DLuders

Rottermannen's Fully-Functional Lego Technic Crawler Crane

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Rottermannen / tv2mustdie posted this

of his fully-functional Lego Technic Crawler Crane which can lift 4 kg (8.8 lbs.) at 50 studs distance -- "4 kg (7 x 3.5" Hard disks) at 50 studs radius. Slewing and crawlers working. 5.2 kg ballast + 1.8 kg central ballast." It can lift 7 kg (15.4 lbs.) at a closer distance. His Flickr photoset has 13 pictures with descriptions of how his various load tests developed over time.

He description of his MOC:

"LEGO Technic Lattice Boom Crawler Crane

Lattice boom crawler crane with 9 kg lift capacity made from LEGO Technic.

max. lifting capacity 9 kg at 200 mm (25 studs)

max. load moment 18 Nm

Main boom 432 to 1152 mm (54 to 144 studs)

Lattice jib 420 to 1120 mm (60 to 140 studs)

Crane weight (base + superstructure) 2.7 kg

Central ballast 1.8 kg

Superstructure ballast 6.2 kg

The superstructure is mounted to the base through a turntable powered by 1 small power functions electric motor enabling slewing under full load. The superstructure is equipped with 4 winches and 6.2 kg of counterweight.

The base is equipped with 1.8 kg of ballast and crawlers powered by 2 small power functions electric motors enabling the crane to move with full load.

The lattice boom consists of 2 to 5 sections (54 to 144 studs length) and is connected to an A-frame which is raised and lowered by 2 times 12 falls powered by 2 winches each with 1 large power functions electric motors. The hook is lifted with 2 times 12 falls powered by 2 winches each with large power functions electric motors.

T

he jib is raised and lowered by 1 winch with 1 small power functions electric motor (12 falls) and the jib hook is lifted with 8 falls powered by 1 winch with 1 small power functions electric motor.

Non lego parts:

2 axial steel roller bearings are fitted to the turntable to allow slewing with max load moment. The crane will have similar load capacity without them but slewing will not be possible.

1 mm braided ropes are used on all winches."

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Very impressive, however one thing sticks out to me: all of the reinforcing is done using technic bricks rather than liftarms. Is this a stylistic choice? It seems to me that most of them could be replaced with liftarms, resulting in a significantly lighter structure. A 1x12 technic brick weighs 4.2g, while an equivalent 1x11 liftarm weighs only 3.0g, a more than 25% reduction. I can't tell exactly how many there are in the main arm (jib? sorry I don't know the terminology) that could be replaced, but there's at least a few dozen.

Wouldn't using liftarms make a lighter structure, hence able to lift more weight? Is that part of the challenge, or are liftarms less rigid?

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Wouldn't using liftarms make a lighter structure, hence able to lift more weight? Is that part of the challenge, or are liftarms less rigid?

Technic bricks can be joined end to end without lapping them by using plates. Beams can't. This can be a big space savings for cranes.

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That's an awesome MOC.

Very impressive, however one thing sticks out to me: all of the reinforcing is done using technic bricks rather than liftarms. Is this a stylistic choice? It seems to me that most of them could be replaced with liftarms, resulting in a significantly lighter structure. A 1x12 technic brick weighs 4.2g, while an equivalent 1x11 liftarm weighs only 3.0g, a more than 25% reduction. I can't tell exactly how many there are in the main arm (jib? sorry I don't know the terminology) that could be replaced, but there's at least a few dozen.

Wouldn't using liftarms make a lighter structure, hence able to lift more weight? Is that part of the challenge, or are liftarms less rigid?

I'm guessing it was because with the studded beams you can use plates to brace/hold together the joins.

Edited by dandexter

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I would not expect to be able to lift 9kg using a crane with such construction. Really very impressive. And the ability to move with full load makes it even more realistic.

Is that part of the challenge, or are liftarms less rigid?

Bricks are stronger than beams. They bend less than beams.

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@ Hopey: In this Eurobricks post, tl8 published his thorough "Investigation into the Strength of Lego Technic Liftarms and Brick Beams, and of Liftarm Pin Connections" PDF document. His conclusions after testing dozens of items:

"Liftarms are better in tension than studded [Technic Bricks].

Brick Beams are better in transverse [shear] than studless [liftarms].

Liftarms are stronger in transverse [shear] with the pins on the side.

Connections to other components will fail before the Beam (either connections themselves, or the connection area of the Liftarm)(i.e., the (unstressed) centre of the Liftarm will not fail).

Pin connections will probably pull apart before they fail catastrophically.

The more pins, the stronger the connection.

In transverse 3 pin overlap, with 2 pins used is almost as strong as 3 pin overlap and 3 pins used

Liftarms in transverse [shear] conditions wont fail (but will bend) if the pivot points match the end of the connection

Lego is quite strong for its weight"

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