Pardon the INTRUSION - GT40 Safety

Randy V

Admin
Lifetime Supporter
Pardon the INTRUSION - GT40 Safety

In the process of building my GT40 and watching others build theirs, I realized that I wanted to take a few steps to make my car a bit safer / more crashworthy.

The doors on most of these cars are just fiberglass with no metal support structure.
I wanted to somehow do the following;

1) Add some sort of positive reinforcement to the door that would function as an Anti-Intrusion device around the same height as the standard automotive bumper here in the USA. Steel will slow down an intruder faster than will fiberglass.

2) I've not been fond of the idea of mounting a door latch solely to the fiberglass with no reinforcement - that reinforcement / mounting structure was to be added.
Inner and outer Latch Plate reinforcement. The originals were also done this way as best I can tell.

3) The door handles on most of these cars are mounted to the fiberglass handle-pocket with little more than a 3/8 (10mm) bolt run through the thin fiberglass. This will not do for my car. Steel is much stronger.

-----------

Anti-Intrusion Beam;

I will be tying the Door Hinge bolt (1/2" Grade 8) to the Latch-Plate on the door.
One of the things that concerns me about adding this beam is that is this;
If the beam is bent (and we have to accept the fact that it will be in a collision) - it may well draw the rear latch plate towards the front of the car. This "could" JAM the latch. If the Latch Lug is attached to something strong - you may well find yourself with a door that will not open.
My latch lug will be attached to the roll-cage.

How do I solve this?

By making a bind resistant anti-intrusion beam with a floating front mount.

----

Materials -
Anti-Intrusion Beam / Door Release Handle Mount:
1-1/2" x 3/4" x 1/8" Mild Steel Channel Iron

AI-Beam Slider:
2" x 1" x 1/8" Mild Steel Rectangular Steel Tubing

AI-Beam Rear Mount / Door Release Handle Mount:
1-1/4" x 1-1/4" x 1/8" Mild Steel Angle

AI-Beam Slider Mount;
5/8" x .125 CM Steel Tubing
2 - 1" Mini-Hose clamps (to dampen vibration/rattles)

Rear Latch Plate:
1/8" 2024 - T3 Aluminum Alloy

Bolts:
1/4" - 20 GR5
1/2" - 20 GR8 (door hinge pin)

Door Latches (Standard RCR Issue):
Mini Bear-Claw by Autoloc

----

Total Weight of AI system and Door Release Mount (with all bolts) 6.5#

----

Yes - I know that some of this steel is rusty but it will all be cleaned and painted with enamel prior to final installation.

----

The Seed that I started with for the Anti-Intrusion Beam;



AI-Beam Rear Mount / Door Release Handle Mount:




AI-Beam Slider Mount ( I cut the access panel for ease of installation )









Slider mount for AI Beam in action






AI Beam and Door Release Handle Mount
(End Caps are needed to bolt them into the door)




Drilled & Tapped in place #7 Drill, then 1/4" drill through the outer layers











Not much "Meat" to put a 3/8" bolt through for the Door Release Handle


The Release handle will now bolt through a custom steel channel




So in the end, I've added roughly 6.5# to the door, but I think it will be worth it in the long run.

I'll post more of the door release handle and linkage I've designed (and yet to fabricate) once that aspect of the car is finalized..

On my website I will post full instructions and measurements when I get a chance.
 
Last edited:

JimmyMac

Lifetime Supporter
Randy,
I hope that you don't mind me saying so but that was an excellent job and your acticle should be in the "How to Do" section.
 

Dave Bilyk

Dave Bilyk
Randy,
second JimmyMacs' comments.
I would guess that some careful research and thought was needed to arrive at a workable solution, so this is Engineering with a captial E. Well Done.

Dave
 

Randy V

Admin
Lifetime Supporter
Thanks guys...

It's my understanding that things like this are required on vehicles in Australia and elsewhere.. Perhaps this may be "sufficient" for them - or not.. I've asked a couple of people now (GT40 vendors) for their insight during the design phase of this project but have not heard back from them.

If anyone knows that this would be sufficient to pass a vehicle inspection that mandates side impact protection - please let me know and I'll be happy to work towards a full instruction set to be made available here on GT40s...
 

flatchat(Chris)

Supporter
Great work Randy --as you say, its mandatory here in Aus. and all locally produced cars including Cobras and GT40s have had this system for many years now -- air bags next I suppose :uneasy:
 

Peter Delaney

GT40s Supporter
Randy, as mentioned by Chris & Geoff, we have to have intrusion bars here in Aus. The interesting innovation that you have introduced is the "sliding joint" concept to cater for some deformation of the bar & still allow the lock to open (& thus maybe save your life) !

The bars we have here are solidly fixed front (to the hinge plate) & back (to the door lock plate) - there are 2 of them in each of my DRB doors. Any significant deformation of these bars would surely jam the door lock in position - not ideal when the point of impact has been the door (read : just above the fuel tank) !

I guess that the issue is the severity of the impact & the degree of deformation :

- No bars ==> you get deformed

- Your "sliding joint" bars ==> a margin of safety before the bars deform & jam the doors

- Solid bars ==> jammed doors straight up

It would be interesting to see what Trevor Booth has to say about all this ?

Nice piece of engineering !

Kind Regards,

Peter D.
 
Randy, well done.
The genius of some people constantly amazes me. There are some great engineers on this forum.
Garry
 

Trevor Booth

Lifetime Supporter
Randy,
your anti side intrusion bar (ASIB) is well done, I might suggest that a channel section would not be satisfactory as it will deform into a flat plate upon impact

however by way of explanation

The ASIB is an energy absorbing structure intended to deform certain distances under certain loads as prescribed in US CFR 49 part 571.214. There is initial, intermediate, and peak crush resistance. The load can be up to 3 1/2 times the kerb mass of the vehicle. The displacement at peak crush resistance is 18"

The door hinge and the door latch are an integral part of the performance of the ASIB.

you may have noticed on some vehicles that they have a round peg with a flat washer on the end for the striker, they may also be like a stirrup and some vehicles have a round peg on the door which fits into a hole in the body.

The are all intended to connect the door latch to the body (B pillar) likewise the hinges to the A pillar and transmit the load thru to the body/chassis.

Your proposed sliding mecahnism is in fact detrimental to the performance of the ASIB as it allows uncontrolled displacement of the ASIB in the initial stages of load application.

Worry not about being able to open the door afterwards chances are it will be able to be opened and I might suggest that after having sustained an impact there wont be much left of the door in any event !!.

What you dont want is for the rear end of the door to become disconnected from the B pillar and push the whole door in.

As well as the ASIB you need to pay particular attention to the A and B pillar in the mannner in which the loads are transmitted from the door to the body.

Whilst I have visited the RCR establishment I did not pay particular attention to how the striker is supported on the B pillar.

Hope this helps to provide an understanding of the role of an ASIB
 

Randy V

Admin
Lifetime Supporter
Thank you again guys - please feel free to use whatever ideas / processes that make sense for your build..


Hi Trevor - Thank you VERY much for reviewing my work... It's most appreciated!

Randy,
your anti side intrusion bar (ASIB) is well done, I might suggest that a channel section would not be satisfactory as it will deform into a flat plate upon impact
If not channel - use an I-Beam? My last Corvette (was a 1996) used a 3-4" wide piece of steel that looked the work like a guard rail (wavy shaped). I suppose that might be a good shape but where to find the materials...


however by way of explanation

The ASIB is an energy absorbing structure intended to deform certain distances under certain loads as prescribed in US CFR 49 part 571.214. There is initial, intermediate, and peak crush resistance. The load can be up to 3 1/2 times the kerb mass of the vehicle. The displacement at peak crush resistance is 18"
Wow... 18" is a long ways.. I was thinking / working towards 6 to 8" Even if the slider bolt were bottomed in the slotted beam - it would still pivot / bend over an inch more before the beam would be in direct contact with the hinge bolt tube..

The door hinge and the door latch are an integral part of the performance of the ASIB.
I was indeed counting on the latch plate and hinge system for my anchors.. Looks like I was working in the right direction...

you may have noticed on some vehicles that they have a round peg with a flat washer on the end for the striker, they may also be like a stirrup and some vehicles have a round peg on the door which fits into a hole in the body.
As is mine - Mini Bear Claw latches:



The are all intended to connect the door latch to the body (B pillar) likewise the hinges to the A pillar and transmit the load thru to the body/chassis.

Your proposed sliding mecahnism is in fact detrimental to the performance of the ASIB as it allows uncontrolled displacement of the ASIB in the initial stages of load application.

Worry not about being able to open the door afterwards chances are it will be able to be opened and I might suggest that after having sustained an impact there wont be much left of the door in any event !!.
You see - this is one of the fears that I have... Having been trapped in my Corvette after having been t-boned at about 25-30 MPH by a 4500# car - I had to pull myself out from under the steering wheel and over the console and out the passenger side door.. Problem was that the door was jammed shut / my wife who had hit her head badly on the side glass was in the passenger seat.. I just wanted a chance to deflect / absorb "some" of that energy of an invading car - without being trapped in the car.

What you dont want is for the rear end of the door to become disconnected from the B pillar and push the whole door in.
Agreed!!!

As well as the ASIB you need to pay particular attention to the A and B pillar in the mannner in which the loads are transmitted from the door to the body.
A-Pillar on the RCR is very stout 3/16" thick Alloy. The A-Pillar hinge mount is 1/4" thick steel





Whilst I have visited the RCR establishment I did not pay particular attention to how the striker is supported on the B pillar.
How the door striker is mounted is left up to the customer as is the internal or external mounting of the latch itself. It's good that it's open because there are various schools of thought on "how" to do it - esthetics - etc..

My striker bolt/pin will be solidly mounted to a roughly 4" long piece of 1" x 2" x .125" steel that will be welded to the main hoop of the roll-cage.
I figure that would be a lot stronger than almost anything else I've seen. Actually this mount would be essentially a copy of at least one other RCR builder that chose to go this route.

Hope this helps to provide an understanding of the role of an ASIB
Your help and insight is invaluable to me... I will more than likely make further changes to this system based on your input..

I'm not worried about adding even more weight to the car. It's light enough where I doubt I am making a substantial impact on handling given the limited track use the car will see..

Thank you again!!!
 
Last edited:

Chuck

Supporter
Randy:

Really nice work. And the added benefit, I suspect, is that the doors will close with a solid, authoritative, THUNK !
 

Trevor Booth

Lifetime Supporter
Randy,
you could add a flat to the channel you have already made and turn it into a box section. Allow the flat to protrude say 15-20 mm each side.

The wavy section ASIB is a very good energy absorber flattening out all the depressions.

See attached for typical section. The 197 wide section is ex Mitsubishi Cordia, Good for a 1100 kg car and door length of approx 1200 mm. The 190 wide section is ex Nissan S13. Cant recall material spec but about 350MPa yield.

You could cut one out of a door at the junk yard.

The proposed method of attaching hinge and striker sounds ok, The A pillar is very sturdy and the mount to roll bar is a good idea. The 0.125" thick matl may be a bit light particularly if the pin /striker is bolted thru it. Some local reinforcement would be a good idea , perhaps a large washer with a different diameter to the one supplied with the striker/pin.

Here is another wild idea-- fill the door with foam -- you would be amazed at how strong and energy absorbing that will be.

Please understand the foregoing is considered informative only, it is no guarantee that it will materially reduce the risk of injury.
 

Attachments

What about a honeycomb system? Flip the channel over so the flanges hold a series of long steel tubes (1/2" conduit?) on the doorskin side of the channel. You could weld in a couple of flat plates to hold everything together. I guess my thought is this would be, in essense, similar to the "highway barrels" used to slow down cars that would otherwise fully impact bridge stantions. The honeycomb would collapse and absorb energy before the channel begins to deflect. Just a thought.

If I can figure out how to add images, I'll add a couple of sketches.

Eric
 

Attachments

Anti-Intrusion Beam

Modern cars have intrusion beams but they are made of H.S.S. High Strength Steel. It is completly different from mild steel. You are not suppose to ever try straightening or welding this material for repair or modification for it wil become weakened and useless. The chemical composition and heat treating is incredably more ridgid than mild steel. In all respect I think the mild steel will offer very little protection. When I have worked with similar C-channel I have been able to change the form with a simple 5 pound dead blow hammer. The C-channel is also a weak design for the way in which one would expect it to be hit in the event of an accident. If mild steel would be used I would find something with more beam height for strength on impact. Just my opinion, please take no offense.
 
Top