Teo LEGO Technic

Thanks! Yes that could work very well, do you know how deep the hole goes inside that piece, is it 4L? If so I could replace one of the light grey CV joints with that sliding joint and put a 4L axle between them, which would give a whole stud of play to the system, which is more than enough.

Update July 10 It's been some time since the last update, but unfortunately, I was too busy to make any progress. Finally, I made some time this weekend to make some headway, and here it is - a working prototype for the suspension on the rear 2 axles. After several different strategies, I settled on this bogey-style strategy as the best one, mostly because it keeps the distance between the axles closest to constant so that the connecting drive shaft doesn't fall out or get squeezed in, allowing the mechanism to function properly. It is braced very rigidly both longitudinally and transversally, and the high and low mounting points of the links keep it from bending sideways under the torque of the drivetrain, of which there will be lots. The only issue I would like to fix happens when the axles tilt sideways respective of one another. When this happens, the distance between the axles starts to decrease, which applies pressure and friction to the central driving axle, which causes power loss. Currently, this is the only part of the mechanism limiting the side-to-side motion, causing all the more friction. One solution I was playing with was to add torsion bars, but the issue I found was I wasn't able to make the torsion strength soft enough without having ridiculously long arms connection the axle links to the axle under torsion. Any advice on how to fix this problem, as well as any other suggestions, are welcome as always

Good point, I agree that this is usually the case in LEGO. This is a very interesting solution, I like it! As @gyenesvi points out it isn't very robust, and for example wouldn't fare well in a trial truck scenario, but as a proof of concept it's a very creative solution Update May 27 It's been a busy time, so little progress has been made. I'm a bit blocked currently deciding how to properly link and brace the 2 rear live axles, both to each other and to the chassis. The main movements I'm trying to focus on bracing are longitudinally so that the force applied by the axles pushing the car up a slope has minimal play, and transversely so that the axles don't move side-to-side when the truck is climbing sideways over obstacles. Here is a picture of some progress: I like very much @Zerobricks's solution on his Wildcat which allows the rear axles to articulate respective to each other without pressing on any shock absorbers, so that the wheels make maximum contact with the ground, and yet still have shock absorbers used to absorb impact if, for example, all 4 wheels are to be pressed at the same time. To implement this, I plan to replace the grey linkage bars in the image below with this LEGO approximation of a leaf spring suspension: Please post any examples you guys know of where other builders have achieved something similar, I'm trying to get a better understanding of how this should be done. More progress to come soon hopefully!

Glad you're enjoying it! Yes I believe that's what you were saying right @TexasEngineer454 ? Personally that wasn't an option for me on this build because I'm modeling a trial truck that has live axles on all 3 axles. In general my issue with independent suspension in offroad vehicles is that the ground clearance isn't as good as live axles with portal hubs, and the ground clearance under the centre of the axle is reduced when the suspension is pressed, which is not the case with live axles. But it can definitely be made to work, as @Zerobricks did for example on his Wildcat 6x6.

As you say, it holds very well there is no play at all. You're definitely right, using a steering axle with the ball joint end attached to an axle has a lot of play, in the range of a few millimetres even. The way I braced it in this configuration however, it is no longer able to pivot in all 3 planes of motion, but rather only hinge on the axle. It is basically acting as a liftarm at this point, so it would not work for say independent suspension, but it works fine for a live axle where the wheel hub remains in the same plane relative to the steering rack. It doesn't provide a lot of strength if you were to have a force pushing it up, as it can slide off the axle end when you push on it, but this is not a danger in this case because all the force acting on it will be side to side, where it is rigid. I agree, it seems to be an inherent limitation of the part itself. The only way to make a longer steering arm realistically is to use 3x3 half-stud liftarms, which as I said before will knock into the driveshaft, and reduce range of motion. That's not a bad idea, but the issue is that there is still an ~1/2 stuff offset, which the steering link can compensate for, unlike a beam. As well, the narrow midsection of the steering link enables it to still fit when it gets closer to the suspension arm, as the steering hub inscribes an arc at either end of the steering motion.

I implemented the double rack, and rigidity is indeed improved a little, although most of the play comes from the inherent play of the steering components, and without a longer steering arm it cannot be reduced. As I mentioned earlier unfortunately a longer steering arm doesn't fit in the rims. I did, however, find a solution to the "toe-out" problem - by placing the steering links on 3L axles with flat pin-stops, I managed to bring the link 1/2 stud closer to inline, so that the issue is almost non-existent now. Here's a closer view of the new connection:

You're right, it does indeed cause a slight toe out at the wheels. I will test it out soon in a basic chassis to see if it is an issue, but I'm hopeful it won't be noticeable on a trial truck. Furthermore, I've always found that on LEGO trucks, with steering play, the torque of the wheels pulling the car forward tends to "toe-in" the wheels, so if they start out a bit "toe-out", they may end up actually parallel. Good point, I would have liked longer steering arms. The issue is I want to use the servo motor for compactness, and it only rotates 90 degrees in each other direction. If I were to lengthen the steering arm, that will reduce the turning radius of the truck, which already won't be amazing on a 6x6 with a long wheelbase. These are also great ideas. I tried to use 42099's strategy actually, but unfortunately, the steering axle touches the rims with that configuration when using Defender rims. When I tried using a 2x4 liftarm, it wouldn't fit in the rim in Attika's configuration, and placing it with the long arm inward makes for a really bad Ackerman geometry. I also tried a 3x3 liftarm, but when steering it touches the driveshaft, again limiting the steering angle. One modification I could make to fix the "toe-out" issue is to raise the tow ball position by one stud and move it one stud out to fit. The issue with this is it gets farther from the hub, and the precision is reduced, so I think the better compromise is to have more sturdiness. Do you recommend double racks to improve rigidity/reduce play? Or to stop the gear from skipping on the rack-and-pinion steering? As it is currently built, the steering motor runs out of torque without skipping gears, but I will try using double racks to see if I get more precision. Appreciate the tips as always

I think I solved the rack wobble issue. I added a slider axle as you recommended, and since it is fitted directly underneath the rack, it provides a lot of rigidity. I also added some liftarms on the sides for a bit of extra bracing. Overall, it works excellently

Hey! I can gladly provide more detail, what were you wondering about exactly? Can you give me an example of what you mean by a "slider axle"? Do you mean attaching an axle to the steering rack, which in turn is attached to the axle along sliding pinholes?

Update May 13 It's been a busy few weeks, but it's time for an update. My parts shipped, so I could experiment, beginning with the front axle. I decided to forget about incorporating a diff lock, as it's hardly necessary for a trial truck, and instead to focus on robustness and a good range of motion. I currently have two designs that I'm choosing between. The first one is wider, heavier, and slower, but is more robust, using @Zerobricks' custom portal axle design from the Tiger 6x6, combined with a 24-tooth worm gear attached directly to the steering rack for maximum precision, and driven by an axle-mounted M-motor so that the worm gear limits any play in the system. It looks like this: While this is a good option, my main complaint is that it is quite bulky, the steering is quite slow (and obviously not return-to-center), and I wasn't able to implement a clutch system, so the parts are put under a lot of tension when the steering is fully turned in either direction. Despite the tension, there is no slippage anywhere. Option 2 is my favourite. It uses @Attika's live axle design using the planetary hubs but modified to work with the Defender rims, allowing for a steering pivot that is very close to the center of the tire. I also removed the differential and substituted the steering system with a rack-and-pinion system, plus a servo motor. The main disadvantage of this system is that the steering has more play, but aside from that it practically has all advantages. It is narrower and lighter than the other one, so I could build a truck at a smaller scale with it, which would be nimbler. The steering is fast and return-to-center, and the planetary hubs simplify the transmission, so there is less power lost to friction. The ground clearance is the same in the center and only slightly worse close to the wheels. Overall I love the elegance and efficiency of this design. I attempted to reduce the play by using a longer steering arm, but there wasn't any solution that I could find. While it is possible to extend the hub with 2x4 liftarms when using regular rims, they don't fit in the Defender rims, and using 3x3 liftarms that can protrude enough from the rims doesn't work either, as they touch the driveshaft when steering and severely limit the steering radius. As it is, the steering radius is excellent on both axles. The plan for the rest of the truck is to use a 2-speed gearbox powered by 2 XL motors and install a winch. This will take up all 4 available BuWizz ports - drive, steering, gearbox, and winch. Using the second design, the truck would be significantly smaller, and so the power-to-weight ratio would be better. As for the rear axles, I was looking at using a bogie-style suspension to allow lots of articulation, but in real trucks, they are usually made using leaf springs. Does anyone have any suggestions? I was looking at the 6x6 Wildcat for reference, but it uses independent suspension instead of live axles: https://www.youtube.com/watch?v=cEBgLdNghpQ&t=91s Suggestions are welcome as always!

Oh, I see, that makes sense. I'm used to thinking that the flex point has to remain stationary for independent suspension, and I forgot Attika uses an independent suspension setup repurposed as a live axle.

The only model I've seen Attika make since his Ultimate Pickup is this, and it's only a teaser: https://www.youtube.com/watch?v=BpIwocFrzKI Can you attach the link for the build you're referring to? Do you mean I should brace the red diff in a 7 x 11 frame and drive it with a 28-tooth gear? Just so we're on the same page, longitudinal mounting means perpendicular gears are required: I very much like the idea of having a diff lock only on the front axle, as this makes it easier to create a more robust perpendicular gear system on the rear axles, where most of the torque is going anyway for steep uphill climbing, while also maintaining a good steering radius so the front wheels don't 'drag' when turning with locked diffs. It also simplifies the system by reducing the number of diff locks required. This is an interesting idea, although it would look a little odd with a live axle front suspension and independent rear suspension. At that point might I not be better off just using pendular suspension on the rear, with small turntables to take the friction off the drive axle? I ordered the parts today, including the planetary hubs, new CV joints, 28-tooth double-bevel gears, and 2 more CLAAS tires for a total of 6 (among others). Parts won't arrive until end of the month, so meanwhile I will experiment on Studio.io with different solutions.

Sounds good That will keep the weight down a bit, and save me some cash

That's a clever idea, I like it. It will make it so that it's not possible to incorporate a gearbox, but on the plus side it will make it so that every axle will have more power than just one XL, when it needs it. Do you think 1 BuWizz 2.0 is capable of powering 3 PF XL motors?

How do you mean that I can connect them with locks, do you have an example that uses that? Good point! One issue I have with Attika's design is that the greater ground clearance is achieved using the old CV joints at the differential, which may not take the full torque as well, and also pop out sometimes. As well, the dark grey side only has a 2-stud axle, which works for connecting it to a differential housed in a 5x7 frame, but would not work for a solid axle that I plan to use since I will not have differentials. This makes me wonder if perhaps I should either use your design and sacrifice ground clearance, or I may modify Attika's design to use universal joints (although those are also weaker under high torque). No worries, it's a good point to bear in mind :) Given the new design, I will order some parts today. Progress is going to have to wait until they come, at least in terms of the physical build.

Great progress! That thing is going to be an absolute powerhouse in terms of its power-to-weight, but as others have pointed out, it will be important to brace everything in the transmission as securely as possible to avoid gear slippage with the torque of 4 XL motors. Usually, I make sure, when using XL motors, to have all gears braced on either side immediately with beams. On the other hand, your steering setup with 2 gears on the rack and those massive portal axles looks great! The only disadvantage of the massive clearance may be that it can fall over easier due to a higher center of gravity, but overall it looks like I will be hard pressed to come up with a worthy challenger for our truck trial

That's a great idea! I saw a similar design recently from you, @gyenesvi and noted it down as an idea to try in future: I guess I will be using this technique sooner than I thought . It looks like the new CV joints have a very good range of motion, unlike the older ones, which is more than enough for steering purposes, as well as more robust than U-joints as you pointed out before @Zerobricks. Because this will enable me to make the axle narrower still, I wonder if it isn't a bad idea to scale down the MOC, perhaps choosing a 4x4 model instead? This would enable me to use BuWizz + 2 XL power setup on a lighter build, and so improve the power-to-weight ratio. I could still make the build large enough to use CLAAS tires, perhaps just having them a bit oversized for the chassis, similarly to what you did @HorcikDesigns on your Praga. This also will mean I don't have to invest more money into additional batteries and motors which is a plus . I would probably go with any 4x4 chassis that has front and back live axles, perhaps a Jeep Wrangler or something similar. Why do you think this will happen? It seems to be working fine on Attikas pickup?

I will definitely brace it very well. For your setup, did you have it braced on either side with beams? I'm hoping that will be enough. Just looked up your truck, it's really great looking and performs quite well . Mine will be a bit bigger, not quite to scale with the CLAAS tires, but close. Yes the steering will definitely suffer a bit, I know exactly what you mean by "pushing itself straight." I think I will stick with the regular CV joint, as the stronger ones indeed take up too much space, and I think they can take enough torque for my needs. What solutions would you use to improve the scrub radius? I don't see any reasonable way to bring the steering pivot any closer to the center of the wheel rim. Perhaps there is some solution involving kingpin inclination, but that goes beyond what I currently understand, so if anyone wants to explain a solution I would be interested

Thanks for the info! For a pretty basic setup, the result is fantastic, congrats again!

I think overall the most robust is still the mighty live axle, but that's definitely a good solution for a medium-sized MOC Definitely an option, but do you think they would ship in time? I wasn't able to find sooner shipping times than mid-June. That's an interesting idea. I think overall the benefits of lockable diffs are outweighed by the drawbacks for a heavy trial truck, so I will go with a no-diff setup. By leaving them out you save space, increase robustness, and save weight as there is no need for any mechanism, pneumatic or otherwise, to power the locks. At the slow speeds that this heavy truck will be driving it seems like an unnecessary addition, and as much as it pains me to let them go, it's a necessary sacrifice in the name of performance. I built your custom portal axles from the Tiger 6x6, and their robustness is amazing, I am thoroughly impressed! It will operate even nicer than the Unimog portal axles as the steering pivot is closer to the center when combined with the Defender rims. Since I am eliminating a differential, there is no concern anymore about how to position the locks. In terms of your other suggestions, I will implement them all once I buy the necessary parts, but I had one question. Do the new CV joints enable a large enough angle to be used at the hub for steering? I'm thinking it may be worthwhile sacrificing a bit of strength there to have a better turning radius, and only use the large CV joints at the axle input location, what do you think?

That's a sweet MOC!! I'm especially impressed by the speed it achieved, perhaps I should look into a similar power setup as well, as the physical remote is an improvement in my opinion over a smartphone touchscreen controller. The suspension is also an interesting approach and seemed to work very well, especially once you added the anti-roll bar. I'm excited to see your entry for the truck trial competition .

No, I don't plan to power the axles separately, as I want to hook them all up to a single gearbox. Yes, I will have a working winch. Do you mean it'll be better for climbing sideways on a slope? My concern with independent suspension is that the ground clearance isn't as good, and it's hard to put a lot of torque on it. Sounds good, thanks . Ideally yes, I would like to use the new Daytona bevel gears as they are thicker and could take more torque, but they are priced at $3.50 each on Bricklink, so unless someone knows a cheaper option that's off the table. I will try custom portal axles like you say, probably the ones from your Tiger 6x6, along with the 7x11 frame, and post progress when I'm done. Thanks, and yeah you should start a WIP! As for differential locks, I was also considering eliminating them. Aside from the loss in power in corners, especially at higher speeds, my main question is what perpendicular bevel gear combination can handle the most torque? Is it the 12-tooth and 28-tooth gear? Sounds good! Hope you'll enjoy the process

Hey everyone! For the first time Toronto, Canada is going to have a Truck Trial race . This is my WIP topic for my entry - a 6x6 truck based on the Praga trial truck, as seen below: The goals for this model are as follows: Performance prioritized over looks - a bulkier or uglier design that is more robust will be favoured over a cleaner design. The primary goal is the best possible offroad performance Highly robust transmission and steering - I want to make sure that none of the mechanical functions are going to fail under pressure 6x6 drive with diff locks on all 3 axles 2-speed gearbox Winch My plan for this MOC is to reuse many of my successful design ideas from my most recent Unimog U5000, but with a couple of key improvements: Reusable ideas Robust transmission setup - by gearing down the transmission close to the wheels, pressure is reduced on sensitive components such as universal joints and differentials Gearbox - the gearbox design, based on @Sariel's heavy-duty gearbox idea, was very reliable Pneumatic diff lock mechanism - this was also working very well Features needing improvement Steered hub robustness- the steering hubs on the Unimog were too weak Steering strength - the small linear actuator used for steering turned out to be too weak under the weight of the finished model, as @nerdsforprez originally anticipated (if only I had listened ) The first decision I have to make is how to power the model. Although I was happy with the power output of 2 XL motors with BuWizz on the Unimog, this MOC will be even heavier, so I can either gear the motors down further or power it with 4 XL motors and 2 BuWizz (which is the more fun but more expensive option). I also have to decide how I am going to build the robust front axle I want. I'm leaning towards using the LEGO Unimog portal axle hubs. Despite their poor turning radius, they are probably going to be more robust than any custom portal axle I could possibly build, but if anyone disagrees I would love to hear your arguments . As for the steering mechanism itself, I am thinking of either using a large linear actuator, although it will be difficult to fit in the limited space without limiting turning radius, or alternatively, a large rack and pinion with a worm gear setup. I am leaning towards the latter, but this will be a bit more tedious due to the extra gearing to reduce the speed and the fact that I would like to add a clutch mechanism of some kind so as not to break any components. Here is some WIP for the front axle: I am looking to make this my best trial truck yet, so all comments are welcome and appreciated! I'm looking at you @Zerobricks, you said there was room for improvement on the Unimog and you could give me some advice on my next MOC , so please feel free to do so!

Massive improvement on the original! My favourite difference is the design of the handlebar area, you eliminated those ugly holes in the original

This model is just gorgeous @Anto! In particular, I love that huge diffuser at the back, and how the rear spoiler moves independently of the rest of the bodywork with the suspension. Did you find that the brick-built panels on the sides of the spoiler fall off easily, or was that not an issue? My biggest question for you is what tools did you use for the video editing, cause it's just stunning The transitions are so crisp, and look like the Hoonigan videos, what video software did you use? The camera movements are also really cool, how did you make those smooth dolly shots and pedestal shots, were they shot handheld or did you use some kind of LEGO contraption? Overall amazing work