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In lugnet.technic, Thomas Avery writes:
> In lugnet.technic, Gordon Bentley writes:
> > Booms made of Technic beams like this are remarkably strong. I am working on
> > a crane as well (who isn't!) and have tested the boom to 100Kg direct load
> > and it doesn't even look like moving. I was pretty amazed about this result
> > myself.
>
> Yep, that is pretty amazing. Got any pics? How long is the structure, how is
> it constructed?
It is currently only the boom base section and a hammerhead top section.
They total just under 1 meter. I used beams for the chords(the vertical
members at the corners), they are joined with a tile and plate sandwiching
the beams. The beams have their dots toward the inside of the boom. The
lattice on the "side" of the beams is just 12L beams with friction pins
connecting. The lattice going the other way is 10L beams which go on the
outside. This way, you can place them at 1/2 Unit spacings which is almost a
perfect fit with the mast 8L wide.
I will definitely post pics when I have more structure finished.
>
> The problem, or rather potential problem, with a Lego truss is that failure
> is catastrophic (and I speak from experience here). You'll have one joint
> pop apart under load, and then the rest comes crashing down.
Yes, I know about that one. I made the (really dumb) mistake of lifting the
weight off the crane while testing a few months back, and ended up wearing
most of the crane! It recoiled back because of the counterweight. Apparently
this is a common source of accidents in the real thing.
>
> > So far I've finished the rotating frame, boom, A-Frame and winches,
> > turntable and cross-frame. Testing with this on a flat base, I find the main
> > limitation is the load that the winches will take without the gearbox
> > pulling apart. I have succssfully lifted 12 Kg with a 4:1 block. At 16 Kg,
> > the winch broke, but the rest of the structure is fine. These are controlled
> > lifts where the weight is picked, either luffed, or rotated and put down
> > again. Note I am working at Technic Figure scale of around 20:1. My ultimate
> > goal is to lift 40-50 Kg.
>
> Well now, we'll just have to see some pics of this! You've certainly got our
> interest.
>
> TJ
I really want to wait before posting any pictures to finish the structure.
As I said I don't currently have crawler frames, so it's a bit artificial at
the moment.
I also expect to reach the limit I'll need to build a superlift system. So
it will be a while before this is done.
Thanks for the comments.
Gordon
PS I managed the 16Kg lift on the weekend. It is amazing to see it lift
this. The winch motor almost stalls at this load, might have to recharge my
NiCds. It is a gear motor through a 81:1 gearbox for interest.
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Message is in Reply To:
 | | Re: The Big Crane At Brickfest
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| (...) Yep, that is pretty amazing. Got any pics? How long is the structure, how is it constructed? The problem, or rather potential problem, with a Lego truss is that failure is catastrophic (and I speak from experience here). You'll have one joint (...) (22 years ago, 26-Jul-02, to lugnet.technic, lugnet.modelteam)
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