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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#41
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determining the load on a corner "post"
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... On Tuesday, September 4, 2018 at 11:08:33 PM UTC-4, Jim Wilkins wrote: "pyotr filipivich" wrote in message ... Lifting Unit raises I-beam up by [bottle jack | screw jack | cam | "other"] powered by [electric | steam | pneumatics | Hydraulics | magic]. My Lifting Units are tripods of pipe or tubing that support chain hoists. The legs are joined at the top by a simple yet clever flexible arrangement of bolts and chains I devised 20 years ago that leaves the legs free to move around and divides the load between both sides of each leg, I think, in a manner that lets K=1 in the column equation. Likewise the pipes rest on actual balls or their near equivalents to keep the axis of thrust centered within the tube. https://en.wi "kipedia.org/wiki/Euler%27s_critical_load If I could prove the design's weight bearing capacity I'd reveal it, but I can't so you hereby know that a very simple folding pipe tripod is possible. All parts are common consumer hardware though they aren't necessarily used as intended. The load rating can be determined with on-line column calculators. I proof test them with a load cell when pulling stumps, which won't drop if anything fails. So far only one 5000 lb load cell has failed, and two legs and bottom ends were retired for their battered conditions. They move loads horizontally by walking the legs forward while the load is lowered, then raising it enough to slide. It's slow but requires only relatively level ground solid enough to support the leg baseplates. I would enjoy seeing your lifting tripods. I made something similar, but the top was three sockets made of pipe welded to a plate. Worked well enoug to lift a small horizontal mill off a trailer. Dan They aren't too different from the original that a neighbor used to pull engines. There was chain wound around the top and rather haphazardly attached to through bolts. IIRC he tossed another chain over it to hang the chain hoist. I liked that it folded parallel to carry and the legs could be repositioned independently if they sank in. |
#42
Posted to rec.crafts.metalworking
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determining the load on a corner "post"
"pyotr filipivich" wrote in message ... "Jim Wilkins" on Tue, 4 Sep 2018 23:09:41 -0400 typed in rec.crafts.metalworking the following: "pyotr filipivich" wrote in message . .. Lifting Unit raises I-beam up by [bottle jack | screw jack | cam | "other"] powered by [electric | steam | pneumatics | Hydraulics | magic]. My Lifting Units are tripods of pipe or tubing that support chain oooh - Tripods! Martian Walkers! Yes, of course, Pinky, are you pondering what I'm pondering? I think so brain, but were are we going to get a team of trained Hippos in tutus? tschus pyotr no, really, a good idea, too. -- pyotr filipivich "With Age comes Wisdom. Although far too often, Age travels alone." Sorry, no tutus. This is the hippo that watches over my doings: https://www.metmuseum.org/art/collection/search/544227 His partner atop the microwave is a Russian matryoshka (nesting doll) of Soviet leaders. |
#43
Posted to rec.crafts.metalworking
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determining the load on a corner "post"
On Wed, 5 Sep 2018 12:10:57 -0400, "Jim Wilkins"
wrote: wrote in message ... On Tuesday, September 4, 2018 at 11:08:33 PM UTC-4, Jim Wilkins wrote: "pyotr filipivich" wrote in message ... Lifting Unit raises I-beam up by [bottle jack | screw jack | cam | "other"] powered by [electric | steam | pneumatics | Hydraulics | magic]. My Lifting Units are tripods of pipe or tubing that support chain hoists. The legs are joined at the top by a simple yet clever flexible arrangement of bolts and chains I devised 20 years ago that leaves the legs free to move around and divides the load between both sides of each leg, I think, in a manner that lets K=1 in the column equation. Likewise the pipes rest on actual balls or their near equivalents to keep the axis of thrust centered within the tube. https://en.wi "kipedia.org/wiki/Euler%27s_critical_load If I could prove the design's weight bearing capacity I'd reveal it, but I can't so you hereby know that a very simple folding pipe tripod is possible. All parts are common consumer hardware though they aren't necessarily used as intended. The load rating can be determined with on-line column calculators. I proof test them with a load cell when pulling stumps, which won't drop if anything fails. So far only one 5000 lb load cell has failed, and two legs and bottom ends were retired for their battered conditions. They move loads horizontally by walking the legs forward while the load is lowered, then raising it enough to slide. It's slow but requires only relatively level ground solid enough to support the leg baseplates. I would enjoy seeing your lifting tripods. I made something similar, but the top was three sockets made of pipe welded to a plate. Worked well enoug to lift a small horizontal mill off a trailer. Dan They aren't too different from the original that a neighbor used to pull engines. There was chain wound around the top and rather haphazardly attached to through bolts. IIRC he tossed another chain over it to hang the chain hoist. I liked that it folded parallel to carry and the legs could be repositioned independently if they sank in. Or, by moving one leg at a time, you could "walk" a load across the yard so long as you kept the load from swinging. |
#44
Posted to rec.crafts.metalworking
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determining the load on a corner "post"
"Gerry" wrote in message
... On Wed, 5 Sep 2018 12:10:57 -0400, "Jim Wilkins" wrote: ... Or, by moving one leg at a time, you could "walk" a load across the yard so long as you kept the load from swinging. Only with loads light enough to move other faster ways. If the hoist chain, which is on the axis of the load's center of gravity, swings out beyond a line between the legs the tripod will tip, and lifting a leg out of the hole it digs swings a hanging load. A 2 ton chain fall without any load is nearly enough uncontrolled weight to tip the tripod while walking it. Generally I lower the load and loosen the chain, then walk the legs almost to the tipping point. When I ratchet up the load it slides forward into the center. If it's light enough I push it further with one foot while lowering, but a half ton log or boulder won't kick very far. Progress is less than 2' per lift, sometimes much less. After tediously moving that boulder about 30 feet with a tripod I rebuilt my 1 ton shop crane into a trailer with a hitch so I could back the load into place with my tractor. |
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