Subject:
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RE: All Terrain Crane
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 25 Jun 2002 18:45:49 GMT
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Reply-To:
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<RHEMPEL@BMTS.avoidspamCOM>
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Viewed:
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2148 times
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> > I used to work for PAT, a major supplier of LMIs to Demag, Grove,
> > and others.
>
> Any chance of a wee explanation about how these things work? The trouble
> with looking deeply into a subject is that it usually generates even more
> questions that you had in the first place, and this is exactly what happened
> here. I remember reading about old mechanical LMIs but not modern ones!
Ha! There IS something you don't know about cranes!
Basically, they have pressure transducers on the hydraulics that control boom
luffing. Then there's a really complicated bit of software that's customised
for each and every crane geomoetry that takes into account the boom angle, boom
extension, jib attachment and angle, etc and calculates the limit of operation.
The cable drum is for things like the anemometer, but it also provides
an indication of boom extension. There is also a boom angle transducer
in the box....
Some cranes also need to take into account the slewing direction because
the moment changes as the load passes around the outriggers.
I once worked on recalibrating one of these systems on a crane that
was damaged when it fell over with no load. The boom was left up for
a show and then it rained overnight. The ground got soggy, the outriggers
dug in, and the load radius got bigger and bigger until ....
Once the crane gets to the tipping point, the results are pretty
spectacular. Even if the operator lets the load go, or manages to luff up
in hopes of reducing the radius, the resulting forces tend to make the
crane fail spectacularly.
Modern cranes are very safe, but I would never stand closer than the
boom radius unless I was on the crew.
Cheers, Ralph
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Message has 3 Replies:
 | | Re: All Terrain Crane
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| Darn it! I felt sure you were going to say there was a gyro or something involved! I've been thinking that an RCX compatible gyro sensor is the logical companion to the latest new sensor idea I've been working on - an accelerometer. Now, if I could (...) (22 years ago, 25-Jun-02, to lugnet.technic)
| | | Re: All Terrain Crane
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| (...) Indeed. Here in Melbourne recently, a tower section was being added when the counterweight detached & fell, killing one worker. (URL) (22 years ago, 25-Jun-02, to lugnet.technic)
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Message is in Reply To:
| | Re: All Terrain Crane
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| "Ralph Hempel" <rhempel@bmts.com> wrote in message (...) Any chance of a wee explanation about how these things work? The trouble with looking deeply into a subject is that it usually generates even more questions that you had in the first place, (...) (22 years ago, 25-Jun-02, to lugnet.technic)
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