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Showing results for tags '8421'.
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[MOC] RC 4 Axle Mobile Crane
kubic posted a topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Hi, it's been a long time since I posted a model. So here I am with another crane. I know that many people build them, but I really like this subject and I think I'm improving with every model. To begin with, I'm sorry for the quality of the photos - the weather has been bad for about a week and it doesn't seem to change. The axle setup and the outriggers are the same as in 8421. I used these stabilizers, because they don't require much space and work better then the ones I've previously used. Here is the list of functions, also visible on the renders below: -XL Motor geared 1:2.33 for drive. The third axle is driven with a differential and no suspension, so the off-road capabilities are minimal, but it drives well on flat surface -Servo for 6 wheel steering with correct angles -M Motor geared 1:40 for outriggers. They hold the model very well. When the batteries are full, they can lock themselves without any help -M Motor geared 1:168 using 56t turntable. It is equipped with four rollers made of wedge belt wheels, which is a big improvement over my previous cranes. It has no problems rotating with some load -L Motor geared 1:8.33 driving a single linear actuator for luffing. I didn't think it would be enough, but it does its job fine. The bad thing with using a ready-made actuator is the boom angle. It is only about 67 degrees, so it limits the amount of load the crane can lift -L Motor geared 1:24 + 1:2 with pulleys for winch. It is an overkill for this model, but I didn't have any more M Motors and the L has got a lot of attachment points. It could easily lift over 1 kg, but the crane itself limits it -M Motor for extending the boom. The motor is inclined to fit in the boom. It drives the rack via a u-joint and a worm gear. The boom has three sections and is based on the Grove GMK6400's excellent one I only have three IR Receivers, so luffing is controlled through a PF Switch located in the rear of the superstructure, but I forgot to include it on the renders. It is very easy to access and you don't have to hold the remote. I decided to put the battery box in the carrier for aesthetic reasons. I have just bought the rechargeable box, but it was not planned to be in this model. The box is a structural part of the build, but can also be removed by pulling out the connectors with chains. The model is lit up using 8 LifeLites LEDs with their battery just below the PF BB. All of them are in the cab and they give a nice effect. Lack of BB in the superstructure results in a big problem with counterweight. My previous crane had 0.75 kg of counterweight and this has none. It limits the lift capacity by a lot. The crane can lift 800 g on the front with retracted boom, 500 with boom retracted and superstructure slewed by 90 degrees and only about 100 g slewed and fully extended without swaying. The winch has no problems with over 1 kg, but with the values bigger than above the crane just leans over or puts a big stress on the turntable. You could probably lift more before tipping over entirely, but that's not what it's all about. The model has some manual functions. All doors open and the operator's cab can be lifted by hand. It uses a simple scissor lift and a manual lock to extend and tilt at the same time. Also there's a compartment in the rear behing some small rotor blades, which includes a fire extinguisher held by a pin. I had some space left, so I decided to put it there. The crane is equipped with many details, which for me really make the build. I have included all the lights, chains, beacons, exhausts, seats with armrests and headrests or an additional winch on the boom, which only sits on a friction axle pin, but adds to the looks when the crane sits on the shelf. Anyway, here is the gallery with some more pics. I can take more photos if you want. All of the functions work well and reasonably fast. The only slow one is the winch, but it would be harder to gear it up without an impact on the looks. I'm happy with the model and hope you'll like it too. Here is the video: I also have a link-only (don't want it on my main channel) video with some WIP photos. The build is just filled with wires. Apart from the stuff listed above it also has four extension wires. I went with the classic yellow color. For many people it's boring, but it is actually my first yellow Technic MOC. My two previous cranes were white and red because of the lack of parts. It matches the Mercedes star very well I'm happy with this MOC. I also fell in love with the 11 x 5 sloped panels :) Only things to change would be to move the superstructure backwards by a couple of studs and add pendular suspension on the driven axle. I will probably show another MOC this month. Thank you for reading! -
Rebuilding 8421 XL problems, HELP PLEASE!
Beeman posted a topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Hi there, perhaps you all know this page: Designer Han I am working on rebuilding the 8421 XL. But I got some problems with the links at the crane arm. Did somebody rebuild this one? I have to connect a special number of links and other links together. I did it like is is shown on the instructions...but my crane arm isn´t working. Perhaps you can help?!