2GodBDGlory

42043 Mercedes-Benz Arocs 3245 Original: Functions: Two-axle steering with different ratios and HOG control Full live-axle suspension Knob-operated outrigger extension Basic outrigger leg deployment using pins Dumping bed Latch to allow the rear gate to open or remain closed Knob-operated crane arm rotation Pneumatic operation of the first crane arm joint Pneumatic operation of the second crane arm joint Pneumatic extension of the boom Pneumatic bucket

Alright, here's my presentation of the completed model! There's probably not much new information here if you've been following the WIP updates, but it's good to have all the info in one spot for future reference, and I've now got better pictures and a video: Aesthetics: Luckily, the original set isn't very complicated, so I was able to make a decent rendition of it under the limitations of small scale, few white parts, and, of course, a general lack of skill and excitement for building bodywork. I am rather pleased with the result, with a detailed grille, and otherwise inoffensive proportions (I suppose inoffensive is a rather subjective word--I may not be offended by it, but if even one person out there decides to be offended by it, my claim will be proven false!) Steering: The steering was mildly complex, using a compact system of a 8:24 gear setup, and then a rotating beam used to steer both of the front two axles. Different lengths of the lever points on this beam meant that the second axle didn't steer as much as the first, as it should be. (Image from the WIP stage) Suspension: All four axles technically had solid-axle suspension, with the front two axles being supported by small Lego springs placed over flick-fire missiles, the latter of which allowed for a good amount of play in the system, allowing the two sides to be sprung independently. The rear used a sort of swing arm system, with rubber bands for the spring. The model was really too light (and flimsy) for the suspension to be of any effect, but it had a good amount of travel. Outriggers: The outriggers were based on old 8L gear racks, and were operated by a knob, through a few bevel gears. The legs were simple pins that could be pushed down manually. Bed: The bed could be tilted with a manually operated small linear actuator, and there was a small manual latch on the rear to determine whether the rear gate could swing open or not, just like the original set. Crane arm rotation: The crane could be rotated using a knob on a tall axle (simulating the original set's exhaust pipe), which then ran two 8T gears that meshed with the 28T turntable. It was simple, and worked fine, though I generally had to press the control axle inwards to keep its 8T gear engaged when stresses got high. (Space was very short for reinforcement, unfortunately) Pneumatics: I wanted to keep the same pneumatic functionality as the original set, which meant four cylinders on the arm, to run the two joints, extend the arm, and close the bucket. Because it would be completely impracticable to run eight hoses down from the crane arm, I decided to operate the cylinders on the single-acting system used in official sets in the '80s. This meant that any cylinder could be used as a pump (I used an '80s vintage red cylinder), and that an external distribution block would be required to separate the compression and suction strokes. This block then sent its two outputs to the two outer ports of each of the four valves (in the cab), which then sent a total of four hoses to the arm from their middle ports. The system worked quite well, though extension and bucket operation often required many pumps (and their cylinders tended to stick during the first operation of a session--simply moving them by hand once would free them up to work normally). This picture shows some of the pneumatic components in better detail This one shows them in action Overall, the model was quite satisfactory! All the functions worked fine, and it looked pretty good by my standards! It was regrettably floppy, with pretty much everything being built off of a frame like this one, but I'm not sure how I could have improved it without sacrificing functions or increasing the scale. It wasn't catastrophic or anything, just not nearly as stiff as an official set! Anyways, I've enjoyed this project, and I think the result is a fitting tribute to this great set--the first Technic set I ever bought! Here's the video: More pictures at: https://bricksafe.com/pages/2GodBDGlory/tc25-mercedes-benz-arocs

Thanks! It's working pretty well, but I think the tight hose routing is putting some resistance on the system. Yeah, something like this would be a cool set! I'm not sure if it'd really be that cheap, though, since it's very densely built, and has pneumatics. I'd be quite curious to know the part count! As for instructions, it's not something I typically do. I had thought about making a Stud.io model of it, but I'm still way at the bottom of the learning curve for that, and the model is pretty complex. I'll see! Yeah, or just make the model a little bigger so there's room for the extra hoses modern pneumatics would require

Well, I think this will be my final update! Not a whole lot has changed since last time, but a lot of what I did was strangely hard due to lack of space and attachment points. Basically I added: Orange lights on roof Second axle mudguards Red bits near the crane (Where the valves would usually go) Black beams over and under outriggers Rear mudguards Wheel chocks Rear bumper Now I think all I have to do is put together some final pictures and video, and make a full presentation of the model!

I'd be curious to see how a pullback vehicle with suspension would work! That's a good choice of set!

A couple minifigure rings could work, or maybe you could make this part work: Part 6643

Looks like a cool event! So the primary goal is to have the reliability to make it 2.5km, but at the same time have enough off-road capability for some mild off-roading

Nice work! The flexing frame is an interesting choice, but I do imagine it would work just fine for Lego. What is this overland expedition event? Is it some kind of race, but with more of a focus on endurance?

Exactly! Better to have something look right than follow a strict scale even when it looks worse.

Thanks! Good suggestion! Checking it against my Stud.io model of the original set definitely agrees that it should be higher (though I thought I had scaled it correctly before--you're probably right that the cab is a bit too high). I'm thinking one stud would be about right, but I can experiment.

I spent a while on the model this afternoon, though it doesn't look a whole lot different. I finished all the pneumatic tubing, and now all the functions work! It honestly wasn't as nightmarish as I'd feared, but I'm glad it's done! I did have to cheat the roof up half a stud to get the extra hoses to fit in well enough, though. I moved the grille back in to sit flush, reinforced the crane rotation knob, and reinforced the steering knob. I also added some rearview mirrors The next things I'll have to do are raise the first section of the crane arm (if possible without extending the hoses--I don't want to have to do that!), since on the original set it goes well above the roof, while mine is well below it. Otherwise, I'll need to build some fenders, add a rear bumper, and see how I can reinforce the outriggers and bed dumping. I think most of the challenging parts are done now, though!

My guess would be that one of them engages with the shifting mechanism, while the other one is used to make it snap into position.

Wow, that's an impressively compact front axle! I think I built a similar one once, but two studs wider, so the suspension arms meshed at their end holes. I like it!

Ooh, thanks for the analysis! The fact that you see four neutral positions seems like a clear indication that those four positions could be turned into gears by using a second pair of catches. So I think this is likely!

Yeah, I considered that, but they do stick out and look kind of ugly, and might not actually make it much easier to operate. It's not too bad as it is, so I'm satisfied.

Yeah, I'll have to manually pull the pump back up. Because of the single-acting system, pulling the pump back up is actually sucking air to run other cylinders, so it does require some power. The original old sets did put springs on these for pumping, but I don't have them, so it'll be manual (since I don't have room for any external spring mechanism). It also gives me the option to leave it stored in the down position, which looks quite a bit better. In theory, I could use a small cylinder as a pump here, but I couldn't get enough pressure with them, requiring the bigger one. Yeah, I'm still undecided Yeah, this was really the only place I could put them, but it's fairly convenient for control! I'd agree that it's unfortunate how close the levers are to that tile, but there's really no way for me to move them up, because the body of the upper valves are only 1.5 studs away from the roof, leaving only 0.5 studs between the output ports and the roof, which is really the bare minimum!

Wow! This reminds me of the excitement I had back in 2018 when the Chiron was unveiled! We get: 24T clutch gear: A super obvious gearbox part, that we should have had for ages! This and the 32T gear were the most obvious holes in the gear collection, so I'm very pumped about it! I'll have to 3D print and start using them soon, since it's "legal" now! EDIT: With some help from this guy (https://grabcad.com/dk)'s 24T differential model in his Land Rover Defender, I've now got a model all ready to go for that! Fancy inverse wave selector/sliding catch: I've got mixed feelings about this one. It looks super smooth and nice to use, but at the same time, it's massive! I think for most applications I'd stick to the old wave selectors, but these look very interesting anyways! I'm curious about the description of them having 8 positions. Are some of these positions duplicates of others, or are they all different, allowing for easy 8-speed gearboxes? Stepper wheel: This looks fairly handy, though I guess it remains to be seen how compact and reliable it can be. 2L driving ring: This one's a big surprise, but I'm quite pleased with it! I think 3L ones were really only worth it from 2015-2018, since the wave selectors made them somewhat obsolete. Having a 2L one that works with modern gears will allow for even more compact gearboxes, and the 8 teeth on them is a boon for backlash! Yep, this design is the first thing I thought of when I saw that!

So, here's that update: As you can see, the grille has been moved out half a stud. I don't need to do this, but I think it might give the front a bit of texture. I'd like to hear what people think about it! In here you can see the four pneumatic valves With the roof off, you can see the old red cylinder/pump, the distribution block, and the first part of my pneumatic tubing. So far I have all the hoses on the "control" side done, which is a lot of hoses on a single-acting system like this, since you need two hoses going to each valve. I'm happy with how well everything has fit so far, so hopefully I can find space for the four additional hoses I'll need to route to the cylinders on the arm.

Hehe! Years ago I mislabeled my drawer of those as 4mm, and even though I realized it was wrong, I never changed it, and I guess it's rubbing off on me! I'd agree that it probably is, and at any rate ought to be, a legal technique for this contest, but I think avoiding it is preferable where possible! Thanks! Yeah, that does sound handy, but I'm not sure how you'd manufacture such a part, since it'd have to be a hybrid of rubber and plastic, wouldn't it? Thanks! What do you mean by simpler? I've tried moving the grille out half a stud on my next variant (to be shown soon), which makes it look a bit less boxy, though maybe not quite like the original set. Anyways, I can get opinions on it once I post it!

Cool! I might have to look into printing that for myself! I recently picked up all the EV3 electronics (minus the touch sensor) from my brother for ~$90 CAD (~$70 USD), after he bought the kit for about that from a thrift store, so if/when I get around to playing with it a bit more, such a solution would be very handy!

Yeah, I'm pretty sure I remember seeing people just running their EV3s off of rechargeable batteries constantly plugged in! Personally I'd probably make a custom adapter to eliminate batteries entirely, but I think the rechargeable should be a good off-the-shelf solution.

Nice choice of set! This is one I was considering too. I'm looking forward to seeing the result!

Looking nice! That is a real classic set, and those tires look very nice for it! I don't know if I've seen them used in Technic before, but they look handy!

Whelp, here's tonight's update! I haven't really made any mechanical tweaks, but I've got the cab pretty well figured out: I'm planning on using this 1980s-vintage single-acting cylinder as a pump for my single-acting pneumatic system, and this spot in the rear of the cab seems to work pretty well. After all, the original set had a cutout in this part of the cab for the battery box, so I reckon I can have a cutout myself if I want one! The next big job will be trying to get all my pneumatic hardware into the cab, but I'll also need to work on a bit more aesthetic stuff, like mudguards, reinforce the cab attachments, reinforce the bed attachment and support, and then just generally reinforce everything I have space left to reinforce!

Yep, they will! That is good inspiration! That's even a whole two studs skinnier than mine, which is impressive This is a technique I've used a lot in my personal models, but this is a contest with standards, so it probably is best for me to change it, especially since it... didn't even work for what I wanted it for. I've got a different solution on my desk right now, which is slightly bulkier, but not too bad, and still has some room for tweaking. Mmm, good point, Pneumatic control in general is going to be tricky.