Need some help with cantilevered assembly Question
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Posted by: pityocamptes ®

07/17/2007, 18:24:36

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Hopefully someone here can help me. My schooling is in computer engineering, and so I lack knowledge in mech eng. Anyway, I am helping a friend build a small hoist on his ranch that will be used for processing pigs and other medium to semi large animals. The tubing is square, structural grade tube, and is 2x2x.125

The assembly is 82 inches high with the top cross beam being 36 inches long. In the middle of this top cross beam will be a pulley that has a winch cable going through it. The winch will drag the animal a short distance and eventually pull it up so that the animal is suspended under the top beam for processing.

I would appreciate any help to try and figure out what the failure load for the assembly would be, especially the 82 inch side pieces. I would also be interested in load and deflection data. I assume a safety rating of .55 the maximum load would be standard?

Can anyone post the formulas that would be used to compute the information I desire? Perhaps someone would also be kind enough to help me out if I post back with questions. I appreciate any help offered. Thanks!

Picture attached.


 

Hoist1.bmp24.3 KB  






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Re: Need some help with cantilevered assembly
Re: Need some help with cantilevered assembly -- pityocamptes Post Reply Top of thread Forum
Posted by: CCR5600Design ®

07/18/2007, 13:16:00

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pityocamptes,

I was studying your drawing...

I came up with a few thoughts to share.

First, as Randy mentioned, an A-frame arrangement would allow for increased loads and better stability.

Second, if you were to mount the winch to the horizontal tube at the top of the frame, you would not have to worry about as much cable getting in the way of the processor. This could alleviate a potential work hazard.

Third, Your drawing and description did not indicate what type of surface (terrain) the processing would be taking place on, but if it is concrete or asphalt, you could mount the A-frame on a set of locking casters to minimize the side-pull on the cable and potential tipping. Simply pick up the animal with the A-frame and roll it to the processing area rather than dragging it and risking contamination by grinding stuff from the floor into the carcass.


Just a few ideas... You are welcome to take them or leave them as you please.

Good luck!

Ron





"What we need are more people who specialize in the impossible." - Theodore Roethke


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Re: Need some help with cantilevered assembly
Re: Need some help with cantilevered assembly -- pityocamptes Post Reply Top of thread Forum
Posted by: randykimball ®
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07/17/2007, 22:15:59

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Let's make it easier than that.

I think you are talking about two upright tubes with a 3ft cross beam.

If you can anchor cables out at a 30° angle from the uprights (like what the electric company does to brace from wires pulling a pole some direction) and attach brace cables with turn buckles you can brace this rig similar to how a sail boat can brace a thin mast against huge sail loads. These braces should run on the front and back side of each upright // to the direction of the drag load. You can fudge a few degrees for working room, but don't get carried away. (the cables are out similar to the A frame bars of a swing set) I'd feel better if you would double up on these uprights welding a 3" long horizontal member between them every 18". Weld the assembly with the doubled direction of the uprights like an arbor with the ends of the cross member in the center of the top 3" horizontal. Build it about 20" wider at the bottom than the top (spread for work room under the rig and to stablize the rig).

Now I'd bridge the cross brace with the same material to form a pyramid from end to end about 8 inches tall with a verticle member in the center. For your attachment loop weld a bent piece of 1/2" round bar stock from the hardware store up both sides of this verticle member to form a loop under the cross member. This provides plenty of overlap for weld strength. I would then additionally weld one 4" long piece of tube out front and back of the center of the cross member. Then weld two sticks of 1/2" rod from the ends of the cross member bridged over these to form a bridge truss on each side of the cross member. This is to provide strength against the drag forces.

Now take four pieces of 1/2" rod and weld four corner braces from about 12" out in the cross brace to about 12" down on each of the four upright tubes.

But, I'd puzzled why you don't want to make an A frame like a swing set but with verticle members at the ends and with the brace methods I have described. That would be much stiffer (safer)and would do away with the cables.

Sorry I can't provide a scetch but I'm away on vacation in my coach and don't have the hardware to do so.

If you don't trust your welds use some scraps to weld overlaps at all the vital joints. It is the welds that will make this work.

Keep the turn buckles taunt but not over tightened. (or just build the A frame with verticle members at each end......)

Good luck!





The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by randykimball at Tue, Jul 17, 2007, 22:32:23


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Re: Re: Need some help with cantilevered assembly
Re: Re: Need some help with cantilevered assembly -- randykimball Post Reply Top of thread Forum
Posted by: CCR5600Design ®

07/18/2007, 12:52:44

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Randy,

Sir, you are the consummate engineer! Even on vacation, you find yourself delving in design. Man, grab a fishing pole and set yourself in a comfortable lawn chair! Geez! What are you trying to do? Make us look bad?

HA HA!

Have a great vacation!

Ron





"What we need are more people who specialize in the impossible." - Theodore Roethke


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