Posted June 16, 2024Jun 16 Hi Folks! Here's my latest build, this time an RC model on the scale of 56mm wheels, the smallest scale I have built so far. My goal with this build was to see whether I can build a 4x4 RC chassis with complete and realistic, properly articulating 4-link live axles and linkage based steering, while keeping the cab area free for a complete and relatively clean interior. As you guessed, it worked out, and in the end as a bonus, I managed to squeeze in a 3:1 ratio 2-speed RC gearbox as well. For the form factor, I choose a pickup, as those have a better fitting shape for this chassis. To show the result and how it performs on some challenging terrain, here's an action video: Features Powerful 4x4 drivetrain using 2x PU L motors Steering by PU L motor via linkage Powered by Buwizz 3 battery Realistic 5-link live axle setup both front and rear 2-speed RC gearbox with 3:1 ratio, operated by PU L motor Complete interior with seats, dashboard and a gearstick Openable doors, hood and tailgate Chassis design As usual, it all started out with the most complex part; the front axle. For a while, I have been experimenting with a small axle design with good ground clearance, without differential and just brick built wheel hubs held from the top. I tried to keep it slim, and finally, I came up with this solution, which uses a couple towballs on bars put inside axle-pins to achieve the required density. The blue axle-pin with friction holds the towball very well, but the tan one without friction does not. However, I discovered, that the new pearl dark grey frictionless axle-pin does hold the bar very well, and that's what made the steering linkage possible. The steering arms are also connected at the bottom by a 9L link. Another tricky part was the mounting of the springs low but stable enough so that it does not go way too high in the chassis, all while leaving space for the steering servo in the middle (the flatter PU L motor can just fit). Furthermore, the driveshaft enters at a variable angle, making the use of a second joint unnecessary. In front of the axle, there's mounting point for a Panhard rod as well. The rear axle was derived from the front one, simplifying it by fixing the wheel hubs. Given the two axles, I started designing the chassis with the fact that the position of the steering servo was given, just reaching up to the height of the springs, giving enough space for the axle to articulate. That meant that the drive motors needed to go on the floor if I wanted to keep the cabin space free. This setup has a disadvantage; the motors can be in the way for the mounting of the suspension links on the chassis end. Luckily, in this case the links connect very deep to the axles, so that meant enough space left for the motors in the middle. I went with my usual setup that leaves space in the middle between the two motors, and checked out whether a gearbox could fit. And the new shorter driving ring from the Yamaha set was just perfect for the job, it resulted in just the right amount of spacing. I had to make some significant down-gearing before the gearbox though to make it practically useful with a 3:1 gearing ratio, using the new 24T clutch gear, and to make the model strong in low gear and fast in high gear. Also, I needed to use the long CV joints to allow the driveshaft length to be uneven / vary, resulting from the angle. Here's the X-ray view of all the functional parts. Finally, the seat and the dashboard have just enough space to fit in, along with the Buwizz 3 unit in the back of the cab. I could even add a gearstick that actually moves with the gearbox, albeit tilting sideways. Bodywork The bodywork started with the idea of using the small fender parts (roughly matching the 56mm wheels) that are available in blue but with a print, so I had to remove all the print with an eraser, which took quite some time, but worked out fine in the end, the result is a nice clean blue fender (I also considered building it in orange, but some key panels were missing in orange), and I have added some brick built fender extensions on the back, and some shorter ones on the front as well, that still allows the wheel to steer and articulate without getting caught in it. Furthermore, I needed to select a real model that has a hood shape that's big enough to hide the front axle / servo. A pickup was ideal for that, so I started experimenting in that direction. Also, I have done a bit of search on Ford F150, and came across this nice model of Anton Kablash, using the same fenders in blue. I really liked the construction of the hood and the windshield, so I borrowed that, but designed the rest to my liking. Namely, I wanted to replicate the front grille in some simple way, for which I managed to use a combination of bricks and technic beams, and also cut out the Ford sticker from the Raptor set (just good size). Also, the headlights; it struck me that a rotated sideways transparent brick build could work out, and in the end I managed to squeeze it in, and add a simple bumper below it. Connecting the bumper to the fender was a bit tricky though :) Not perfect, but does the job. Another area I wanted to focus on were the doors; I wanted to make them openable and have a clean door line. The new small panels work nice here to prevent too much beam stacking. The brick built rear taillight idea is also taken from Anton's build, adopted to my needs. Finally, I could make the tailgate also openable, while still keeping things solid. The bed area is just deep enough to look like a bed, and I intended to integrate the L motor and the springs into it as much as possible. I had to leave some holes for the cable routing though, and I wasn't able to hide them even more, but they look a bit like some cargo :) The roof is fixed in a solid way by the center column and the B pillar, the model can be lifted by the roof. Here are some photos of the real life build as well. More pictures are available on my Bricksafe. Free building instructions are on my Rebrickable page. Let me know how you like it! Cheers, Viktor Edited June 16, 2024Jun 16 by gyenesvi
June 16, 2024Jun 16 Outstanding. The ball pin not being extended always had been an upsetting thing for small axles, and you did an very appreciated discovery ! The bodywork is very eye plaisant, do you know how much better does it perform without it's weight to climb rocks ?
June 16, 2024Jun 16 Superb build! I like how you made the suspension work, the gearbox and overall compactness. These types of build feel very satisfying.
June 16, 2024Jun 16 lovely model dude! I saw it earlier on youtube, you did a great job with the axles too!
June 16, 2024Jun 16 Very fun and all-around vehicle, which Lego should really aim with their model. Just look how much play kid would get (if this would be a Lego set). The body is clean and without flaws - I love front headlights and hood opening, with that little movement of small black panels. On top of that, you made those instructions free. Viktor, you are spoiling us too much, haha. :D Great work, I always say that, but I must admit - you never disappoint. Keep up the good work, cheers!
June 16, 2024Jun 16 Such a great build, love the bodywork and front, it really has that "tough car" look that you expect from this kind of a vehicle! And on top of that free instructions, thank you very much! I gonna keep an eye on that rebrickable page and hopefully see some builds in different colors as well.
June 16, 2024Jun 16 A deceptively simple build but I can see a huge amount of thought and planning, really paid off. Excellent job, very inspiring for me, thanks.
June 17, 2024Jun 17 Author Thanks all for the feedback, this little fellow is getting more positive vibes than I expected :) On 6/16/2024 at 1:21 PM, Milan said: Frontpaged. Thanks a lot! 23 hours ago, Bluehose said: The ball pin not being extended always had been an upsetting thing for small axles, and you did an very appreciated discovery ! Yeah, indeed, one of the parts I miss the most. 23 hours ago, Bluehose said: The bodywork is very eye plaisant, do you know how much better does it perform without it's weight to climb rocks ? I haven't tried that, but in this case it might not matter much, because it is kind of overpowered already with two L motors. It rather spins the wheels under itself than gets stuck, and in that case the extra weight actually helps. 18 hours ago, Krxlion said: Very fun and all-around vehicle, which Lego should really aim with their model. Just look how much play kid would get (if this would be a Lego set). The body is clean and without flaws - I love front headlights and hood opening, with that little movement of small black panels. On top of that, you made those instructions free. Viktor, you are spoiling us too much, haha. :D Great work, I always say that, but I must admit - you never disappoint. Keep up the good work, cheers! Thanks a lot, agree that Lego should focus more on small RC models (and not like in the upcoming Porsche with not really reusable electronics). The small black panels at the base of the windshield are not my invention, I took that from Anton Kablash's design, exactly because they are spot on :) 12 hours ago, Johnny1360 said: A deceptively simple build but I can see a huge amount of thought and planning, really paid off. Indeed, it's like that. I have been experimenting with something in this scale for years, and now finally it came together. 16 hours ago, CK28 said: Such a great build, love the bodywork and front, it really has that "tough car" look that you expect from this kind of a vehicle! And on top of that free instructions, thank you very much! I gonna keep an eye on that rebrickable page and hopefully see some builds in different colors as well. Thanks, sometimes, it's easier to get the right look in a smaller scale :) Enjoy, curious how many different variations people come up with!
June 17, 2024Jun 17 I try to add something meaningful when I post on other's MOCs. All I can say is WoW! There is a ton of difference between first and second gear, which I think is a great choice. Really adds to the play of the model. Not sure I can recall something having such as difference between first and second gear. Well done. THe looks are outstanding. Spot on. I live in the US and these trucks are everywhere. You captured the essence perfectly. Last thing I will say is the suspension and first gear are a great combo. Truly, it looks like the real thing when it is climbing around in the first part of the video. Just wow. I may have to be building this one...
June 17, 2024Jun 17 Wow, I'm not a car fan but this is truly beautiful! The fact that you managed to cram 4 motors and a battery box into something this small, without sacrificing the looks, is outstanding.
June 17, 2024Jun 17 Dude, I saw this on rebrickable too and was curious what other details might be here. This is a wonderful model, especially considering the fact that: 1) its small; 2) it has four motors, battery box, and gearbox crammed in; and 3) that it functions well and looks good. Quality MOC, definitely premium quality.
June 17, 2024Jun 17 Beautiful model, you have a real gift for perfecting Technic 4x4s. Would love to build it.
June 18, 2024Jun 18 Awesome job! You packed so many features into such a small scale while keeping the original car's look! But I have a question about BuWizz. Sure, switching between two gears is easier than three or four. How do you feel about using the standard LEGO PU L-motor with the BuWizz 3.0 power unit? I’ve dealt with this issue before and had some frustrating experiences with BuWizz 3.0. The battery life is super short, and it shuts down with two BuWizz motors under sudden load. Even the glitches when calibrating the steering system were something I could tolerate. The main disappointment was the mode where you need to turn the motor shaft to a specific angle for semi-automatic gearbox operation. In my first model with BuWizz-motors https://youtu.be/jYv_sIpuESY?si=PCMg3kit-Y835ClE, I used the original LEGO PU hub for steering and gearbox shifting, and it worked perfectly. (https://www.eurobricks.com/forum/index.php?/forums/topic/196222-ready-to-go-lego-building-blocks-for-mocs-gearboxes-axles-and-more/) But the LEGO hub is big and heavy. In a speed model https://youtu.be/Zi_6nXqfC8M?si=QNg_EhfYjqb7Hf85, I had to rely only on BuWizz 3.0... The smartphone interface is terrible. Setting up a 4-speed gearbox is tricky, controlling a speed model is incredibly hard, and the settings keep messing up... These are just my personal thoughts. They come from comparing the LEGO PU hub to BuWizz 3.0. But really, you can't compare a big company like LEGO to a small one like BuWizz... Edited June 18, 2024Jun 18 by SimplyLegoTechnic
June 18, 2024Jun 18 Thank you for the detailed description. Really well designed model with a great use of new parts such as 24 tooth gear and the gear shifter. I skimmed over the instructions and have a question regarding the pin on the steering rack at page 62, step 69. What pin is that on the left side of the rack where the bar with the ball joint gets inserted?
June 19, 2024Jun 19 Author Thanks a lot guys, glad you like it! I'm really happy that people are pleased with the looks, truth is that often it is easier to build something polished on a smaller scale, as it's easier to get good curves and less holes. Also glad that people appreciate the technical side if it as well :) On 6/17/2024 at 8:03 PM, nerdsforprez said: I try to add something meaningful when I post on other's MOCs. All I can say is WoW! There is a ton of difference between first and second gear, which I think is a great choice. Really adds to the play of the model. Not sure I can recall something having such as difference between first and second gear. Well done. Thank you, yeah, the new 24T clutch gear is really useful in this respect, and since the model has good power to weight ratio, the speed difference really comes out. On 6/17/2024 at 10:39 PM, lmdesigner42 said: Beautiful model, you have a real gift for perfecting Technic 4x4s. Thanks, that kind of became my specialty, and there's a lot more to do in this area :) Hope TLG will pick up some bits sooner or later.. On 6/18/2024 at 8:18 AM, SimplyLegoTechnic said: But I have a question about BuWizz. Sure, switching between two gears is easier than three or four. How do you feel about using the standard LEGO PU L-motor with the BuWizz 3.0 power unit? Unfortunately, I share most of your frustration with Buwizz. Maybe it's not so bad in a small model like this, as there are no power outage issues or short battery life in this case, as the motors are smaller. But year, steering needs a lot of fiddling to get smooth (while Control+ or Pybricks is quite okay out of the box), and for the gearbox, I haven't experimented too much yet, this was my first model with that, but I quickly gave up and resorted to just using it as a fixed 90 degree stepper motor as I recall, that works okay for my use case (that's why in the video you can see that I can also set it to neutral). Even though I often mix up the buttons and try to rotate it in the wrong direction.. so I should give this more testing. 8 hours ago, Zerobricks said: Thank you for the detailed description. Really well designed model with a great use of new parts such as 24 tooth gear and the gear shifter. I skimmed over the instructions and have a question regarding the pin on the steering rack at page 62, step 69. What pin is that on the left side of the rack where the bar with the ball joint gets inserted? It's a frictionless axle-pin in the recently released pearl dark gray color. That's why the instructions say the color is important, because this color (probably due to different material / surface / tolerances) holds the bar really strong according to my tests with many pin and bar combinations. By the way, the regular blue axle-pin with friction also holds the bar strong, that combo is used for the lower suspension links.
June 24, 2024Jun 24 Author Initiated by a fan, a PF version has been made for this MOC. The drive motors are easy to swap, and the servo for steering can also be replaced relatively easily by lowering the steering linkage at the front (the servo just passes under the hood, with a little hole necessary near the windshield to allow it to open). The gearbox motor was more problematic; in the PF version it is controlled by an M motor with clutch protection. Still, the switching sounds a bit more violent (clutch cracking) than it would ideally be, but it works fine (built and tested). Furthermore, the PF version is powered by a Buwizz 2.0, but alternative hubs could also be used. I have adapted the instructions for the PF version as well, can be downloaded free.
June 25, 2024Jun 25 13 hours ago, gyenesvi said: Initiated by a fan, a PF version has been made for this MOC. The drive motors are easy to swap, and the servo for steering can also be replaced relatively easily by lowering the steering linkage at the front (the servo just passes under the hood, with a little hole necessary near the windshield to allow it to open). The gearbox motor was more problematic; in the PF version it is controlled by an M motor with clutch protection. Still, the switching sounds a bit more violent (clutch cracking) than it would ideally be, but it works fine (built and tested). Furthermore, the PF version is powered by a Buwizz 2.0, but alternative hubs could also be used. I have adapted the instructions for the PF version as well, can be downloaded free. Thank you very much, otherwise I was already planning to do something similar myself. Tell me, please, is the set of parts for the PF version very different? Edited June 25, 2024Jun 25 by Igor1
June 25, 2024Jun 25 Author 8 hours ago, Alex Ilea said: Looks good! Did you notice any performance differences between the two systems? No, not really, they feel the same, though I haven't driven the PF version that much. 4 hours ago, Igor1 said: Tell me, please, is the set of parts for the PF version very different? Not that much different, and even though RB has the part list for the PU version, the PF instructions have the correct part list in the end for that version only, so you can look it up.
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