after years of only reading occasionally at Eurobricks it is time to present my latest MOC at Eurobricks: A caterpillar 365C ultra high demolition excavator.
(If the youtube video disappeared:
)It started with excavator 8043. But I did not like the bucket, because playing with this bucket is difficult. In most cases LEGO bricks will not get into the bucket but will just be pushed away. So I searched for alternatives and I came across demolition excavators. A LEGO demolition excavator would be great. And this demolition excavator should be able to demolish a LEGO house, this would be incredible. But is this possible?
I realized quickly: this is not just a 8043 modification, this requires a complete new design.
I started with the jaw. This has to be very small. If the jaw is too long, it will be impossible to breakaway Lego bricks. And the jaw must be turnable about 180° to demolish ceilings and walls at different heights. The clamping force should not depend on the angle position of the jaw, bricks should not drop from the jaw when the jaw is moved. After some trials I found a solution using a string (well visible in the video).
I built a prototype with this string solution and made a trial: will the clamping force be high enough to enable the jaw disassembling a 1x8 brick? Yes! The clamping force is just enough. So I could answer the question of principle: it is possible to demolish a LEGO house with a LEGO excavator.
As the next step I designed the bucket arm. This should contain two power function M-motors and friction clutches for closing the jaw and for moving the jaw. For both functions maximum power is required without overstressing the M-motors. The bucket arm should not be wider than 5 studs. I took some time, but the design of the bucket arm was not so difficult.
Then I designed the undercarriage. I adopted the design principle of Jurgen Krooshoops 8043 modification and put the gear reduction into the undercarriage. In comparison with the undercarriage of the 8043 I designed a considerable longer undercarriage.
Now the most difficult part: the upper structure. Main task: lifting the boom. As a first trial I used three linear actuators parallel. The upper structure was made mainly of liftarms. During the first trial I heard a lot of clicks, but the boom did not lift a little bit. I enforced the gear box, but all subsequent trials just ended up with ugly noises. The required force for lifting the boom was just too high.
So I increased the distance between the lower linear actuator bearing point and the boom bearing point. So there is less force necessary for lifting the boom. But now the adjustment range of the linear actuators is not sufficient for lifting the boom vertically. So I added two additional linear actuators to archive the required adjustment range. In total I use now 4 linear actuators for lifting the boom.
I designed the gearbox inside the upper structure following these principles:
- use of technic bricks instead of liftarms wherever possible
- bearing of gears on both sides of the gears, it must be impossible for gears to move apart
Next trial: the XL-motor is moaning a little bit, but the boom is lifting. Hip, Hip, Hooray!
Now I started with detailed design of the upper structure, finally 2 XL-motors, 4 M-motors, 4 IR receiver and 2 battery boxes have to be placed inside the upper structure. Two battery boxes? Yes, I need the weight of two battery boxes as counterweight and the electric power should last for at least one day during an exhibition.
As I did not have all required parts in yellow I built the excavator with available parts. So right now the excavator design was finished, but the excavator was multicoloured.
As next step I built the excavator in ML Cad. During this step some improvements were implemented. After finishing this I knew exactly which parts I needed and I bought them.
And then I did something I really like: building a MOC following a building instruction I created on my own.
Last I created stickers and then my demolition excavator was complete.
This demolition excavator was designed for demolishing a LEGO house, so I needed a house for demolishing. Of course not a single family house, I needed a tower building. Based on pictures of real tower buildings and a reasonable floor plan I built a tower house in ML Cad. And then I bought the worst available parts, the house must not look like new, it should look like ready for demolishing. Building the tower building according to the ML Cad building instruction was not difficulty, it just took quite a lot of time as 11,000 parts had to be assembled.
At the end tower building and excavator were ready just in time for the LEGO FanWelt Exhibition.
PS: Demolishing the tower building with the excavator is fun for hours.