Les flèches

Lattice crane

Boom and jibs

Booms are intersting parts to build in Lego. It has to be strong and light. If a part dismount during a lift, it's catastrophic, everything brokes !

Modular design

On lattice cranes, booms are modular. Usually, provider supply standards elements you can assembly, depending on lifting needs.

See here different possible combinations :
SH : Heavy lift boom
SH/LH : Heavy lift boom and fixed fly jib
SSL : Heavy lift with Superlift (derrick) and supplementary counterweight.
SSL/LSL : Heavy lift boom and fixed fly jib + Superlift
SW : Luffing fly jib
SWSL : Luffing fly jib with Superlift

Main boom : 2 versions

At beginning, I only wanted to construct main boom. It's made of standard elements easy to put together. First section (35cm) is fixed on superstructure. Second straight section (40cm) is put before final section.

Then I modified it in order to make the crane more modular. Final section is modify to receive fixed fly jib or luffing fly jib, or doing a normal lift. On picture you can see 2 main boom straight sections, the jib (on top), its head and the 2 yellow A-frame for luffing fly jib. (See Complete main boom V2)

Luffing fly jib and A-frames

Luffing fly jib is made to do lifts over buildings : a straight boom may touch building. Fly jib leave main boom vertical.

Also, it isn't necessary to lift the whole 150m boom in one part, generating an enormous torque on superstructure turntable. It's possible to maintain head of fly jib on the ground while lifting boom, and rolling freely. 2 A-frames (yellow parts) are added to lift fly jib.

Derrick or Superlift

To reduce efforts on main A-frame while heavy lifts, crane builders have add a specifi element : the superlift or derrick. It's a boom 2 or 3 times longer than A-frame. It replace the A-frame and it's possible to add a big counterweight under it. I haven't yet construct it (lack of parts...).

Cables and pulleys

Stays is made with a Ø2.5mm wire. Each stays is motorized or adjustable. Depending on lift configuration, main boom has to be vertical or inclined.

For winches wire, I use a thinner cable (Ø1.5mm) to reduce wire volume and get long cables on winches (25 or 30 meters at all). Pulleys are non Lego, self-made.(see Superstructure).

Hook

The hook is ballasted in order to tighten wires. It use 4 pulleys, for heavy lifts.

More boom parts photos