Ngoc Nguyen Posted January 8 Posted January 8 (edited) DEVELOPMENT It's time to level up the mini replica game, and for the next entry in my collection I wanted to work on the 42128. For a Technic head 42128 is easily one of the best models in recent Technic, as it has a lot of functions. It is also an interesting model to build a mini replica from, since its original scale is 15 studs wide, which means the mini version will be the 9 studs wide scale. There hasnt been many official 9 studs wide truck in Lego Technic. The most recent one is the 42167 Mack LR, and the second most recent one is the truck in the set 42023 released way back in 2014. I have done only one mini replica in this scale, which is the mini 42078 B model, but it was not a model designed from scratch but a mod of the 42167. Therefore I want to truly challenge myself with this model. The original 42128 turned out to be very conducive to the shrinking of a factor of 3/5. Most of the main parts in the original 42128 have lengths that is multiples of 5. For example, the width of the rear body, from behind the cabin to the end, in the original 42128 is 35 studs. The height of this body is 10 studs. The hood is 11 studs long, while the cabin and the sleeper is 14 studs long, which add up to 25 studs from the front to the sleeper. The cabin from floor to ceiling is 10 studs. All of these numbers make it easier to calculate the corresponding dimensions in the mini model. When it comes to functions, the first thing I decided is that there will be no openable hood. At this scale there's no space for a drive train, let alone a differential, and if there's no drive train, then there's no point to do a fake engine. Not to mention, the structure under the hood around the front axle is only 2 stud tall, so an openable hood with cause that area to not be structurally supported. On the other hand, making the hood fixed to the chassis will allow more possibility with styling the hood and routing the steer axle. And that's the direction I chose for the front. The next problem is the outriggers. In the original models, the side and rear outriggers are linked. However, in this small scale, there might not be space for a linking drivetrain. Therefore I decided to make the rear outriggers and side outriggers two separate functions. This creates the next problem, which is the crane rotation. In the original model, there are only four knobs on two sides, and they control 4 functions: linked outriggers, tow arm, third axle, and crane rotation. Now one knob is used for the second outrigger function, one of those four original functions must be controlled from elsewhere, or is not controlled at all. I noticed that the area under the cabin and the sleeper is not fully utilized, so I routed the crane rotation to the sleeper, which is where the HOG steering used to be in the original model, and I put the HOG steering further front. The rest of the functions are pretty straightforward. Both the tow arm and the third axle lift use a simple worm gear that meshes with a 20z gear. The side outriggers is also driven through a wormgear, Everything is simple and fun until I did the test build. The crane rotation turns out to just not work. Originally, I used a pair of 12/20 gears that is connected to a trio of perpendicular 12-20-28 to drive the turntable. It turns out the crane is very heavy, so that gearing is not enough to steer it. Another problem is that the 20z gear is parallel with turntable, so it is not secured on top and often breaks out, causing the 12z to skip. I spent a whole two day redesigning that part along with surrounding structure. This is how the final gearing of the crane rotation. You can see that the controlling knob goes through a bunch of gears to gear down the ratio to reach the turntable. The hardest part is to squeeze a worm gear into the drivetrain, but in the end I managed to do it. This is how all the functions are driven in the chassis. Overall I'm very happy and very proud of my model, and I hope you can feel the same too if you decide to build it. Instruction: https://rebrickable.com/mocs/MOC-206979/nguyengiangoc/mini-42128-heavy-duty-tow-truck Function sheets: Edited January 8 by Ngoc Nguyen Quote
Ngoc Nguyen Posted January 8 Author Posted January 8 (edited) Model in action: Edited January 8 by Ngoc Nguyen Quote
Ngoc Nguyen Posted January 8 Author Posted January 8 For this mini replica I managed to achieve a new level: The proportion is so accurate that at first look quite a number of people thought it's the original 42128! Quote
NV Lego technic Posted January 8 Posted January 8 You seem to struggle with rotating the crane, and I heard a cracking noise once. Is there an issue.? Quote
Ngoc Nguyen Posted January 8 Author Posted January 8 1 minute ago, NV Lego technic said: You seem to struggle with rotating the crane, and I heard a cracking noise once. Is there an issue.? Crane rotation needs quite more force than normal, indeed, as it tils heavily towards the end. Normally when I put force into the knob and rotate it slowly there is no problem. Quote
2GodBDGlory Posted January 8 Posted January 8 Looks impressive! There's a lot of functions in the original set, so shrinking it must have been a challenge. It really does look like the original! Quote
Ngoc Nguyen Posted January 8 Author Posted January 8 5 minutes ago, 2GodBDGlory said: Looks impressive! There's a lot of functions in the original set, so shrinking it must have been a challenge. It really does look like the original! Thanks a lot for the support! Quote
jorgeopesi Posted January 8 Posted January 8 Awesome mini work I also thought it was the original set . Quote
gyenesvi Posted January 8 Posted January 8 Really nice minification, probably your best work on the topic! Nailed the looks really well, both the proportion, scale, color scheme, immediately recongizable and easy to confuse at a quick glance! Amazing that you could replicate so many functions (of an already dense model) on a significantly smaller scale, great work. About the crane rotation, there are two stages of 20:12 up-gearing in that drivetrain, I guess that's what makes it hard to operate, would be good to swap out one of those. Is there maybe room inside the cabin to change the gearing, maybe to wards the side? I'm thinking the 8:8 gearing could be swapped to 12:20, moving the drive axle further off center, and then the next gearing could perhaps be a 20:16 instead of the 20:12, though not sure if there's room for the 16T next to the worm gear.. Quote
Jundis Posted January 8 Posted January 8 Brilliant miniaturization, both in looks and functions :-) Quote
Ngoc Nguyen Posted January 10 Author Posted January 10 On 1/8/2025 at 9:48 PM, jorgeopesi said: Awesome mini work I also thought it was the original set . Haha thanks you're not alone in seeing it wrong On 1/9/2025 at 3:44 AM, pow said: Tight! Are you Tuco (Breaking Bad reference) On 1/9/2025 at 1:25 AM, Jundis said: Brilliant miniaturization, both in looks and functions :-) Thanks a lot! On 1/8/2025 at 11:04 PM, gyenesvi said: Really nice minification, probably your best work on the topic! Nailed the looks really well, both the proportion, scale, color scheme, immediately recongizable and easy to confuse at a quick glance! Thank you for the praise! I do think this is my best mini model so far as well, at least in terms of look. It's very fortunate that the original contain dimensions that are easy to shrink by a factor of 3/5. On 1/8/2025 at 11:04 PM, gyenesvi said: Is there maybe room inside the cabin to change the gearing, maybe to wards the side? I'm thinking the 8:8 gearing could be swapped to 12:20, moving the drive axle further off center Unfortunately on both sides there are supporting structures of the cabin. Very tight space in there. On 1/8/2025 at 11:04 PM, gyenesvi said: then the next gearing could perhaps be a 20:16 instead of the 20:12, though not sure if there's room for the 16T next to the worm gear.. There are only two gears that can stay directly above the worm gear and don't interfere with the blue 20z gear: a 12z gear or a 8z gear. Space constraint is a huge headache for me when I design this part. Quote
Zerobricks Posted January 10 Posted January 10 As someone who also miniaturized a set full of functions, I can see you put a lot of effort not only in miniaturizing, but also finding alternatives for pneumatic functions. Well done! Quote
Ngoc Nguyen Posted January 10 Author Posted January 10 58 minutes ago, Zerobricks said: As someone who also miniaturized a set full of functions, I can see you put a lot of effort not only in miniaturizing, but also finding alternatives for pneumatic functions. Well done! Thanks a lot! It's nice to have someone who shares the same experience On 1/8/2025 at 11:04 PM, gyenesvi said: Is there maybe room inside the cabin to change the gearing, maybe to wards the side? I'm thinking the 8:8 gearing could be swapped to 12:20, moving the drive axle further off center, and then the next gearing could perhaps be a 20:16 instead of the 20:12, though not sure if there's room for the 16T next to the worm gear.. Actually, I'm a fool... You were right. Earlier I said this. 3 hours ago, Ngoc Nguyen said: There are only two gears that can stay directly above the worm gear and don't interfere with the blue 20z gear: a 12z gear or a 8z gear. And I realized I have not actually tested the possibility of putting the 8z gear there instead. So I opened the Studio file and messed around. I moved the pair of 8z-8z gear to the bottom, and the 20z gear to the top, and voilla, it actually worked! Quote
gyenesvi Posted January 10 Posted January 10 2 hours ago, Ngoc Nguyen said: And I realized I have not actually tested the possibility of putting the 8z gear there instead. So I opened the Studio file and messed around. I moved the pair of 8z-8z gear to the bottom, and the 20z gear to the top, and voilla, it actually worked! That is yet another, nice looking way to route it, so instead of 20:12 up-gearing, now you have 16:20 down-gearing, in total more than 2x difference, which should significantly ease the crane rotation! Hope the bracing also works out fine around it and it gets smoother! Quote
Ngoc Nguyen Posted January 11 Author Posted January 11 Now that I've implemented the new gearing for the rotation, the model is in its most perfect form and I can finally move on to the next one yay. But before that I would like to share some design highlights, which are the solutions that I used in this set and felt very good about. Front Mudguard: The only solution that works is two #4 connectors, but they will be off center. Therefore I offset them with cranks and the cranks are held on the other side by thin 3x3 liftarms. Bullbar + number plate: This white piece keeps the bar in place and serves as the fake number plate. Sun Visor: A full liftarm is too bulky, while a half liftarm can't be secured through one point only. Fortunately I remember the existence of this plate, very useful. Steering: Since the truck is 9L long only, the distance between two steering connectors is only 5L. Therefore usually at this scale the steering is not done with a steering rack, and at first I didnt think it was possible either. Fortunately I discovered this way of connecting it. It sticks out a little bit but since it's black it's hidden quite well. Compact rear body: In the original model the rear body is 10 studs tall. When shrunk by a factor of 3/5 the rear body of the mini model should be 6 studs tall. But the best part is that I don't even use 6 studs for all the gearing and mechanisms. Only the side walls are 6 studs tall. The middle sections are confined in a 5 stud height. And there's nothing that sticks out below the floor either. Crane design: In the real life truck that 42128 is based on, the lights are mounted on the crane and should rotate with crane. In the official 42128, the lights are mounted behind the cabin instead. I managed to put the light on the crane and got the slanted design of the body too. That's all I want to share. Overall I'm very happy with and proud of this set. Quote
pow Posted January 16 Posted January 16 On 1/10/2025 at 10:27 AM, Ngoc Nguyen said: Are you Tuco (Breaking Bad reference) Had to search for. What i saw ended pretty violently. Quote
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