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BOAC
20th Jan 2013, 16:04
I see they will be dismantling the 'modified' tower crane at St George's Wharf this coming week. I am intrigued by the way these things get put up and down - can anyone enlighten me? I understand the whole shebang is jacked up at ground level and a new section inserted/old removed - some jacks!!! - and how is the balance kept during the lift/lowering?!? Presumably the side stay supports are designed to 'slide' up and down?

G-CPTN
20th Jan 2013, 16:18
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Of course the problem will be with imbalance - they might need a helicopter to lift the counterbalance weights before they lower it.

Cremeegg
20th Jan 2013, 16:19
Very different methods depending on type of crane - may be freestanding or maybe attached. Try typing "tower crane erection" into YouTube and you have hours of fun watching how they do it.

Imbalance not a great problem if well planned. Most counterbalance weights lifted by the same mobile telescopic crane that lifted the rest of the stick and boom.

stuckgear
20th Jan 2013, 17:04
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BOAC
20th Jan 2013, 17:08
Fantastic! Thanks all.

hellsbrink
20th Jan 2013, 17:09
There's a 600 tonne "mobile" crane at the site, a Terex TC2800-1, which is to be used to dismantle the old crane.

G-CPTN
20th Jan 2013, 17:11
The damaged crane has no jib (and probably no controls).

G-CPTN
20th Jan 2013, 17:38
St George's Wharf Tower roof stands 181 metres (594 feet) with the crane clear above that height.
http://i.dailymail.co.uk/i/pix/2013/01/16/article-2263250-16F87670000005DC-887_634x798.jpg
Photograph from:- Helicopter crash in Vauxhall, London: Eyewitness accounts as flower market worker is hit by falling gear box | Mail Online (http://www.dailymail.co.uk/news/article-2263250/Helicopter-crash-Vauxhall-London-Eyewitness-accounts-flower-market-worker-hit-falling-gear-box.html)

It will stretch the capability of a standard TC2800-1 which tops out at 192 metres (630 feet).

If they can slide out one of the sections (which seem to be below the top of the building) then they will have a goer.

hval
20th Jan 2013, 17:49
G-CPTN,

Taking out sections is going to be very, very difficult with the boom and balance weights on. Your normal piece of kit may not be able to do it. It will have to be a beefed up version.

As for taking the counter balances of this will be a good idea, even if just to get the balance correct as it stands.

The slightly dented boom (one owner, no crashes, low mileage) should be secured some how before anything is done - subject to an assessment of how stable it currently is.

Advice may be gained from those engineers who had to take down tower cranes after Hurricane Sandy in New York.

G-CPTN
20th Jan 2013, 18:09
How heavy are the individual counterbalance weights?

A Sikorsky Skycrane can lift up to 9 tonnes.

A Chinook can lift 12.7 tonnes, but is it certified, and are there any operators capable of such work?

I guess the boys from Hereford could give it a go . . .

hval
20th Jan 2013, 18:28
How heavy are the individual counterbalance weights?

Simple answer is that it depends on the crane. Two tonnes per weight is fairly usual. But it really does depend upon the crane

Milo Minderbinder
20th Jan 2013, 21:39
Is there room to build another crane alongside?

G-CPTN
20th Jan 2013, 21:53
Two tonnes per weight is fairly usual.

In which case helicopter lifting capacity isn't a problem, though it might be precarious for the guys atop the crane fixing the slings.

Unless the helicopter could lower a long line whilst hovering high up.

Fraught with difficulties if the slings get caught on the crane and the heli crew have to drop them (and the weights?).

BOAC
21st Jan 2013, 09:08
Recovery crane assembled in Vauxhall following helicopter crash | Demotix.com (http://www.demotix.com/news/1738970/recovery-crane-assembled-vauxhall-following-helicopter-crash#media-1738953)