Re: 250 LbsRe: How Big Is The Disc

"Bob La Londe"  wrote in message news:10204dd$2jbi9$1@dont-email.me...
I use whatever is easiest for lifting.  I looked everywhere for my dad's
old chain fall, and after I bought one I finally found his in one of his
old trucks.  I've got multiple cable pullers, a tractor with front
implement forks, & 2 chain falls now.  LOL.  Pulling a burned out
compressor out of an AC condensing unit works really well with a
straight pick across the rungs of a 12 foot step ladder and a cable
puller.  Whatever works.  I sold an old Cummins engine a while back and
loaded it with a tiny little cable puller, a giant cheater bar, and an
old steel A-frame that barely fit around the bed of the truck.  It was
all I had at that location.  Whatever works.
Bob La Londe
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I made do with "whatever works" for a long time. What I've described was finally satisfactory at low cost. The people across the street had a tripod of 2" pipe to pull and swap engines between old vehicles that inspired me to design and make my own adequate hoisting equipment instead jury rigging which sometimes broke.
I switched from cable to chain pullers mainly to gain more lifting height under fairly low support, and liked them well enough to repurpose the cable pullers for horizontal and angled pulls. A two ton lever chain hoist is much easier to operate near full capacity than a similar cable puller as the reel fills up. A chainfall is necessary when the hoist is too high to reach.
I now have 1 and 2 ton chainfalls, lever chain hoists of 1/4, 1/2, 3/4, 1 and 2 tons, and uncountable cable pullers, mostly damaged from rapid wear of soft steel stampings. When running the sawmill most of the chain hoists are in use for either handling logs or storing lumber.
The enabler was online column loading calculators like this that showed the surprisingly high capacity of 2" x 8' chain link fence posts and 2" x 10' electrical conduit as long as the loading is purely axial. The fence posts have the 2-3/8" OD of 2" pipe, the conduit its ID.
Pipe is stronger but a 100 Lb tripod of it is difficult to set upright when its center of gravity is above shoulder level. A 10' tripod of 2" conduit is manageable without back strain.
https://amesweb.info/Beam/Column-Buckling-Calculator.aspx
A long thin column's load capacity depends on the metal's elastic constant instead of its (greater) compression strength. It will bow rather than crush like a short column.*
The only sign of hoisting overload that I've seen after heavy logging abuse has been the top bolt holes being pulled oval. I changed from hardware store Grade 30 to logging Grade 70 chain to upgrade the tripods for the 4500 Lb logs. Overhead-rated chain of Grade 80 and above has shorter links that won't accept a bolt or shackle pin to adjust length except at the ends. My manual chainfalls don't apply the electric hoist starting shock load that Grade 80 and above will tolerate better. It stretches when overloaded while lower grades may be brittle.
To keep leg column loading axial I put acorn caps in sockets at the bottom and pinned the top connection with the loading shared between both sides. The acorn caps for 2" conduit are old cast iron ones from a fence dealer's junk drawer turned down to press fit inside the conduit. The acorn shape holds on a level baseplate better than ball caps. So far even the thin cast aluminum ones on fence posts have held up unless punctured by a rock.
The sockets are holes in metal base plates, some flared like trumpet horns with hammer and anvil. The downward flare and bent-down corners have kept them from sliding on turf. On loose sand the plates need to be larger and dug in at an angle. I tied the bases together on the gantry tripods. A wye is less of a tripping nuisance than a delta, and easier to reposition.
Although I calculated the load capacity I'm not confident enough to claim a number, or show how I joined the tops of the tripod legs. There are several top bracket versions to copy. I haven't seen mine anywhere, which may be a bad sign. I proof tested my work by trying to pull large stumps.
https://www.amazon.com/4400LBS-Digital-Industrial-Electronic-Hanging/dp/B0B28FJYG9
*Surprisingly at the load where a column starts to bow its load capacity is the same no matter how far it bends, until it fractures. I saw this lifting a small log with shear legs of 12' 2x4s, the bent leg would remain stable wherever I pushed it with my hand.