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Three years after my previous model, the Hoonipigasus, here is finally a new MOC that I can present! But what’s that super long title? In other words, it’s a truck made by Matt! A truck designed to rescue vehicles stuck or damaged in off-road environments. Introduction This is a commissioned MOC by Benjamin Lorteau. He wanted this truck to be 100% manual, using the wheels from the Audi RS Q e-tron #42160, and featuring several steering modes thanks to two knobs, one controlling the front axle and the other the rear axle. I was free to do pretty much whatever I wanted as long as the initial constraints were generally respected. Here's a little paragraph from Benjamin: When the idea was proposed to me, I immediately saw strong potential. I thought it was possible to build something very interesting, the opposite of what is increasingly found in the Technic range, with lots of mechanically boring cars. The project would be based on an innovative mechanism allowing multiple steering modes, working in a similar way to the Claas Xerion #42054, while still being compatible with suspended axles. The model also had to stand out with a very good building experience. I will come back to this specific point later. Design I tried to reproduce the lines of the real truck as faithfully as possible. The visual appearance is split into two parts: the cab at the front and the exposed chassis at the rear. At the front, the cab stands out thanks to its yellow color, while the rest is entirely black. The cab was not easy to build, since the real model features many surfaces lying in different planes (doors and rear cab pillars, top of the hood and sides for example), as well as curves that are very difficult to reproduce at this scale, such as the roof. A panel with a curvature over one stud gave a result that was too thin, while two studs resulted in something too thick. I chose to simplify certain lines to ensure a smooth appearance, while staying as close as possible to the original design. The shape of the hood was made possible thanks to the new angle connectors #7. They allow for a simple, clean build and a faithful result. The rear section came together more naturally. It was “just” a matter of building the chassis cleanly, adding the rear winch, building the arm, and adding the toolboxes and the roll bar. This required a significant amount of optimization. After all, it was necessary to fit: The rear suspension The steering mode selection mechanism The rear chassis winch The arm The toolboxes All of this in a very limited space. Suspension What would an off-road recovery truck be without a good suspension? I reproduced the original suspension as faithfully as possible. It consists of suspended axles held by links, forming two opposing trapezoids at different heights. The suspension is responsive and allows for nice axle articulation, achieved solely by the weight of the vehicle - there’s no need to press down on the cab to compress the shock absorbers. Opening parts The following elements can be opened: Doors Hood (left and right sides) Toolboxes The toolboxes are built using studful parts and are attached to the chassis with pins and an axle. The doors do not have stops in the open position, so they can be opened until they touch the front wheels. I chose not to add any in order to keep the build simple and part-efficient, and I felt it matched well with the rugged style of the vehicle. All-wheel drive and fake engine Just like the real truck, my MOC features all-wheel drive, without a central differential, driving a fake V8 engine. The engine doesn’t spin very fast, partly by design choice. Indeed, the motion is transmitted through the differentials with a 22t/14t gear pair, then from the central axle the motion goes up to the engine via a 12t/20t idler/12t gear train, and finally two 8t gears. I could have added gearing, but it would have made the build less clean and more artificial. As with the door opening, I preferred simplicity. Winches and arm There are no fewer than… five winches on this model! Two of them are located at the front and rear of the chassis, to get out of difficult situations or tow a vehicle. These are mounted on a friction pin and are controlled by pulling the rope and using a gear. The choice of a friction pin was made to save space and to offer a different holding technology compared to the other winches. The other three are used for the arm. In all cases, they feature a ratchet allowing the rope to be held without any slipping. One of them controls the raising and lowering of the arm via the same pulley system as the real truck. The arm’s range of motion is slightly under 90°, with the upper limit being vertical, which can prevent the arm from falling back down. The last two control the towing cables. Their construction is light but sufficiently robust. 3-mode steering Alright, enough with the small classic functions, now we’re getting to the core of the model. What it was built around. As I mentioned at the beginning, I wanted steering behavior similar to that of the Claas Xerion #42054. But I couldn’t simply reuse the mechanism from this set, since my MOC features suspended axles, which requires steering to be controlled by a rotating axle rather than linkages. With linkages, the suspension would have influenced the steering. To counter that problem, it would have been necessary to add a translation/rotation conversion mechanism, which would have been a real mess. (Actually, using linkages wouldn’t be impossible with the right geometry, but it would add complexity and likely reduce reliability.) I based my design on a very simple principle that has existed for centuries: bevel gear transmissions. You’ve probably noticed that when the crown gear of a differential is placed on the left or right, the bevel gear connected to it will not rotate in the same direction for a given wheel rotation. That’s why, on chassis with multiple driven axles, the differentials don’t all have the same orientation. That’s what I needed: a mechanism with a bevel gear transmission, capable of reversing the direction of engagement - but using knobs to avoid losing wheel alignment. So I came up with this: Steering is controlled by the vertical axle. This axle is directly connected to the front wheels. The different steering modes are achieved by swapping, or not, or disconnecting, the rear axle steering shaft relative to the front axle - just like the Claas Xerion. When the grey knob on the carriage is up, it engages with the upper knob of the vertical axle. The front and rear steering axles rotate in the same direction: this is crab steering When the grey knob is down, it engages with the lower knob of the vertical axle. The rear steering axle rotates in the opposite direction to the front axle: this is 4-wheel steering When the grey knob is centered, it is disengaged: the rear axle is disconnected. However, this introduces an extra difficulty compared to the Claas Xerion: the linkage system naturally locks the rear axle on the Xerion, which is not the case with my system. So I added an automatic locking mechanism. When the carriage is in the central position, locks block the carriage knob. When the carriage is moved, the locks spread apart thanks to rollers pushed by slopes located on the carriage. The selection lever rotates almost effortlessly, but it can sometimes be a bit hard to grab since it is close to the toolbox. Just like on the Claas Xerion, the wheels need to be straight for the change to occur - within a certain tolerance. Since for each axle the steering shafts rotate slightly less than 90° in each direction (thanks to stops), you can’t, for example, switch steering modes when the truck has its wheels turned to the right in crab mode and end up in front-wheel steering while the rear axle is locked to the right. Well, it is possible - but you really have to want it and perfectly align everything while forcing against the stops. Front-wheel steering: Crab steering: 4-wheel steering: The selection lever rotates a cam fitted with a roller. This roller raises or lowers the sliding carriage of the moving knob. Position holding is ensured by the rubber band located at the front, which presses the rollers rollers against the slopes of the carriage. The carriage/slopes/elastic/rollers assembly naturally tends to return the carriage to the central position. For the upper and lower positions, a toggle point prevents the carriage from returning to center, enabled by a green connector located near the rear suspension - the travel is not ±90° but slightly more. Using a long CV joint makes it possible to compensate for the change in distance between the carriage knob and the rear axle steering shaft when the carriage moves, in addition to suspension travel. And that’s it - you know everything now! Build and instructions I did a significant amount of optimization work to achieve a build that is both elegant and enjoyable. I wanted to create a model that would stand out from most MOCs, which often feature poorly optimized construction and an unpleasant building experience. The construction is done through small assemblies that are attached to the main structure, as LEGO usually does. I reworked each sub-assembly until the build felt "obvious" and intelligently designed. (Well, I hope that’s the impression you get! ) The instructions came naturally thanks to the work done during the build process. I wanted them to be more “challenging” than current LEGO instructions, while avoiding all the pitfalls encountered with alternative brands. Concretely, I made sure that all parts in a step are clearly visible so none are missed, avoided (except in rare cases) mixing callouts and parts added directly in the same step, optimized the build order to avoid rotation steps, or prevented issues where a previous sub-assembly blocks progress, for example. Everything else came naturally during the build, and I didn’t have to do anything at the instruction stage regarding build contrast (use of colors), assemblies that don’t fit properly, etc. The goal was to make the build more stimulating by avoiding chains of single-part steps, without the difficulty coming from poor instructions. Basically, it’s a rally with a good co-driver, not an orienteering race with a bad map. It’s not perfect though - there are, for example, a few assemblies where I prioritized aesthetics over strength, such as the studful parts around the front and rear winches. But it’s the best I could do for now. Result: a MOC with only 1211 parts, featuring: 5 winches 3-mode steering Suspension All-wheel drive with fake engine Opening parts For reference, 1:10 scale sets usually range from 1500 to 1700 parts. Building instructions: Rebrickable Stickers: send a request to Forwartsticker Parts: (coming soon, on MOCBoxing) Video All photos can be found here: https://www.flickr.com/photos/162173007@N06/albums/72177720331182416/with/55013628563 That’s it for this truck. I hope you like it! -
Finished MOC Do you remember my Reform Metrac H7X ? Reform also produces the Muli: As the project of my Citröen DS doesn’t really progresses, I do this project in WIP, to compensate. ^^ The functions will be close to the Metrac ones: 4WD with a 4 cylinders fake engine Steering with 3 modes Front and rear PTOs And I add: A pneumatic pump to add pneumatic tools Central joint (it’s only the front axle on the Metrac) Openable cab with a lever and a pump actionning a pneumatic cylinder. The best function! But this MOC will not be manual, because there is not so much room in the chassis. (I think it’s possible, but the playability will be extremely bad) So it will be remote controlled, using the BuWizz. So: Driving by 1 XL by axle Steering: 1 servo by axle. To have the 3 steering modes: a M motors controls a PFs switch -> it changes the sens of rotation of the rear servo, or it stops it. The pneumatic pump is powered by a M motor That was the start: And now I’m here: On these two pictures, you can see the rear PTO. On this side, the pneumatic pump: And here is the mecanism which allows the possibility to get 3 steering modes: The chassis is very, very compact. I think you can put an elephant on it, it will not move at all. For the tools, I think I’ll make a pneumatic arm (The pneumatic cylinders of the Mercedes truck would be very helpful, but I don’t have this set) And for the front I don’t know, so if you have ideas, tell me!