and reworking the back-to-base angles. Ironically, it ended up at exactly the industry standard 10 degrees!! Now... it works perfectly...

Wish I'd known about Ultrashield before I bought a seat!

Phokaioglaukos

Agree that a cage is only safe with a helmet, but I thought a roll bar (like the DAS bar) was fine when driving on the street without a helmet. What am I missing?

TD in DC

John,

My Kirkey seat has yet to be installed (I was trying to get the 944 ready for a DE tomorrow, but it will not be ready). I can probably return it for an ultrashield. Which ultrashield did you get, and do you have any advice on how I should mount it in my '84 944? Is the mounting hardware fabbed, or is there something else I should buy.

TD

fatbillybob

Redlineman,

What is the "proper" angle of the seatbase to the floor?

fatbillybob

Geo,

I don't think the stick pointed at your spine with a back brace is any worse than the stick of the steering wheel pointed at your chest. In fact we are probably more likely to get hit by that than the back brace. Distribution of load is the key so if the PCA etc say 30 square inches 12 square inces of plate on the back brace pole or whatever there should be enough distribution. You can always have more square inches. Also, if a properly designed cage with seat bolted to cage and cage features like seat rails that go from the base up to the harness bar the seat can deform less under your conditions regardless if it is plastic or metal as it is supported along its entire length from seat leading edge to shoulders. Is your beef with back braces not really the concept of seat back bracing but really with the way back braces are made/installed today for non-pro racers as an "add on" device with zero testing?

JackOlsen

This gets repeated a lot, and it might be that it's true. But is there any actual data to back it up? I drive a car with a full cage, and I frequently also drive it on the street. I know that the cage 1) helps protect me from rollovers at the track, which are far more common than impacts, and 2) helps protect the cabin itself from intrusion/deformation in the event of an impact.

The often-repeated theory is that a high-density padded cage is more likely to injur the driver than the multiple unpadded steel components of the car itself. When I think of the rolled edge of the roof, the sharply angled steel of the A- and B-pillars, I wonder if this is true. Earlier in the thread, John made a point about flat versus rounded objects and their characteristics when you hit them, and it was part of a very intelligent and articulate post, but I wonder how likely it is that I'd make a nice, flat contact with my roof, A- or B-pillar, and -- regardless of the shape of the steel -- I think I'd still rather get hit by a bat covered with high-density padding than the un-padded steel that's there in a stock 20-30-year-old 911.

Some people cite the proximity of the cage as the hazard -- it's closer to the head than the steel pieces of the car. But John's post also talked about the danger of velocity achieved before impact: the whip action. A padded bar closer to my head is a potential hazard, certainly. But so is the unpadded steel that I'm going to hit with greater velocity with a few more inches of travel.

I bring this up not because I think I'm any kind of an expert on this. I'm not. In fact, I'm eager for people who know more than me to set me straight. But as a layman, I think that my cage is giving me a net gain in safety, in spite of some trade-offs. Am I wrong?