Roll over bars
- Thread starter wealdenengineer
- Start date
Seymour Snerd
Lifetime Supporter
Ron -- thanks for the link; I didn't realize the GCR was free on the web and my SCCA m'ship is lapsed. I'll check it out.
I take your point about percentages, but have had a specific interest in this question from the beginning. I considered buying a GT40R and running it on the street and looking at Lance's street car which has a cage the bar is clearly lethal. Yes, entry and exit with the cage as-is is wacky, but then if the front bar could be made removable maybe so can the side bars.
In the GCR it looks like the critical (and ambiguous) language is this (p.88):
Later on it says that "roll cage bracing" may be removable. So the only out I see is to use the "two side-hoop" arrangement and interpret the "tube connecting the two A-pillar tubes" as being "bracing" and therefore removable. 
I take your point about percentages, but have had a specific interest in this question from the beginning. I considered buying a GT40R and running it on the street and looking at Lance's street car which has a cage the bar is clearly lethal. Yes, entry and exit with the cage as-is is wacky, but then if the front bar could be made removable maybe so can the side bars.
In the GCR it looks like the critical (and ambiguous) language is this (p.88):
Instead of a single front
hoop, two side hoops (down tubes) may be used. Alternatively,
a top “halo” hoop following the roof line from
the main hoop to the windshield with forward down tubes
following the A-pillars to the floor may be used. Regardless
of which one of the two approved tubing configurations
there shall be a tube connecting the two A-pillar
tubes at the top of the windshield.
a top “halo” hoop following the roof line from
the main hoop to the windshield with forward down tubes
following the A-pillars to the floor may be used. Regardless
of which one of the two approved tubing configurations
there shall be a tube connecting the two A-pillar
tubes at the top of the windshield.
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Always sad to lose a friend so sympathies to all those affected.
To me the issue may arise because of using racing components on the road. In particular I am thinking of harnesses. When you use these on track you make sure they are done up very tightly and you use all 6 points. Plus you have a crash hat on. When on the road in the same car the temptation is to use only 4 points of the harness (perhaps not as tightly done up either) and no hat as it is more comfortable for a road run. But that is not how those peices of kit were designed to be used so when the worst happens they do not function as they should. Cages are for racing not road use, as a generality, and so the expectation is for crash hats to be worn. Franks concerns about proximity to cage struts is valid when in a road going car. Put the rights parts on the car for the way it is going to be used. And then use them properly. If you don't put a HANS device on properly with proper HANS designed hat, belts or seat they can do more harm than good in a lesser accident.
To me the issue may arise because of using racing components on the road. In particular I am thinking of harnesses. When you use these on track you make sure they are done up very tightly and you use all 6 points. Plus you have a crash hat on. When on the road in the same car the temptation is to use only 4 points of the harness (perhaps not as tightly done up either) and no hat as it is more comfortable for a road run. But that is not how those peices of kit were designed to be used so when the worst happens they do not function as they should. Cages are for racing not road use, as a generality, and so the expectation is for crash hats to be worn. Franks concerns about proximity to cage struts is valid when in a road going car. Put the rights parts on the car for the way it is going to be used. And then use them properly. If you don't put a HANS device on properly with proper HANS designed hat, belts or seat they can do more harm than good in a lesser accident.
Ron Earp
Admin
Later on it says that "roll cage bracing" may be removable. So the only out I see is to use the "two side-hoop" arrangement and interpret the "tube connecting the two A-pillar tubes" as being "bracing" and therefore removable.
There is no out here. That roll cage bracing refers to exactly that, the roll cage bracing, not the roll cage. A perfect example is the rear roll cage bracing on my Lola. It is tied to the rear main hoop using sliding couplers and the bracing is removable as well. But the "cage" is all welded together and non-removable. If you aren't worried about a logbook then it won't make any difference.
I haven't ever looked at the GT40R cage in depth so cannot comment if it is SCCA/NASA legal or not. As mentioned on the forum before, the SPF GT40s are sometimes used in historic competition and there the cage rules are, well, historic and in a lot of historic cars the cages basically non-existent. If you are thinking about building up your SPF for modern racing it is best to get with the tech inspector before you start and get him to help lay out your safety cage, particularly if he'll be issuing the logbook.
Good points Malcolm. Use the safety gear properly and for the intended purpose.
Seymour Snerd
Lifetime Supporter
I'm sure you're right; sorry for torturing the issue; I was just really hoping....
Seymour Snerd
Lifetime Supporter
Just to put a finer point on this, correct me if I'm wrong but: racing harnesses and street belts differ in a very important way: harnesses are designed to minimize stretch, and assume you are tightly belted in. On impact the intention is basically that motion of your torso is minimized, independent of deceleration.
Street belts, OTOH, are intended to stretch and thus decelerate you until just before you hit the dash or airbag.
This suggests to me that in a mid-level crash wearing a racing harness, especially a little loosely, you run a much high risk of collar bone fracture, etc, than otherwise and in fact if loosely belted you can suffer much higher levels of deceleration than with street belts.
And the "little loosely" part isn't really optional in my experience: when I had 5-points in my NSX (in addition to the stock belts) I once experimented with driving in traffic fully belted in. It was ridiculous in terms of my ability to effectively use the mirrors, reach the radio, etc. No one in his right mind would do that routinely.
When I crashed my Cobra race car, I entered the turn at just under 140 MPH, slid off the exit of the track and went airborn at 120 MPH, flew 88 feet the first time and after the bounce few another 30 or so feet and was still doing almost 70 MPH when I hit the tree head on.. Speeds and course all mapped faithfully by my G2X data acquisition system.
When I went to take my harness off to get out of the car, I found that my harness was very loose. I *always* pull may harness so tight, I can barely get a finger between the shoulder harness and my chest.
My helmet and harness were both sent to Pyrotect (the manufacturer) and checked out. I spoke with the owner of Pyrotect about the harness being stretched. He told me that it did exactly what it was designed to do and because it did it's job and my HANS device and helmet did their jobs, that I was uninjured (save for a slight sprain in my right wrist)... The harness was re-webbed with new fabric, the helmet was examined and pronounced fit for continued service.
The deceleration rate was calculated to be over 33 Gs as the car went from almost 70 MPH to zero in 22 inches (the distance from the front of the Cobra's nose to the front of the frame crossmember..
I'll take a harness that stretches over one that doesn't any time...
To add a side note to Randy's off.
A deceleration injury goes beyond the distance you traveled during the stop. The harness holds you intact with a little stretch but not allowing the body to be thrown forward, hitting other things in the car(same for the Hans device). With a seat belt, the limited amount of belting and the exaggerated stretching of the belts, and consequently the impacting of other objects like the steering wheel or dash or airbag if present are what cause the injuries we see. The forces acting on the body "internally" are where the damage is done.
Simplistically speaking, the driver in a regular car has two forces acting on his body in a head on collision. The deceleration of the impact absorbed somewhat by the belt, and the steering wheel impacting the chest. This means the rib cage stops in 0 inches or is pushed back if the column is being pushed back itself. This action amplifies the G forces acting on the body. Being healthy helps,but the deceleration to the heart, and aorta is what kills most head on collisions or leaves them paralyzed. The heart is slammed forward along with the ascending aorta. Being fluid filled their density is greater than the organs(lungs) that surround them. Therefore they(the lungs) are displaced and the ribcage is what stops their forward movement. This movement causes a tearing of the arteries that go to the spinal column.
Probably 98% of head on collisions with "seat belts" die on the scene. Somewhere in the neighborhood of 50% of those that survive the collision die in route to the hospital or die after reaching the facility from blood loss. The other 50% that survive are paraplegic as a result of their injuries.
So you can see the need for the harness to be a tight fit.
Bill
A deceleration injury goes beyond the distance you traveled during the stop. The harness holds you intact with a little stretch but not allowing the body to be thrown forward, hitting other things in the car(same for the Hans device). With a seat belt, the limited amount of belting and the exaggerated stretching of the belts, and consequently the impacting of other objects like the steering wheel or dash or airbag if present are what cause the injuries we see. The forces acting on the body "internally" are where the damage is done.
Simplistically speaking, the driver in a regular car has two forces acting on his body in a head on collision. The deceleration of the impact absorbed somewhat by the belt, and the steering wheel impacting the chest. This means the rib cage stops in 0 inches or is pushed back if the column is being pushed back itself. This action amplifies the G forces acting on the body. Being healthy helps,but the deceleration to the heart, and aorta is what kills most head on collisions or leaves them paralyzed. The heart is slammed forward along with the ascending aorta. Being fluid filled their density is greater than the organs(lungs) that surround them. Therefore they(the lungs) are displaced and the ribcage is what stops their forward movement. This movement causes a tearing of the arteries that go to the spinal column.
Probably 98% of head on collisions with "seat belts" die on the scene. Somewhere in the neighborhood of 50% of those that survive the collision die in route to the hospital or die after reaching the facility from blood loss. The other 50% that survive are paraplegic as a result of their injuries.
So you can see the need for the harness to be a tight fit.
Bill
This is a very sad thing to hear of, a tragic loss for his family friends.
From a collective point of view I think its important to learn what we can from the tragedy so hopefully one of us does not repeat this in the future.
Thinking about this has raised some questions in my mind, hopefully the answers will be useful in building future cars.
1. Do we know the distances involved to the front roll bar hoop in question or what is thought to be a safe distance? Does anyone have experience banging their head on things that you thought were far enough away not to?
2. In these situations is it all the head movement or is the roll cage coming back combined with the head going forward?
In production cars the plastic trim on the A pillars has a energy absorbing function also, for example the Ford Focus I had in the states was recalled to fit softer trim. In the case of my car (see below), I intend to pad all of the roof - wind sheild structure on the inside as per the instructions in this doc, also in the doc there's a diagram on page 35 showing the area around the seats that should be free head space, (which I've followed in my design) does this look to be sufficient?
From a collective point of view I think its important to learn what we can from the tragedy so hopefully one of us does not repeat this in the future.
Thinking about this has raised some questions in my mind, hopefully the answers will be useful in building future cars.
1. Do we know the distances involved to the front roll bar hoop in question or what is thought to be a safe distance? Does anyone have experience banging their head on things that you thought were far enough away not to?
2. In these situations is it all the head movement or is the roll cage coming back combined with the head going forward?
In production cars the plastic trim on the A pillars has a energy absorbing function also, for example the Ford Focus I had in the states was recalled to fit softer trim. In the case of my car (see below), I intend to pad all of the roof - wind sheild structure on the inside as per the instructions in this doc, also in the doc there's a diagram on page 35 showing the area around the seats that should be free head space, (which I've followed in my design) does this look to be sufficient?
My friends 17 year old daughter, who was in the car at the time of the accident, still lies in hospital on full life support with major head injuries. I am sure all our thoughts are with the girls mother who is having to cope with the loss of a husband and seriously injured daughter. Frank
Hi Frank,
That's terrible my heart just sank reading that.
That's terrible my heart just sank reading that.
Hi Frank,
Best wishes for today, I know it will not be easy but I will be thinking of you.
Paul
Best wishes for today, I know it will not be easy but I will be thinking of you.
Paul
Howard Jones
Supporter
I have a 17 year old daughter also...................I can't think of anything to say except......god bless her (your friends daughter), keep her, and heal her.
While not exactly in line with what you were suggesting, Ian, I'd like to make a comment and hopefully someone with more knowledge than me will have an answer that can help me understand. Why is the cage designed with the front crossbrace at a lower level than the rear crossbrace? Is there a benefit to that? If one thinks there is an aerodynamic benefit, I would dispute that, as it appears two different crossbraces at two different heights would present more resistance than two in a single plane as the cage parts the air. Is it required by the regulations of the racing organization? It seems to me that as one were fitting a roll cage, the height of the crossbar right in front of the forehead would be something that would be carefully thought out and checked many times.
Right you are, Pete....but in the past I have done so.....use to have a sand buggy that I raced and it was street legal, so I drove it to the grocery store, etc. People asked why I wore my helmet when the buggy had a roll cage, I just told them that the extra protection would be of great benefit if I were ever to roll it or suffer impact on the street. Never really gave much thought to the idea that it might look a bit goofy :stunned: , not that it would have kept me from wearing the helmet.
My sincere condolences go out to the family and friends of those who suffered this accident....sadly, nothing we can say or do can diminsh their pain at this moment, but hopefully their spiritual beliefs can grant them some relief from the grief.
Doug
Frank, so sorry to hear the terrible news of your friend and his daughter. We can just hope that the daughter makes a complete recovery.
Just a thought but is there room for an air bag in a '40 between the drivers head and the roll cage element just above the windscreen?
On the subject of helmets in cars on the road, I have seen a number of Aerial Atom drivers and also Caterham 7 drivers wearing helmets in that situation and it didn't appear to me as being in any way peculiar but , on the contrary, entirely appropriate in that sort of car.
Incidently, my RF has side impact bars in the doors which makes them very heavy - but I don't like to take them out (difficult as they are bonded in) in case I might need them one day.
Chris
Just a thought but is there room for an air bag in a '40 between the drivers head and the roll cage element just above the windscreen?
On the subject of helmets in cars on the road, I have seen a number of Aerial Atom drivers and also Caterham 7 drivers wearing helmets in that situation and it didn't appear to me as being in any way peculiar but , on the contrary, entirely appropriate in that sort of car.
Incidently, my RF has side impact bars in the doors which makes them very heavy - but I don't like to take them out (difficult as they are bonded in) in case I might need them one day.
Chris
Chris, I dont know enough about air bag installs ( Anybody here help ? ) but I would expect there is a set distance for each type of bag, and I guess that having a explosive bag a few inches from your forehead may be more lethal than life saving ! I spoke to the girls mother yesterday, it is exactly one month from the accident, and she is still on life support and unconscious, not much improvement yet, but we hope she will respond when the brain swelling goes down.
You cannot take an airbag out of any car, fit it to your homebuilt and expect it to reduce injury or save your life. The opposite effect is likely.
Air bags are car specific, designed to deploy and deflate at certain rates. There are many factors which control the rate of deployment, crumple rate of the vehicle, seat belt extension, seat belt anchorages to name a few. The air bag is intended to "catch" your head before it smashes into something solid (eg steering wheel) and slow it down before it does hit the solid object. It does this by inflating before your head is "caught" and then deflating at a controlled rate by holes in the non impact side allowing air to escape. Car companies spend millions perfecting the timing of air bag deployment and deflation. In the event that your head smashes into the air bag whilst it is still inflating then it is akin to hitting a brick wall, the impact face of the bag could be travelling at 200 km/h. In the event that your head smashes into the air bag after it has commenced to deflate, the benefit of the airbag is lessened and your head may still smash into the steering wheel with life threatening consequences.
SO - dont get suckered into fitting an airbag in your homebuilt car, the chances of it saving your life are ZERO !!
Getting back to the topic of the thread- roll over bars - There exists a prescribed relationship between ones head and anything in the vehicle it may come into contact with. It is termed the head impact zone and may be found in vehicle safety standards i.e. UNECE, eec directive , US CFR's. Aust ADR's. Any object within the head impact zone is required to contain certain energy absorbing characteristics, if it does not then it must not be there. Roll bars have basically no energy absorbtion when struck by ones head!!. The head impact zone is ascertained by swinging a defined Arc about the designed hip postion of a vehicle seat. If you are contemplating fitting a full roll cage, do the research, spend the time and the money to have it correctly designed and installed.
Now, - the padding on the roll bar, well that will stop the helmet getting scratched as your brain turns into scrambled eggs.
Be very careful, an inappropriately designed and installed full cage roll bar is a killer.
Air bags are car specific, designed to deploy and deflate at certain rates. There are many factors which control the rate of deployment, crumple rate of the vehicle, seat belt extension, seat belt anchorages to name a few. The air bag is intended to "catch" your head before it smashes into something solid (eg steering wheel) and slow it down before it does hit the solid object. It does this by inflating before your head is "caught" and then deflating at a controlled rate by holes in the non impact side allowing air to escape. Car companies spend millions perfecting the timing of air bag deployment and deflation. In the event that your head smashes into the air bag whilst it is still inflating then it is akin to hitting a brick wall, the impact face of the bag could be travelling at 200 km/h. In the event that your head smashes into the air bag after it has commenced to deflate, the benefit of the airbag is lessened and your head may still smash into the steering wheel with life threatening consequences.
SO - dont get suckered into fitting an airbag in your homebuilt car, the chances of it saving your life are ZERO !!
Getting back to the topic of the thread- roll over bars - There exists a prescribed relationship between ones head and anything in the vehicle it may come into contact with. It is termed the head impact zone and may be found in vehicle safety standards i.e. UNECE, eec directive , US CFR's. Aust ADR's. Any object within the head impact zone is required to contain certain energy absorbing characteristics, if it does not then it must not be there. Roll bars have basically no energy absorbtion when struck by ones head!!. The head impact zone is ascertained by swinging a defined Arc about the designed hip postion of a vehicle seat. If you are contemplating fitting a full roll cage, do the research, spend the time and the money to have it correctly designed and installed.
Now, - the padding on the roll bar, well that will stop the helmet getting scratched as your brain turns into scrambled eggs.
Be very careful, an inappropriately designed and installed full cage roll bar is a killer.
Four months on and very little improvement in the girls situation.
