Does anyone know where to find simple tables or tools for figgerin out what size & thickness steel is needed for typical backyard projects? Like trailers, cranes, and stuff.
I am a woodworker / contractor by trade and have fiddled around for years building the occasional trailer, bracket and hitch carrier. I have been pretty good at building strong and durable projects by lookin at the metal and guessin. But that is really not a good process. For all I know I am buying steel that is way heavier than I need or running the risk of failure.
I know nothing is better than testing before use and for the hitch carrier, after I built it and installed it on the car, I jumped up and down on it and it didn't bend so I knew it would support less than I weigh. It also didn't weigh so much that the springs on the car kept if off the ground. LOL
I don't have an engineering degree but I can use a computer. If there is an online calculator or something?
What I need immediately is to design some lifting arms for my trailer, sort of like a boom truck would have. I need to know what size square steel tubing would be required.
For example, if I attach two arms to the rear of a trailer with drop legs to support the load to the ground. The arms are 60" apart and attach at the top to a crossbar that is 60". Attach a pulley to the center of the cross bar, run a cable from a winch located on the tongue 10' back and through the pulley down to a sling attached to a log that weighs as much as 2 tons. If the arms are against stops about 24" above and 24" back from the pivot. With the arms at a 45 degree angle and 10' long. see picture.
As the log is lifted it will be dragged toward the trailer. When the hook reaches the pulley, the arm boom will be pulled towards the front of the trailer dragging the log onto the trailer. When the log is as far forward as desired, the arms will have tilted as far forward as the front stops allow and the winch is reversed to lower the log onto the trailer. A pair of ratchet straps will hold back the arms from slamming forward as they pass vertical.
So then with 8' sticking past the stop, how do I figure out how to select a cross section shape and how thick the steel needs to be? I think that if the log weighs 4000#, the level fulcrum pressure would be 1/5 to 4/5ths or 20,000# ??? at the pivot. But at a 45 degree angle isn't it less? Or is the amount insignificant?
Assuming I drill a hole thru square tube and use a solid round pin. What size pin and what additional bracing at this point? And the cross bar would have the 4000# plus the force of pulling the log forward on it.
I know...liability and all. I am not asking anyone to assume any liability. Just point me to some tables or something so I can mess up the calculations on my own. For wood framing there are all sorts of span tables for determining what size joist for a cantilever. Surely there is something for steel.