Brushless motors in the lego world - general topic

[Asakbar78]

On 9/2/2025 at 7:58 AM, gyenesvi said:

I decided it's time for me to enter the game :) So here it comes, my first brushless motor! A small one to start with.

A few days ago I bought myself a Bambu A1 Mini 3d printer, and started experimenting with making a housing for brushless motors.

Features

• Dimensions: 3x3x6 studs
• Weight: 34 gr
• Reduction: 24x down-gearing with 2-stage planetary gearbox of PF M motor
• Speed: around 1100-1200 measured RPM, but around 1500 on paper

Design

I decided I wanted to base my design on SurpassHobby 24xx motors, based on the ideas of @HorcikDesigns presented in this thread. For me, the ideal form factor is the 3x3 one, which those motors fit perfectly, and because with a planetary reduction, we can keep that form and get good amount of reduction.

So my key idea was to take apart a (3rd party) PF M motor, and take out the planetary reduction for my purposes. The PF L motors also has essentially the same reduction, but its internal housing has a bigger shape due to the L motors bulge, and so I could not use that. I went on and bought a SurpassHobby 2435 3300 kv motor. When I started looking for an ESC, I came across this super small Injora one, and since I used its brushed counterpart already, and I was satisfied with it, I decided to order one (it can handle 25 A continuous and 60 A peak current, 2-3s LiPo, has adjustable BEC output up to 3A, and is waterproof). I realized that there's an accompanying mini outrunner motor as well, they come in a combo, so I bought that as well (17x21 mm only, 2800 kv). The wiring is really plug and play, you just need a battery with an XT30 connector, and a receiver.

To my surprise, the motor comes with a 11T gear that's a perfect match to the gear inside the PF M motor, so it meshes perfectly with the planetary reduction. Furthermore, it also comes with a couple of 2M screws that I needed for the assembly, so I set out to print a housing for this one first.

The housing consists of 3 parts. First is the front face together with the planetary housing.

Second is the mounting wall.

And the third one is the back cover (it's optional, but good to have). The rear holes serve as ventilation openings, as well as they are inverse studs for mounting.

The assembly sequence is as follows. First, the wall is screwed to the motor from the inside with M2 screws that comes with the motor.

Second, the planetary reduction slides into the two horizontal slots of the wall (the planetary housing has two horizontal tabs on the back to fix it against rotation).

Third, the front face can be screwed on at the corners from the back using M2 screws.

And last, the back cover can be pushed into the slots on the wall mount from the back. It's a really tight fit, so it does not come off.

Optionally, the inverse studs on the back can be used to fix the motor or add further mounting points.

More pictures are available on my Bricksafe.

 

I haven't yet built it into any model, only tested the bare motor. The control is insane, it has super slow startup, it can go as slow as about 1 revolution per 25 seconds, but with enough power that I could not stop it with my hand.. And then it can go up to 1200 RPM. I'm really curious how it will perform in a model :)

 

I am planning to make a similar motor using the SurpassHobby 2435, but of course without the back cover, but first I need to buy some M3 screws for that one. Any ideas where to get them in various sizes?

This is absolutely sick I love it. Please let us know how it goes. 

 

Hi all, I have recently bought the whole starter brushless conversion gear. (A2212, 35A esc, 2x 1500mah lipo 3s, dumborc x6 controller/receiver)

I don't have a 3d printer or anything like that so I was considering just using a worm gear to reduce the speed from the motor. I went with the 930kv to reduce the amount of gearing I have to do. I make a lot of off road creations and was planning on making a really capable (but not too fast) model. Ive made them before simply using large motors and a buwizz and I use silicone spray lubricant to keep it all from binding. Do you think ill be able to pull it off without damaging anything?

[HorcikDesigns]

Not to discourage you, but using worm gear in offrad car at such speeds with plastic parts is great DIY project to learn basics of friction welding (buggy motor is enough to do this). I would recommend to find a different way to reduce the speed, or find somebody in your area with 3d printer. 

[Krxlion]

1 hour ago, Asakbar78 said:

This is absolutely sick I love it. Please let us know how it goes. 

 

Hi all, I have recently bought the whole starter brushless conversion gear. (A2212, 35A esc, 2x 1500mah lipo 3s, dumborc x6 controller/receiver)

I don't have a 3d printer or anything like that so I was considering just using a worm gear to reduce the speed from the motor. I went with the 930kv to reduce the amount of gearing I have to do. I make a lot of off road creations and was planning on making a really capable (but not too fast) model. Ive made them before simply using large motors and a buwizz and I use silicone spray lubricant to keep it all from binding. Do you think ill be able to pull it off without damaging anything?

Maybe trying to use planetary wheel hub to reduce rpms. Its not ideal way of reduction, but as a start it will work. I remember combining myself that method with same motor model, and using small plastic card part (take a look at my message before).

[Krzychups]

On 9/1/2025 at 11:58 PM, gyenesvi said:

I decided it's time for me to enter the game :) So here it comes, my first brushless motor! A small one to start with.

Nice! I wonder if the problem is that the motor casing can become hot and melt, as well as restrict motor cooling.

[Asakbar78]

13 hours ago, HorcikDesigns said:

Not to discourage you, but using worm gear in offrad car at such speeds with plastic parts is great DIY project to learn basics of friction welding (buggy motor is enough to do this). I would recommend to find a different way to reduce the speed, or find somebody in your area with 3d printer. 

Thanks. I was wondering why no one had talked about it previously on here so there must have been a reason lol. I will probably go for 2 or 3 sets of 8 tooth to 24 tooth to see how it works, and if that doesn't work I will try find someone with a 3d printer. 

[gyenesvi]

20 hours ago, Krzychups said:

Nice! I wonder if the problem is that the motor casing can become hot and melt, as well as restrict motor cooling.

Thanks! The back section is completely optional, not necessary for functioning, so it can be left out to allow more cooling.

However, there's a slight other problem with the back section: it cannot be taken apart without breaking off the mounting tabs (they kind of get jammed in the hole and rather break than slide out). Also, it is just in the way for the large head of the HD CV joint as I am building my 4WD off-roader.. So I might just do away with the back for now.

[Tup4n]

@Krzychups here is photo. As you can see, it uses standard hole for Lego axels. 

 

[gyenesvi]

Version 2 of my motor housing! :)

As I started to build, I realized that it would be good if the sideways mounting holes would be vertically in the middle of the motor, because then it would be possible to hold it between two beams that are just the right height for dropping the output shaft right under the motor with one gear mesh; the simplest ever driveshaft (see below). So I designed another housing, where I could add pinholes in a row, and even round off the whole thing, and change the assembly so that it requires less screws, holding the back panel from the side. I also removed the back cover to prevent the motor from overheating. This version looks like this, as slim as it could get:

The first pinholes (towards the face) are full stud deep, while the rear ones are only inverse studs for half pins.

The new mounting points hold the whole 3L front section firmly, so there is no need for stabilization on the back. At the same time, it can be assembled using only the screws that come with the motor, and it is easy to disassemble and assemble again multiple times (the wear of the screw holes does not matter, because it is actually the head of the screw that holds the back wall). Another advantage is that now the wire can come out in a diagonal, allowing the motor to be tilted 90 degrees and mounted from the front without the wire interfering with the beam that runs next to it. The motor can also be mounted so that the wire comes out on the top, if needed.

This is how it looks in more detail:

Of course, it is possible to combine the two designs, and make a square version that has more mounting holes than the first version had:

Now as for building, this is how the most compact 4WD off-roader driveshaft for live axles could look like (two gear ratios are possible):

I have built this into a small scale 4x4 chassis and the performance is just great, super smooth control, great top speed! I guess I'll just open a new WIP topic for showcasing it!

 

Edited September 7 by gyenesvi

[HorcikDesigns]

Good job! 

[vergogneless]

A quick post to show you the front axle of my next mini 4x4.

 

What I was aiming for:

• Maximum 9 studs between the wheels

• Fit in the 6 planned ball bearings

• Be really strong because it’s for bashing

• Metal CV joints

• A good steering angle

• Compact and not too tall because of the servo

• Plan a neat routing for the servo motor cable

• Have mounting points for the future design using only conventional Lego pieces

 

I managed to reach this goal after a long process and several prototypes, and in fact it’s even under 9 studs wide (the steering arm you see in front is 8 studs).

I’m obviously going to replace the plastic gears with metal ones.

All that’s left is to make some 3D tweaks to widen the areas where the ball bearings will sit. I also have some ideas to add more mounting points for regular bricks, and to think about how to connect it to the chassis, what kind of suspension, etc.

I’m still a bit unsure about that part.

 

It’s made up of four main parts:

• The central body

• The wheel hubs

• The steering arm with the servo arm

• The cover to close the underside and lock everything together

The whole assembly is secured and locked either with Lego pins or with MTP screw connectors.

 

 

 

 

 

 

 

[Asakbar78]

Hey all, what motors do you think would be good for wheel mounted motors? something around 100kv seems ideal but idk what you all think.

[keepbricking]

hi guys 

can someone design some liftarms and a diff case with MR105ZZ bearings

would be very thankful

I can't really source R156ZZ bearings in India 

I am thinking of buying bambu lab A1 mini 

any recommendations for what filament to use for printing the mentioned above so i can use in my 6s setup ?

 

very cool gyenesvi!

 

also can someone design heavy duty cy joints just like in lego and maybe 

a planetary wheel hub

the hub is not necessary but would be thankful

i don't know how to design and don't even know which software to use but i can get it printed

I haven't even bought the a1 mini yet

[gyenesvi]

@keepbricking you will be better off if you learn 3d design yourself. 3d printing does not work so simply, you often have to adjust your design to your printer and material, so other people cannot really do that for you.

I suggest using Onshape free online 3d designer tool, and this tutorial for learning:

I have learned to design stuff in about 2 days just recently :)

35 minutes ago, keepbricking said:

I am thinking of buying bambu lab A1 mini 

any recommendations for what filament to use for printing the mentioned above so i can use in my 6s setup ?

I am using Bambu PLA with that printer. But not sure if any material can survive a 6s setup, including original lego parts..

35 minutes ago, keepbricking said:

also can someone design heavy duty cy joints just like in lego and maybe 

a planetary wheel hub

Why would you print those? They exist in lego, and they would be really hard to print. Also, you can buy cheap clones of those on AliExpress.

[keepbricking]

aliexpress generally doesnt ship to india

i can cnc machine parts with the help of SCAD files 

my cousin has access to cnc machining

it is too expensive to buy sets just for heavy duty cv joints

als MR105ZZ BEARINGS 

specification - 5mm inner diameter 4mm width 10mm diameter

[gyenesvi]

8 minutes ago, keepbricking said:

it is too expensive to buy sets just for heavy duty cv joints

You don't need to buy sets, you could just buy the individual parts then from lego.com. You won't be able to print them anyway. And I don't understand why CNC machining could be any useful here..

[keepbricking]

2 hours ago, gyenesvi said:

You don't need to buy sets, you could just buy the individual parts then from lego.com. You won't be able to print them anyway. And I don't understand why CNC machining could be any useful here..

if you can't design then no problem 

but these old cv joints just aren't holding up 

and I don't have any aliexpress and lego doesn't deliver pieces here

i can cnc machine stell axles but I need files for those cv joints AND their connectors

[2GodBDGlory]

7 minutes ago, keepbricking said:

if you can't design then no problem 

but these old cv joints just aren't holding up 

and I don't have any aliexpress and lego doesn't deliver pieces here

i can cnc machine stell axles but I need files for those cv joints AND their connectors

Sounds like some frustrating constraints in getting parts! If you don't have access to buying individual parts, but do have access to a CNC machine, maybe you could make that happen, but you'll probably have to do a fair bit of work beforehand. You can export .obj files of parts from Studio part designer, which could be a rough basis for working off of, but tolerances are unlikely to work in the real-world. Alternatively, you might be able to find STEP files from sets that this guy has modeled: https://grabcad.com/dk, though you'll probably need to edit those too.

I second @gyenesvi in saying that you'll probably need to learn CAD for yourself, with Onshape and Fusion 360 being good free options

[keepbricking]

14 hours ago, 2GodBDGlory said:

Sounds like some frustrating constraints in getting parts! If you don't have access to buying individual parts, but do have access to a CNC machine, maybe you could make that happen, but you'll probably have to do a fair bit of work beforehand. You can export .obj files of parts from Studio part designer, which could be a rough basis for working off of, but tolerances are unlikely to work in the real-world. Alternatively, you might be able to find STEP files from sets that this guy has modeled: https://grabcad.com/dk, though you'll probably need to edit those too.

I second @gyenesvi in saying that you'll probably need to learn CAD for yourself, with Onshape and Fusion 360 being good free options

THANK YOU  

Finally someone who understands

yeah I think i'm going to learn cad now and experiment a little

CNC here can be much cheaper than buying TF or MTP products since normally its very hard to ship here

If i could just get files then metal parts would be so easy to get

[DadScientist]

OK, I have an electronics question for the audience, because I'm better with Lego than I am with R/C... so far. 

I spent a fair amount of time playing around with janssnet's brushless buggy from YouTube. And I've been trying really hard to figure out what he's using for an ESC. The motor's only a 2838, but the ESC  still looks really small... it almost looks receiver-sized. (see screen grab below)

Compared to the ESCs that came with my motors, it looks really tiny. I almost started to think it was a drone ESC. (I bought one to try in this application, but haven't tried using it yet.) And ultimately I started to wonder if that's how he managed to not snap off his Lego U-joints: Maybe he's using an undersized ESC, and not running the motor at full power?

The video's 4 years old, I'm sure there are some things he's forgotten. But, my question is: Is it actually ok to run an under-powered ESC for a brushless motor? Do you run the risk of overheating the ESC, or just slowing the motor down?

 

 

Edited September 23 by DadScientist

[janssnet]

Quote

But, my question is: Is it actually ok to run an under-powered ESC for a brushless motor?

It sure is a while ago! Tried to find the ESC in the archives, no luck.

For these kind of projects 30A - 40A ESC will most likely be sufficient. HobbyWing's Quicrun ESCs work great and have a small footprint.

In general, don't under-power your ESC. It will indeed overheat, especially when the battery and motor are capable of handling more AMPs then your ESC.

Not snapping the joint was a surprise, absolutely!  Proper gear ratio and proper alignment of the middle of the joint with the rotation point of the rear section helped.

Regarding the use of drone ESCs. I'm very close getting AM32 ESCs ready for these kind of LEGO projects (BLHeli-s and BlueJay work great already). However, takes much longer than expected, but it's encouraging.

Aiming for some speed records with this 1/8 In Wheel Drive first. Will get back to LEGO projects right after .......

 

 

 

 

 

 

 

 

[DadScientist]

Oh, hi!

That's good to know, thanks! I'll definitely look into Quicrun.

Life has gotten busier lately, so I've had less time to really dig into the buggies. I've built two or three versions so far, and I'm slowly spinning my notes into more posts over on Substack. (The latest entry is here)  I also gave a solid try at making your 42124/ outrunner motor project come together. I got really close to getting it dialed in, but then had to put it to one side. I'm slow-rolling the posts, and trying to maintain a weekly schedule. That way I can maintain it as an active project, while I wait for more headspace to get back to the experiments I have on deck. Hopefully those schedules line up, and there's no gap in the schedule. 

Back in March, you'd posted this:

"Current status, after all the LEGO prototyping, constructed a very competitive 1:10 on road race car, driven by 4x 1300kV in-wheel motors, controlled by an ESP32 and a 4in1 BLHeli-s ESC (not an AM32). Waiting for a test by world's #8 ranked RC-driver ;) If any interest happy to post about it." 

Is that the same car you just put up? How did that test go, if it's happened? (Curious to hear about your other exploits.) 

 

 

[janssnet]

Wow, great content on Substack and thanks for your kind comments. 

This was the 1/10 car back in March. Most of it 3D-printed. Ran pretty good. In fact ran so good that it attracted some attention, which then led to putting this 'In Wheel Drive' technology into an Infinity 1/8 chassis. That's the car in the previous picture. 

Results are encouraging but all these cars have one serious flaw: Drone ESCs have no proportional brake. You can work around it, to some degree (that's what the Arduino is for), but at higher speeds (we're aiming for 100+ km/h) you need more control.

Having that said, today was a good day, received a custom AM32 firmware version with  proportional brake that seems strong enough for direct drive. Will test it first in the 1/8 and, if successful,  the next chassis is waiting: Schumacher 1/10 running  4s lipo and 4 x1300kV...... Will not bore the forum any further with this, since no LEGO involved, but, as said earlier, will return with (hopefully) an interesting LEGO project in spring 26.

[DadScientist]

I can’t say that I’m bored. :-)

It is funny looking at the chassis. It takes a second to realize there’s no motor strapped to it, and then I have to check again… I know the motors are in the wheels, but it still doesn’t look right. How fast did it go?

I can say that I’ve been waiting for some downtime to play with transmitter programming and learn more about sensored motors. I feel like there’s a torque/ acceleration limit, and probably an RPM/ speed limit… but controlling the motors is the obvious gateway to slower acceleration and a higher top speed.

Thanks for the kind comments on the Substack. Having built a few versions of the buggy, I have plenty more to say. It was a fun experience to figure out what you’d done.

Cheers!

James

[keepbricking]

hello 

Can someone give me any stl file 

ANY STL file

 to  a heavy duty cv joint just like in lego

or a universal joint

i don't have enough joints to make my 6s setup AWD

and from what I've heard, lots of power and RWD don't go hand-in hand

so can someone please provide the stl file to a heavy duty CV or a uni joint

 please I don't have time right now my exams are coming up

[keepbricking]

please guys

any file

i have to go get it machined tomorrow