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Thanks for the reply Dennis. So far, I haven't hit problems with the axles.
I am making sure every load bearing axle has at least two shear planes for
this reason. Also doubling up on gears (tandem) and making sure all axles
are supported everywhere seems to help.
I have had one interesting "failure". My turntable is braced by a beam
running from the rotating frame through the turntable to a flat plate under
the crossframe. This plate bears against the bottom of the structure to
transfer loads to it. I originally used a pair of half-thick studless beams
for this connection. One day the plate jammed, the drive continued to turn
the rotating frame, though it did slow down a bit, until it had twieted the
beams through around 120 degrees. They didnt crack, or break. They just
slowly stretched. I now have tow half-width beams with a 90 degree twist.
Haven't found a use for them yet! I now use two standard beams side-by-side
to do this job, and havent had any problems since.
Two things I have learned include "symmetry is essential" which means the
structure should be identical from left to right. If it isn't the crane will
lean as it takes up the load, and this will increase the moment about the
base which makes it lean more, which ....
"Dont use beams in bending" Think in terms of trusses. The beams only ever
take direct tension or compression forces. THere is much less flex this way.
I am aware of your cranes! They are very impressive, and I doubt I will ever
reach that level. They were one of the main reasons I got interested in this.
Mine is definitely a Technic model rather than Model Team though. I am
putting as much detail in as possible(Operators cab with opening door, with
latch, control levers, warning lights, siren, tilting cab, access ladders,
V6 motor run from luffing winch motor, air cleaner, exhaust, manifolds, boom
backstop, etc.), but it is still Technic. It's taken a LOT of rebuilds to
get all this into the available size. I've been working on it for around 18
months so far!
Regards
Gordon
In lugnet.technic, Dennis Bosman writes:
> Gordon,
>
> When you wan't to lift such a heavy load the technic axles are too weak. So
> you have to use other materials than LEGO. I've made a 4.2 metres high
> Liebherr LG1550 and know how far you can go with it. A hundred kg's seems
> impressive, but is impossible. I know a guy who build a crane with a very
> strong beam. The maximum he could lift was about 15 kg's I think. I studied
> the boom: it really is strong. LEGO is plastic and plastic is not the
> strongest material in the world. When it was, most crane where made of
> plastic ....
>
> Dennis
>
> In lugnet.technic, Gordon Bentley writes:
> > In lugnet.technic, Dennis Bosman writes:
> > > 9.5 pounds = ... kgs??? Sounds heavy, so the crane has a great lifting
> > > capacity. Is the boom strongs enough??? You have to take care of sufficient
> >
> > Dennis,
> >
> > 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.
> >
> > 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.
> >
> > Now I've just got to keep buying sets to get enough parts to complete the
> > crawlers. And some pulleys for a bigger set of blocks.
> >
> > Regards
> > Gordon
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Message has 1 Reply:
 | | Re: The Big Crane At Brickfest
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| Gordon, (...) The axles of my crane were supported as well. I put six black bricks under the chassis. You nearly couldn’t trace them. Many people thought the crane was supported only by it’s heavy support arms. But as LEGO-ist you know that’s far (...) (22 years ago, 1-Aug-02, to lugnet.technic, lugnet.modelteam)
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Message is in Reply To:
| | Re: The Big Crane At Brickfest
|
| Gordon, When you wan't to lift such a heavy load the technic axles are too weak. So you have to use other materials than LEGO. I've made a 4.2 metres high Liebherr LG1550 and know how far you can go with it. A hundred kg's seems impressive, but is (...) (22 years ago, 29-Jul-02, to lugnet.technic, lugnet.modelteam)
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