Jerry Hey wrote:
Paul, on the longer Schertz beams could I weld plates inside the beam
in the form of a W truss to stiffen the beam instead of a strut
brace?
Jerry
That would not help. Just make it 1/4 or 1/2 inch deeper.
The strrength goes up with the square of the depth. A 1 inch deep
beam is 1. A 1.25 inch deep beam is 50% stronger. a 1.5 inch deep
beam is 125% stronger.
Paul Lamar
Paul, Please do the numbers and tell me what the hat section depth
should be for 30" between Barry centers. I am going to have a bunch
of this stuff bent up. One size hat section fits all. Thanks,.
Jerry
Bill Schertz did it for a 1 by 2 .063 wall tubing with is equivalent
(as far as bending is concerned) to a hat section 1 inch deep 2 inches wide
with one inch wide flanges. The strength is directly proportional to
the width and proportional to the cube of the depth. Not the square
as in my last message. I was looking at the wrong formula.
Here is the formula for Roark. "I" is what counts as far as the strength
is concerned. Ignore the rest.
How deep is your hat section? How wide and how wide the flanges?
Here is what Bill got for the 1 by 2 inch .063 wall tube 27.62 inches center
to center. The bold numbers are the stress for a 1" by 2" rectangular tube.
Namely 56,200. Note the stress goes way down to only 19,000 PSI for a
2 by 1-1/2 rectangular tube.
Here too is an FEA of the beam. A stress level of 1.0+005 is 100,000 PSI.
4130 is good to about 125,000 psi heat treated. With out heat treat it
is good to about 65,000 PSI. A light green means it is 6.0+004 or 60,000
psi. It is hard to say what the exact stress without an FEA. All we can do
is over design it by a 1.5 or 2 to one safety factor.
To be on the safe side put the struts in there for 30 inches center to center :)
BTW This is a one time thing that only happens in a hard landing.
Paul Lamar
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