From: muratlanne@gmail.com   
      
   "Jim Wilkins"  wrote in message news:v9md7n$19n8k$1@dont-email.me...   
      
   My gantry hoist is meant to be set up by hand in the woods to lift and move   
   a log or boulder, and disassemble for compact storage. Though it works very   
   well on the sawmill it has too many compromises to be a good pattern for   
   general use indoors.   
   jsw   
   ------------   
   A key difference between mine and standard gantry designs is the free   
   standing tripod legs, which allow the beam, trolley and chainfall to be   
   raised without other help, but to be light enough to set up by hand they   
   aren't stiff enough to withstand the cantilever loading of the standard   
   design. The beam hangs from chain and loads the legs in pure axial   
   compression.   
      
   At least I think it does, I can't mathematically or experimentally prove how   
   well the compound angular geometry distributes loads equally among all 6 leg   
   cross bolt ends. Three are pretty certain, the others not so much. They are   
   free to try.   
      
   There may be other ways to design a self-assembling gantry crane, perhaps   
   temporary or fold-out extra legs that make the end posts free standing until   
   the beam is bolted in place. Mine is set up such that I can lift the beam   
   and move the loaded trolley from outside the leg and beam areas.   
      
   The method I use to attach a temporary outdoor beam extension to the fixed   
   gantry in a storage shed is to put a folding W frame ladder at the center of   
   the beam position, place boards across the rungs nearest the beam height,   
   slide the two 3" channels that form the trolley track onto the boards, which   
   support them while I loosely attach the shed end, and then set up and   
   connect the braced post at the outer end. Removing the boards lets the   
   ladder be lifted off the beam. Although channels aren't ideal for the   
   trolley track each is light enough to lift above head height. When I bought   
   the 3" channels I didn't know that a few 4" ones with higher capacity were   
   behind the bushes on a separate pile.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)