Brushless motors in the lego world - general topic

[Krzychups]

@keepbricking, I'm afraid it won't be as you want to. I'm not sure if you want to 3D print them or CNC them. If you need CNC parts, they need to be specially designed. I don't have such .stl files myself. Unless you want my amateur technical drawings of the U-joint that I made once. I guess you have 6s battery because you use it for your drone(s). In my opinion its better to have 2s or 3s. You will destroy your bricks.

@janssnet, regarding your 1/10 scale chassis, what tires and motors do you use? On my side I have 4108 bl motors and they're too big for 1/10 scale tires...  

I'll get back when I'll have my iWD car ready to show.

Edited September 28, 2025 by Krzychups

[keepbricking]

UPDATE: i got DAT files from Ldraw.com

really useful website

now i just need to export them in ldview and change them to stl

all kinds of parts there

found uv joint,axles,heavy duty joint and everything

im probably gonna CNC the transmission parts 

but i also have a servo adapter

that i'm going to print tomorrow

i mean tomorrow i'm going to my cousin's office

he has CNC machine at hand

20 minutes ago, Krzychups said:

@keepbricking, I'm afraid it won't be as you want to. I'm not sure if you want to 3D print them or CNC them. If you need CNC parts, they need to be specially designed. I don't have such .stl files myself. Unless you want my amateur technical drawings of the U-joint that I made once. I guess you have 6s battery because you use it for your drone(s). In my opinion its better to have 2s or 3s. You will destroy your bricks.

@janssnet, regarding your 1/10 scale chassis, what tires and motors do you use? On my side I have 4108 bl motors and they're too big for 1/10 scale tires...  

I'll get back when I'll have my iWD car ready to show.

Thank you for your understanding and no problem now

[gyenesvi]

Another batch of orders have arrived, so here is the next brushless motor I am making: the big brother of the Injora Purple Viper, the Fat Viper, which is 2200 kv. This is a 28 x 19 mm motor optimized for more torque, controlled by the same Injora ESC as the smaller one I previously posted. The overall construction is very similar, just the mounting face is a different shape due to the bigger size of the motor, this time it is 5x3x3, 5 units being its intended height.

Due to the bigger size of the motor, its mounting holes are also further apart, so I had to change the mounting wall accordingly. Here are the steps for constructing the motor.

First, the wall is mounted with M3 screws.

Then, the planetary gearset is added, sliding into the horizontal sockets.

Finally, the face is added and secured with two screws from the side.

It can be taken apart by unscrewing and pulling the wall out, helping the process with a knife at the horizontal holes above and below the motor. Running is similar to the smaller one with the purple Viper, but a bit slower and more torquey.

As for mounting and building in, the idea is that beams can be run above and below it, but not directly next to it, because of the width of the motor. Also, a driveshaft could not be run right under it, hence probably two stages of driveshaft lowering will be required. Thus, the housing is tall to create axle holes two studs below the output, where the driveshaft will drop.

With this motor I will probably build something with 68 - 80mm tires.

[keepbricking]

hello guys is there a website with lego technic stl files

couldnt convert the ldraw files to stl 

so had to design my own uni joint

but that also failed as it was almost smaller than the lego one

so is there any stl or 3mf file of lego 8mm heavy duty cv joint as that seems to hold up great

[2GodBDGlory]

53 minutes ago, keepbricking said:

hello guys is there a website with lego technic stl files

couldnt convert the ldraw files to stl 

so had to design my own uni joint

but that also failed as it was almost smaller than the lego one

so is there any stl or 3mf file of lego 8mm heavy duty cv joint as that seems to hold up great

I think I suggested it to you before, but I think the best option is to install Studio Part Designer, import that part, and then export it as OBJ. You'd still probably need to edit it, though

[gyenesvi]

A question to @Krxlion and @janssnet or anybody having experience with AM32 ESCs. I have been looking at the Ali links provided here as well, and find that those AM32 ESCs do not have a switch to turn them on/off. I have been wondering how you guys solve this issue? Just unplug it from the battery? I have been looking at mini switches like the ones on other ESCs, but I don't quite get how they work. The problem is those mini switches can take very little amps (like 50 mA), while those ESCs can withstand 20-30 A as well. So I can just put the switch in between the battery and the ESC. How do those switches that work on other ESCs? Am I missing something here?

@vergogneless I just saw your mini 3d printed axle here (I saw the post before but the pictures did not load back then), great work! I did not know those MTP U-joints are only 2L, is that right? Those MTP 3/4 liftarm connector screws are also neat, but outrageously expensive.. I have been wondering if I could just use something like M5 screws driven into the printed hole for similar purposes on the steering knuckle (frictionless connection).

[Variteck]

Hey everyone, I'm back with an update on my brushless trophy truck. I'm happy to report that after about 45 minutes of driving everything is working fine, no plastic parts have melted, and it's pretty fast!

Short summary:

- It's a modification of the original Goober Reboot trophy truck

- Weight: 1,5 kg.

- Width: 27 stud.

- 3200kv brushless motor, powered by a 3S 11.1v LiPo battery, through a 45A ESC.

- Red differential. 

- The transmission mechanism as a whole allows for a 29-fold reduction, including the approximately 5-fold reduction provided by the 46490c01 wheel hub.

The only metal parts added to the original LEGO pieces are ball bearings to house the pinion shaft rotation and a few washers. In this photo you will see a 7x5 frame ruined by previous attempts:

 

To support the high rotation speed of the axes I used the hole-in-the-hole technique that I have already described in this forum: the axles did not spin directly in the technic holes, but instead inside pin connectors that in turn spin in 1x2 stud housings, for example part 92907 (Axle and Pin Connector Perpendicular Split).

 

In this way the friction is shared between the housing and the connector. The backlash between the rotation axes is really minimal and does not affect the final result.

 

https://bricksafe.com/files/Variteck/trophy-truck-panoramica-/trophy-truck-aggiornamento/IMG_20251008_090618.jpg

 

Here are two videos of the transmission in action:

https://bricksafe.com/files/Variteck/trophy-truck-panoramica-/trophy-truck-aggiornamento/VID_20251008_091255.mp4

https://bricksafe.com/files/Variteck/trophy-truck-panoramica-/trophy-truck-aggiornamento/VID_20251008_091627.mp4

Soon I plan to install larger wheels (104mm tractor tires or slightly larger RC tires) and take a speed measurement!

Edited October 8, 2025 by Variteck

[janssnet]

10 hours ago, gyenesvi said:

and find that those AM32 ESCs do not have a switch to turn them on/off.

Not only the AM32 ESCs, counts for most drone ESCs. Yes, unplug the battery is best, since the amps can become far to high for small switches.

You can put a switch in between your BEC supply and leave the batteries untouched, but not ideal to keep current on your esc while at rest.

[gyenesvi]

2 hours ago, janssnet said:

You can put a switch in between your BEC supply and leave the batteries untouched, but not ideal to keep current on your esc while at rest.

Do you mean put a switch between the ESC's BEC output and the receiver? Because on the AM32 ESCs I was looking at, the BEC is built onto the ESC board, so that's the only chance. But he BEC output is still usually about 1-2 A max, so still sounds high for the micro switches.

I wonder what is done in ESCs that have the switch built in. Which connection does it break? And also, those ESCs are designed to be left on the battery, and just turned off, no?

[gyenesvi]

I finally wired up my SurpassHobby 2435 motor to my Injora ESC (I needed to solder some connectors to make them compatible). It is working, however, it feels like it's spinning the motor relatively slowly, given that it's a 3300 kv motor on 12V LiPo (feels/looks kind of like a Lego L motor). My Injora motors are running fast on the same ESC, and I tried setting the ESC parameters, but nothing seem to have changed. Does anyone have an idea what I could try (besides testing how it should actually run on a SurpassHobby ESC)? By the way, do you think these things should be cross-compatible?

Edited October 11, 2025 by gyenesvi

[Ryokeen]

On 10/11/2025 at 7:44 PM, gyenesvi said:

I finally wired up my SurpassHobby 2435 motor to my Injora ESC (I needed to solder some connectors to make them compatible). It is working, however, it feels like it's spinning the motor relatively slowly, given that it's a 3300 kv motor on 12V LiPo (feels/looks kind of like a Lego L motor). My Injora motors are running fast on the same ESC, and I tried setting the ESC parameters, but nothing seem to have changed. Does anyone have an idea what I could try (besides testing how it should actually run on a SurpassHobby ESC)? By the way, do you think these things should be cross-compatible?

Should be cross-compatible but stuff like timings might be different for each motor/brand. Also(not sure what exact ESC and injora motors you have, think it's a 1721 and that is quite a bit smaller) it could be that even a 2435 motor draws to much current and some protetion kicks in.

[gyenesvi]

5 hours ago, Ryokeen said:

Should be cross-compatible but stuff like timings might be different for each motor/brand. Also(not sure what exact ESC and injora motors you have, think it's a 1721 and that is quite a bit smaller) it could be that even a 2435 motor draws to much current and some protetion kicks in.

According to the specs, the 3300 kv 2435 draws 22-24 A max, and the Injora ESC can deliver 25 A continuously, and 60 A peak, so I don't think it's that (the battery is 75C). And the ESC also works fine with the bigger Injora Fat Viper motor, which peaks at 50 A (even the 1721 peaks at 30 A). Also, a SurpassHobby ESC is rated at 25 A.

[Ryokeen]

10 hours ago, gyenesvi said:

According to the specs, the 3300 kv 2435 draws 22-24 A max, and the Injora ESC can deliver 25 A continuously, and 60 A peak, so I don't think it's that (the battery is 75C). And the ESC also works fine with the bigger Injora Fat Viper motor, which peaks at 50 A (even the 1721 peaks at 30 A). Also, a SurpassHobby ESC is rated at 25 A.

I see, should work fine. As i said could be a timing issue(when to "activate" which coils). But as an advice..you should now be that close on your amp limits of the ESC as the motor stats (except kv) are not always that correct. But from what i've read i would assume that they use special timing/startup mode or even some weird encoded sensored data so other motors might just not work properly

[janssnet]

On 10/13/2025 at 5:15 AM, Ryokeen said:

Does anyone have an idea what I could try (besides testing how it should actually run on a SurpassHobby ESC)?

Should spin very fast based on your specs.

- You're sure your battery is loaded and giving the correct voltage (some esc have a low voltage protection)?

- Can't find anything on Injora ESCs, can you configure them? Sure you are using it in the correct mode (FWD/REV or FWD/REV/BRK)?

- Have you (re-) calibrated the ESC with your transmitter (neutral, full throttle, full reverse) or with the servo-tester?

- Can you configure start-up speed? If so, give it a boost start

- Are you sure this ESC can handle sensorless motors?

 

Edited October 14, 2025 by janssnet

[Krxlion]

On 10/11/2025 at 7:44 PM, gyenesvi said:

I finally wired up my SurpassHobby 2435 motor to my Injora ESC (I needed to solder some connectors to make them compatible). It is working, however, it feels like it's spinning the motor relatively slowly, given that it's a 3300 kv motor on 12V LiPo (feels/looks kind of like a Lego L motor). My Injora motors are running fast on the same ESC, and I tried setting the ESC parameters, but nothing seem to have changed. Does anyone have an idea what I could try (besides testing how it should actually run on a SurpassHobby ESC)? By the way, do you think these things should be cross-compatible?

I had the same experience with SurpassHobby 2838 BL motors, back when I was trying them. This is what I was talking about a long time ago, those motors feel like they have narrower range of speed. I have some tests on my private computer, but when I compared A2212 1000kv motor with 2838 (I believe 3200KV) from Surpass Hobby. The last was driving pretty slow, and the difference between low/max throttle much smaller compared to first motor. I was testing that on SurpassHobby ESC's, I still have two of them, but use no more, because now AM32 is in the game. ;)

PS Sorry for not replying for quite a while. I was quite sick for two weeks.

[gyenesvi]

5 hours ago, janssnet said:

Should spin very fast based on your specs.

- You're sure your battery is loaded and giving the correct voltage (some esc have a low voltage protection)?

Yes, just measured, it's at 12.3V now.

5 hours ago, janssnet said:

- Can't find anything on Injora ESCs, can you configure them? Sure you are using it in the correct mode (FWD/REV or FWD/REV/BRK)?

They are AM32 based, so they are configurable, and I have tried many different settings (motor poles, KV value, turning variable PWM on/off and setting PWM frequency to different values, turning sinusoidal startup on/off, turning brake on/off, etc).

5 hours ago, janssnet said:

- Have you (re-) calibrated the ESC with your transmitter (neutral, full throttle, full reverse) or with the servo-tester?

Checked that, but it should not be an issue as it seems to work fine with Injora motors

5 hours ago, janssnet said:

- Can you configure start-up speed? If so, give it a boost start

Yes, but the startup is not the problem, that is quite smooth actually.

5 hours ago, janssnet said:

- Are you sure this ESC can handle sensorless motors?

Yes, Injora motors are sensorless too.

 

3 hours ago, Krxlion said:

I had the same experience with SurpassHobby 2838 BL motors, back when I was trying them. This is what I was talking about a long time ago, those motors feel like they have narrower range of speed. I have some tests on my private computer, but when I compared A2212 1000kv motor with 2838 (I believe 3200KV) from Surpass Hobby. The last was driving pretty slow, and the difference between low/max throttle much smaller compared to first motor. I was testing that on SurpassHobby ESC's, I still have two of them, but use no more, because now AM32 is in the game. ;)

Well that's interesting to hear, so maybe this is how they work normally? Which would be kind of weird. I'll try to borrow a SurpassHobby ESC for testing to see how it works with that..

Was it the same on AM32 ESC? Have you tested that?

[Krxlion]

22 minutes ago, gyenesvi said:

Well that's interesting to hear, so maybe this is how they work normally? Which would be kind of weird. I'll try to borrow a SurpassHobby ESC for testing to see how it works with that..

Was it the same on AM32 ESC? Have you tested that?

I have not, to be honest. Do you want me to run some tests on AM32?

[gyenesvi]

52 minutes ago, Krxlion said:

I have not, to be honest. Do you want me to run some tests on AM32?

Well, I was just curious, would not expect better results than on its own SurpassHobby ESC.. besides, that's what I am doing with the Injora ESC as it is AM32 based.. but I also recently ordered a bare AM32 board from Ali, so will test that as well.

Do you think that the same programming board and software can be used for all AM32 ESCs? I have it for the Injora and did not order separately, from the videos it looks like the same software being used.

[Krxlion]

11 hours ago, gyenesvi said:

Well, I was just curious, would not expect better results than on its own SurpassHobby ESC.. besides, that's what I am doing with the Injora ESC as it is AM32 based.. but I also recently ordered a bare AM32 board from Ali, so will test that as well.

Do you think that the same programming board and software can be used for all AM32 ESCs? I have it for the Injora and did not order separately, from the videos it looks like the same software being used.

Software and programming board - Yes. Firmware will be different for each type of the board.

https://am32.ca/downloads

You can see that there is plenty of firmwares. It would be best if you could check which one works with your am32 esc.

[janssnet]

On 10/14/2025 at 8:15 PM, gyenesvi said:

They are AM32 based, so they are configurable, and I have tried many different settings (motor poles, KV value, turning variable PWM on/off and setting PWM frequency to different values, turning sinusoidal startup on/off, turning brake on/off, etc).

If you can post a screenshot of your settings, we might be able to find something.

I recently noticed on my (Hobbywing) ESC that AM32 - 2.19, with Running Brake Level < 10 does not work well. Same issue, motor doesn't speed up. 

[gyenesvi]

21 hours ago, janssnet said:

If you can post a screenshot of your settings, we might be able to find something.

I can only post it later, I have no access to it now..

21 hours ago, janssnet said:

I recently noticed on my (Hobbywing) ESC that AM32 - 2.19, with Running Brake Level < 10 does not work well. Same issue, motor doesn't speed up. 

However, first I'll try this, because the Running Brake Level is at 9 now (that was the default setting for some reason), and I only tried lowering it, not pushing it up to 10. Previously I only experienced that it does not work well for value 1 (screws up sine startup).

[vergogneless]

On 10/8/2025 at 10:27 AM, gyenesvi said:

@vergogneless I just saw your mini 3d printed axle here (I saw the post before but the pictures did not load back then), great work! I did not know those MTP U-joints are only 2L, is that right? Those MTP 3/4 liftarm connector screws are also neat, but outrageously expensive.. I have been wondering if I could just use something like M5 screws driven into the printed hole for similar purposes on the steering knuckle (frictionless connection).

Thank you 

 

Regarding the front axle I presented, I’m using classic 3L metal U-joints.

I actually finished this model a while ago. In the meantime, I went to Sweden for three weeks for work, and I’ve been back in France for a few days now. That said, this model is awesome, works like a charm, and has exactly the same dimensions as my previous small blue buggy, except now it’s 4x4!

 

Here are one or two photos:

 

 

 

 

 

I’ll present it in more detail later, probably alongside the new version I’ve been working on since I got back.

 

This time, I’m using 2L MTP U-joints. I’ve found solutions to make this version even more compact and optimized.

We’re talking about an additional 1L in ground clearance and 3L saved on the total length. I’m keeping the same width because I’m now incorporating MTP metal wheel hubs. Plus, I’ve managed to integrate an independent oil-filled shock absorber system at the rear. I already have some ideas to replicate this on the front axle, but that’ll be for a V3.

 

I’m also using the alternative geek servo motor for the first time, which, as strange as it may seem, appears to be more precise in returning to the zero point than the 2kg geek servo in initial tests.

 

Here are a few photos:

 

 

 

 

 

 

 

And to come back to the MTP metal connectors, I completely agree with you that they’re quite expensive. But I find them absolutely essential in many cases.

 

Using threaded rods can be a substitute, but in my opinion, there are quite a few drawbacks.

For my part, I still use M3, as you can see in the photo, which can fit inside Lego connectors (with adapted washers to stop the screw head from passing through the pin holes). And since the nut can slide up to the offset of the pin holes, you don’t even need to put a connector inside the pin hole: the rod stays well-centered.

 

I made this choice because with larger diameters, you end up with oversized screw heads and much bulkier and thicker nuts, which can be problematic.

 

And of course, replicating frictionless movement with threaded rods seems complicated to me. It’s probably possible, but MTP will remain my first choice 

[gyenesvi]

On 10/15/2025 at 9:21 PM, janssnet said:

If you can post a screenshot of your settings, we might be able to find something.

I recently noticed on my (Hobbywing) ESC that AM32 - 2.19, with Running Brake Level < 10 does not work well. Same issue, motor doesn't speed up. 

Well, setting the Running Brake level to 10 did not solve it, rather it may have even made things a bit worse I think.. I tried somewhere in the middle, like 5, and maybe it is a bit better.. which is weird in itself, it should not effect things I guess.

However, after playing around with more settings, I think I FIGURED IT out!! It started with noticing that reverse felt somewhat faster than forward, which I didn't even try in the beginning..

The key is the Low and High Thresholds on the Input window. These were set to 750 and 2100 respectively (I guess they mean Hz), while the Servo Neutral was set to 1502 by default (weird value). As far as I understand, the throttle signal should be between 1000 and 2000 Hz, with 1500 being the neutral, so I set it to these values, and viola, now it is spinning much faster, in both directions. Oddly enough, if I change the low threshold, the forward max speed changes, but I think this may be because the throttle is reversed on my transmitter, so the low threshold is actually for forward now.. And this also effects my Injora motors, they are spinning faster too!! (If they weren't crazy enough already)

 

That's another nice level of engineering @vergogneless

44 minutes ago, vergogneless said:

For my part, I still use M3, as you can see in the photo, which can fit inside Lego connectors (with adapted washers to stop the screw head from passing through the pin holes). And since the nut can slide up to the offset of the pin holes, you don’t even need to put a connector inside the pin hole: the rod stays well-centered.

I understand about MTP connectors, they indeed are a good idea/design. About M3 screws and washers, it's not clear for me how you would use them in lego connectors. What do you mean? Can you illustrate it with a standalone example?

By the way, I like the use of the even smaller GeekServo!

Edited October 18, 2025 by gyenesvi

[vergogneless]

1 hour ago, gyenesvi said:

About M3 screws and washers, it's not clear for me how you would use them in lego connectors. What do you mean? Can you illustrate it with a standalone example?

 

Here are a few illustrations, I hope they’ll work for you !

And just for your information, with M3.5 you can’t slide through the connectors, it doesn’t fit!

 

 

 

[gyenesvi]

On 10/18/2025 at 3:31 PM, vergogneless said:

Here are a few illustrations, I hope they’ll work for you !

Thanks, I see how it's used now, I thought somehow it would be driven into the pins, but I see it simply goes through.