Juan Lopez

Matteo, Why would a roll cage be unsafe in street driving?

mamoroso

I fear that without wearing a helmet you run the risk of hitting the cage directly with your head.

The counterpoint to that is that the frame of the cge should not be too distant from say the A pillars and I think hitting the A pillars with the head is as dangerous.

But I have no experience at all and I might just be talking nonsense.

Juan Lopez

The cage's tubes will reduce available space but the compartment wil be significantly stiffer. Good (Roll Bar specific) foam helps a lot.

macnewma

This is something that I have thought a great deal about. I am by no means an expert on any of this stuff.

Right now, my car has a rollbar, 5pt harnesses, and Recaro seats. I have thought about getting a H&N, but I am unsure of which one. The Isaac one seems interesting. It is also simpler than their full model. Any opinions on this one?

924RACR

I was present for the first test of this device - well worth it, nearly as good as the original in frontal, and far less in cost. Would certainly get it if I didn't already have the full ISAAC (Intermediate, IIRC).

kurt M

In my opinon yes. You are improving the protection from stock without reducing it during for the more common for most of us street driving. My own experience and by no means to be considered the one path. I went from stock to a truss to a roll bar when I relised I was going to be doing this for a while. Car is GT6 and thus a cage is not required even for PCA club race. I use Recaro composite seats with a padded load spreading back brace. I don’t want the seat to fail as then I am no longer well contained by the restraint system. Without the back brace you have to rely on the seat and its mount. How many DE race seats are bolted in like stock with the original little bolts?
Composite and aluminum race seats can fail as well. My car is street legal but is 99% track driven now and only sees the street when testing recent work and changes or setting in brake pads.

The TUV looks at the seat systems as well. Stick a roll bar in a 76 or whatever older 911 with original stock seats and you are not at all the same as the GT3 setup.

Foam roll bar padding the type that you can squeeze and compress is of little if any use for absorbing energy. (It can only absorb as much as it takes to compress it. You can compress it with you hand using little energy).
In a real impact you go right to the bar with almost full energy intact. About all it is good for is saving you head from nuisance dings when you are working inside your car The rigid foam type it the stuff to use but it is made to work with a helmet in between your head and the bar. Round hard bars are good at compromising skulls flat surfaces are less so.

macnewma

So what is the downside to it? And how do you get out of it?

RedlineMan

Hey All;

Re: H&N - Get one. End of story. Any H&N is better than nothing, even a Hutchins. The R3 is interesting. The HANS and Isaac perform the best as I have seen it. I have a HANS. It can be trying at times because of its bulk (mostly with seat halos), but once you learn how to use it, it is not that much different than not having one.

Re: multi-pane mirrors - By all means. I have used one for years and swear by them. Getting my paint sucked off on a regular basis (150hp in the RED rungroup) makes it a bit of a necessity. I used the Wink brand mirrors for years, both 3 and 5 panel. They work great, but warp over time. I made one this year out of aluminum. Works great. Wouldn't be without one.

Re: Harnesses - 6-point minimum. The type ("V","T","Direct") governs the correct installation, but ANY 6-point properly installed is the way to go.

Re: Seat Braces - YES! The FIA is wrong on this one. You DO NOT want the seat to move or flex. You want NOTHING to move if you can help it, because movement leads to whip, and whip is the killer. NASCAR seats are bolted SOLID top and bottom.

Re: Side Nets - YES! Not easy to render, but VERY effective. Seats that flex/twist spill drivers out. Nets are all that's left to stop them. Someone asked how you can travel that far? In the average 30-40G hit, your hips will move 4-6" and your upper torso 16-18" ! That is with belts tightened by someone standing there yanking on them, far tighter than you can do from a seated position.

KE=.5MV^2 Half the mass times the velocity SQUARED! 30-40G is possible at 30mph. The human body can withstand incredible abuse, but only in a linear fashion. If bodies could be completely restrained, fatalities would nearly cease. If seats are allowed to twist, belts to stretch, no side nets, heads unrestrained, then the resulting whip action is what is most lethal. Poly 6-point belts stretch less and stop body motion quicker, braced halo containment seats retain the body better, H&N devices restrain the most vulnerable portion of the human body between the skull and shoulders. Side nets are there if any of these fail.

Re: Harness mounts - I DO NOT buy into the "must-have-a-roll-bar-if-using-harnesses/race seat" debate. BS! As Kurt said, look at percentages. I feel harnesses will get you out of more trouble than in... sort of like using the throttle. Using harnesses with a stock seat DOES propose some real compromises. I feel you at least need a seat with belt holes in it.

Trusses may be best for street driven cars, especially in metro areas where accidents are more likely, especially rear-enders. Roll bar? Yes, why not? Just take the previous into account and make your best informed decision. ANY bar/cage needs SFI Spec 45.1 high density padding EVERYWHERE that you might conceiveably contact it. Bars are better than cages for street, no question. The problem with cages is that even though you use HD padding, the bar does not offer a flat surface to deflect load, but an object protruding INTO your space. It makes a lot of sense to surround your head tubes with SFI Spec 45.1 (flat) padding to "flush out" these surfaces a bit.

Sheeeeeesh... this is complicated. Lots of stuff to know, and hard to type it all in one sitting. More to follow if necessary.

mamoroso

Point taken.. so what do I ned to properly secure my racing shells?
The Recaro sliders have only 4 holes and the size is just big enough for the stock bolts.

Having said that the stock bolts must have been certified from TUV, no?

I am open o suggestions.

So my next actions will be to
- order a harness truss (was looking at the Brey Krause R-1025 for my 911)
- order a HANS
- order a HANS 6 point harness

I will look into seat braces... but since I am not going with a roll cage for the moment I need to find one that can be mounted somewhere on the B pillars.

Again I am opent to all suggestions for harnesses and harness truss/mounts.

Thanks everybody for your help!

fatbillybob

Watch out using HANS and simple harness bars. Go to the HANS sight and review how they need to be installed. The quality of the HANS action is related to precise mounting instructions. The ISAAC is a more idiot proof device and can be used under more circumstances but then the controversy continues. As John says use A device but chose what is appropriote for your current safety system. IMO the effectivenes of HANS is directly related to the stiffling cockpit designs of the open cockpit cars and the similar internal design of NASCAR interiors with huge full containment seats that look like an F1 tub. These designs magnify HANS effectiveness which is in dealing with straighline impacts. The ISAAC claims lateral support abilites and retention on the shoulder belts. Thus may be more applicable to those with simple safety systems like typical plastic wingless 5 hole seats, lack of interior side nets, and 5 point harnesses. Lets face it we have all seen it and some of use have done it. I see expired belts, belts with cuts, 5th point sub straps over the front of stock seats, shoulder belts on stock seats causing divergent angles on the harness, wrap method shoulder straps kept together with zipties, leaking corrosion on fire systems etc....

mamoroso

OK I will look into Isaac as well. There is a HANS dealer 60 miles north of where I live.

I will certainly go there and ask them if the device needs a HANS seat, roll cage etc to be effective. Thanks for the heads up!

fatbillybob

Dr. Baker etal,

With Full containment seats should the interior sidenet be large enough to capture the shoulders and head or should the interior net need only be large enough to capture your head since you are held in by containment wings and the 6 point harness? It seems to me that window nets are too far from the seats. To have window nets function as well as interior nets they need to be closer. Therefore, for sake of rules mandating windownets but need for lfetside head retention and need for possible quick evacuation if the head is all we need to control it may be possible to have a small triangular net running from rollhoop down tube to A-piller toptube to catch the head. Is that suggestion a been there done that? I have never seen such a net. Opinions?

Thanks!

kurt M

BK makes a seat back brace that mounts to the BK truss. I must admit that I wonder if it is a good idea to do this as the seatback brace will impart a twisting load on the truss if pressed upon in an impact. I don't think the truss is set up to take the torsional loads that a rollbar cross bar could. I have only seen images of the setup so there might/must be something that I am missing.

gbaker

FBB,

(BTW, it's not Dr., it's Mr. Everytime I've performed surgery the patients were at room temperature.)

Current thinking is that side nets should be large enough to contain the head. This assumes the driver is using the newer designed seats which laterally support the shoulders. Older designs offered support at the torso, which we know can break ribs and injure the shoulder blade as it is bent over the side support.

Check the oval track catalogs. These nets are popular with sprint car drivers.

I should note that the net idea is a finger in the dike, i.e. it works as a stop-gap measure but is not the way to go long term. Every time more safety stuff is added to the car it becomes more dangerous with respect to egress. Ideally, the head and neck restraint would reduce head loads in all directions.

BTW FBB, your comments above...

...are spot on. In a very tight cockpit the HANS device can be very effective. Beyond that its performance drops off rapidly.

TD in DC

gbaker:

If I understand you correctly, you are saying that a properly operating neck restraint device such as a HANS should largely eliminate the need for window nets, which could make egress more difficult.

Likewise, what you, fatbillybob and others may be suggesting is that it is easier for a system like HANS to operate correctly in a very constrained cockpit because it might not be as easy for the device to slip or move at impact. It is more difficult for it to operate correctly (or rather, there may be more chances for failure) in an open cockpit design with lots of space for movement.

Since I will be driving a NA 944 with full cage and a kirkey deluxe seat (with seat bracing), is there any type of neck/restraint system that might be more effective than others for this specific setup. In other words, could it be that the different brands out perform each other in different situations. I realize I may be re-opening a can of worms, but I am getting a little more conflicted about my purchase plan as the day wears on (although now I am certain to purchase one type or another).