Could you? Would you?
- Thread starter Keith1
- Start date
The Ford GT uses square tubing throughout...and the hydraulic 'crusher' machine used to test the strength of 'same broke trying to crush it.
'Nuff' said regarding whether to use "A" vs. "B", I think...
That aside, I agree with Jack's assessment: "Round tubes require so much more preperation and fixturing."
'Nuff' said regarding whether to use "A" vs. "B", I think...
That aside, I agree with Jack's assessment: "Round tubes require so much more preperation and fixturing."
Round tube is much stronger and less prone to torsional flexing than square for its equivalent weight. FIXTURING WTF is that all about ?? Must be a merican thing.
Bob
Bob
Unfortunately, I suppose because it's me, they are not treating my request seriously.
It was not a question designed to promote a different form of chassis construction i.e. Alloy monocoque or discuss the relative virtues of square tubing, it was purely from an engineering standpoint what the possible advantage/limitation analysis of constructing a scratch built GT40 chassis from round tubing would be.
(It might be on my bucket list)
It was not a question designed to promote a different form of chassis construction i.e. Alloy monocoque or discuss the relative virtues of square tubing, it was purely from an engineering standpoint what the possible advantage/limitation analysis of constructing a scratch built GT40 chassis from round tubing would be.
(It might be on my bucket list)
While true, round tube is stronger pound for pound (or kilo to kilo), round vs. square of similar dimension shows that round is about 75% lighter, but square is considerably stronger. For more equivalent strengths/weights, as an example, 3/4" x 0.065 square is about the same strength and weight as 1" x 0.058 round. So, depending on how tight things fit, and how proficient you are at cutting, chamfering, and welding round tube, square may be a better choice.
Ian
This is an off the shelf Pro Stock Chassis designed for what +1,000 hp? I understand the rear frame rails may well end up being square tubed but 90% of this is round tube.
There are thousands of ready made off the shelf chassis for most racing applications and they are 90% + round tube.
If square tube is stronger lighter and cheaper, why don't they use it? Is this picture essentially just a kind of 'survival cell' only?
The chassis in this picture are being built of 90% + round tube. Would they have been better to build them in square?
There are thousands of ready made off the shelf chassis for most racing applications and they are 90% + round tube.
If square tube is stronger lighter and cheaper, why don't they use it? Is this picture essentially just a kind of 'survival cell' only?
The chassis in this picture are being built of 90% + round tube. Would they have been better to build them in square?
Pat
Supporter
Keith,
My formula race car is made of both. When I asked the designer about it he said you actually need some flex in a frame, it keeps it from breaking. Especially if you are running high torsion loads like engine torque or cornering loads. But there are also places that need to be rigid and places to allow some flex.
Hollow square tubing of the same cross section is not only better at resisting bending load (higher second moment of inertia), it's also better at resisting torsion. However, a chassis build far easier to bend and fit together using round stock than square tubing. To make my point, look at a tube frame diagrams just posted and imagine them using square tubing. All that said, the primary factor in a frame's rigidity is how the members are laid out rather than the cross section of the material.
So I think the right answer may be both…
Consider this example which may be quite familiar.
My formula race car is made of both. When I asked the designer about it he said you actually need some flex in a frame, it keeps it from breaking. Especially if you are running high torsion loads like engine torque or cornering loads. But there are also places that need to be rigid and places to allow some flex.
Hollow square tubing of the same cross section is not only better at resisting bending load (higher second moment of inertia), it's also better at resisting torsion. However, a chassis build far easier to bend and fit together using round stock than square tubing. To make my point, look at a tube frame diagrams just posted and imagine them using square tubing. All that said, the primary factor in a frame's rigidity is how the members are laid out rather than the cross section of the material.
So I think the right answer may be both…
Consider this example which may be quite familiar.
Attachments
Yes Colin liked his 'X' chassis. Good answers thank you. When ever I look at a GT40 spaceframe, I am struck by how ugly and agricultural it looks, not at all like that beautiful Porsche 908/10 on other threads or even the 917K original type both of which look to me to be elegant yet well composed with their round tubes.
I never quite understood it, but if I had the money, fitness and aptitude, I would be into making a scratch built round tubed GT40/Lola T70 etc. I could own one of those, or any kind of mono you care to name, but I would never ever want to build or own a square tube chassis car. For me personally, it's academic, I know.
But, it's a question I've been wanting to ask for long time and I am getting to the stage when I want to ask previously unanswered questions that bother me. That's one off the list - there will be a lot more I'm sure.
The answer is: I could build one if I wanted and it would be OK.
I never quite understood it, but if I had the money, fitness and aptitude, I would be into making a scratch built round tubed GT40/Lola T70 etc. I could own one of those, or any kind of mono you care to name, but I would never ever want to build or own a square tube chassis car. For me personally, it's academic, I know.
But, it's a question I've been wanting to ask for long time and I am getting to the stage when I want to ask previously unanswered questions that bother me. That's one off the list - there will be a lot more I'm sure.
The answer is: I could build one if I wanted and it would be OK.
I think the birdcage Maserati is good showcase for the tubular chassis, a true work of art.
AUTODROMO: Maserati Tipo 61 Birdcage
Bob
AUTODROMO: Maserati Tipo 61 Birdcage
Bob
Agreed, beautiful. Requires a lot of fixeration though
What about all that weldering ? :lipsrsealed:
Bob
If there is no buckling (and assuming the same alloy), there is no strength (or longitudinal) stiffness difference between a round and square tube of equal weight. The main factor that comes with a real-world application is that round tubing is typically available in a stronger alloy, and for equal weights, round tubing is less prone to buckling.
Strength and stiffness are generally independent of each other (alloy-wise), so a properly designed space frame chassis (with no individual component buckling) will have exactly the same stiffness in round or square tubing, even if the square tubing has a lower tensile strength. The bottom line performance of a chassis is its stiffness. Unless you screw up the high stress areas, strength comes along for the ride.
Terry Oxandale
Skinny Man
I would continue to use the square tube in a '40 project (which is what I've used in the current Manta project) vs round tube, mostly because any shear panels that are wanted are easily installed versus using round tube, and nut-serts used to attach various pieces to the frame have an nice flat mounting surface in a lot of places. The down side from my observation is the loss of cubic inches taken up by the tubing that could be used for other necessities. I think the round tube would be easier to construct vs square (given the proper cutting tooling), and looks nicer in the end, but square seems to be so much more practical for the reasons noted above.
Jack Houpe
GT40s Supporter
Lamborghini used tubes in the spaceframe of the countach, Maserati did on the birdcage and both considered strong enough so why not, Lamborghini countach used some type of adhesive and rivets to secure the panels.
It would be interesting to see what would happen if, say, the Ford GT chassis design were replicated using round tubing, and then subject it to the same crush test wherein the Ford unit broke the test machine.
In the end it all just may boil down to a combo of both the design AND the style of tubing used as to which one is more suited than the other in a particular design/purpose/need situation.
In the end it all just may boil down to a combo of both the design AND the style of tubing used as to which one is more suited than the other in a particular design/purpose/need situation.
Keith:
I tossed the idea of round tubing before I started. The shape of the Gt40 chassis and then the cladding lends itself easier to square. Having drilled holes to install the interior sheet metal drilling a round tube for rivets a pain. My old stock car all tube was round except the main frame rails. So my answer is no.
I tossed the idea of round tubing before I started. The shape of the Gt40 chassis and then the cladding lends itself easier to square. Having drilled holes to install the interior sheet metal drilling a round tube for rivets a pain. My old stock car all tube was round except the main frame rails. So my answer is no.
