Estimating weight of overhead cranes

Since these things are predominantly made of standard structural steel components, a bit of measuring and comparing to specs in a structural steel chart should tell you the weight per foot for the materials and a bit of calculating for the total.

Here are the pictures, you can open then in separate tabs to see more detail, they are actually quite detailed.

And look specifically at the last picture, all the yellow stuff in it is mine.

Thanks. It makes sense. The problem is this. It is 2.5 hours away from me. I have to tell my driver how much of it to pick up without ending up overweight.

Look at this picture to get an idea. You can kind of figure out the size, the main bridge (top part of the picture) is exactly 50 feet long and about 48" high.

I assume you have actually seen the crane in person. So you are wanting people that have never seen the crane to give you a better estimate than you can generate.

However I understand that portable truck scales are made ( just like the ones the highway patrol will have ) and they might be something that you could use. Sorry I have no idea of the cost or the manufacturer.

Dan

I have not seen it.

That's the problem.

I also want to be able to estimate weights of cranes that are still up in the air.

Yes, good point.

Another thought. You could give your driver copies of the pages showing s tandard structural steel components, a tape measure , and a calculator. He should be able to come up with a fairly good estimate. Well maybe you sho uld also give him a cell phone too so he can consult with you while he is l ooking at the crane.

Dan

Oh, that's a simple one. Just learn to levitate, Ig. Then you can get as close as you need with that 300' tape measure.

Have you asked any of the crane companies or local rigging companies for help there? One builds 'em and the other installs 'em, so they should know what a certain mfgr's model weighs.

That might be handy to have on hand for the greedy cops who might stop your driver.

I believe there is some setup for semis that can give you a reasonable load weight reading from the pressures in the air suspension. Not truck scale accuracy, but close enough to keep you out of trouble I think. You can probably find info on them and hack together your own variant of it.

It wouldn't hurt to give your driver a structural steel book, some calipers and a tape measure. Not that difficult to measure say I beam width, height, flange and web thickness and look in the book to find the pounds per foot, then multiply by the length and get a pretty accurate weight on the piece you are getting ready to load onto the truck. You could probably use your programming skills to make a nice smartphone / tablet app to do this and perhaps even make some money selling the app.

Thiis is interesting. Both the truck, as well as a couple of my trailers, have air ride suspension. I think that the pressure in the suspension bags is directly proportional to the weight. I think that all I need to do, is install pressure gauges connected to the bags, and have a conversion table, and I am done!

Too simple. Try a Raspberry Pi or similar with some pressure sensors and a correction table to give a nice readout. Spend some time calibrating by loading known weights and you should be good. Put a magnetic back on the display unit so you can stick it to the back of the cab when loading and have the LCD display change color to yellow then red as you get to overweight so you can easily see from the forklift. Have calibrations for each trailer you can easily select, a deduction for the forklift weight if you need to load that before leaving, etc.

I think you can identify the weight per foot from the style (I, WF), height and web thickness. In my old AISC Manual of Steel Construction the easily measured web thickness increases with the weight per foot. The web thickness and flange width increase by the same amount as the weight per foot increases, supporting the story I've heard that the mill sets the weight by varying the roller spacing. The height or "depth" also increases, making the flamges thicker, but you can't measure it with pocket-sized tools like a mike or 6" dial caliper. This shows the roller setup:

A plate 1" thick and 12" square weighs ~40 lbs, or 5 lbs for each 1/8" of thickness.

-jsw

I don't do anywhere near the heavy rigging that you do, so this very portable 10,000 Lb hydraulic load cell is enough to weigh anything I might want to lift. I paid $60 for it

-jsw

Actually, rwls.com seems to have some pretty good digital gauges at reasonable prices. Probably easier to just buy and install vs. hack your own. 202-DDG-02 looks pretty nice for

OK, so, to boil my question down to a simple sentence, it is as follows:

How to guess the weight of an overhead crane, given 1) Capacity and 2) span. I am not allowed to climb on it and measure thicknesses, etc.

This is a very practical question and if I can find an answer, I am sure that it will be helpful to make money.

I just realized that it is not as complicated as I thought.

For example, say, I can ask a question, "find the weight of an optimal I-Beam that would support a given weight and span a given distance".

Well, this is actually the most common engineering question. I am sure that there are helpful I-beam calculators that can give me suggestion for an I-beam, given weight, span and acceptable deflection.

If so, then, the weight of an I-beam crane is just that. For other cranes, such as double girder, box girder and so on, it will be slightly different, but similar and proportional.

I understand that a crane has components other than I-beams, such as end trucks, hoist, etc, but again it should be simply adding a percentage allowance to the I-beam calculation.

I will dig a little to get an answer.

That is a reasonable start, but it does not account for the safety factor. I would not be surprised if the rated weight is one third of the weight that would cause failure.

Dan

Iggy, please send me an email at carl . ijames at nothispart verizon dot com that I can reply to.

OK, so, to boil my question down to a simple sentence, it is as follows:

How to guess the weight of an overhead crane, given 1) Capacity and 2) span. I am not allowed to climb on it and measure thicknesses, etc.

This is a very practical question and if I can find an answer, I am sure that it will be helpful to make money.

I just realized that it is not as complicated as I thought.

For example, say, I can ask a question, "find the weight of an optimal I-Beam that would support a given weight and span a given distance".

Well, this is actually the most common engineering question. I am sure that there are helpful I-beam calculators that can give me suggestion for an I-beam, given weight, span and acceptable deflection.

If so, then, the weight of an I-beam crane is just that. For other cranes, such as double girder, box girder and so on, it will be slightly different, but similar and proportional.

I understand that a crane has components other than I-beams, such as end trucks, hoist, etc, but again it should be simply adding a percentage allowance to the I-beam calculation.

I will dig a little to get an answer.