Square Steel Tubing Calculation (and related design questions)
Let me state up front that I'm not an engineer. I've come to this forum looking for some advice/assistance.
A good customer has put me in a position that I don't care to be in, however his business is too valuable to refuse. We custom build a machine (to his specifications). He has a need to raise and lower the entire machine 36". The machine is enclosed in a steel 4" square tube "roll cage" (for lack of a better description). He wants us to use the vertical square tube supports to build a lift assembly. In other words, he wants to use pneumatic cylinders to lift the machine. In fact, he has suggested that we use pneumatic cylinders located inside of tubing that slides inside of a larger bore tube to raise the machine (he does not want to use hydraulics). The machine weighs 6,100 lbs. and is near uniformly weight distributed. (The reasons he is not figuring this stuff out himself is too complicated to get into in this forum.)
Now, I know from research that if I am using four air cylinders to lift 6,100 lbs (and adding a fudge factor of approximately 1,500 lbs), each air cylinder bore will need to be 5". Thus, his 4" vertical square tube will not house the air cylinders. Here is what I propose, but I want to run it past the experts first:
[LIST][*]Replace his 4" vertical square tube with 7" square tube (0.188" thick wall to allow 6" square tubing to slide up/down inside tube)[*]Use 6" square tube (0.188" thick wall) as the "extension leg"[*]Install the 5" bore air cylinder (outside dimensions = 5.5" x 5.5") inside both tubes; connect cylinder and rod ends to the 7" and 6" tubes[/LIST]
Now for my questions:
[LIST][*]Will the thickness of the 6" and 7" tube be sufficient for the weight it must support?[*]How many inches or feet of overlap should I have for the 6"/7" tube so I don't have to worry about the machine being wobbly or unsafe when it is elevated? (Something tells me it should be at least 33% overlap... probably from my days working as a carpenter... lol)[*]Would you use a double acting air cylinder to control lowering the machine?[*]Would you use hitch pins to hold the machine in the elevated position once it has been raised?[*]Check valves on the air lines with a manual ball valve to depressurize (for lowering the unit)?[*]Is there an easier way to do this?[/LIST]
If this is off topic for this forum, please direct me to the correct forum. All assistance is greatly appreciated. Thank you.