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Old 03-14-2010, 06:48 PM   #1
sgtlethargic
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Default square [tubing] roll bars?

Has it ever been used for roll bars? I'm looking at the cover picture for "Cool Cars Square Roll Bars" and it looks like round tubing; I was thinking they used to use square tubing. I'm thinking about using square tubing for my stalled HA/GR project. It seems square tubing would be easier than round tubing for the garage guy to cut, fit, and weld. There probably won't be any bends.

Thanks,
Kurt
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Old 03-14-2010, 06:53 PM   #2
1934coupe
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Default Re: square [tubing] roll bars?

I believe they are refering to the shape of the roll bar, not the shape of the material. Those rollbars were mitered and welded in all the old style rollbars I've seen including the first one put in my race car in 1962.

Pat
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Old 03-14-2010, 07:21 PM   #3
exStreamliner
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Default Re: square [tubing] roll bars?

From what I can tell the early "round" roll bars were tubing capped filled with dry sand which were heated and bent over a wheel... procedure was done twice... matched both pieces and welded them together... at least that is the way my 33 was done in the day... I found large radius dies and the bar on my 27 was the same outside radius when it was done the modern way and in one piece... so retro style bars are possible without being square... unless that is the look you are after
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Old 03-14-2010, 07:22 PM   #4
Flatheadguy
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Default Re: square [tubing] roll bars?

I am not a Structural Engineer, but the first thing I thought of is the relative strength of square vs. round tubing. I suspect (instinct engineering) that of a given size (incl. wall thickness) that round would have greater strength in all modes. Plus, I've always found round to be easier to bend. And, the miter is no big deal. Someone will chime in and either flame my thought or agree.
An interesting question though. Makes us "think".
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Old 03-14-2010, 07:30 PM   #5
Larry T
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Default Re: square [tubing] roll bars?

This one had 2" square tubing, 45 degree cuts for the corners, no reinforcing plates and one bar going to the rear for support. I ran it through the 70's and never got questioned about it. When I got around to cutting the rollbar out it was about .090 wall thickness. The car ran 120 MPH at Green Valley. Never considered what would happen if I rolled it.
Larry T
BTW, I don't think square tubing rollbars are legal ANYWHERE any more.

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Old 03-14-2010, 07:34 PM   #6
Dale Fairfax
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Default Re: square [tubing] roll bars?

In the beginning (of roll bars), round tube or pipe was used because it was commonly available. A lot of them were black pipe. I even saw galvanized pipe in a lot of hardtop stockers in the early fifties. Square tubing was available but not common-it was too expensive.


Quote:
Originally Posted by sgtlethargic View Post
Has it ever been used for roll bars? I'm looking at the cover picture for "Cool Cars Square Roll Bars" and it looks like round tubing; I was thinking they used to use square tubing. I'm thinking about using square tubing for my stalled HA/GR project. It seems square tubing would be easier than round tubing for the garage guy to cut, fit, and weld. There probably won't be any bends.

Thanks,
Kurt
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Old 03-14-2010, 07:36 PM   #7
rjaustin421
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Default Re: square [tubing] roll bars?

Square tubing was seen on northeast oval track modifieds from around 1960 (as far as I can recall) to 1965 or so. It was a heck of a lot easier to work with than round but obviously does not have the strength of round tubing. It was gone from the scene by the mid 60's or so probably by everyone following Nascar's lead in requiring round tubing.

I would not want to test it in a crash and by the time you got the cage triangulated enough to have adequate strength for the various angles of impact the cage would be the weight of an average steel bridge.
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Old 03-14-2010, 08:06 PM   #8
rustyford40
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Default Re: square [tubing] roll bars?

We had no way to bend the pipe so we welded them in a square shape. And go racing we used 11/4 black irion pipe. We used the same pipe to build our trailers. We did not need ramps as soon as your wheels hit the trailer it would bend to the ground and you could drive on. when towing you got used to seeing sparks. No lights no licence plats no fenders one axel and junk yard tires. That was racing in the 50's
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Old 03-14-2010, 08:15 PM   #9
shmoozo
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Default Re: square [tubing] roll bars?

I can't speak for anybody else, but when it comes to roll bars I can't imagine wanting to build one for a hot rod today that didn't comply with the current rules for the major drag racing sanctioning organizations. It's not just there for looks, after all. It's there to help keep you alive in the event of a roll over.
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Old 03-14-2010, 08:36 PM   #10
k9racer
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Default Re: square [tubing] roll bars?

I ahve seen several circle track cars with square tubing.. The most famous were several cars built by Red Farmer.. He won a lot of races with them.. When asked why he use this type of materal his reply was that one of his friends gave him a truck load.. After he used sq tubing it was monkey see monkey do and a lot of cars had them.. It was easy to cut and weld.. As far as roll bars I have seen 2 peices of black pipe welded to the chassis and a Bumper on top .. I have a roll cage mad from aluminum.. At that time the rules said black pipe so it was painted black.. This cage was in Bud Lunsfords skeeter car and won a lot of races. At nashville tenn fair grounds the pit stewart had a sledge hamer and checked roll bars with hard hits.
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Old 03-14-2010, 08:36 PM   #11
sgtlethargic
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Default Re: square [tubing] roll bars?

Quote:
Originally Posted by Flatheadguy View Post
I am not a Structural Engineer, but the first thing I thought of is the relative strength of square vs. round tubing. I suspect (instinct engineering) that of a given size (incl. wall thickness) that round would have greater strength in all modes. Plus, I've always found round to be easier to bend. And, the miter is no big deal. Someone will chime in and either flame my thought or agree.
An interesting question though. Makes us "think".
The term "mode" seems to be a great way to put it. I think the circular shape has an advantage and that square tubing would need to be thicker walled to be equivalent to round tubing. The funny thing is, I basically forgot I have most of a roll bar kit from a Chevy II that I could modify to fit.

Just another thought: I wonder if there's more effective strength in the direction of the "edges", as in if square tubing was rotated 45 degrees.
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Old 03-14-2010, 08:38 PM   #12
exStreamliner
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Default Re: square [tubing] roll bars?

Building period correct rides doesn't mean using lesser quality steel - it is the era correct look... and we have better and safer options... I never plan to race or need roll bars in my cars but I like the look and in a worst case situation - I'm safer for it
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Old 03-14-2010, 08:38 PM   #13
rustyford40
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Default Re: square [tubing] roll bars?

Quote:
Originally Posted by shmoozo View Post
I can't speak for anybody else, but when it comes to roll bars I can't imagine wanting to build one for a hot rod today that didn't comply with the current rules for the major drag racing sanctioning organizations. It's not just there for looks, after all. It's there to help keep you alive in the event of a roll over.
Yes today you have a roll cage. we didn't have that in the 50's people got hurt and they started to change the rules that is how the roll cages started. we used black iron pipe thats all we could find at the junk yards or may be 1/12. Now you must use chrome molly or something like that. We showed the wrold that black iron made a bad roll bar. I never saw square tubing.
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Old 03-14-2010, 08:48 PM   #14
50dodge4x4
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Default Re: square [tubing] roll bars?

Just to balance things out, back in the the early 90s, our local dirt track allowed square tube to be used in roll cages in the "lower" classes. There were at least 15 cars running in the hobby class with the square tubing, one of mine included. Through the course of the 3 years we run them, I can tell you without much doubt they were as safe as any round tubing cages at that time. Cage design and the quality of the welds, given the same thickness and relitive size of the tube had a lot more to do with safety then the shape of the tubing. We distroyed many cars in that class, some pretty major crashes. A T bone at the end of the straight was enough to bend any cage (long 1/2 mile measures at the inside of the track and the hobby class was timing in around the low 28 sec laps.) and roll overs,flips, and contact with the cement wall were not uncommon. In a hard crash, square tube tends to crush (flatten out) a little easier then round, but I've seen enough round tube shear off to scare me a lot.

In this day and age, I'd probably build the cage with round tubing simply because it is accepted everywhere, but I would not be afraid of a well designed and properly welded square tube cage at less then Nascar speeds.
Gene
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Old 03-14-2010, 08:54 PM   #15
sgtlethargic
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Default Re: square [tubing] roll bars?

Another thought is that some HA/GR dragsters have a hoop near the rear (effectively a roadster with a roll hoop), and therefore don't have much rollover protection except for flat ground with nothing sticking up, like a concrete barrier.
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Old 03-14-2010, 09:05 PM   #16
Antny
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Default Re: square [tubing] roll bars?

Rectangular and square tubes develop high stress concentrations at the bends (edges) when under load and can fail easier than a round tube. So in order to get the same strength as a round tube cage, the square tube will have to be much larger in cross section. It can be done, it's just not an efficient material for this application.
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Old 03-14-2010, 09:09 PM   #17
DAVEG2
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Default Re: square [tubing] roll bars?

I've seen square tubing fail in stock cars. Not a pretty sight.
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Old 03-14-2010, 09:14 PM   #18
Flatheadguy
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Default Re: square [tubing] roll bars?

See? I knew some others would add their well thought out analysis. (smiling) I will admit that back in the late 60s - early 70s, Trans-Am and IMSA Camel Series cars had full roll cages that were, of course, designed to protect the integrity of the cabin (driver area) but another main concern was chassis stiffening. Which was more critical? Uh,.....(smiling) I know that I could jack up any of my cars a foot off the ground at a corner and the car would teeter totter...no flex anywhere. And the doors would open and close perfectly. By rules, they were not welded shut in those days.
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Old 03-19-2010, 11:06 PM   #19
KING CHASSIS
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Default Re: square [tubing] roll bars?

Here is one.
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Old 03-20-2010, 12:07 AM   #20
50dodge4x4
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Default Re: square [tubing] roll bars?

Quote:
Originally Posted by KING CHASSIS View Post
Here is one.
Looks like the square roll bar held up better then the rest of the car!

As for the earlier post stating they have seen square tube cages fail, I think anyone that has been around racing very long has seen every type of cage fail at some level, and its never pretty. I think we have also seen those wrecks where we wonder how the person ever survived and other times when we wonder how someone even got hurt. The reality is, when its your time, its your time, and when its not, its not. Doesn't matter what we think we can do to alter those facts. Gene
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