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Movable Crane out of Wood?

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  • Movable Crane out of Wood?

    We have all seen the use of an engine hoist for picking things out of the beds of pick ups but what about a movable A-Frame type of crane. While in my working days I used these made from steel what about wood. What would be the minimum size lumber for weights in the 1500 to 2500 pound range. This would of course have to be able to span the width of a full size pick up. Two 2x8s for the cross beam with the balance out of 2x6s or 4x4s?. Plus this would have to fit in the garage door
    Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

  • #2
    Tree limbs was what we used to use...

    Yeah, I built me a permenant A-frame with Ibeam and trolley. 10' tall, 14' wide and it spans the shop double doors.

    I still would like to build something capable of lifting two tons onto a truck. AND be knock down into parts easily put up by one person.

    According to the engineering book, it take a heavy Ibeam to span 8 feet and lift 2 tons in center. More than one person can put up. Deflection is a concern also. Feet must be tied together to keep unit from deforming.

    we had a aframe made from Boiler tube, light, and I had a car hanging from it outside. It sits now on casters and I rate it at less than 1,000 pounds since the legs are unstable. Book says it is not good for that much weight. Meaning, it will fail eventually.

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    • #3
      I'd think the size would be highly dependent on the species of wood used. Some well seasoned, rough sawn hickory would be my first choice, probably followed by oak.

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      • #4
        Yes, you can do it with wood, but for this kind of application, metal is better, if only because its properties are more predictable. Wood properties vary tremendously with species, moisture content, growth pattern, how long you've left it out in the rain, and on and on. Find a copy of "The Wood Handbook" at a good library. Originally published by the US Forest Products Labratory, reprinted commercially, but I don't know if it's still available.

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        • #5
          I would make all members from at least two and preferably three members glue laminated and screwed together. This insures that if there is a weak spot in a single piece it doesn't provide a single point failure. That is the principal with glulam trusses in buildings.
          Free software for calculating bolt circles and similar: Click Here

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          • #6
            A couple of points...

            First, never use a tree branch as a crane.

            I have been around far too many trees that have been rotten or have dry rot or have internal defects. There are just too many ways for a tree branch to be severely weakened internally but yet look perfectly good on the outside. In my neighborhood alone, we have had four separate incidents where trees that looked good have almost caused property damage and lost of life due to using them for lifting purposes.

            When using wood to build a crane, you need to remember that you are hanging the weight from one point versus spreading it over the beam like in a floor. That means that you need to overbuild the crane in respect to what you would think that you would need.

            TMT

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            • #7
              I needed a small crane once so I spent around 20 mins screwing two A-frames made out of 2x4s together and suspending some winches from them.. When I was done, I just unscrewed them and re-used the 2x4s for whatever. You can make them as strong as you want and if you make them without destroying the wood, you can re-use the wood for other things afterwards.



              I just used a strong pipe over the top of the A-frames, and some 8" C-clamps to hold two winches... It worked really well and only took 20 mins to make from scratch. I got really good hoisting and positioning with two winches.



              -Adrian

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              • #8
                What are you fitting the engine up to? Is that project done now? How about some pictures of the finished article. TIA

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                • #9
                  <font face="Verdana, Arial" size="2">Originally posted by Steve Stube:
                  What are you fitting the engine up to? Is that project done now? How about some pictures of the finished article. TIA</font>
                  I call it my PsychoKart for obvious reasons.

                  Here are a bunch of pictures of it:

                  http://www.bbssystem.com/viewtopic.php?t=59

                  -Adrian

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                  • #10
                    If you want to build a handy lifting horse wood is a good start provided you don't try for too large a span or intend it for too heavy a load. Limit the span to what you can back a pick up under with precision - 9 feet or so between the legs and the weight to a ton or so. Any more and you have to increase the width and depth of the beam out of proportion to its convenience in handling due to weight. Erecting the thing quickly becomes a three man job.

                    I built a lifting horse from 12 ft 4 x 4's and a 10 ft 4 x 8 all select quarter sawn Doug fir for strength and reliability. All 4 legs were braced to the beam with 2 x 4 and the legs were strutted about 4 ft from the ground. I padded the top edge of the beam where the chain hoist was suspended by bolting on a 1 ft piece of 4" x 3/8" flat bar so the becket chain wouldn't bite into the wood.

                    If you intend to use the lifting horse regularly it really should be made of metal. 8" aluminum I beam and 3" sch 40 pipe are damn expensive but superior to wood and lighter to erect while being capable of greater loads. If you design well you can make the thing adjustable and easy to erect and transport.

                    Look at Wallace gantries

                    http://www.wallacecranes.com/trialum.htm

                    for some ideas. Notice how adjustable they are.

                    [This message has been edited by Forrest Addy (edited 04-23-2005).]

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                    • #11
                      Well you named it correctly, no brakes or ejection seat. It does have quadrasound, maybe if you can't hear the crash, it won't hurt. Oh sure. Its a killer machine alright!
                      Thanks for the photos.

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                      • #12
                        I found an old rigging book at the library that went through rigging with wood extensively. I don't remember much from the book as I read it more for novelty than for serious study of wood and manila...Maybe you can find something similar.

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                        • #13
                          Spin, I believe that you will need something pretty substantial to lift that much weight with any kind of span.
                          For quite a few years I used a take down gantry in my shop for pulling engines etc.
                          I used three 2X8 pine boards, laminated with screws and glue, for the main lifting beam.
                          On one wall there was another laminated beam attached to it with lags. This stood up from the floor and had a pocket to hold the top/cross beam.
                          On the other side I had an "upside down" T with A bracing going to the bottom. This also had a pocket for the cross beam.
                          I'd put the cross beam into the pocket that was against the wall, lift it up and prop it with a 2X4, then slide the "upside down T" under the beam and drop the cross beam into the pocket.
                          I had through bolts that held it all in its final position.
                          Was pretty handy and could be taken down again in about ten minutes.
                          The cross beam was about 8 feet long, just about right for driving a vehicle under.
                          This was made to lift about 900 pounds maximum...like a big block chevy and transmission pulled as a single unit.
                          I don't believe there was much of a safety factor there. A few times a motor would catch and you'd end up with more weight than you planned.
                          The cross beam would start groaning and crackling.
                          I was always going to add a steel plate across most of the span but then I wouldn't have been able to lift it myself.
                          As Forrest mentioned....quarter cut fir would have been a better choice and perhaps 2X 10 or 12. But that would still have been pretty heavy to lift that high.
                          I used the floor joist reasoning when building this but I missed one thing...floor joisting is designed to work as a unit. The joists running beside and the flooring attached to the tops of all the joists combine to add strength.
                          When you just have one joist, there is really nothing to stop deflection to the sides. This is where my beam got me into trouble. If the motor/tranny started to swing it could get pretty spooky in a hurry.
                          My son was just getting into hot rods and was planning to pull some engines etc.
                          I had to go out of town to work for six months and wasn't comfortable letting him use this so I sawed it up and bought him an engine hoist to use. It was a huge old hoist that the Kenworth dealer used to use.
                          Worked fine but took up massive amounts of floor space.
                          To date, nothing has worked as well as the gantry for unloading out of the back of a truck though. It just wasn't heavy enough.
                          After unloading my lathe the other day I'm thinking about putting in a heavy steel "I" beam frame right around the outside of my shop doors and cementing the works into the ground.
                          Be careful!
                          Russ

                          [This message has been edited by torker (edited 04-23-2005).]
                          I have tools I don't even know I own...

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                          • #14
                            Has anyone made a hybrid type lift? Part steel and wood. Why couldn't the top beam be a welded configuration with "box pockets" to receive the 4x4's. A 1/2 inch rod welded across the bottom in ^ fashion with a stub center support should hold anything a backyard mechanic would want.

                            I have used a tree limb like Gypsie but I had to lean/wedge a 2x6 under the unsupported end. It worked but I was nervous!

                            At present I use a a small utility trailer bed that is about 10" off the ground and a motor lift. Once the load is lifted I drive the trailer out from under it. It has worked well for some other projects around the house such as moving my shops around and yard waste.



                            [This message has been edited by Your Old Dog (edited 04-23-2005).]
                            - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                            Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

                            It is true, there is nothing free about freedom, don't be so quick to give it away.

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                            • #15
                              **** I was young and bulletproof (so I thought) when I used to use a oak limb to pull engines.******

                              I was joking. (I've had over 100 broken bones) So I might not have been that funny. I got a broken toe on the right foot right now, don't think much of it till I step or stand wrong then the telegraph messages start. Ya gotta learn to ignore the little things.



                              ------------------
                              David Cofer, Of:
                              Tunnel Hill, North Georgia

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