Brushless motors in the lego world - general topic

[vergogneless]

On 1/5/2025 at 7:01 PM, Aurorasaurus said:

I'd like to share a little something I've made on the weekend: A brushless trophy truck (chassis)

Sorry about the black bars on the video, the google photos tool for adding videos together is very primitive and I didnt feel like turning my computer on and using DaVinci for a 30second clip I forgot to record in 1080p.

This setup is: 1400kv 2212, hobbywing 10bl60 esc, dumborc x6fg, geekservo, 1500mah 3s lipo, metal differential from zene.

This truck wont last much longer, it has a tendency to roll because of where I placed the esc and because it's quite narrow. The next one may also be AWD, but we'll see.

Thanks for your time, and have a lovely day :)

Super cool to see this kind of experimentation—show us how it evolves!

 

On my side, I’ve come across some amazing products on Ali, including a bunch of servo motors I’ve never seen before, and some other items I’ll let you discover.

 

This one seems really interesting—it’s bulkier than our usual Geekservos but appears to offer a force of 5kg instead of the 2kg we’re used to. Has anyone tested it yet?

There are also other servo motors in different formats, offering the same force as the original Geekservo:

 

This one also claims to deliver 2kg of force but is supposedly equipped with metal gears:

 

Then I stumbled upon this—a kind of battery box, although I’m not super familiar with this type of hybrid device that seems to allow control of classic Lego motors. It might interest some of you who want to dig deeper into this:

I also think I’ve found metal axles, which I’d guess are aluminum. Judging by the price per unit, I can’t think of what else they could be. But there’s no information about the material in the description:

Lastly, here’s a device that seems to be a Bluetooth speaker:

I also spotted a small smoke machine with the same type of connection.

[gyenesvi]

It's interesting to see that there are so many servos and other lego compatible accessories out there. I have also seen a larger servo, and though of trying it, but then the small 2kg GeekServo is so powerful compared to lego ones that I thought I don't need stronger ones for now (for a car such as steering/gearbox); but could be interesting for other machinery.

[Aurorasaurus]

Reading through this topic I've seen a lot of us are using 3d printed parts to hold bearings. I've been trying to make wheel hubs with 3d prints and bearings and metal U joints, and gluing all the parts together. But now the glue on my wheel hubs broke. My friend suggested setting the bearing inside the hub while its printing, and I initially wrote this off, because the plastic itself would be the next easy thing to break. But then I thought about it some more, and realised that if we can find a strong enough material, it may be very possible to make wheel hubs this way. The only problem is finding what material to print in. I've used PETG and PLA, and neither is strong enough for really intensive applications. I'm aware of carbon fibre and glass reinforced filaments, but I think those only serve to be more rigid. Does anyone know if my understanding there is correct? Ideally, we need a material that is very strong even in very small areas, because of the limited size of a wheel hub. Anyway, I've rambled for long enough, heres how I broke my wheel hub:

 

[Krzychups]

29 minutes ago, Aurorasaurus said:

My friend suggested setting the bearing inside the hub while its printing

It might be a good idea, I haven't thought about it. I would have to figure out how to stop 3D printing and then turn it on in my ender S1 Pro 3D printer. Regarding materials, I've planned to print them from nylon at 0,2 mm nozzle to get better details (that's why I've bought Garolite G10 sheet to print nylon which is a very good plate even for other materials, I don't need to use glue stick). Maybe polycarbonate might work with it. Nylon is a strong material, but hard to print, as well as polycarbonate. I wonder how robust PLA+ would be. I'm still waiting for my metal parts for wheel hubs and planetary gearbox.

@Aurorasaurus, @Variteck good work with your trophy trucks!

What is your experience with gearboxes using brushless or other powerful motors? I've made a simple gearbox with 3D printed parts because I don't have them, but it has got some problems.

@Aurorasaurus, you say that Lego gears or diffs don't work well with such a power of brushless motors. What about the yellow differential?

[Aurorasaurus]

11 minutes ago, Krzychups said:

@Aurorasaurus, you say that Lego gears or diffs don't work well with such a power of brushless motors. What about the yellow differential? 

The yellow diff is okay, but I managed to skip teeth using the yellow diff, which is why I think metal diffs, or 3d printed diffs which you replace constantly, are the only way. Of course if you had a lower power setup, the lego diffs are okay.

13 minutes ago, Krzychups said:

I wonder how robust PLA+ would be.

I'm going to find out in the next little while. I need to order more bearings so I have enough to experiment with.

On another note, I've been using 5mm id 8mm od 2.5mm depth bearings, they are fine for lego. I put one on either side of each pinhole, so 2 per stud. They are cheap.

15 minutes ago, Krzychups said:

What is your experience with gearboxes using brushless or other powerful motors? I've made a simple gearbox with 3D printed parts because I don't have them, but it has got some problems. 

If you mean just a series of gears for getting reduction, I've found normal lego gears are well up to the task, as long as you use bearings and lubrication. I broke my wheel hubs and still never skipped gears, in my trophy truck. But if you mean changeable gears, I think that is a very different beast. The lego clutch parts are too weak for 2x pf xl motors in some cases, brushless would destroy them. Maybe some kind of classic heavy duty gearbox could be made to work.

20 minutes ago, Krzychups said:

I'm still waiting for my metal parts for wheel hubs and planetary gearbox.

I'm looking forward to seeing what you have to say about those, wheel hubs are the number one problem stopping brushless lego from being actually viable in my eyes. I think our wheel hubs should connect to lego wheels, using 6 pins instead of 3.

[Ryokeen]

5 hours ago, Aurorasaurus said:

But now the glue on my wheel hubs broke

That's one of the reasons why no hobby grade RC car uses glued in bearings. It just won't hold. What is done there is that there is a small notch between the bearings so that the outer one can't slide in and the inner one can't slide out. The outer bearing get's pressed in by the hex adapter and the wheel, the inner bearing get's pulled outwards by the thicker part of the axle(in the metal U-Joint atempt the small splint thought the joint and axle).

Sometimes along with the notch, different outer diameters for inner and outer bearings are differend aswell. The inner bearing got the bigger outer diameter to prevent movement. But anyways almost always 2 bearings are used with a notch(small inside "ring" in the wheelhub) to limit movement of the bearings. But fitting that in the space of a lego wheelhub means very thin bearings.

[Krxlion]

13 hours ago, Aurorasaurus said:

 

I have tested this exact simple gearbox with brushless setup. I was skipping gears a lot. For me, the trick to not skip gears in gearbox is simply having it supported one by another.

[Aurorasaurus]

2 hours ago, Krxlion said:

simply having it supported one by another. 

Do you mean on both sides? If I understand correctly, this gearbox is reinforced on both sides, so shouldnt have too much of a skipping problem?

[Krxlion]

Above quick demonstration of what I mean. The 20 teeth gear is the driving gear (by the motor), and rotation goes to gears below and their two drive shafts. As you can see in this scenario, the black gear has nowhere to go if it tries to skip, because on each side there are 24 teeth gear on a way. It's just a demonstration, but the concept worked on my several brushless setups.

[Krzychups]

On 1/9/2025 at 7:51 PM, Krzychups said:

What is your experience with gearboxes using brushless or other powerful motors? I've made a simple gearbox with 3D printed parts because I don't have them, but it has got some problems.

Well, I've tried to make a 2 speed gearbox for my crawler. I've printed 24 and 36 teeth gears, a 3L nylon clutch, and some sort of switch also made from nylon, but that part has actually melted. By the way, I found this gear on Thingiverse: https://www.thingiverse.com/thing:5887041. But if the Lego clutch is weak for 2 XL PF motors, I won't try again. Keep in mind that 3D printed parts are not ideal, so when I've disassembled this gearbox, I've found that the 24 tooth gear was merged to the axle. Here's a photo of my gearbox: 

Spoiler

 

On 1/9/2025 at 8:13 PM, Aurorasaurus said:

I'm looking forward to seeing what you have to say about those, wheel hubs are the number one problem stopping brushless lego from being actually viable in my eyes. I think our wheel hubs should connect to lego wheels, using 6 pins instead of 3.

What exactly do you mean? I totally agree with you, wheel hubs are the main problem, then the motor housing. I prefer RC wheels, because there's much less chance of wheels falling off. There are also a lot more types of wheels on the market compared to Lego ones.

I've been experimenting with @HorcikDesigns live axles parts. They are very cool. So far I've made a crawler, but it's not the final version. I still need to buy diffs, and some parts for bodywork. In the picture you can see the front axle with the diff lock. I'm using the SG90 servo, because it's cheaper and smaller than the geekservo and some 3D printed parts like tie rods and parts for the bearings. I've designed a special part to mount the servo. I'm using 80 mm Injora rc shocks, but I haven't filled them with silicone oil yet xD. The speed is about 3,5 km/h.

My crawler is powered by brushless motor with metal planetary gearbox, but it's not the final version yet. As I said, I'm waiting for metal parts. 

Spoiler

 

Spoiler

Here are some videos:

Spoiler

This is my previous diff locking system, it works quite well. This sound is weird, but it isn't from my car xD.

 

Edited January 11 by Krzychups

[Variteck]

Good morning everyone. I have a question: I bought these two brushless motors with the shaft completely smooth, without grooves. How do you apply a gear to them?

[Brano]

Hi all, i see that some of you are trying to connect rc motor to lego. I tried several metal gears and this one fits lego gears perfectly without slipping. Check my "prototype"😅 but i would like to build something slower and more "torquier"

 

[Variteck]

19 minutes ago, Brano said:

Hi all, i see that some of you are trying to connect rc motor to lego. I tried several metal gears and this one fits lego gears perfectly without slipping. Check my "prototype"😅 but i would like to build something slower and more "torquier"

thanks Brano. So the completely smooth shaft doesn't cause sealing problems?

 

[Aurorasaurus]

25 minutes ago, Variteck said:

I have a question: I bought these two brushless motors with the shaft completely smooth, without grooves. How do you apply a gear to them?

I have used a vice and press fit gears onto them, if you have the appropriate metal gear. But if you want to attach Lego gears, I advise you to glue a 2L axle connector to the shaft. But every pin hole your moving axles go through will need bearings or it will melt.

54 minutes ago, Krzychups said:

Here are some videos: 

I like this, the use of a smaller servo for the diff lock is nice too. And the snow is so beautiful.

54 minutes ago, Krzychups said:

What exactly do you mean?

 

Spoiler

Like this, 6 pins can be used to hold the wheel, rather than the 3 you find on Lego wheel hubs. Using 6 pins, I have not had my wheels come off once, even in a 37km/h crash.

Spoiler

The front wheel came off, but the axle stayed complete and went under the car.

 

24 minutes ago, Brano said:

but i would like to build something slower and more "torquier"

You can connect a planetary wheel hub and then use pulley wheel to get 5.4x reduction, with the strength of injection moulded inner gears. After that, maybe you can use planetary wheel hubs again at the wheels.

You can also use the internal reduction from a fake PF XL motor and a 3d printed part, with a metal gear, to get 37x reduction from the output of your A2212. I posted about this earlier in the topic.

Edited January 11 by Aurorasaurus
Formatting

[Variteck]

4 minutes ago, Aurorasaurus said:

I have used a vice and press fit gears onto them, if you have the appropriate metal gear. But if you want to attach Lego gears, I advise you to glue a 2L axle connector to the shaft. But every pin hole your moving axles go through will need bearings or it will melt.

 

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Oh my god, so you can't use the screw-fixed m1-12T gears?

 

[Brano]

Metal gear is tighten by screw to smooth shaft so no problem with slipping

[Variteck]

Speaking of wheel hubs: I'm working on fitting my 1,5kg Trophy Truck driven by brushless motor with Didumos turntables-based wheel housing . Has anyone ever tried it, have you ever tested their resistance at high speeds?

[Aurorasaurus]

56 minutes ago, Variteck said:

Has anyone ever tried it, have you ever tested their resistance at high speeds? 

I used them on a buwizz motor powered vehicle, they add more resistance than I liked. I also managed to melt a small turntable with buwizz motors once. You will need lubricant on these, and then they will turn smoother but with a different kind of resistance. But I think they'll be strong enough for brushless models.

1 hour ago, Variteck said:

Oh my god, so you can't use the screw-fixed m1-12T gears? 

Maybe you can, I havent tried this.