I'm building a small rolling gantry with telescoping legs. Each leg should be
able to hold 1 ton of weight. The legs are made of 3/16" wall structural steel
square tubing, which is A500 steel, which withstands a minimum of 39,000 psi at
yield point according to my steel handbook.
I figure the pin will only push on half of the hole. The surface area of half of
a hole = PI*DIA*3/32.
What I'm not sure of is how to actually design the pin & hole. Can I just
multiply my half hole area times 39,000 to get a raw number, which I then derate
until I'm comfortable? Or am I looking at this wrong?
To use an example, if I use a 5/8" pin in a 5/8" hole, the pin presses down on
half of the hole's area. That surface area I get as .184 sq. inches, and
multiplying that times 39k gives me about 7179 pounds, or about 3½ tons.
If I use a 3/4" pin/hole, I get 8614 pounds - more surface area.
Going up to a 1" pin, I calculate 11486 pounds.
Am I doing this right? How big a derating factor would *you* be comfortable with?
- posted 14 years ago