Andrew, I don't understand all of the structural calcs, and I am wondering if I have violated some tongue-drilling rule by drilling a hole for the chain support vertically about 4 inches away from the hitch, as well as a vertical hole where the innner tube slides within the outer tube right in the front of the tear. (the hitch assembly is connected to the end of the tongue with holes drilled from the side and vertically as well).
Suppose we were to drill holes in the center of two identical 3 foot long square tube sections of tongue stock, one drilled vertically and the other horizontally, with welded connections at each end holding them parallel to each other. Then insert a hydrolic jack between them and start jacking them apart. I find it hard to beleive that the section with the vertical hole would bend before the other. I am but an old commercial construction superintendent, somewhat aware of the shear moment of the sides and the compression and tension created on the upper and lower sections of the square tube. Wouldn't horizontal holes violate the strength of both of the sides, more than holes in the upper and lower sections, one in tension and the other in compression?
You may be right, but it makes me want to do an actual field test to see what happens. Structural engineering is not my strong point, and I can only look to Dave for pointing out this potential problem at the Spamboree. Thanks Dave............
Roly ~~ all of this thinking makes my head hurt!