When I look at the drawing in post #16 I see that you are now lifting a "square" of wood.
The most important thing is to keep this "square" in that shape.
The standard way to do this is to put a "Z" like brace from the lower right corner to the upper left corner.
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Yea I suggested that in #15 as I think an "X" would be the most structurally safe. Perhaps if the wood in the lift area that is susceptible to friction is painted and greased up then the friction can be dramatically reduced
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Did any of you read where I said that I am only going to lift the load for 6 to 8 inches? I can even reduce that to 3 to 4 inches for all that's concerned. I don't think that an X or any bracing of that sort is needed as I have 6 horizontal cross pieces for additional support so that alone prevents the four vertical uprights from moving not to mention that the vertical uprights are supported between four 4 x 4's at the bottom. As far as reducing friction I have given thought to 1)staining the wood with a polyurethane product, like MinWax PolyShades stain which leaves a hard very slick and smooth surface 2) gluing thin strips of stainless steel in the sliding area which I already have on hand. I don't think the hoist is going to tilt either as it has a 40" x 80" base and the hoist itself is very very heavy
Note: If reinforcing the extended arm becomes necessary I have given thought to placing a 3/4" galvanized pipe on the top and/or bottom of the arm
Last edited by Code Dummy; Jun 18th, 2017 at 05:14 PM.
The base of the hoist is going to keep it from tilting. I agree with your there.
From my view the whole point of the counter weight is to stop the "lift square" from racking - twisting under the weight of the lift arm.
That same problem can be addressed with either bracing (Z, X, K or V) or cabling the corners to each other. Transferring of the force from the lift arm to the lower right corner of the square.
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I still don't see what you have against a pulley, winch, comealong, etc that several of us have suggested. Given your side view above, the CG would be within the wheelbase. Your current lifting arm could also act as the top brace piece you show. Pulley or whatever out on the end of the arm. No need for any counterweights, springs, jacks, slides, etc. KISS
Why don't you draw a picture no matter how terrible it is and show me what you are talking about. I can't have any over hanging devices (like a winch mounted on the ceiling)
The point of the counter weight was to keep the center of gravity inside the square formed by the wheels based on the pictures shown in the original post. In that picture, the weight was outside the square formed by the wheels. In the picture in post #48, the weight is inside the square formed by the wheels, so no counter weight is needed.
There's no need to worry about the shift shown in picture #48, because it's impossible. After all, just to draw the picture, you are showing two lengths of wood that are the same length extending between the load arm and the bar where the jack is located. In the second picture, those two lengths of wood are no longer the same length. For that to even be possible, one of those beams would have to stretch (that won't happen), or one of the beams would have to compress (that would result in total, explosive, failure of the beam).
My comments were based on the original picture. If you build the picture in #48, then a counterweight doesn't do anything except change the forces on various attachment points and members. You mentioned that you were using 2x4s and that the weight was 150 lbs (roughly). The load arm may have to be heavier than that, but probably not, unless it's really long. If the white circles in the pictures are bolts rather than screws, I doubt the forces on the system will be an issue. Some of those bolts will see a strain greater than 150 lbs, but that's the worst of it.
Why don't you draw a picture no matter how terrible it is and show me what you are talking about. I can't have any over hanging devices (like a winch mounted on the ceiling)
Here's a hack on your drawing. I added a crossbrace though I think a sharper angle (e.g., 45) would be even better. A plywood sheet screwed to the entire side would be best. No way that would shift under load. Frankly, I don't think you need any reduction for just lifting 130 lbs max a few inches unless you don't weigh much so I just showed 2 simple pulleys for no reduction but you could design in other pulleys to make it easier. Just tie off rope somewhere on the vertical support (e.g., like a flagpole).
With topshot's picture you WOULD add a counter weight IF you decided to shorten the "bottom beam".
I would take that cross brace and cut it in half and put a horizontal member at the mid point of the large vertical space - so that you had TWO cross braces
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With topshot's picture you WOULD add a counter weight IF you decided to shorten the "bottom beam".
Correct. If the hanging weight is outside the wheelbase (like the original pictures posted in #1), you need a counterweight to be safe. Technically your fulcrum point would then be the left wheels so you'd still be OK for a little while since the wood to the right of them weighs a fair bit, but why flirt with trouble. What if you tried to do 150 instead of 130? Or you knocked the thing so it swung even further out?
I'd be inclined to at least add a couple more pulleys. 150 lbs is not so easy to lift straight up. If you weight more than that, then you could tie a loop in the one end and stand on it to lift the weight. You'd then have to remain standing on it while you tied it off. A simple cleat would be good for the tie off, but there would be so much weight on it that it would be hard to let the weight down. It wouldn't be so easy to tie off, either, with a cleat. Another option would be a hook. You could stand in the loop to push it down to the hook, hook the loop, then get off. To lower the weight, you'd have to stand in the loop again, and it wouldn't be so easy at 150 lbs. A few more pulleys would cut that to a much more manageable weight.
A potential issue with my design would be you definitely want to chock at least a couple wheels since the hoist would tend to want to move as you were pulling the rope unless you were pulling straight down perhaps.
Originally Posted by szlamany
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