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Bogdan Valceanu posted a topic in LEGO Technic, Mindstorms, Model Team and Scale ModelingHi guys, I’ve been following the forum for some years not, but I’ve been mostly a “lurker in the dark”. But, after 2.5 years designing and building when I had some spare time, I can finally share my 1:20 crawler crane MOC with you. For now it has somewhere around 40.000-60.000 parts (don’t know exactly how many). I’ve tried to build it as close as possible to a real crane in terms of assembly and functionality, with the usual constrains that you have with building out of Lego at this size and scale. As a disclaimer (and as a direct apology to Lego purists), the slewing bearing is not lego, but a cross roller bearing. The drive of the bearing is Lego, using the ¼ gear racks from the 42055 BWE. Took me about 6 monts to find a bearing that fits in size with the internal gearing of the gear racks, so that the driving axles still fit trough. Also, if you look really close, there were some occasions where I got out the Dremel for some adjusting (mainly panels), as I didn’t want to sacrifice strength, or design. Again, sorry to the purists. The crane is powere by 4 BuWizz, one in each central counterweight (between the crawlers), and one in each superstructure counterweights. I love the fact that you can still operate the BuWizz while it’s charging, so I have a power bank battery next to each BuWizz. Like this you get hours and hours of play time even with a large heavy model like this. The drive is as follows: - Each crawler is powered by 4 PF XL Motors (and one BuWizz per crawler) geared down 240:1. The motors don’t drive the ends of the crawler, but 8 sets of 2 gears underneath each of the crawler chassis. Due to weight reasons I used metal axles from Eezo’s Brick Machine Shop from the US. -Slewing is done again by 4 PF XL Motors which sit in the base of the superstructure. - Each winch is driven by a PF L motor. They were powered by 2 PF L motors, but because the winches are worm-driven I had some issues with them not running synchronous and overloading the motors. The winches can be individually taken out from the superstructure for maintenance and use 1mm wax rope. Structurally the main building technique for the crawlers, undercarriage and superstructure is an array of 5x7 technic frames. I’ll come back on another post with some pics of the various building techniques and technical details. Maybe I’ll also do a more detailed video on this sometime soon. The crane is not finished yet. I still need to build the superlift tray and telescope, which will be EV3 controlled so that it self-adjusts, and sadly I need to rebuild all the boom. Until a main boom length of 4.5m everything is ok, but with more than that it starts to bend too much. In the video below I’ve build 4m of boom, because it was pretty windy when we shot the video. The goal would be 7m someday. I want to keep the boom in the main boom+short fixed jib configuration. A luffing jib would be easier to lift (most large Lego cranes that I saw are built in a luffing jib configurations), but as I work in wind turbine assembly, I want to build the boom configuration that we use mostly. Here some pictures from the assembled crane: https://www.flickr.com/photos/164584645@N03/ And here a video about the crane (without wanting to advertise for the channel) As mentioned before, I’ll follow-up with some more pics from the building phase and building techniques. I hope you guys like the crane.