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@LabManager, this is really amazing! I have always wondered how it would be possible to convert the PF signal to a proper servo signal. You seem to be the guy to understand it, so hopefully you can explain to me some further details that I still unclear to me. What I don't clearly understand is what are the roles of the custom PCB and the ESP32. As far as I understand, what the custom PCB does, apart from simplifying the wiring, is that it takes the C1 and C2 PF signals and that comparator thingy generates one signal out of the two? And then the ESP32 takes that one signal and maps that into the PWM signal required for the servo? For that you had to program the ESP32 to do the right thing, but the ESP32 has a PWM signal generator built in, right? What I have really been wondering though, is whether all this could be done with existing electronics components, without using an ESP32, just a custom PCB with the right components, such as a PWM signal generator. Does such an electronics component exist at all? Would it be possible to make a PCB that does just that without the need for programming it?

That's interesting!

That would be neat, but I don't think anything bigger would fit into the 3x3 space. I think even a 22T gear would touch the limits, but not sure.

If so then why are other themes adding new (even technic) parts and recolors like crazy? Some of them never used in the technic line. They are even adding technic parts that could have been very useful if actual technic usages would have also been considered. Just a few recent examples: Some more buildable/reusable towball arm would have been more useful. Would have been more useful with 2L pin instead of that long bar that sits there uselessly. Not bad, but expected this with 2L axle first, maybe more usages for that variant. Recolored for a botanical set where it's hardly visible, but not for multiple recent green technic sets..? Such a part would have never been recolored for a technic set I guess. Especially not to a color that is very similar to the only existing color (yellow). I don't even understand how this got recolored, even the yellow would have looked okay in that star wars set.. These examples just tell me that 1) the addition of new parts is not really a big issue, 2) they don't really try hard to bring the maximum out of the part selection. I guess they have some part quotas to limit new ones, but they don't really try to think systematically or negotiate across themes. Yeah, I understand that and agree with it unfortunately. Actually, the most practical ones missing are only the 4L and the 6L, not too many parts. Bricks are quite different in my opinion, because in system builds, it is much easier to join bricks to form longer parts. Bricks are meant to be stacked with overlaps and also they are designed visually to form a continuous looking surface. These are not true for liftarms though. Even though I wished for many lengths of links in this thread, in practise, introducing just the 5L and the 7L would go a long way already, exactly because we can almost build 5L and 7L suspensions, all other parts are available (towball arms, driveshafts), except the steering links. In fact, if I had to bet, I would have thought the 5L to appear sooner than the perpendicular version of the 6L.

Well, I just explained why I think it would be beneficial for them cost-wise. I don't agree with this for two reasons. For one, I'm talking about basic structural parts. Even if all those would be covered, there would be tons of other opportunities to release new interesting functional and aesthetic parts and keep AFOLs excited. Second, such AFOLs who keep track of the part selection and are longing for new ones are a very small minority. Most people who buy lego have no clue about what parts exist and are not collecting parts. They are collecting sets. They don't really care what new parts the sets contain, they mostly care about how it looks or what it models. Of course we've all heard about this and this is exactly what I was referring to. But it should not apply here. Again, exactly for the reason that I'm not talking about specialized on-off parts, but about basic, generic, reusable ones. But I think this past problem and the resulting policy has its (adverse) effect today. If this is the case then it should be revised, because I believe it is now hurting more than it is helping. I brought this specific example, because I think even using a recolor of the thin ones would look a bit messy (though better that the original), because you'd need to stack 8 of them into the door construction I showed above. I agree it is practically unnoticeable in the McLaren, mainly because there the suspension arms are almost horizontal and the suspension travel is minimal, in which case it does not cause toe in/out. It would manifest itself in a longer travel off-road suspension. But if the idea was to make parts that can be used in other circumstances as well, then an expensive supercar set would have been the perfect place to introduce that new part that would be required in other places to accompany that suspension arm. I wonder if they will use the suspension arms in something off-road, and whether they will introduce the 7L link, or just go with incorrect geometry again. That happened in case of the Ford Raptor. For that they did not introduce the 5L link and it was possible to feel the toe out when plying with the model. My problem is that there are only a handful of official models every 2-3 years that could introduce these new suspension parts, and they keep missing these opportunities.

Yeah, that was so far my best idea too, but I'm not into PCB design either.. Actually, I think space would be tight for cables as well, so I was wondering whether it would be possible to make it just using those needle-like thingies soldered to the PCB in the right places and then just connecting the different components (ESC and receiver) through those needles. I guess that would minimize space requirement and simplify assembly as well. Also, things like turn on button and status LED should be soldered to the PCB at the right place. But not sure if such a PCB can be made with an online PCB manufacturing service. Anybody with such experience / knowledge?

I like the direction, I have also been thinking of buying some chinese battery box (like this) and repopulating it with RC electronics inside. However, it would be great to go one step further in reducing the cabling, and to reuse some of those PF ports, charging port, and the turn on button already in the housing. Any ideas for how such things could be wired in? Unfortunately, I think in those chinese battery boxes, everything sits on a PCB that holds the motor controllers as well, that we'd like to replace..

Exactly.. The more I see about release of new parts, the less I buy this argument; it always felt somewhat arbitrary to me. I don't think it's about economics calculations, maybe some rigid old principles, and a huge amount of shortsightedness. I think a good sense of economics would dictate that the most economic way of managing a range of parts for a building system on the long run (and well TLG is there for the long run) is to have them systematically cover the base cases. Because such systematicity leads to simplicity in building and design, and simplicity leads to efficiency and ultimately, low cost. A key thing here is NEED, and how it's defined. In some sense, nothing is needed, if you don't want to build all the things that are not possible today. TLG could just keep pumping out sets built from the current part selection for the next 10 years, it would work in a sense. However, many parts would be useful. So I think it's better to think about whether the utility of a part would outweigh its cost. And I think, that may have the wrong perception within TLG. For one, the cost of making moulds for such ubiquitous parts like liftarms would amortize very fast, as they would be used everywhere (sure there are other costs of managing all the part selection but that's what TLG is really good at seen by the amount of parts coming out in other themes). For two, I think TLG really underestimates the cost of working things around. It cannot easily be measured in material cost, but in engineering hours spent on designing things that are hard to build because of the non-existance of simple parts that would lead to obviously simple solutions (I think the cost of working things around is often underestimated in many companies, because the management hardly sees how much extra effort the engineers spend on fixing problems that should not have come up in the first place with proper foresight). Also, there is the cost of the extra parts in sets that are only there because of the added complexity of the workaround itself. As for the concrete examples of 4L and 6L liftarms, here are my latest ones that came up recently (but they came up many more times). There's this new suspension part that I thought I'd try to build something with Only problem is that it is 7L, and TLG forgot to put a new 7L steering link into that super expensive supercar set, because, well, it's not needed, it can be sold with incorrect steering geometry as well, people won't notice anyway. So I thought, well, we have 9L steering links, so I could try to build a 9L suspension arm out of it, it has two pinholes in the ends that can be used for extending it with 2 studs, that would require a.. right.. 4L liftarm. Great :) The 4x2 L shaped version does not work here because the L shape is in the way for the suspension itself, and the 4L thin liftarm has axle holes in the end which would prevent the suspension arm to rotate in many situations because the most useful connectors to fix it have axle holes. So two obvious simple usages (for 7L and 9L) are out, and we can start finding ways to hack things around to make this new part really useful. For the 6L, here's an example that I made a few weeks ago about the G-class. The rear doors are just a big cluttered mess, and with a couple of 6L liftarms, it could have been easily improved a lot (the 5L flip-flop could have also been useful but not that necessary for looks as it is covered by the black stripe anyway). Right is the official, left is the improved. Sure, agin, it's not really necessary, people are already used to cluttered looks of lego cars anyways..

Holy crap, that’s a bunch of very useful novel parts! So many things I’m missing and would make much sense!

Wow, those are pretty expensive stuff! I understand that, but that does not make the geometry correct, the pivot points are still shifted (suspension pivot vs drive axle pivot). Can you please investigate this when you review it? Especially for high angles of the suspension. I wonder if length difference becomes noticeable / problematic.

This is genius, once I looked at these kind of walking mechanisms but did not find this really simple implementation, and so cool that it even has a cool shaping / details. Thanks for the instructions!

Somehow I completely missed this topic, probably I was on vacation in the middle of the summer :) Cool build, I like the use of 3 GeekServos for different purposes, it really shows their potential, and the diff locking system. It's a pity though that it takes up a lot of space and the drive motor and battery had to be pushed up so high. The use of the brushless motor with the planetary reduction is quite interesting though :) And the shape / body is nice too!

Thanks! About the front wheel overdrive, often used in RC crawlers, the idea is that for crawling, it is better if the car tries to pull itself up instead of pushing itself, because then it's less likely to flip itself over. Also, if it catches a ledge with the front wheels, those have more grip than the rear ones, especially if the car is at a pretty steep angle. At this point I don't know if that actually makes a difference in lego because it might not have enough weight / tire grip, but it was a simple but interesting challenge to make it. I think the stacking would not be a real problem, because the L motors can be geared together really easily due to their possible distance, in a way it is even an advantage that the gearing can be adjusted. Actually, I find that stacking the buggy motor format to the same axle is more problematic, because it wastes a lot of space and results in half stud gaps. As for cooling, I wonder if that's actually required that much. I haven't had any problems with overheating so far, I mean I never felt the motors would heat up, and maybe the more down-gearing due to the planetary gears help with that, as the motor has more torque with less struggle? I don't know the physics of that. But this is with a totally enclosed motor housing, and some cooling gaps could definitely be added as on the buggy motor, no? Or would that make it structurally weaker? Thanks, thought you'd like it for that reason :) Thank you! Indeed, I realized that even XT30 connectors take up a lot of space because they don't allow the cables to bend in their immediate neighborhood. And actually the first connector on my cables picture above does exactly that, one end plugs directly to the ESC and the other is the PF port. But I did the other ones to be able to split the cable to two PF ports. Did you have a solution for that, like soldering two PF connectors onto the same output? Or did you just stack multiple motors on one PF port? I'm not sure if it could handle that, I've heard some people melting the plug with 2 buggy motors..

Thanks a lot! Of course I will make more models with this gear, I have several sketches on different scales. Also, with this chassis I'm thinking of different bodies. And I bought another set of batteries, ESC, receiver.. I'm especially curious about smaller models with a single (red) XL motor and a GeekServo and small battery. About the motors, you are right that there are some chinese variants that have high RPM but low torque, I think those ones are black / dark orange-ish color, called furious L motors, or something like that. But these red ones seem better, I have measured them to make sure :) Thanks, glad you appreciate it!

No worries, I did not take it as mean, just wanted to point out that it's not the actual axle build here what is important, it's just a quick illustration, but those parts that allow such builds, and then it's up to you how you use them and how you strengthen it all. For example, in this case I could use a 3x3 L shaped liftarm instead of the vertical 3L thin liftarm, that would be more rigid next to the 5x7 frame and would also double up the axle hole at the outer end at the top. And also, instead of the 2L red axles, I would use 3L axles with stop and extra bush at the other end to make things stronger. For larger builds it is indeed possible to use already existing longer liftarms with towball sockets, as many of us do so in spite of these parts. Actually, many of my 40 year old thin liftarm parts are also broken around axle holes (and they were already broken 30 years ago), but so far I never had such issues with newer parts. Maybe the material is also different, or I build more solid structures and put less stress on them..

Yeah, I was thinking either that or sand.. I guess water would be hard to keep inside (and even fill). Indeed, I did play with the idea of building a complete pickup variant as a more scale model when I saw some RC model of it this year at an exhibition over here. Now that @Lipko keeps me thinking about the scale, I found a pickup version that I really like and could be used for scaling. Maybe indeed it would end up closer to 1:10, because it seems to have bigger wheels. Here is a rough sketch I cooked up quickly in Studio for the bed. I guess I'll have to get two more of those fenders.. BTW, these fenders are really not great for these kind of cars, they just curve in the wrong place / direction, the bottom should go inwards, instead of coming outwards.. I wish there would be different fenders as well..

Which part are you referring to? Obviously, the thin liftarms can always be doubled up for more strength where needed, this is just an example build for a smaller axle with about 62mm wheels, but a wider variant would work with 81mm wheels too. And I have built large motorized models with similar thin liftarm solid axle structure and never broke anything. I mean, what big forces would act on them? The force of the motor does not. The weight of the model is dampened by the springs. I mean crawlers though, not fast ones. Solid axles are not for those anyways. Sure there would be plenty of use cases. And multiple people have made a 3d printed version of this towball socket already (I have some too, needs testing though). Also, the same build could be made with Audi hubs. But smaller scale models can also make use of planetaries when they need torque and precision not speed, like crawlers.

As much as I would also like to have such parts with friction (even a 2L version is listed in this thread), I also get that it might never exist for that reason. Although I am not sure it would be that hard to remove; in many cases, it is enough to remove the outer beam that it is in, it will pull the pin with itself because of the stop end. Or just loosen up the structure enough to be able to put a nail (or another stop head) under the stop head and pull it out. And unfortunately, seeing the not so systematic nature of technic parts, I could believe that it was introduced for some other purpose, and we just got lucky to have it..

Sure, that would be possible (would then require a 4x2 thin L-beam), but my point was to see how small scale we can go. At such small scale (lighter model / soft springs) I think even the crosshole connection would hold, the hub itself also adds some some stiffness, but if that's not enough, I'd use a 3x3 thin L-beam for the vertical / top part. That would definitely strengthen it I guess. Or was your comment not about the axle but about the curved towball socket part? Adding an extra hole would screw it, not leaving space for springs on the top for example, and not allowing it to be used in the lifted variant.

Finally, I managed to level up my Studio part design skills to make the towball arm part that I'd really like to have for planetary hubs (as some people have already 3d printed). And here's what we could build with it. The obvious variant; simple, strong construction with plenty of space for connecting springs / linkages. Good ground clearance, and variable width with 4L / 5L thin beams. And if the rest of the part selection was more systematic (parts already mentioned in this thread, like 2x3 thin L-beam, towball socket with axle hole, an old CV-joint male part with 1L axle, and an updated variant of a the planetary hub with steering arms like on the Audi hubs, none of which are one-off parts, but could be used in many situations): then it would even be possible to build a lifted variant! How cool that would be? :) A fake portal axle at 13 studs width!

Which model year? :)) For a 1980 model, which this one is modeled after, I found 161 cm body width, which would result in about 1:9.5 scale if we scale it by the width. But I suspect that scaling it to other parts would result in something different. For example the stock wheels on those ones were just 73.3cm in diameter, that would translate to 81mm stock tires on 1:8 scale. But anyways, this is not a scale model, that's not the point. I just tried to illustrate the size of it, and it definitely feels bigger than 1:10 scale lego cars. It's something like your Dakar car in size. What scale is that? I think I could settle on 1:9. How about that? :)))) Yeah, that was it with the original 12:12 gearing in the axles and asymmetric drivetrain I write about above. Since then I have redesigned it with less overdrive and 12:20 gearing in the axles, which relieves some stress from the gear mesh. Seems better now, but maybe over time it would also wear out somewhat..

Another cute little build! That hood shape is indeed strange, but nice that you found a building technique for it! The brush attachment is pretty cool :)

Thanks for all the comments! Sure they make it better, though I think these cheap RC ones are not that great either, they are not as sticky as I expected. In the 107mm range, I have some proper RC4WD tires, I'll test those next on a different chassis :) Also, I have been thinking of adding more weight to the wheels to make them more grippy. RC cars use lead on the rim, real crawlers use water inside the tires, in Lego it is possible in some cases to put another, maybe thinner tire under the outer one.. Yeah, I keep thinking about that as well, there are some nice experiments in other threads.. I think two promising directions are the A2212 type outrunner motors (either in XL housing, as you suggest, or in a custom 3d printed mount with 1-stage planetary gearing) or the 24xx type inrunner motors with a custom planetary gearbox attached. I haven't seen any that would fit into the L motor housing though. As far as I understand, as @msk6003 says, the M motor uses 130 size, and the L uses something like 180 size maybe. And yeah, that's the only one I know of that would fit there, but it's quite expensive, about $50. Maybe in a custom 3x3 housing (3d printed) it could work, and the planetary gearset of an M motor could be reused. That would be an interesting direction to try.. Thanks, unfortunately I don't have such footage, not sure if I'll be able to make some before I dismantle it.. Thanks, I had some trouble determining the scale, but I figured that wheel arches come from a 1:8 car, which uses 81mm tires, so this one with 95mm ones should be around that scale as well. Also, 1:8 scale translates to 76cm wheels in real life, which is kind of believable for a stock version at least.. In any case, I would not think it would be smaller than 1:9, but definitely bigger than 1:10. Thanks, yeah, the digital build helps with the presentation, and even GeekServos are available as custom parts :) As for the front wheel overdrive, the idea is that for crawling, it is better if the car tries to pull itself up instead of pushing itself, because then it's less likely to flip itself over. Also, if it catches a ledge with the front wheels, those have more grip than the rear ones. At this point I don't know if that actually makes a difference in lego because it might not have enough weight / tire grip, but it was a simple but interesting challenge to make it. Actually, real crawler buggies go even further, the most versatile ones have separately detachable front / real wheel drive, and they can change on the go where they want to put the power. So instead of overdrive, they simply can switch off rear wheel drive. That's a good question, might even be so! Well I did not overthink that part, maybe because that's what truggies are like in reality and RC models. Thanks! Yeah, I wish Buwizz made these kind of motors, they seem to have part of the resources for it already. I actually proposed the idea to them, but they think the buggy motor has a better form factor.. Sure, if you want direct drive to the wheels then it's good, but if you want to build a drivetrain, then they are super difficult to work with, take up a lot of extra space (and half stud offsets) and have too high RPMs for slower cars.

Hi Eurobrickers! This time I'm here with my first build that explores non-lego electronics components for maximum off-road performance :) I have always been curious about what proper RC electronics could do with Lego, how far the performance could be pushed without damaging lego parts or using metal parts. So this is the first chapter in this exploration. As usual, I am more interested in off-road stuff as opposed to super fast cars, such as crawling, precision, maneuverability and good suspension. I start on a fairly large scale for two reasons. One is to see what the electronics and the parts can handle, and second is that on this scale I can maximize the performance os suspension / drivetrain. For crawling, live axles are great, planetary hubs are a must to minimize the stress on drivetrain components, and on this scale the axle design of @Attika is superior, especially with deep rims and 95mm RC tires, so I started with adopting that to my needs and building a generic chassis around them and the electronics components. For the bodywork, I choose a truggy because they are designed for crawling and are typically minimalistic, which is good for weight saving. And when I started searching for truggies, most of what I found turned out to be a Toyota Hilux, so I just went with that. The largest wheel arches are a good match for 95mm tires, and dark blue was a color in which they are available and I already had many parts in, so it was an easy choice. Features All wheel drive with about 6.5% front wheel overdrive Triangulated long travel 4-link live axle suspension on both axles Independent 4-wheel steering, servos on the axles Detachable body (single piece), openable doors Custom electronics Buggy motors inside L motor housing for drive GeekServos for steering Injora ESC 3s LiPo RC receiver and transmitter (FlySky) Custom cables with PF connectors Chassis, suspension, drivetrain I started with the design of the axles based on that of @Attika with the planetary hubs, but I made them 4 studs wider wrt the original 17 stud design because of using the deeper rims and also for a wider stance. My main objective was to integrate the GeekServo on top of it. A key simplification factor I used is the lack of open differentials (would be locked for crawling anyway), this way reducing the space requirement of the gearing, and allowing a flatter profile and lowering the servo while fixing it in a simple and solid way. The steering linkage has really small amount of slack, and the 8T gear on the rack allows very powerful steering. In fact the GeekServo is so strong (especially in this configuration), it can steer the wheel under any circumstances on any surface I tested. On the rear axle, I managed to lower the springs for a more compact suspension to leave space for the bed above it. The suspension is a 4-link triangulated one using 9L links that keeps the axles in place even without a panhard rod. In the drivetrain I wanted to experiment with front wheel overdrive. First I built one with 25% overdrive using 16:16 gearing on the back and 20:16 gearing on the front. It worked, however it felt a bit too much and was not flawless; the 20:16 gearing offset the front driveshaft to the side which created an asymmetric load at the point of the driveshaft entering the front axle which generated quite some wear over time. Also, first I used 12:12 gearing inside the axle as a closed differential, which also worn out after some time. After seeing an RC video that tested 5-6% overdrive against 25-30% overdrive, and concluded that significantly more than 5-6% is not really beneficial for climbing, I thought I'd try a more modest one. The current one on the image below uses 20:12 = 5:3 gearing in the front, and 2 stages of 20:16 gearing on the rear, resulting in 25:16 ratio. The ratio of the front/rear is then 16:15 = 1.0666, so roughly 6.5%. Most importantly, this setup is symmetric, keeping both ends of the driveshaft centered. At the same time I used a 12:20 gearing inside the axle as a differential, taking some load off. So far it has not cracked.. Here is the overall chassis. The motors look like L motors, but they have their insides replaced with that of a buggy motor, as that has the same size as the L motor's, so fits perfectly. This modification is not my own, but was done by @Jantayg and he lent me the motors for testing (the pinion gear was replaced and the thermistor was taken off and soldered back in). They are quite amazing. I measured their speed and torque against the Lego L motors, and found that they have about 1.8x speed and 1.65x torque, so almost 3x power overall!! At the same time, their speed is also in a very reasonable range, about 900 RPM on a 3s LiPo, which means good speed control but a good amount of punch at the same time, quite perfect for lego crawlers. All in a very good form factor! I only wish such a motor was available off the shelf. Luckily, the red chinese PF replicas you can find on Aliexpress approach these ones in performance; I ordered some and measured that they have about 2.5x the power of a lego L motor, only a bit worse then these modified ones. I haven't yet tested those in a build though.. Control Electronics For control, I am using this Injora ESC. It's quite small, about 5x3x1 studs in a nice housing that can be easily attached to Lego parts with sticky tacks and has a turn-on button and status LED. It is designed for smaller scale RC crawlers, but for lego motors it is more than enough, and allows for quite precise speed control. In fact, in the video the model often moves slowly not because that is its max speed, but because I wanted to move with precision; its top speed is much faster than that. Apart from that I use a FlySky transmitter and receiver, and a 3s LiPo. I also had to make some custom cables for connecting the motors to the ESC and splitting the output of the ESC for the two motors to avoid stacking them on the same PF port (I made several versions). Unfortunately, currently the cables result in a bit of a mess.. It would be nice to house these electronics in a 3d printed box or something.. Bodywork For the bodywork, I was aiming for something simple but rugged, but at the same time I wanted to test how the whole setup would work with some actual weight, whether I can later try to build a more detailed scale model at this large scale. I really like 95mm tires, both Lego and RC ones (I bought these inexpensive ones from Aliexpress, option TN1003), as they go really well with large 15 stud fender parts, both the Defender ones and the ones from sports cars. So as I mentioned in the intro, a Toyota Hilux truggy seemed like a good choice, and the Bugatti fenders went well with that, along with some long curved slopes for the hood available in dark blue. I wanted to replicate the characteristic front grille, which I managed by using large window pieces and a lot of small grille parts :) The rest of the body is a just a few large panels and beams, and a simple bed to accompany it with some roll-bars, all connected together to a single piece so that it can be mounted in the chassis on a few points, like in a 'real' RC car. Here are some more renders and images of the complete model. More images are available on Bricksafe. I haven't made instructions for this because of the large amount of custom parts, but the Studio model is available on Rebrickable. Altogether, the model has very good handling, both for speed and steering, and I am quite satisfied with the power of the motors. This all shows to me that Lego RC has much more potential, than the official electronics. And out of all these components, the only 'dangerous' one for the plastic parts are the powerful the motors, but even that danger is minimal in this setup; for smaller models it would even be less (even with this heavy model, the wheels rather spin under it than get stalled). It was really fun playing with this model and making all these video footages! Let me know how you like it and what you think about all those possibilities with custom electronics! Cheers, Viktor

Really cute one, and I like the way the electronics is squeezed in such a small place, but covered so nicely with a clean body and it even has interior!