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They don't have to mesh with Lego gears, I only used them as illustration here, all gears in there would be custom non-lego ones, with any desired characteristic (diameter, tooth size) that fits (actually, a quick search shows that 9T gears don't seem too rare). The important constraints would be: the bottom gear has to be in system, so it should roughly fit into a 3x3 area, including a thin covering bottom wall the bottom axle has to pass by the large middle gear, so the middle gear cannot get too large relative to the bottom gear I wonder that if another gear mesh would be added to the current 11:40 setup (or for example to a 9:36 setup), in the above geometry, satisfying the above constraints, what would be the achievable final gear ratio. I think something above 5x could be reached, as those gears seem to have smaller teeth than lego gears.

That makes sense, thanks! Upon giving it more thought, here is a sketch of the gearing that I have been thinking about, that might work out and would only be one step more complex. The upper (red) and lower (yellow) axles are in system, 4 studs apart, and the middle grey axle is out of the grid, but 3 studs apart from both axles. Actually, the red axle does not need to be in system, so that could be lowered or moved to the side as well, depending on the size of the motor. The down-gearing in this case would be 5x, which would result in the 1500 RPM range with a 1000 kv motor on 2s LiPo, still kind of safe for lego parts. The bottom axle could be 1 stud above the bottom of the chassis in this case, the complete height could be reduced to 6 studs, the width would increase instead (asymmetrically), and the thickness would also become 3 studs instead of 2. The questionable point in this is the 8T gear on the motor shaft, I know that that one is typically metal, but don't know if it is easy to find one, most motors I saw come with 11T. Do you guys know if there are smaller ones? Do you think this could be doable?

This looks really interesting and well designed, promising candidate for 4x4 vehicles. Neat that the gear is spinning in bearings. Why is it required to print the 40T gear from two parts? Unfortunately, I have one problem with these gearbox setups when it comes to integrating it into Lego builds, and I don't quite understand how real RC gearboxes solve it; maybe someone can enlighten me. The problem is that the main driveshaft ends up too high in the chassis. In this case, it's 2 studs above the bottom, which would result in high angles for the joints going to the diffs in case of smaller scales (shorter shafts). Furthermore, the large gear blocks the path for another axle, so it is not even possible to make a 2-stud step downwards with another gearing. How do RC gearboxes circumvent this? As far as I understand they use kind of asymmetric, multi-step gearing (possibly with extra spacing gears inserted) to arrive to the bottom to a not too big gear. Ideally, the main driveshaft should be about 1 stud higher than the bottom of the chassis. Do you think it would be possible to design such a gearbox adapter? How complex would it get? 1000 kv motor on 3s LiPo with this gearbox still results above 3000 RPM, which is still a bit too high for Lego to use safely I guess. Half of it would be enough, which would require more down-gearing.. What does that exactly mean? At first I thought you'd want to change the outer diameter to 24mm instead of 28mm to fit 24mm motors, but it seems you are talking about something different?

This is beautifully built, I like the mix of functional technic chassis with studded finish. The door mechanism is especially cool and seems smooth. I admire people who take so much time and parts to build a single model in such detail. Great work!

I still like this idea so will be monitoring the progress with interest! Just out of curiosity, what company makes such gearboxes, how did you find one? I think a double stage reduction between 1:16 or 1:25 could work out well for some use cases! Even with planetary wheel hubs, it all might end up in a good range for some purposes, like rock crawlers. What exactly do you mean by that? Is it that the minimal low speed is still too fast? I have just recently managed to test a complete (brushed) setup in a real application, I will present it here soon in more detail, but I can already share some interesting details. I used modified motors: Lego L motors (so 1:25 planetary gearing), where the actual motor inside was swapped in from a buggy motor (they use the same sized motor, but the motor inside the buggy is about 2.5x more powerful). This results in a motor that is slower than the buggy motor because of the planetary reduction in the L motor housing, but it has more torque. I used two of these motors coupled, driving planetary wheel hubs with 1:1 gearing (no diff needed in a crawler, just 12:12 gears instead). All that built into a large scale 1.5 kg crawler, driven by a good quality brushed ESC and a 3s LiPo. The result is pretty amazing for me. For one, the system has very good low speed control, can easily crawl around the cm/sec speed, in a stable way. It is pretty powerful, moves the 1.5 kg model up a 45 degree slope with ease when it has good grip (or if the slope is steeper, it either spins the wheels under it or twists some axles in the drivetrain). At the same time, the top speed is pretty acceptable too, something like you'd achieve with two Lego L motors powered from a Lego battery but in a lighter model without planetary wheel hubs (like the Audi for example). Nothing really fast, but it definitely has enough punch required for some dynamic climbs, and to move across terrain in a non-boring speed. I'd definitely be interested in buying such a thing as a finished product.

Exactly my thoughts. They literally took the best selling alt build on Rebrickable and made it into a set. Even the color scheme and some details are the same. That does feel lame, even though they were probably able to make it more accurate because of not being a limited build.

Not sure why, but I completely missed this build. Maybe I was on holidays at the time.. Anyways, it looks really interesting, I like the simple and streamlined bodywork, and I have been wondering lately about this setup for drive and the front suspension. It is using slow output of motors, right? Wonder how much of this could be replicated using Audi hubs.. Can you tell/show more about the front suspension geometry? I can't completely make out how the caster tilting is achieved. When you say broken pythagorean geometry, do you mean the triangles are a bit forced? I see that the core of the chassis and the motors themselves are not tilted, only the suspension arms around it, which is something I have been thinking of doing but haven't gotten around yet. Also, how does that effect the steering linkage? I guess the steering shaft and linkage isn't tilted either, so how do you get a good geometry that does not result in toe in/out? Is it approximate? Does the toe change during articulation? Or is it something that you just omit because it has some slack anyway, and it corrects itself during running?

Also agree on the more attention :) saw this but did not have time to reply and then I guess it went down in the list of topics and got forgotten.. Anyways, looks well polished on the outside, nice chassis and great performance, I even like the experimentation with the custom parts, how does your hub compare to the Audi hub? What are the differences? from what I can tell, the steering arm seems asymmetric. Is that key to make the suspension spring fit? Are there custom parts in the driveshaft as well, like shorted CV joints? Is the video showing the first version only, and the second is unfinished yet? Will the body (have to) be different in the second?

Oh, I get it then, indeed, that's common with this approach, but yeah, I would have chosen the same as you did. I have a similarly scaled model that I will publish soon, and in that I do the same as you, only difference is that I have 9 wide axles and hence can use a 9L link for that instead of the 7L half beam, and it's good enough.

Thanks, well, I meant all the linkage and joints together, as compared to a direct steering (motor to steering rack), I imagine it would be similar with gears. For me already the joints introduce quite a bit of play, though true that the whole system is not precise enough to notice too much of it, but still, things add up. Of course at full lock the play can be prevented with physical limiters. And what introduces negative camber (or did you mean caster)? The linkage geometry?

Are there any off-road variants? Did not find, but this also seems to be in the Replacement Parts section which is asking for login, weirdly enough..

Cool build, I like the looks! What's the intended use of such buggies in real life? Fast, but light off-roading, like bumpy dirts roads? I mean they're probably not designed for heavy terrain due to the less ground clearance I guess. I wonder about one thing regarding the drivetrain. Have you tried using planetary hubs and Audi diffs instead? I wonder which of the two is faster. I experimented with such a setup lately (actually no diff, just 1:1 transfer with 12T gears), it has good speed (cannot tell how it compares to yours), but it also has plenty enough torque to climb such bumps that yours starts to struggle with. I have not tried the Audi hub though, and wonder if that would be faster, though was suspecting that it would not have enough torque for heavier terrain.

Sorry in advance for all the grammar policing, but it's the second topic with this title, so it evoked this in me :D Well, that's one interpretation why this name is wrong, but I did not mean that. Rather, tank climber = something that climbs up onto a tank. So it's not the tank that climbs up onto something else. The two things are different; this is why grammar matters, because if you swap two words, you can get two very different meanings. I guess you wanted to write climber tank (that is, a tank that climbs) instead :) And then comes the second problem that you mention, that it's not even a tank. It's just a tracked vehicle so far. A tank (vehicle) is originally named so because of the big boxy container (that can drive on tracks, but also on wheels, may or may not have a cannon). The essence is the big container, which is absent here. That's why it's not a tank, not because of the absence of the cannon. Sorry again for the too much grammar strictness, but I think your title is pretty misleading, and I am sometimes in the mood for fixating on these kind of things (due to my computational linguistics past) and promoting correct language use. But I understand that it's because english is not your mother tongue (and it makes me wonder whether descriptive adjectives in french (can) come after the nouns?). About the actual build, do you have plans to build something on top of the tracks? Why does it have to be so big? Just to fit the scale of the stairs?

Thanks for the photos, that's a neat linkage for the steering (I guess it introduces some slack, but hopefully still okay for the purpose), and good cable management, great compact build! Wish TLG would cater more for this size of RC builds (both electronics and suspension/steering components).

Hmm, interesting findings, though I was using the 4-port technic hub, I have no city hub at hand. And I don't quite remember which port it was, but I think I had 2 drive (L) motors on A+B, and one steering (L) motor on C or D.

This is so cute! :) Very tight build, that drivetrain is neatly packed, and the body looks really cool, retro vibes. Can we see more of the inside? For example how the steering is done? It took me a while to find the battery as well, and I have no idea where you put the cables.. Hoping for a video :)

It's pretty cool, but you say it is a tank climber, and I don't see any tanks being climbed here. There is no tank at all, and it climbs stairs..

I see. I tried all combinations, other buttons work, except for the trigger and shoulder ones. LOL, that sounds a lot.. I know those settings, just all looks somewhat counterintuitive. For example, some settings are the same for light and heavy, but different for medium. It's not like it's changing monotonously. Pretty hard to find out which way to set it. Also, the presets don't follow the recommendations in the documentation!! If they'd at least follow those, the presets could actually be useful! More meaningful parameter names could also help in the app, and 2-3 main parameters would be enough for many use case, it's just I never remember which ones.. Not really user friendly at all. Oh, and the bonus one; an obvious bug in both Android and iPhone, right when you start out: you give your profile a name, go back to the main screen, and it does not display the name you just gave (remains 'New Profile'). You need to restart the app to actually make it display the proper name you gave. How hard could it be to catch that?

What do you mean by that? Are they mapped to other buttons? Only using the app the second time but already getting really pissed off with it. Besides being full of stupid bugs (such as the app turning off the screen after every few minutes and losing connection, starting drive mode without servo calibration freezes the whole app on the screen that says that the servo must be calibrated, steering is still jerky as hell, etc), it sometimes does not stop the model when I release the joystick, crashing into everything, which can be a real problem when driving with 4 buwizz motors; my second crash in about half a minute resulted in breaking a (rare/costly) flip-flop beam. Thanks.

I'm trying to use Buwizz app to control my model with an Xbox controller from an Android phone. The joysticks work, the D-pad works, and most of the buttons work (the Y button does not work), however, I cannot make the trigger and the shoulder buttons work. Furthermore, if I program the L1 button (should be the left trigger), then the Y button starts to work. Something seems mixed up. Anybody had similar problems? Anybody managed to make the triggers work? Another problem I have is that it does not seem possible to make the joystick and a trigger control the throttle at the same time, but with different max power (say joystick 70%, trigger 100%). Should that be possible? BC2 can do that easily..

Wow, this is very nicely packaged, elegantly constructed and seems to have robust functions operated with minimal electronics. I especially like the operator cabin, and the way the whole thing rotated on the base. One of the few technic builds that I could actually imagine becoming a set. Great work!

Wow, is that how the real car is made? I didn't think there would be so many motors and even 4 gearboxes, that sounds a bit complex.. (though looking at some videos, I guess that's a hi/lo gearbox?) Anyways, in that case, I don't think they'd make the electric version.

That's a good question, because I'm not sure both the diff locks and a complete gearbox (hi-low, DNR, 4-speed automatic parts) could fit in, even with the new gearbox parts. But I'm not even sure that the new gearbox parts are enough to make a compact (linear) 4-speed gearbox, that might require some new gear sizes anyway (they may rather be useful for an 8-speed variant). So I could imagine that they leave out the 4-speed part, and keep the hi-low range and the DNR selector in favor of the diff locks. Or the other way around, they focus on the gearbox, and leave out (some of) the diff locks. BTW, if they do the new electric version, then it makes more sense to focus on the diff locks than on the gearbox, right? Or does the electric version even have diff locks?

That's interesting! Are you sure it's sand green and not olive green like the technic Defender? Even then, the 9L beam would be new. But it does look more like sand green. And it's not really necessary in that color in this set, so probably made for something else. Sand green would combine better with all the available system parts, like the ones in the Icons Defender :) (I think olive green does not have that many parts available..) BTW, what's that little fender part on the quad?

I agree with this! I think this would be different in this case for a couple of reasons. First, in a manual model, the axle would not have to be as sturdy (massive) as in an RC model. Also, no planetary wheel hubs would have to be used here, so the axle could use different wheel hubs that could be easier (thinner) to mount into a live axle on the rear. Most importantly, the front suspension on the G is double wishbone independent, not a live axle, so that would require completely different technique to build the axle. Finally, the new 2L driving ring from the Yamaha allows a narrower locking diff to be built (both in a live axle and in an independent suspension). And best of all, track width of the Defender does have enough space for an extra 2L diff locking ring! So I'm definitely expecting locking diffs on this one, as it's a definitive feature of the G, and then it would be an evolution of the Defender!