Sariel.pl

Model of a “horse head” crane installed on a multi-hulled boat. Features propulsion system with thrusters.

Datasheet:

Completion date: 11/04/2013
Power: electric (AAA battery box)
Dimensions: length 54 studs / width 28 studs / height 62 studs (including propellers, with raised boom)
Weight: 1.32 kg
Displacement: 1.8 kg
Suspension: none
Propulsion: 1 x PF Medium motor geared 1:1.6
Motors: 6 x PF Medium

I was looking for an opportunity to do some underwater filming, to test a boat with thrusters and to play with a “horse head” crane. This single creation includes it all.

Odd as they may seem, the floating cranes are quite widespread and have been known since Medieval Age. They have a variety of uses, from handling cargo and building ships or bridges, to functioning as rescue/recovery vessels by lifting sunken objects.  I have based my design on two hulls connected closely side by side, with a typical harbor crane installed on top.

Since the vessel was intended for working in a bathtub, its speed was much less important than its manoeuvrability and locating the parts of the propulsion system between the hulls, where they can’t collide with bathtub’s sides. The basic propulsion was provided by a double propeller located between the hulls, driven by a single PF Medium motor with a small acceleration. This was further aided by two transverse thrusters – a bow and stern one – driven by a separate PF Medium motor each. Being able to work independently, the thrusters could rotate the vessel or propel it sideways. Combined with the main propeller, this provided a simple, reliable propulsion system that could move the crane in any direction without using rudders. It should be noted that the bow thruster proved less efficient than the stern one.

The crane could rotate through 360 degrees and had a boom built in a “horse head” set-up, also known as a level-luffing crane. The purpose of such a design is to move the load forward and backward along approximately straight, horizontal line. I kept the design as basic and lightweight as possible to keep the vessel’s center of gravity low, but it worked properly, with all the performance of larger and more complex harbor cranes (for instance, they usually include a moving counterweight). The crane’s top load capacity was not tested, but as the video below shows, when lifting a 150 grams heavy object on extended arm, the hulls are close to sinking on the loaded end. Thus the stability of the hulls was the limit of the whole vessel’s lifting abilities.

All in all, this creation was an experiment in several aspects, and it was a successful one. It worked as intended, it was fun to play with, and it avoided any accidents despite being somewhat risky.

Photos:

Video: