Subject:
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Re: New Crane...
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Newsgroups:
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lugnet.technic
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Date:
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Thu, 12 Jun 2008 13:12:49 GMT
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Viewed:
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14834 times
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Impressive supply of Technic beams you have there :-) The completed model is
going to be a monster. Nice job.
In lugnet.technic, Alvin Brant wrote:
> In lugnet.technic, Gordon Bentley wrote:
> > I can't see from your photos how you're stopping the main structure lifting off
> > the base.
> >
> > Correct me if I'm wrong, but crane turntables hold the superstructure down so
> > the load moment is transferred to the crawler base. I've seen photos of cranes
> > tipping and they don't fall off the turntable, they take the base with them.
>
> This is correct. Real cranes have roller bearings that are pinned in place that
> bear the weight and force of the superstructure where it is connected to the
> base.
>
> > I've had a couple of (incomplete) goes at a crawler, and I've used two
> > turntables, one inverted, with the centres tied together and to the
> > superstructure, and the outer rings locked into the base. That way, the
> > superstructure can't detach from the base.
>
> I am going to use a threaded axle through the center to hold the plates down,
> and then typical beams and plates connected perpindicularly by vertical beams to
> hold down the rest...(still working on the final design)
>
> >
> > Great looking model so far though.
>
> Thanks! Check back in from time to time for updated progress!
> >
> > Regards
I've been checking out the design of the dual CC8800, and it appears to not
really require that the turntable resists overturning moments. If the wheeled
ballast carrier in the back is connected, then the main turntable will mostly
see vertical (compressive) loads. If the crane tips, then the wheeled ballast
carrier will lift off the ground, and the whole thing will "hinge" about the
main turntable (I've seen this happen in real life on Manitowoc 2250's with
wheeled ballast carriers - in fact, crane operators will purposely do this so
that it's easier to slew). If you carefully control your load (which is how it's
done in real life), then your rear wheels come off the ground slightly and the
whole rig is carefully balanced on the main turntable. The main turntable will
see a very small amount of overturning moment, but it's controlled by the
careful balance being maintained between the load and the rear ballast.
Hope that makes sense. Here's a shot of the 2250 during a heavy lift. With the
wheels being off the ground, it's easier for the crane to slew and also move on
its crawlers (i.e. you don't have to stop and align the wheels to the movement
of the crane).
http://www.texbrick.com/temp/2250_liftoff.jpg
Of course the first time I saw this, I freaked out and ran over to the yard
leaderman. He explained that it was the normal way of doing things :-)
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Message has 1 Reply:
 | | Re: New Crane...
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| (...) Yeah, check out my brickshelf folder....I still have all the cranes there with the exception of the 18000...So I have a good bit of beams :D (...) Yeah, I have seen the 2250's do the same thing. One thing that I have noticed about the (...) (16 years ago, 13-Jun-08, to lugnet.technic)
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Message is in Reply To:
| | Re: New Crane...
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| (...) This is correct. Real cranes have roller bearings that are pinned in place that bear the weight and force of the superstructure where it is connected to the base. (...) I am going to use a threaded axle through the center to hold the plates (...) (16 years ago, 21-Feb-08, to lugnet.technic)
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