Because I always wondered ....
Jan. 18th, 2005 05:13 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
tyggerjai... and apparently I'm not alone.
So. Cranes. Are, like, really tall. To build a tall crane, you need ... a tall crane. Yoink!
The easy answer, for tower cranes, could be that you just need one mobile crane to erect a short tower crane. Then that short tower crane can erect a slightly taller tower crane (the tallest piece of the crane when you build it will always be the cabin, and the boom will be level with that when it's built. But then, of course, the boom can reach much higher then the cabin, so two tower cranes could "leapfrog" each other.) But I don't know if anyone does it that way. You'd have to either lift the cabin and the boom together, or be constantly dismantling it all - and the counterweights aren't light, for obvious reasons. So that's a theoretical answer. The much, much cooler answer is ... self-hoisting cranes.
You get two types of tall crane on a building site. Mostly, you get tower cranes, which are freestanding. Sometimes, if the building is designed to take to load, you get cranes on the building itself, using the shell for support as it goes up. They both work, generally, on the same principle.
A tower crane will have a double thickness of tower just below the cabin, with hydraulic rams. The rams can lock on to the inner section of tower, which goes all the way to the ground, and lift the outer section of tower and the cabin. Then, you hoist another section of the internal tower up, lock it into place, and settle the cabin on it. Re-set the rams to lock on to the new section of inner tower, and repeat. Reverse to get back down. Thus:
becomes
and then
and finally
This is very cool. But what's even cooler than those are the ones that climb shafts inside the building.
Basically, you can leverage things like lift-shafts, if they're large enough and strong enough. All you need is an empty shaft all the way up the building that can take the load. Sometimes, they're even designed into the building from the start! The crane then has a short tower (one story high), with three components. This one is hard to describe, but each component has retractable feet that extend past the shaft to lift the crane.
Thus:
becomes
Then the middle one will extend its feet to take the load on the next level, and the two outside ones retract their feet, and retract back up to the next level.
This is all intermediate rigging, so I'm not up to this yet. But I think I'll be booking in for March 7, and let the job search slide a little longer. I'm having too much fun!
sol.
.
So. Cranes. Are, like, really tall. To build a tall crane, you need ... a tall crane. Yoink!
The easy answer, for tower cranes, could be that you just need one mobile crane to erect a short tower crane. Then that short tower crane can erect a slightly taller tower crane (the tallest piece of the crane when you build it will always be the cabin, and the boom will be level with that when it's built. But then, of course, the boom can reach much higher then the cabin, so two tower cranes could "leapfrog" each other.) But I don't know if anyone does it that way. You'd have to either lift the cabin and the boom together, or be constantly dismantling it all - and the counterweights aren't light, for obvious reasons. So that's a theoretical answer. The much, much cooler answer is ... self-hoisting cranes.
You get two types of tall crane on a building site. Mostly, you get tower cranes, which are freestanding. Sometimes, if the building is designed to take to load, you get cranes on the building itself, using the shell for support as it goes up. They both work, generally, on the same principle.
A tower crane will have a double thickness of tower just below the cabin, with hydraulic rams. The rams can lock on to the inner section of tower, which goes all the way to the ground, and lift the outer section of tower and the cabin. Then, you hoist another section of the internal tower up, lock it into place, and settle the cabin on it. Re-set the rams to lock on to the new section of inner tower, and repeat. Reverse to get back down. Thus:
/|
/ |
cab/
||||
||
becomes
/|
/ |
cab/
| |
||||
||
and then
/|
/ |
cab/
||||
||||
||
and finally
/|
/ |
cab/
||||
||
||
This is very cool. But what's even cooler than those are the ones that climb shafts inside the building.
Basically, you can leverage things like lift-shafts, if they're large enough and strong enough. All you need is an empty shaft all the way up the building that can take the load. Sometimes, they're even designed into the building from the start! The crane then has a short tower (one story high), with three components. This one is hard to describe, but each component has retractable feet that extend past the shaft to lift the crane.
Thus:
/|
/ |
cab/
_|||_
becomes
/|
/ |
cab/
|||
_| |_
Then the middle one will extend its feet to take the load on the next level, and the two outside ones retract their feet, and retract back up to the next level.
This is all intermediate rigging, so I'm not up to this yet. But I think I'll be booking in for March 7, and let the job search slide a little longer. I'm having too much fun!
sol.
.