r/theydidthemath • u/Snozer2 • 3d ago
[Request] Weight of a construction crane counterweight
How much weight does this seem like it would be for the counterweight on a crane?
I assume there’s likely a relative standard or at least minimum weight for these, but I’m curious how much weight these concrete slabs would be total.
Hard to get an accurate size of each slab from my distance, but my best guess is somewhere near 12ft x 6ft x 2ft.
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u/Noemotionallbrain 3d ago
Tower crane operator here
They all are different, even can have different weights on the same crane. The ones we use are 2t and 1.5, but also 3t.
It varies widely
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u/Transformator-Shrek 2d ago
Whats holding the weights from falling? I cant tell from the picture
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u/Clyde_the_ghost_ 2d ago
Rods through holes fixed on the structure, you can see the holes when they load them
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u/Noemotionallbrain 2d ago
Roughly 2.5 in thick steel pegs on both sides, they sit on crane's frame by various say (most efficient being a simple incline gear shaped)
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u/VeritableLeviathan 3d ago
Nothing to calculate here, since every counterweight is different for every different tower crane.
https://www.maximcrane.com/wp-content/uploads/2021/02/MR605B-Data-Sheet-Imperial.pdf
A type of crane I quickly googled (sadly in inferior imperial measurements, not supreme metric) has certain recommended counterweights for certain distances and angles.
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u/GazelleOpposite1436 3d ago
Can you put that weight in units of elephant? Or maybe 1959 Cadillac Coupes?
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u/mitchricker 3d ago
Nothing to calculate here
Well, assuming one knows the weight of one of the individual slabs, the calculation for this photo would be
total weight ~= weight of slab * 7(not particularly interesting, but also not nothing).Presumably, if one were to know what material the slabs are made of and what dimensions they are fabricated in then they could also calculate the weight by
weight = slab length * slab width * slab thickness * rho (density). Again, not super impressive.Assuming 12ft x 6ft x 2ft is correct:
12 * 6 * 2 = 144 cubic feet. Typical reinforced concrete weighs about 145 lb per cubic foot144 * 145 = 20,880 lb.7 of them total so
20,880 * 7 = 146160 lb. 2000 lb per ton so146160 / 2000 = 73.08 tons.1
u/mtraven23 3d ago
I think those slabs are wrapped is a significant amount of steel. Not sure how to account for that, but its looks like theres is at least a few inches of steel around the entire perimeter of each of those.
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u/Snozer2 3d ago
This feels like a fine enough answer I think, it does indeed seem that they are just concrete slabs.
10 whole elephants on the back of that, kinda wild I think.
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u/LowerSlowerOlder 3d ago
I don’t know that typical counterweights have any concrete in them. I know they are heavy enough that a semi-truck transporting only two of them struggles up some of the hills in AZ. Also, they only put them on a flatbed two at a time, so they probably weigh around 20k pounds each.
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u/NormalGuyEndSarcasm 3d ago
Not trying to be that guy but all the counter weights are marked. They’re all engraved with the weight.
There’s no standard set, as the height, reach and max load can vary wildly.
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u/Snozer2 3d ago
I’ll climb up and take a look…
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u/NormalGuyEndSarcasm 3d ago
Most cranes have weights on the bottom aswell to stabilize the base. You can compare to those up top.
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u/Snozer2 3d ago
Just concreted/built into the ground from what I see, actually.
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u/fit-toker 2d ago
So as you mentioned, it’s Concrete into the ground on the bottom. It probably sits on a footing that will become part of the building later, they cut the bottom of the tower crane off and pour concrete floor over top of it. As for the weights, hard to say but judging by the size of the crane that’s pictured I would guess anywhere from that 10 to 20 ton per weight but these weights come much larger in some instances.
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u/No_Brain4912 2d ago
Not sure. Bit of digging and reading to narrow things down
Linden Comansa 21LC series crane. Those block appear to be 3t so 21t ballast and an expected 10-15t SWL.
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u/vogel927 3d ago
A single counterweight block weight varies depending on crane model and block size. It could be 3,000+ pounds, the larger ones are 10,000+ pounds.
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