Which Company makes "best" replica?

[bdeutsch]

Rectangular frames versus round frames...

Round frames are by their nature, stronger. Any corners, are inherently weaker than their surrounding material.

Bob

[Silverback51]

Originally Posted by bdeutsch

Rectangular frames versus round frames...

Round frames are by their nature, stronger. Any corners, are inherently weaker than their surrounding material.

Bob

The "I" value for a 3.00 diameter, .125 wall round tube is 1.17 inches to the fourth.

The "I" value for a 3.00 x 3.00, .125 thick wall square tube is 1.98 inches to the fourth.

Sorry for the same size a square tube is stronger.

[Anthony]

Originally Posted by Silverback51

The "I" value for a 3.00 diameter, .125 wall round tube is 1.17 inches to the fourth.

The "I" value for a 3.00 x 3.00, .125 thick wall square tube is 1.98 inches to the fourth.

Sorry for the same size a square tube is stronger.

They're really not the same size. A square tube is also about 27% heavier.

Even though a round intake port is the most efficient, your analogy is like saying a square 3" intake port will flow more than a 3" round port, which it will.

[Silverback51]

Originally Posted by Anthony

They're really not the same size. A square tube is also about 27% heavier.

Even though a round intake port is the most efficient, your analogy is like saying a square 3" intake port will flow more than a 3" round port, which it will.

Okay, I was lazy.

Let go with some real frame component sizes and see what we get.

Superformance.
2 X 4 X .160 wall rectangular tubing. The "I" value of this is 3.69 Inches to the fourth.

ERA.

3 X 4 X .125 wall rectangular tubing. The "I" value of this is 3.92 Inches to the fourth.

Kirkham.

4.0 diameter X .120 wall round tubing. The "I" value of this is 2.76 Inches to the fourth.


Now this is just basic strength of materials for structural shapes and does not take into account the other structural bracing and such that makes up the frames. The only way to really compare any of these frames to determine which is the strongest would be to build a FEM model and run it through a stress program to determine what is happening when like loads are applied.

Unless one of the above manufactures has actually done this for all three frames, they cannot make any claims that theirs is the strongest.

Yes, the ERA 3 X 4 X .125 tube is the strongest, but that single component does not make it the strongest frame. All it would take would be one series of truss members to make the Kirkham tube assembly 10 times stronger.

Besides, don't beleive everything you read from manufactures (or politicians) as they are all trying to sell you something.

Is that better?

And thank you for challenging my response. I don't get to play with numbers much at work anylonger. Even this simple stuff was kind of fun.

[RodKnock]

Originally Posted by Silverback51

Kirkham.

3.0 diameter X .120 wall round tubing. The "I" value of this is 2.76 Inches to the fourth.

Per the Kirkham website, 4" round, not 3".

http://www.kirkhammotorsports.com/mfg/frame_index.html

[Silverback51]

Originally Posted by RodKnock

Per the Kirkham website, 4" round, not 3".

http://www.kirkhammotorsports.com/mfg/frame_index.html

You are correct, it is a 4.0 diameter tube.

When I did my calculations I did it for a 4.0 round tube. I just screwed up when I posted the numbers.

I'm going to blame it on the beer.

Thanks for keeping me honest.