I'm no good at long strings of calculations and am apt to make a mistake along the way. So I wrote this into a Javascript some time ago. You still need to understand the basics from above though.
http://www.windyhilllogworks.com/Calcs/beamcalc.htmI set it up to use total load so enter 3750 lbs
I used 1.2 for E and 165 psi for shear
The max moment outputs in foot lbs, my mind wraps around bending torque better that way, busted knuckles imprint deeply
Now, you're probably thinking I ain't got a lick of common sense specifying a beam of that dimension for that span.
Do this, run it the first time using the 3750 lb load, 300" span, 7.25" wide x 11.25" deep beam. Notice the Max moment. Now divide the load and span in half to 1875 lbs and 150". Divide the beam thickness by 4 making it 1.8125" wide. Notice the max moment again.
This is where our common sense usually fails us. In doubling a span the bending force does not double, it quadruples. The span doubled AND the load doubled.
If anyone wants that calc right click and "save as", it'll run offline, its simply the formulas from above.
