What makes this gantry interesting is that it can be taken apart, stuffed in a Ranger or similar mid-sized pickup truck and transported to another location relatively easily. I built this thing when I was in my twenties, but nowadays I like to get someone to help me set it up and break it down, so I don't kill myself in the process. With two people it's doable and I've found it particularly useful to have the portability. I call it Elmer.
To roll smoothly the gantry needs a good, solid concrete surface with no debris or cracks about to snag a caster. The I-beam that slides into the telescoping top pieces is about 8 ft. long, giving a span of 6 ft. between the uprights, sufficient for a Ranger or other mid-size truck to back a load through the gap. The beam measures 2-1/4" wide and 3" tall and by narrowing the gap between uprights to 4ft and by bracing beneath the base with 4x4s (to take the load off of the casters) I have lifted loads as great as 800 lbs. (my "benchtop" CNC mill), but your mileage may vary.
I have several chain hoists and I use the one appropriate to the load. The largest of these is a 3-ton capacity Chinese job that I bought from Northern Hydraulics a while ago for $75.-. Since it costs $35.- to rent a chain hoist, this seemed like a good investment. Be aware that this size chain hoist is a heavy mutha and it is best to have a friend help lift it into place when hooking it onto the trolley that rolls along the I-beam.Also, in any lifting operation, it's best to have a friend around who knows the drill, just for safety's sake...
|Photo #1: Here's the whole thing, in its most compact form with the telescoping top segments slid down all the way into their rolling bases. In this position it just rolls underneath a 7-ft. door or the header on a typical garage.
|Photo #2: Here's a closeup of the top of one of the two telescoping top segments, with a pocket that the I-beam slides through. It's a sliding fit, but not so loose that the contraption can wobble; maybe there's .010 in. or so of clearance, but no more. The pocket is 1ft. long and made of 3/16" plate. The upright tube 1-1/2" square with a 1/8" wall and the gusset is made from 3/16" plate.
|Photo #3: Each telescoping top segment has 7: 5/8" holes drilled cross-wise on 4" centers. Beyond the bottom hole is another 18" of tube, to stabilize the thing as much as possible when it is fully extended. At its maximum height, the bottom of the I-beam is 8-1/2 ft. off the ground. Each telescoping segment fits just inside a rolling base which has one cross-drilled hole so that top and bottom segments may be secured with a hitch pin that is retained with a safety clip (foreground). The upright tube on the rolling base is 3/16" wall, 2" square. The base is 3/16" wall, 2" by 3" and the diagonals are 3/16" wall, 2" square. On the outside top edge of the rolling base's top tube there is a little ledge which was intended to support a jack, so that the whole thing could be raised by one person without getting a hernia, but to date I've always had a few pals around to share the load, so this feature is untested. The hook beneath is to hold the hitch pin, when the telescoping sections are in the full-down position, when the holes are out of alignment with those in the rolling base.
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