Tractorsport Flowbench Forum Archive

Posted: **Thu Mar 22, 2007 8:02 am**

Ok, this is completely irrelevant to anything flowbench, but I figured there's some pretty clever guys here who could help me out.

I have attached a picture to help me explain.

If I place this outside, how can I calculate how much weight I need in the base to stop it blowing over in high winds? I don't need to be mega accurate. The panel is 1.8m x 0.5m. I would be very grateful if someone could show me the calculation in easy steps!.

THanks..

Posted: **Thu Mar 22, 2007 1:50 pm**

Here's how I would do it (in the English system of measurements)!
1. Calculate the force on the panel: worst case wind is directly on the face.
Drag= Cd (Drag Coeff) x q (dynamic pressure) x S (area).
Flat plate Cd = 1.29 (lots of references).
q (dynamic pressure) = 1/2 x rho (air density) x velocity of wind squared. I'll use 60mph ~ 90fps (actually 88, but use 1.5 to convert mph to fps and you will be "close enough for Government work". LOL)
S (reference area) = h x w of your panel (sq ft)
Drag=1.29 x 1/2 x .002378 (sea level) x 90^2 x 12.9 = 160 lb

2. Calculate the moment trying to tip the panel over
M = Drag x moment arm (use 1/2 the "h" dimension - slightly less due to spillage at the top, but OK)
M = 160 x 3 ft = 480 lb - ft

3. Calculate the resistive moment
Mr = Wt x resistive arm
The resistive arm is the distance from the panel to the edge of the base you don't show dimensions on.

You want the Mr to be more than the M, so calculate W = M / rest.arm! Unless this thing is going to fly, double the weight. If that isn't possible leave the weight and double the base dimensions! When you are calculating the weight, don't forget to add in the weight of the base.

Hope this helps! -- Doug

Tractorsport Flowbench Forum Archive

Completely Unrelated Maths Help Needed