I'm waiting for the rain to quit, but i was able to double check all of the loadings and make sure what i wanted to use for everything. I'm not going to bore everyone with a bunch of trig, but with the geometry i randomly chose the guylines will be the same size as the winch line, which is 7/16 wire core. The guyline in the back will doubled so it's in the wll, so that will make ordering wire easy. So gotta hunt down a wire supplier close, I've used lifting gear hire (actually the name of the company) before so I'll call them Monday. I might need to call an old employer to use them as the delivery spot (forklift and industrial spot for a semi), so I'll have to do that too.
I'm thinking of doing 7 x 36 wire for the flexibility, wire core for crush resistance. I'm not planning on abrasion being too bad, but we'll see. I also had a moment of clarity and decided to use some 1/2 wire spliced into grommets for all the tension connections on the poles, so i grabbed some wire at tsc for that. I like that idea better than welding the truck axle up, and it will be more than strong enough. I'll do them with a 4" pipe welded to the outside of the 3" for a better bend radius, with little clips to keep everything in place since it will be up in the air. I also grabbed a bunch of hitch pins to lock the poles in place on their supports. I could have made some from rebar or something, but the drilled holes with pins, galvanized finish, and the fact they were less than 5 bucks a piece almost makes the decision for you lol.
The 2 inch pipe isn't in any column loading charts i can find, but it is very commonly used as the larger size for 1 ton truck mounted ones, with similar length and winch size, and will lift the front end up on those trucks. Further if i consult the charts, 3" pipe is rated for 14k pounds at 15 foot, and the shearleg design using 2 inch will hold at least that by estimating from the sizes bigger. I could do the calculations, but I'm pretty confident I'm good there. The slenderness ratio is 69, so I'm still good there (at 120 you switch formulas because of a different failure mode). The 2 inch pipe up top acting as a pin will be a beam, but it's so short i think I'm good there. The base supports will be likely the lowest strength member on the whole thing, simply because they are nothing but 2 inch pipe sticking out from a 3 inch pipe, with no supports. The welds on those will be the most critical because that's all that will be holding it on and it's a tearing force, which is about the worst you can do. They will only be 6" long tho, and loaded 1.5 inches from the welds, so honestly I'm very confident there too. So from my shoddy math, this should work just fine. Here's a picture of the column loading chart, from the Bible of building anything, aka machinery handbook. If you do dumb stuff like using scrap and welding rod, it's an excellent resource, as is engineering toolbox online. It even has sections to walk you through the math (if you ever need to do math and not simply read a chart), which is helpful because if you don't do it everyday you forget.
