A mobile tower crane build from sets 8421 and 8275 AND 1 additional 32 long axle, by Techno Moves and NXTLiftBoy.
About this creation
A mobile tower crane build from sets 8421 and 8275 AND 1 additional 32 long axle, 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 8275, 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, or, actually, photos when taking it apart are now available at the Photobucket slideshow Additional remarks when you want to rebuild
Apart from the two sets AND 1 additional 32 long axle, you need:
1 patience and a sharp eye, the slideshow is not always easy to follow!
2 about 7 meters of strong rope in 6 pieces of 160, 120, 90, 185, 60 and 70 centimeters, for making it standing up
3 ~240 cm nylon (fishing) line
4 some centimeters of tube that fits tight around an axle, to avoid slipping of the nylon line that moves the trolley. Also the line needs one and a half turn around the axle to prevent slip.
5 12 AA (penlight) and 3 AAA batteries
Start by building the truck part of the crane set according to the LEGO design. From there on, follow the slideshow in reverse.
Oouch, we find this very embarrassing....
Indeed you are right, there is only a single 32 long axle in the two sets together!
We are awfully sorry and apologize.
We figure that the other one has slipped in from tow truck sets that have two such axles each.
I hope you can continue with spare axles and axle extenders? Oh no that does not fully work out either, because the axles need a looong slide upon unfolding the crane and the extenders would block that. Mmmm...
These solutions come to mind:
1 Have shorter axles with extenders replacing the long one.
2 Use a longer piece of the tube to replace a center part of the missing long axle.
3 Use two LEGO axles for the outer ends, and fill the empty space with any rod or axles you have (LEGO or not), which can be connected by pieces of the tube that you can push onto the axles/rods.
4 buy it, they go for about 1 to 2 US dollars on bricklink, see:
5 buy a set that has it, see the sets at: http://www.bricklink.com/catalogItemIn.asp?P=50450&in=S
In case 1 to 3 you still have to manually (dis)connect upon (un)folding the crane.
Whatever you do, thanks a lot for attempting to rebuild this beast, you are the first one we heard of doing so!
Also thanks for sharing your finding with us! It shows us again how hard it is to keep track of our set parts. Ok, we have a "luxury problem" with our sets.
Let us know if there is anything else you run into. We can alway try to help you out :)
Good luck and happy building, hope you'll find a way to finalise it!
NXTLiftBoy and Techno Moves
Quoting duca lara
Great model.I`ve found one downside in the instructions. You use 2 long axes. In the 2 models (8421 and 8275), there is just 1 axe available ! So I had to stop building it !
Thank you all!
I am at times not as responsive as i'd like to be, but your comments are surely appreciated!
Darren: indeed i have a lot of sets, but this is "just" from the two sets: 8421 and 8275.
The unfolding is modeled after the real thing, but simplified in many ways.
man-oh-man ! ... (wow) ... you are lucky to have sooo much Lego technic kits, parts, and pieces ... anyways, about your mobile crane ... this is definitely one of my favorites, because it's sooo HUGE and tall ! ... and because i can tell that you put ALOT of time, effort, and thought into making this beast. :)
!!!!! Amazing model! If pictures speak a thousand words then videos must speak millions. I'm very very very impressed! Makes a lot of the other 5/5s out there look a bit of a joke. Huge well done to both of you : ) that is truly brilliant.