pic: sheet metal 6WD

[Chris is me]

Originally Posted by AdamHeard

The moment of intertia of the cross section is directly related to it's stiffness.

If you google, you'll see for a rectangle, the moment of inertia is 1/12bh^3 (base and height). Base being the side parallel to the axis the beam is being bent around.

So, a 5" tall .050" thick plate has an I = 1/12(5in)(.050in)^3 ~ 5x10^-5.

The same beam with two 1" flanges is that I plus the I of the two flanges. I = 1/12(.050)(1)^3= .004

So the beam with the two flanges has a total I of .004+.004+5x10^-5 ~.084.

.084 / (5x10^-5) ~150:1.

Even if I made a mistake in the math somewhere, this demonstrates the difference flanges make in design. I could go on for pages elaborating this, but it'd better to google and look yourself (key terms being beam, cross section, moment of inertia, etc...). You'll also then understand why I-beams are shaped the way they are.

I meant how much of a strength difference does cutting part of the flange out for the gearbox make? A poster said that it would be much stronger, and I wanted to know how much.