Posting pics for a PM discussion on my Portable Gantry crane.
Notes not included in drawing: Vertical riser has 10 ea 1-1/16" holes spaced 6 inches apart (5 ft of adjustment)
Dimensions do not include the casters, as they are a variable.
Forgot to include top plate width or clamp plate dimensions. Top plate is 7 wide and 15 long 1/4 plate. Clamp plates are 3x15 each and are 3/8" thick. Square spacer is welded to clamp plates and is ½x½ stock. Use grade 8 bolts ½-13 with flanged nuts.
I beam is 8 in tall, 1/4 " web and 4" flanges, American Standard 8 x 18.4 beam. This beam is 12 ft long. most of this same design are now 15 ft with this beam.
Tubing all appears to be 3/16 thick wall.
You can probably buy one of these cheaper than you can make it, unless you happen to have the materials already.
Searches for "portable gantry crane" will bring up the sites for Wallace and several others, who make this same design.
You want this as tall as possible, ceiling in shop permitting, as you have the trolley and hoist hanging from it and you don't want that stuff bumping you in the head.