Sizing A Mobile Crane...

mahlere

ok, if I know the height of the lift, the distance from the lift spot and the weight of the item, what's the formula to determine approximate crane size?

for example, we need to lift a 3500lb chiller 120' in the air, 120' to the side of the crane...

anyone know the formula?

thanks

mickeyco

Are you buying or hiring? If you're hiring, give them the info, they'll know what you need. We have a company out here that owns one of those old army helicopters (the thing is huge and cool) and they use that thing all the time for chillers, large AC's, combo units, etc.

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mahlere

hiring....issue is, we've got 3 different sizes from 3 different vendors....just looking to see who may be right...

Blackhammer

I know what you mean about sizing. I have run into that problem with a boom pump before. Alot of times they will send the smallest they have available that will do the job. I have ordered a 32M boom and had a 61M show up on site. I only payed the 32M price but to see the 61M in action was a site.

dayexco

i don't know much about cranes, but 120' reach, seems like a LOT

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Railman

Yep, hella lot!
Your probably looking at something like this:

http://www.industrialbuilders.com/crane/HT8670_caps.pdf

That's a 60 ton crane!
Drop down to page 7 charts, & look at 35 to 40 deg or so. At 120' & 40 deg w/jib, you get in ball park of what your looking for.
Joe

nap

dang, that's a little bitty one. Had a 300 or 350 footer setting air handlers before. Really cool, especially when it got stuck full out.

you should have seen them guys scrambling trying to get it down, expecially when the lightning could be seen less than 10 miles away (brand new, first job for this crane)

a 350' lighting rod.

call the crane companies. They will tell you what they will use. Pick the one you want and if they call out the wrong crane, well, make sure your contract states they will lift at such and such a price and they choose the size. That way, if they bring one out too short, you don;t pay for a bigger one but they still are bound by the contract to lift.

where the unit is set from the edge makes a diff as well. That big crane was used to set units on a 1 story building but they were so far from the edge, the height was needed to reach that far over AND be able to carry the intended weight.

let them pick the size. it is their unit and their liability.

Gmads

I have no idea what this option costs, but these guys were setting units on top of this building with a helicopter.

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cexcavation

You gotta think outside the box a little more.....just take the unit apart on the ground floor and hire some school kids to ride the elevator up with their backpacks stuffed full of all the random pieces. Who needs a crane?????
Just kidding of course......I have no idea about cranes, but you wouldn't catch me dangling out on the end of a 120'boom nor standing under anything that is

dayexco

lot of difference between 350' UP in the air...and 120' horisontal...that takes quite a structure if nothing else to hold itself up

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neolitic

Been a long time, but I'm sure
they were more than 3500 lb
roof-top units.
We had a 55ton Loraine mobile,
with a lot of jib.

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nap

the set was more that 120 from the edge of the building. that is why you need the height, so you do can keep the boom up rather than angled over.




the one thing he did not include is the distance of the set from the edge of the roof. That 120' crane plus jib is only going to get you on the edge of the roof. If you want to go in, you got to go taller.

for example, if you want to set on a building 120 feet high and you want the set 120 feet from the edge, and just using an arbitrary angle of 45° (obviously varies with weight of load and crane capabilities), you would need a total height of to tip of 340 feet.
that sets the crane 120 feet from the edge of the building.

The angle available of the boom is dependent on the capabilities of the specific crane

that is why you let the crane company make the decision of what size crane to use.

you tell them weight, height of building, how far from edge of building and they can calculate what they need.