From: muratlanne@gmail.com   
      
   "Bob La Londe"  wrote in message news:v9is89$i4f6$1@dont-email.me...   
      
   On 8/14/2024 9:58 AM, Jim Wilkins wrote:   
   > ...   
      
   My plan in case I failed to explain it accurately is to lift the load,   
   roll the trailer forward, and lower the load onto a heavy pallet.  I'll   
   probably put the pallet under the trailer so that total suspension time   
   of the load will be measured in single digits.   
      
   Two things...   
      
   1.  I have looked at prefab gantry cranes and there are many with   
   adequate vertical clearance... and as you mentioned.. 8 ft width.  They   
   do not have an 8 ft span however.  Most are 8' to the center of the   
   caster pivots.  94-ish inches between the uprights.  This makes it   
   impractical for unloading heavy utility flat bed trailers which are   
   typically 8' wide or in some cases 8'6 inches wide.  Wider ones are   
   available of course.  A gantry has the advantage of a being able to use   
   a trolley instead of a beam clamp of course.   
      
   2.  I actually have considered installing a vertical I-Beam to one side   
   of the parking bay. (There are shelves there so it really would not be   
   in the way even though it is an open span building.)  Then installing a   
   horizontal beam from it to the near column.  Braced of course.  This   
   would also allow for use of a trolley instead of a beam clamp.  I-beams   
   tend to be lighter than I would like to use or nearly as much as the   
   cost of a complete gantry crane, even for excess inventory, locally.   
      
   --   
   Bob La Londe   
   CNC Molds N Stuff   
      
   ----------------------------------------------   
   My structural steel is almost all scrap, bought for $0.25 a pound at a   
   recycling yard before Bidenflation, based on quick mental engineering of   
   vague plans/wishes. Most of what I bought could be used somehow, if not   
   exactly as intended.   
      
   A folding shop crane or engine hoist can be nearly as useful at much lower   
   dollar and storage space cost. A load can be moved without swinging by   
   lowering it onto timbers across the legs. I added a caster tongue jack and   
   trailer coupler to the mast end of mine and tow it with the tractor.   
      
   Their disadvantage is that the legs need to straddle or be under the load,   
   so they may not lift from or lower to flat on the ground. A pipe tripod with   
   its feet connected by flat webbing straps (to roll over) can take over for   
   that. Mine are 8' chain link fence corner posts with top acorn caps on the   
   bottom, resting in holes in aluminum plates attached to plywood for pavement   
   use. The taller gantry tripods are 2" x 10' EMT with feet machined from old   
   cast iron fence post acorn caps from a dealer's junk drawers. For level   
   floor indoor use the top leg connection could be a rigid triangle like a   
   camera tripod instead of my fully flexible and sometimes troublesome   
   homebrew.   
      
   A tripod of 2" x 10' water pipe is stronger but difficult to set up because   
   the center of gravity is so high. A column buckling calculator shows that   
   the capacity of pipe,  EMT or a fence post is quite high as long as the   
   loading is centered, thus the end cap balls and sockets, and machined solid   
   balls for the water pipe shear legs.  A truck ran over and bent the third   
   leg so the owner disposed of it to me.  I do proof test them with a crane   
   scale on loads too heavy to lift, or drop.   
      
   The 6" drill press vise I mentioned was to hold off-pavement steel base   
   plates while cutting the hole. The max for my mill's 4" Wilton vise is 5"   
   with the hard jaws removed, which isn't quite large enough on soft ground. I   
   found a clean, lightly used 6" Columbian DP vise that can take 6-7/8"   
   without its hard jaws. After hole-sawing the center I flare the hole like a   
   trumpet bell to make the socket, and fold down the corners to also dig in.   
   These baseplates haven't needed to be tied together.   
   jsw   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)