MobileCraneMK80 . A mobile tower crane build from sets 8421 and 8575, freely after the Liebherr MK80, made by Techno Moves and NXTLiftBoy. .
A mobile tower crane build from sets 8421 and 8575, freely after the Liebherr MK80, made by Techno Moves and NXTLiftBoy.
At times I have been mesmerized by the unfolding of a huge mobile tower crane, which are very nice pieces of engineering indeed. Because Techno Moves owns the brilliant mobile telescopic crane set 8421, and NXTLiftBoy owns the bulldozer set 8575, we decided many months ago to give it a try and recreate such a crane in LEGO. Well, here is the result!
Credits go to TLC for providing the truck, which is almost according to the instructions for set 8421.
When driving the crane has not very modest dimensions, since it measures 54 centimeters long, 16 centimeters wide, 29 centimeter high. Unfolded however, the crane towers almost 100 centimeter above the floor, and is 130 centimeter wide!
In order not to tip over, its stamps have a base of 30x36 centimeters. Moreover all the 12 batteries that power the motors are packed together as a counterweight. The operational weight of the crane is 2.6 kilograms.
Here you see the two IR receivers that allow the crane to be remotely controlled. The central lower piece of the crane houses four motors, besides the batteries!
The motors can of course lift and lower the hook, but they also make the hook slide horizontally, as well as swinging the tower around its main vertical axis.
The lifting motor hoists 1 kilograms easily, but this seems close to the limit for the remainder of the crane. We only dared lifting 1 kg close to the base. At the tip it lifts 50 grams easily. Top lifting speed is about 8 centimeters/second.
It was a major challenge to design a mechanism for sliding the trolley along the horizontal arm. Particularly because the motors have rather short wires, and the batteries were in the counterweight position. We figured out that the motor should stay close the batteries, and we used two very long axles to get the rotation in the top of the tower. Because the tower is from two telescopic pieces, each piece has its own axle. The teeth of two gear wheels, one on each axis, engage precisely when the tower is fully erected. Horizontal speed of the hook is about 6 centimeters/second.
The fourth motor has the power to very slowly raise the crane from the folded horizontal state to the unfolded vertical state! This is achieved with a severely geared down "buggy" motor. It takes about 2 minutes to fully unfold the crane. Here we beat the real thing needing 7 minutes :)
In the YouTube movie you get a good feel about the dimensions of the unfolded crane and how it behaves in real-time.
Instructions on how to build it or, actually, photos when taking it apart are in the making...