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 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 11 hours ago 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?