Roll Cage Information for GT40 Please

[Dean Lampe]

I would love to see a picture of the original cage. You don't have a picture do you?

[Ron Earp]

Originally Posted by Mike Drew

Whether an original-spec cage would satisfy current regulations, I don't know. But at least you could be assured that it was a historically accurate design....

I would like to see one and know the specifics of tubing, wall thickness, as well as mounting points and attachment. I don't think an original cage is going to satisfy any sanctioning bodies' rules that we deal with today.

I'm sure an original cage would be fine in HSR. But HSR isn't for replicas. I'm not sure there would be much of a point of having a historically accurate cage if practical racing use is the goal.

R

[Scott Calabro]

Hi All,

Back in post #14 Howard made an excellent point about removing the side window/s.

So excuse the slight thread drift here OK?

For a car with a full cage this would be a great addition for emergency egress.

40-102

Removable door top conversion. Allows the removal of the door top roof panels in warm weather converting the car into an open top. To replace the panels simply locate in position and tighten Two fasteners.

£995

Cheers,
Scott

[Paul Thompson 'Hooligan']

Looks really nice Iain!!! Bet she's gonna fly (not literally!)

Do I see Air-Jack positions on the rear? or am I miss-reading the pic?...

[Frank Catt]

Current MSA regulations for roll bars in the UK are Cold Drawn Seamless Carbon Steel Minimum yield 350N/mm2 Minimum Dimensions 45 x 2.5mm or 50 x 2mm thick ( I understand 2008 regs may now be minimum 50mm all. This is substantially greater diameter than most refered to above, which seam to rely on 1.5 inch ( 38mm ) tube. The whole fabrication changes with these thicker/ bigger diameter materials, particularly as a diagonal brace is also now mandatory to the hoop just behind the driver. Additionally all tubes must be formed in one length, there can be no welded joints in any tube, just another difficulty.

[Jac Mac]

In the Book 'Shelby GT40' by Dave Friedman on pages 118/119 there are three pics post the crash test that give an indication of the cage design.

FWIW, the removable bar as in Deanes Cage is one element of the cage that I would like to see deleted from cars with a relatively narrow cockpit, there have been too many fatals and severe injury incidents from 'that' bar where the car suffers a side impact as a result of a crash or even sliding sideways off the track into a barrier etc . The cage in the Daytona that Peter Brock ( Aust) died in is an example of this. ' That' bar was only inches from the side of the helmet in what is the weakest point of helmet design. When you get the sideways whiplash effect from a slide into a barrier or from a car slamming into yours if you have spun/stalled on the track the Best Hans Device or full harness in the world will not prevent your Head/Helmet from contacting the bar. This applies to most of the cars being constructed by forum members & I feel that it is time some of you who may be in a position to influence the Rule Makers in your various sanctioning bodies to have a serious look at changing the requirements in this area.

[PaulGT40]

Hi,
Are there any chassis plans out in cyberspace for a tube frame that can be purchased?
Thanks Paul

[Russ Noble]

Hmmm......

Jac Mac, I'm not sure about that one.....

I don't know about the official cause of death for Brocky but from photos I have seen I would imagine that if the bar didn't kill him then the tree would have.

With the sort of impacts you're talking about you're probably going to die anyway from a broken neck?

Unless I saw some supporting evidence from some really in depth studies which addressed the question "Would the driver have lived if that bar was not in place?" I think I would prefer to have the bar. The regs mandate that I've got to have it anyway, so for me it's a non-issue.

I'll try not to worry myself sick about it......

Cheers

[Straight 8 Racing]

I'm not sure if Peter Brocks Death created as much of a stir in NZ as it did in Australia and I am also fairly sensitive to the whole "Kit Car" debate but I am fairly sure that he would have met the same fate driving any car. Some of the antagonists that are less than complimetary about our cars (Porsche drivers in particular) claim that he would have survived in a Porsche, I find this very hard to beleive, with or without the bar the effect of a side impact at 200k plus down to zero K in less than a second will always be the same..... My only querie is would the aditional bar work help in a roll situation ? Turn 1 at Eastern Creek has, for me, has an entry speed of 270K, if things go wrong there is a large area of kitty litter that is great if you enter going forewards, if you enter sideways then its only a matter of time untill you roll, we have tried to provide as much support to the front corner of the cage to help in the event of a roll but as Jac Mac points out your head is extreemly close to just about everything,

Iain

[Julian]

Here is a pic of the half cage installed in my DRB. This complies with the requirements of CAMS regs (Australia) for general circuit racing. A full cage would be nice for safety and chassis rigidity, but I couldn't justify all the extra work plus likely centre spider bodywork removal to fit it all. Plus getting in and out would be even more painful, as mentioed in many previous posts!

Car is getting closer to going properly. Exhaust is the last major item to fabricate now. Then get it painted, build decent motor and toughen up trans. Get it all together and start competing/developing and hopefully winning. Easy if you say it quickly!

[Ross Nicol]

I've spoken with Richard Bendell (the builder of the Cobra Daytona Brock was killed in) and luckily (not a good choice of word in the circumstances) for him, the builder, the car was fitted with a lot of sensors including side Gs, steering angle etc etc and all were data logged.The information proved the car did not contribute in anyway to Brock's death.Apparently the impact with the tree was in the region of 5 to 6 Gs and according to investigators most cars would have been in 2 pieces with that impact. In fact the car is to be repaired. I agree with Jac Mac to some degree as during a race in my 240z at Phillip Island I was turned 90° across the track, when the same guy who spun me rammed the front right wheel.The impact threw my body against the tubular seat frame and cracked a couple of ribs.I will not use tube frame seats again and does anyone know how hard it is to disguise the fact (from your wife) that you can only lie on your left side in bed because it hurts. I live in fear she will try and stop me racing you see.

Ross

[Big-Foot]

Originally Posted by ross nicol

I've spoken with Richard Bendell (the builder of the Cobra Daytona Brock was killed in) and luckily (not a good choice of word in the circumstances) for him, the builder, the car was fitted with a lot of sensors including side Gs, steering angle etc etc and all were data logged.The information proved the car did not contribute in anyway to Brock's death.Apparently the impact with the tree was in the region of 5 to 6 Gs and according to investigators most cars would have been in 2 pieces with that impact. .............
Ross

Hi Ross - With all due respect - I'm not so certain that the sensors on board that car would have shown the "true" instantaneous G force.. Most D-A systems have accelerometers that max out at 5gs in order to maintain a higher degree of resolution at lower Gs...
When I crashed my Factory-Five Cobra at Brainerd International Raceway a couple of years back, my G2X data acquisition system registered the maximum amount of G's that the accelerometer could record which was just over 5gs.
Point in fact, the calculated g force on my body was over 33gs as the car went from just a hair under 70mph to 0mph in 22 inches.
That's what hitting a rather large tree head-on will do for you. The resistance of the fiberglass body and minimal support tubing and oil cooler reduced the G-load by an unknown amount - however - once everything was collapsed up to the main "X" crossmember on the Cobra chassis - myself and the engine and transmission started our deceleration rather swiftly..

All in all - I came out of it unscathed save for a sore shoulder and wrist. Thanks to my good (and verytight - initially) harness and Hans device.
Note - the car went airborn while doing just over 120mph the first time.

While 33gs sounds (and is quite a lot) - many Indy car drivers have survived in excess of 50g impacts. However - they did not get up and merely walk away as I did..

[Ross Nicol]

Hi Randy
I take your point about accelerometers bottoming out, I guess they must have a finite capability like most transducers.The info I provided above is relayed from Richard who is a friend of mine in racing circles.He is also the CEO of Motec so I would assume he and his technical people would be well aware of accelerometer limitations, however it's not my field so I can sometimes be impressed by smoke and mirrors. Sounds like you were lucky to come out of that prang unscathed, hope you bought a Lotto ticket.

Ross

[Paul Thompson 'Hooligan']

Not motorsport related, but when pilots eject from jets, they will generally endure G-Forces of between approx 13G and 22G and usually walk away after the event.

Also:
The highest g-force endured was 82.6g for 0.04 seconds on a water-braked rocket sled by Eli L. Beeding, Jr., at Holloman Air Force Base on May 16, 1958. He was hospitalized for three days. [Source: Guinness Book of World Records] (eek! )

I'm sure that one of the main factors involved is survivability of G-Forces relates to how well ALL body parts/limbs are supported during impact, together with the direction/manner in which the forces are applied.

I seem to remember Malcolm having a 'little off' at Bovington Sprint a few years back that tripped his ignition cut off that I think was set to about 10G... He'll no doubt be able to confirm the details.

[Canuk40]

Hi Ron,

I agree with you on period correct vs new requirements for roll cages. We've had the chief technical inspector here from CASC (like SCCA) and had a thorough going over of the CAV monocoque chassis. Although the basic structure of the car is quite sound and impressed the inspector, bringing the car up to current regs will be even more impressive.

It's all do-able, however the car had best be a track only car, after all the side intrusion tubes, knee bar, diagonals etc are in and padded you'll have to squirm into the car through a little hole not much bigger than the side window openning. It was also noted you may be able to climb in through the exposed roof openning when the door is open.

It's good to hear when people survive crashes and so sad when they don't. Safety is a far greater element of racing and car design today than ever before. F1 used to be a blood sport, now drivers survive horrific crashes. I've attached a report of Robert Kubicas crash at the Montreal GP last summer, 70g's is well below the highest recorded at 179g's - incredible. Kubica survives crash at 75 G - Autoblog

Also for those who like a challenge, also posted is Appendix O from the CASC Handbook describing the proper design of roll cage structures. We are working on an roll cage to safisfy these regs, which I undestand closely mirror those of SCCA, Grand America Cup and American LeMans. Stay tuned...

When I heard of Pete Brocks death it really saddened me, I suppose because he met his demise doing something he loves. The loss is the same, it would seem less tragic however if it were in a plane crash or other accident.