2GodBDGlory

Great writeup as usual! Placing the battery that far forward is a really interesting solution that I may have to try someday! The suspension is also pretty unique. One detail I quite liked was the way you secured the yellow crankshaft part that the steering actuator connects to. The moment I saw the render, I worried that that part would pop off immediately thanks to their very low clutch power, but then I saw you had placed the 1x2 Technic brick overtop of it to prevent that. Nice solution there!

Oops, I seem to have some keyboard shortcut to submit this that I keep hitting accidentally. I'll edit this to my actual question in a minute...

I dare somebody to submit a 1x1x10,000 string of axles and axle connectors to this contest, and pass it off as, say, a really wide steamroller wheel.

Yeah, I think you're right that I'm kind of stretching the limits of what the contest was meant to be, for better and for worse! Good catch about it being 48 studs long; I knew I designed it to be as big as possible, so I do recall thinking it odd that my final volume had that much leeway. I must have just miscounted at the end, so I'll fix that in the post. Thanks!

Good job so far! It's interesting seeing your build process in action. I think this part would work pretty well here; have you considered it? One of these could be helpful under it:

Thanks for the feedback! You're right, those curved panels could have looked good. Unfortunately, I've only got two of that multi-hole type in black, and only one of the fewer-hole type in black, and I don't think I have enough in any other color either, so square it must be! You're right about it looking skinny between the cab and the superstructure, but this was done intentionally. As pointed out in the video, when the boom is lifted, because of a poor pivot point location, the rear end of it sticks fairly far down, causing it to interfere with rotation at times because it will hit the top of the outrigger mechanism. Because the boom needs this extra space, I left it empty there to allow the boom to swing through that arc while raised up, but I don't recall ever actually doing that maneuver once it was finished! Perhaps it would have been better to use that space to reinforce my sagging cab and just rule out that option, but I'm probably not going to change anything at this point. (Too much trouble to take more pictures ) Good observations, though!

Thanks! I do like focusing on features. I'd agree that the proportions are odd, and I think you're right that it's the boom's fault. I believe its length is correctly scaled to the crane I was basing it on, but I never scaled the height of the boom part, and I'm assuming that in order to get the multi-stage setup inside, I had to exceed the height it should have had, cutting down on space below.

Ok, thanks!

Will we have to take a picture with our model in some kind of bounding box for proof of compliance, @Jim? I just finished my entry and will be taking it apart soon, so I just want to make sure I get all the documentation I need before I take it apart. Thanks!

Here's my final update! Since the last time around, all I've added functionally is connecting the steering wheel in the cab to the wheels, but I made a few other tweaks, such as getting rid of the weight brick on the hook, as well as the pulley for the hook, and adding the larger-diameter worm gear to the boom extension to keep it from skipping. Aesthetically, I added the main cab and the operator cab, some lights, and red highlights. Below here I'll just give a normal MOC presentation, rather than a WIP one: ------------------------------------------------------------ Here is my entry for Eurobricks contest TC22, a compact mobile crane. In order to be within the 10,000 cubic stud limit, this MOC was made to a 13 stud width, 48 stud length, and 16 stud height, for a total of 9984 cubic studs. Functionality includes: Steering from steering wheel in cab Outriggers that extend and lower using a rear control knob (actually two knobs hard-coupled together for convenience and symmetry) Rotating superstructure via rear knob Winch via rear knob Lifting boom via rear knob Two-stage extending boom via rear knob Two-output distribution gearbox for boom lift and extension, controlled from one knob and one selector on the chassis, with two outputs on the superstructure. Magnetic "hook" Most of the functions were quite straightforward, but three deserve extra mention. Boom extension. This was the first time I had tried making a two-stage extending boom, so it wasn't perfect, but it was still quite cool. A large-diameter worm gear run off a crank ran a long string of 1x4 gear racks to extend the middle segment of the boom (4x3 studs), while two pulley systems caused the end segment of the boom to simultaneously extend out of the middle one, allowing the boom to extend to a little less than three times its original length. With such a large boom on such a small crane, it looked pretty impressive when extended. Sadly, there was too much friction to extend it effectively from the main knob, and while one could extend it by hand by pushing on a different gear, it would take an immensely long time. Outriggers: The outriggers had to be very compact to fit within the size limitations for the contest. In the end, they were based on two 13L gear racks pressed against each other and connected with gears so they would extend together. Furthermore, the legs were attached to them on a pivot connected to a transverse axle. When the legs reached nearly full extension, this axle would be forced to catch and pull the leg down, allowing for both to be controlled from the same knob. The legs weren't especially stable, but they did help keep the crane stable despite the very long boom. Distribution gearbox: The unusual distribution gearbox was developed in order to allow all three superstructure functions (winch, boom extension, and boom lift) to be controlled from the chassis. The winch was driven by a central axle through the turntable from its own knob, but the other two functions used the gearbox. It was shifted with a small lever on the side of the crane, and would push a setup of a transmission driving ring with a 20T clutch gear on each side up and down. In all cases, this assembly was driven from a single knob on the chassis, but depending on whether it was up or down, it would drive different functions on the superstructure. Because the shift lever could only push the gear assembly up and not down, there was a rubber-band loaded lever on the top to force the gears down when the shift lever got out of its way. Mock-up. Imagine the two sides as connected only by a large turntable. WIP model shifting Overall, I think the model had fairly impressive and interesting functions, and looked decent in my eyes. It definitely had its shortcomings, such as the inability of the boom to rotate while lifted, the extreme difficulty of extending the boom (unless you resorted to an external motor), and the weak chassis (the cab would sometimes scrape the ground.) I don't have ambitions of beating the far more experienced builders in the contest, but I'm glad to have participated, and gone outside my comfort zone a bit. More images at: https://bricksafe.com/pages/2GodBDGlory/compact-mobile-crane

Nice going! It looks like it'll be a really interesting MOC. I would encourage you to give the semi-trailing arm suspension a shot, though! I was just taking a look at it, and I think it would be an interesting challenge and another great touch on this already mechanically interesting MOC.

Thanks for pointing me to that information! It's pretty intriguing that Lego is actually partnering with the Raspberry Pi people to make a lower-cost (higher skill-level, I assume) alternative to Mindstorms.

Very nice! I can imagine that programming that would be quite challenging. One question I have is how you're able to adapt the Lego servo wires to the Raspberry Pi? I was under the impression that that plug type was proprietary for Lego, and not something I'd expect to see for a Pi.

If you follow his link to Rebrickable, there's a video on that page

I just watched your video on Rebrickable, and I'm very impressed with the functionality! Collective and cyclic pitch on the main rotor, plus cyclic on the tail one is very impressive, especially for a B-model of a set without any turntables!

Looking good! I also found 13 studs wide to work well for my mobile crane.

Great! Out of curiosity, how many used to be on a page?

I'm not opposed to trying out a subforum for this contest, but as pointed out in this quote, it does seem like somewhat odd logic used to justify it. We start contests (at least partially) in order to increase activity on the forum, but then during the contest we feel like there's too much activity, resulting in less attention for other MOCs. Perhaps it's true that MOCs do get neglected in contest season, but on one hand having more traffic on the forum in general could definitely result in more people viewing non-contest related stuff. And alternately, if the purpose of the contest is to generate activity, hiding it away in a subforum will only tend to diminish how many people actually look at the contest entries, which are just as much MOCs as non-contest ones that get overlooked (though the constant updates do keep them artificially on the front page). The more I type, the more I become convinced that it would be counterproductive to put them somewhere else. More activity on the main forum is a good thing, right? Maybe I'm just a Eurobricks addict, but I'll always click on the second page if everything on the first page is new to me. (Though I check several times a day, so it never really gets that far for me anymore). It doesn't seem like a hard thing to do to see more new content, but I guess some people just aren't interested? As someone else mentioned, just allowing more posts per page would be really nice, but maybe that's not possible in this forum framework.

Update time! As you can see, I've just about finished the mechanical parts of the chassis, with the only thing I expect to add being a steering wheel in the cab hooked up to the wheels. (HOG wouldn't work well on the top thanks to the boom, and I think despair is the correct response to trying to route it to the back) Here I've got the boom lifted and rotated 180 degrees. Control knobs: Both the far left and far right ones run the outriggers for symmetry, the middle one runs boom lift and extension through the gearbox, the middle-left one runs the winch, and the middle-right one slews the superstructure. Also note the outrigger legs in the retracted position (They flop outside of my 13-stud width, because of a necessary half-stud offset in the geometry forcing them out, but they can easily be pushed into compliance, so I don't think they'll cause me volume issues.) Outriggers extended: I didn't have space for independent leg extension and lowering, and the simple 4-bar linkage type lowering and extending from the crane used in many official sets would have looked too minimal for such a long boom, so eventually I came up with this super compact setup that uses extra linkages to pull the legs down in the same motion. It's based on having friction with the black 10L axle on the left and the LBG 9L axle on the right extend, which forces the extension to pull down the legs. The time at which the legs lower is somewhat random because of variations in friction, but all four legs extend and lower easily in one motion, which is pretty cool. Obviously, these legs provide little to no support... Bottom view: It's really cramped. I've also got the wheels at a half-stud offset, aiming to have only a half-stud of ground clearance, allowing the half-studish protrusion of 12T gear on the top of my boom to fit within my 16 stud limit. Overall, it's getting strange proportionally. As I said, I scaled this to use 56mm balloon tires, but I realized that if I used those, they would be sticking up above the turntable, preventing it from rotating. In the end, these tires were the biggest I could fit. I think my issue with scale is that while the boom is the correct length for my planned dimensions, by the time I added the two-stage extension, it had become too large vertically, forcing everything below it to be squished down. I think this model is going to be more on the over-engineered side than I expected, so I don't see it being competitive in the contest, but it's still fun and I want to finish it. I guess in theory I might finish in time to throw together a second model to submit instead, but then I'd actually have to find something else eligible that I have interest in building!

You're right, that does look about as solid as you could get while having those 16T gears where they are, so it'll probably be fine, as long as the gearbox doesn't put up too much of a fight. The fact that it's AWD (without a central differential, if I followed the thread thoroughly enough) should help, too, since you're not really ever going to have it relying on just the front axle. And yeah, you would need to recreate that gearing on the rear axle to keep it even if you did decide to change it, but I don't think it would be too hard. (Though if you did put in a central differential, there would be no need to ensure that the gearing was the same; you'd just get torque vectoring to front or rear. I think the lower gearing on the front would give it a forward torque bias, though, which is probably not what a rally car would use)

Looking good! I'm a little worried about the gearing at the front differential, though. I mostly build RC models, and the bracing between the 20T gear and the differential would definitely not hold up to that. I assume this is a manual model, so forces will be lower and it might be ok, but one thing I would look into is replacing the 16:16 gearing you have coming from the differential with 12:20 gearing in order to reduce the forces on the differential further, kind of like using a planetary hub. I'm not quite sure whether gearing up or down there, but probably gearing up, so the 20T gear is on the U-joint axle, and the 12T is on the differential's axle. That way, the carrier will have lower torque, and be less likely to skip.

So I take it that this solution works except for the high friction in those axles sliding. I think something similar with sliding beams instead of axles could work, but it would get bulky. ... Pneumatic cylinders could maybe be used to stabilize it, simply for their relatively low friction extension? Even ignoring the ports on it, maybe some brace could be made? What else allows low friction extension? That's all I can think of. Maybe putting more beams on that O-frame to keep the axle straighter would help?

I think you might be looking at the wrong one in that thread. The first thing he takes apart is the large one, which does have the extra output, but towards the bottom of the first page, where he does the small one, you can see that it does only have one output, unfortunately.

This link @1gor put above looks like it could be used to buy them, but maybe you have to have some educational connection to do so? https://education.lego.com/en-us/products/lego-technic-small-angular-motor/45607

Well, electronics are ok, but I think he elsewhere said that no third party stuff was allowed. Either way, though, do go ahead with the model!