My new spreader beam plan (visited steel yard)

This is a continuation of my effort to make a suitable spreader beam for lifting engines and pallets.

I visited a steel yard in Chicago this morning and picked up some scrap. (I am NOT proud of what I paid for other stuff besides scrap).

Anyway, for $20, I picked the following:

1) One 4"x3.5'x3/16" steel plate 2) Two 1.25"x1.25"x3 ft square tubing pieces 3/16" wall (heavy wall)

My plan is to weld them longitudinally, so that, when seen from the side, they will look like this:

o|o `

that is, the square tubing pieces will be welded to both sides of the plate forming "ribs".

That would make a 3" or so structure that, I hope, will be rigid enough not to buckle under loads of up to 1,000-1,500 lbs. I would drill holes in steel plate for hooks and such.

Most of the weight will be carried by the 3/16" plate, with the ribs serving mostly to prevent buckling.

As for welding, I will just use 6013 stick electrodes. Will paint it with some "farm equipment green" oil paint.

i
Reply to
Ignoramus20979
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Igor, that sounds plenty strong. The beam itself won't fail, now watch how you design your load points and you should be OK. You don't need to do 100% welds;

25% skip welds (3" out of a foot) should be enough for the stiffeners. If the steel is rusty, 6011 or 6010 would be a slightly better choice of rod. The paint will last 3X as long with a good coat of red primer under it.

GWE

Reply to
Grant Erwin

That $20 was most of the cost of the HF leveler unit that requires no fabrication and provides the adjustable balance function.

Pete C.

Reply to
Pete C.

Yes, I think that I do not need continuous welds, though I think that it will look better and will be easier to paint with continuous welds.

The steel is NOT rusty.

OK... I have some greya primer, I think, but I could get red primer.

Thanks..

i
Reply to
Ignoramus20979

Yes,... But... This one is going to be quite a bit longer, good for lifting pallets... Though I do not claim to be a big authority on these things...

i
Reply to
Ignoramus20979

Realize that unlike shipping containers, pallets aren't really designed to be lifted by the corners. The pallet jack or forklift normally supports the load from below. When a less than perfect pallet splits in half and drops the load during a lift you'll know what I mean.

Pete C.

Reply to
Pete C.

You will be better served to separate the tubes to the top and bottom of the plate, like such:

[]| []| | or | |[] []|

No, it doesn't meet our natural inclination to make things symmetrical, but it will carry far more load than with the tubes at the center of the plate... Better would be 4 tubes, but I'm working from your materials list...

denny - old plant engineer

Reply to
Denny

Denny, I kind of agree that it would possibly provide more strength, but would't you say that even the original design would have strength far in excess of 1,000-1,500 lbs that I specified.

thanks

i
Reply to
Ignoramus20979

lbs is not "strength" it is a unit for weight.

Nick

Reply to
Nick Mueller

Better ASCII art

| []|[] |

Reply to
Ignoramus20979

It's marginal, at best. At 1500 pounds the max bending stress will be about 21000 psi, which is at the limit for common structural steel in braced construction, and I'm not accounting for the holes in the plate. You've got an unbraced, slender beam.

Will your beam fail? It probably depends on how the load behaves while it's in the air. Is it safe for lifting 1500#? I'd say no.

Ned Simmons

Reply to
Ned Simmons

Hm, Ned, how did you calculate it? It is interesting.

i
Reply to
Ignoramus20979

Plain old statics and strength of materials. Machinery's Handbook has the Cliff Notes version if you want to check my work, though it may not have numbers for allowable stresses or data on buckling of beams without lateral support.

Ned Simmons

Reply to
Ned Simmons

Ned, I am lost, but there is lateral support? The cross section would look like this

| []|[] |

the [] symbol depict a 1.25" square tubing with 3/16" wall.

i
Reply to
Ignoramus20979

Denny's approach is considerably stronger due to considerably better section modulus.

If you don't want to accept the answers you sought and Ned and Denny offered, do your own math. Formulas in Machinery's Handbook and in Marks' Handbook.

I checked your numbers, Ned. Got the same result.

Reply to
Don Foreman

Don, I would never build anything that does not meet your safety approval. What I am not sure is if I was clear enough in conveying what I want to build. I drew a picture of what I want to make and will take a photo of it tonight.

i
Reply to
Ignoramus20979

Seems like the subject that I have to educate myself about is called lateral torsional buckling.

i
Reply to
Ignoramus20979

There are at least three things that would worry me.

  1. The factor of safety on the plate's stress is very low for a lifting device, even without holes. You may actually exceed yield around the suspension hole in the top-middle of the plate.

  1. Adding the tubes at the center of the plate do stiffen the beam laterally, but do not count as bracing. The concern here is that if the beam deflects too much in a horizontal plane it will become unstable and collapse.

  2. The thin bottom edge of the plate may be prone to buckling in compression. Google "web crippling" for more insight.

If the beam fails as a result of 2 or 3, you're not likely to get much warning. The calculations for 2 & 3 are not nearly as straightforward as figuring stress. If you use a small wide flange beam, or other standard structural shape, the figures are available in tables.

Ned Simmons

Reply to
Ned Simmons

I knew someone would - I was careful .

Ned Simmons

Reply to
Ned Simmons

Thank you Ned, I understand that.

But the plate is not being compressed, it is being pulled? Am I missing anything.

OK... I will think about it, as wel as about ways to test this device once I make it. Since I have a shop crane rated for 2 tons, with a 8 ton ram, I have some test possibilities.

i
Reply to
Ignoramus20979

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