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
The prototype hat section is .063. It is 2.250" wide, 1.5" deep and
the flanges are .750 wide. Does this mean that this hat section is
125% stronger than Bill's? If so, is it strong enough to stand up to
"HARD" landing test without further support? If I put the Barry
centers at 27" then what? I just used a 24 inch MILD STEEL piece as
a ramp under my heavily loaded 3/4 ton pick up with a 454 adding to the
load. There was a small amount of bending of the 3/4" flanges at the
lower end but the beam remained absolutely flat. It is not distorted
at all. I think this would be equivalent to a 48 inch beam in the
aircraft . A 30" beam would only have an unsupported span of around
8.5" Is that the wrong way to think about it? I know you will want
to know how much weight beam actually supported and I don't know. Still
this test does give one hope. Jerry
I am proud of you Jerry :) I like a guy willing to static test his products.
It probably will be strong enough. However the tire is distributing the load a bit.
Nice quick and dirty test however.
For a better, more accurate test use two blocks of wood under the ends
and cut a pieces of 1/2 steel in the same shape as the end housing.
Bolt the steel plate to a junk oil pan and support the front end of
the oil pan with another block of wood. Use a 12 by 18 piece of 3/4
ply on top of the oil pan to support the tire.
Don't drive the truck up on it but jack it up and then let it down on
the whole works.
Your truck empty weight is around 5000 to 6000 pounds with 60% on the front.
3600 on the front 1800 on each front wheel which is about the right load.
Paul Lamar
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