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CSX 2000 Roll Bar 'Test' - Circa 1964
Roll bars always seem to be a lively topic around here, thought some might be interested in this ...
Been reading Bill Carroll's Ford Cobra Guide and came across an interesting bit about roll bars for the CSX2000 cars initially prepped by Shelby American for their racing program. They used 1-1/4" diameter, 3/16" wall, chromalloy steel tubing. "When the installation is complete mechanics make a simple but definitive test. Using a chain fall, they lift the car by the roll bar and sway it back and forth. Though the roll bar is off center, and the car hangs at an angle, the bar proves its stiffness and strength. In racing, more than one Cobra has been stood on its head without damage to the carefully engineered and installed roll bar or driver." Source: Ford Cobra Guide Bill Carroll ©1964 second printing 1974 page 80 This test only puts a 1 g static load on the roll bar / car in a direction unlike what it would probably see in an actual roll over. That being said, according to the book the roll bar certainly did its job. The key is likely how and where the roll bar is tied into the frame. A clever 'test' per se … it's one way I suppose to check if all the bolts were properly installed ;) |
That would be why they look so skinny, they were making up for it with alloy and wall thickness. Good stuff.
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Truly is good stuff............ Should be the way all are tested, bet most would fail the test........
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http://www.clubcobra.com/photopost/d...8405508_9X.jpg http://www.clubcobra.com/photopost/d...8405508_1X.jpg http://www.clubcobra.com/photopost/d...8405508_5X.jpg
This CSX4000 failed the final test............Ron |
That's my car! The roll bar and supporting tubes won't do that again.
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Thought that car looked familiar.....
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That's your car Nick? What's the story behind that one?
Larry |
I bought the wrecked car and have rebuilt the frame. I will post some more details and pics. The original owner crashed it and thankfully survived. Anyone who has looked at it agrees he would not have survived wearing his shoulder straps as they would have held him up in harms way. It is yet another example of the GT II tires just not being up to the job in these cars.
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Glad to hear that the original owner survived.
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You can see from this shot the 3/4 square tubing with a light wall used to mount the rear brace of the bar. The tube has been drilled through with fairly large bolts now much stronger than the tubing so that are also trying to crush it when you do them up and remove so much cross section it weakens it considerably. Originals used nut serts through only one wall that were very small and to my engineering brain don't look up to the job though I haven't calculated their combined shear strength. This tube is also poorly triangulated partly with the top trunk tubes that are not only bent to fit the body they are held in place with small tabs so they can be bolted in after a one piece trunk has been installed. Effectively a tack welded bracket. My solution to that was heavier wall tube and to weld in sleeves for the bolts that now act as a crush preventive and make the tube stronger than it originally was there. I hope this isn't considered a thread hijack and it all seems on topic to me. Shall I continue or start a new thread?
http://img219.imageshack.us/img219/8174/comp004.jpg |
Not quite sure where this photo is taken on the damaged car...But I would like to see a few photos of the hoops outside leg at the end where its secured to the chassis and the actual mounting lug for the hoop on its outside leg. A while back, a Superformance had a similar accident and the method of securing the outside leg of the hoop left something to be desired...
Update Text appeared on the photo after my post |
Nick,
Definitely on topic, feel free to add more information ... additional photos would help as well to understand what you found on your car, and how you fixed it. Thanks! - Tim |
So...just for interest, and the uninformed (ie me) - who makes the chassis and peripherals for CSX4000s?
Fair enough, if your Cobra came from Supercheap Cobras Inc. then maybe you can't expect it to be gold-plated underneath, but if a Cobra has, let's say, Shelby American's name on it, one would expect the roll bar to live up to expectations. (Apologies to Supercheap Cobras, if they they exist!) Cheers, Glen |
Here is a view a little further back showing the roll bar support.
http://img837.imageshack.us/img837/3391/comp001.jpg The parts out of the car being replaced http://img849.imageshack.us/img849/4875/proto001.jpg |
What the original roll bar brace hardware looks like
http://img821.imageshack.us/img821/962/3021385.jpg http://img84.imageshack.us/img84/6320/3021388.jpg These are nutserts through only one wall BTW |
The fix (hopefully never to test) on mine, heavy wall tube with bolt tubes welded in.
http://img684.imageshack.us/img684/2034/bartubes002.jpg http://img31.imageshack.us/img31/844/bartubes001.jpg |
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If Shelby really tested their roll bars by lifting the car off the ground with a chain, that clearly shows backward thinking on their part. Think about how stupid that is...That's testing the opposite forces required to make a roll bar useful.
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Presumably, everyone here knows the 427 Cobra factory roll bar was outlawed by the SCCA and other sanctioning bodies as of '68, since by their examination they felt it would not stand up to a rollover. Which is why in race photos from '68 on, the cars have full-width bars in sanctioned events.
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