# Estimating weight of overhead cranes

I do not have a lot of experience dealing with overhead cranes. I need to have an approximate idea of how much a bridge crane (just the
bridge unit, not the rails) would weigh, given span and capacity.
The present case is a 10 ton, 50' long bridge crane weighs. I already bought it, it is disassembled, but I need to figure out the weight for transportation purposes.
What I bought is actually a complete gantry system that is shaped as a lowercase 'r'. It has one traveling leg on one side only, and the other side rides on elevated rails. I bought it including stationary columns, top rails, the traveling column etc. Paid 1,700.
But at this time I am mostly concerned with figuring out the weight of the bridge. Again, it is 10 ton capacity and 50 feet long.
Any clue what it may weigh?
thanks
i
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Ignoramus16418 wrote:

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.
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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
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http://goo.gl/UKuXgL

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On Tuesday, December 2, 2014 8:58:03 PM UTC-5, Ignoramus16418 wrote:

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
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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.
i
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On Tue, 02 Dec 2014 20:48:21 -0600, Ignoramus16418

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.
--
Believe nothing.
No matter where you read it,
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Ignoramus16418 wrote:

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.
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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!
i
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Ignoramus16418 wrote:

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.
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"Pete C." wrote:

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 <\$500
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You just need a regular PSI gauge, and a conversion table.
i
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Ignoramus976 wrote:

Yes, technically, but that unit is far more refined and easy to use. It's also cheap compared to your other operating costs related to a semi and certainly any overweight fines.
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On 12/02/2014 10:04 PM, Ignoramus16418 wrote:
...

Are they really 100% air-supported? I don't know they're not; just thought there would be a separate parallel mechanical support path as well...altho I guess it only changes the proportionality constant unless it's nonlinear. Which could still calibrate albeit not with single constant.
The grain trailers here nor the tractor aren't so don't have a comparison...
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dpb wrote:

Proportional enough that there are commercial load scale products for it. The RWLS stuff says it reads to 100# increments which isn't bad vs. the 20# increments of a typical CAT scale.
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On 12/07/2014 8:06 AM, Pete C. wrote:

That doesn't say anything about what the calibration curve actually looks like, though...can calibrate a very nonlinear response as noted above...
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message wrote:

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 http://www.rwelectrodes.com/10000-LB-GAUGE-p/601-8100.htm
-jsw
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On Tuesday, December 2, 2014 9:43:56 PM UTC-5, snipped-for-privacy@krl.org wrote:

l
a

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
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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: http://www.steelconstruction.info/Steel_construction_products
A plate 1" thick and 12" square weighs ~40 lbs, or 5 lbs for each 1/8" of thickness.
-jsw
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Here are the pictures, you can open then in separate tabs to see more detail, they are actually quite detailed.
http://ricklevin.nextlot.com/public/lot/15505300?image_id3892410&section=photos
i
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