Brushless motors in the lego world - general topic

[Tup4n]

With the summer is comming my brushless RC McLaren P1 is ready to get back on the road!

 

[NV Lego technic]

Impressive speed for such a large vehicle!

[killerfrost]

Here's a few parts i made that work with RC parts as well as lego parts. The idea for these was to use the new CV axle with the wheel hubs as well as be able to insert a 10x5x4mm bearing to convert to metal rc parts. the transfer case takes those same wheel bearings and the motor set up from here ( https://www.zenebricks.com/products/high-performance-rc-brushless-esc-accessories-for-motorized-lego) and any lego diff. so far ive tested these with pla and works great. the opening for the wheel hub also fits any metal cv axle that is 11mm in diameter or smaller. tested with pla @100%infill and printed at a 45 degree from table and so far no issue. printing the spindles flat caused them to snap in half from my experience. could also be my printer too. https://www.printables.com/model/1266255-rc-lego-parts

[killerfrost]

On 3/16/2025 at 3:43 AM, Krzychups said:

Hello everyone! 

I'd like to share the results of my work with you.

I've done reverse engineering. It looks almost like Zene's differential, maybe with some small changes. Instead of metal adapters, I'll print them from nylon (the black parts). I highly recommend printing from strong material. The final cost is about 4 times cheaper than buying the differential from Zene. The needed parts are:

• the 3D printed adapters and housing,
• 4x M2x10 screws and 4x M2 nuts (you can use different types of screws, but the max head screw diameter is 4 mm),
• the differential,
• 1x M3x3 DIN 913/ISO 4026 - hexagon socket set screw with flat point,
• 2x 12x8x3,5 mm bearings (they comes with the diff) and 1x 15x10x4 bearing,
• the 4 mm diameter metal rod cut to about 11 mm with a flat surface on one side.

 

 

By screwing the hex socket set screw, you lock the shaft with the attached gear. What type of grease should I use to lubricate the sprockets and is there any point in filling the diff with rc silicone oil? 

I'll share the stl files with you.

So, what I need to do is to buy screws and other parts! What do you think about it? 

Cool!

I would like the file to be able to print this.

[Aurorasaurus]

@killerfrost Is there any reason for using 10x5x4 bearings instead of 5x8x2.5 bearings? I have been able to get 5x8x2.5 bearings in packs of 10 on aliexpress for shockingly low prices, and they work perfectly.

[killerfrost]

i didnt know about those size bearings, i can definitely resize the holes to accommodate those. I went with the larger ones because of the wheel hub design. i wanted to make it dual function and give the printed spindle more surface area to sit on when its snapped into place. the 2.5mm is really thin for just plastic and it seemed fitting to make the part atleast a half stud (4mm). the part in purple sits inside the hub. this is where the 10x5x4 bearings to go into that hole instead of the spindle.
 

[Knott]

R156ZZ is the ideal bearing size,  inner diameter 4,76, almost the size of Lego axle, outer diameter 7.938, slightly shorter than liftarm, no wiggly and loose axles

Edited April 15 by Knott

[killerfrost]

the part in blue is where the bearing sits. the part to the right is where the the cv axle and the spindle or bearings fit into. the purple cone is the slope for the spindle to snap into place.

3 minutes ago, Knott said:

R156ZZ is the ideal bearing size,  inner diameter 4,76, almost the size of Lego axle, outer diameter 7.938, slightly shorter than liftarm, no wiggly and loose axles

thank you, i will look into those and make design tweaks

[LegoTT]

Hello, zenebricks link in the first post doesn't work

[killerfrost]

22 minutes ago, Knott said:

R156ZZ is the ideal bearing size,  inner diameter 4,76, almost the size of Lego axle, outer diameter 7.938, slightly shorter than liftarm, no wiggly and loose axles

looking at the sizes, these wont work in the wheel hubs as its an either or for the bearing or spindle, the black one has the bearing in it. i will incorporate the R156ZZ into the transfer case though as that just takes axels.



 

 

10 minutes ago, LegoTT said:

Hello, zenebricks link in the first post doesn't work

https://www.zenebricks.com/products/high-performance-rc-brushless-esc-accessories-for-motorized-lego

[Knott]

Yes, for wheel hub you need something larger, for axle support and gearbox R156ZZ works perfectly.

[killerfrost]

I'll post the updated gearbox later tonight. im thinking of using 2 bearing per axle hole. there 2.5 mm tall and i have 8 mm to work with, i figure one on each side of the axle hole. it would use 6 bearings in total if i go that route. thoughts?

[Aurorasaurus]

1 minute ago, killerfrost said:

I'll post the updated gearbox later tonight. im thinking of using 2 bearing per axle hole. there 2.5 mm tall and i have 8 mm to work with, i figure one on each side of the axle hole. it would use 6 bearings in total if i go that route. thoughts?

For supporting gears in my brushless models I use 2 of a custom part with 4 of those 5x8x.25 bearings per piece. I find it works really well, I never had any issues with it. Here's a link to the bearings I'm using. They come in lots of 10 and I must have about 70 of them now...

https://bricksafe.com/files/Aurorasaurus/brushless/gear support block.stl

[killerfrost]

20 hours ago, Aurorasaurus said:

For supporting gears in my brushless models I use 2 of a custom part with 4 of those 5x8x.25 bearings per piece. I find it works really well, I never had any issues with it. Here's a link to the bearings I'm using. They come in lots of 10 and I must have about 70 of them now...

https://bricksafe.com/files/Aurorasaurus/brushless/gear support block.stl

sweet! i made changes to the transfer case design to use 6 of the smaller R156ZZ bearings. https://bricksafe.com/files/Killerfrost/truck/new-project/Transfer case.stl

 caster hub https://bricksafe.com/files/Killerfrost/truck/new-project/Caster hub.stl

regular hub https://bricksafe.com/files/Killerfrost/truck/new-project/hub.stl

large spindle https://bricksafe.com/files/Killerfrost/truck/new-project/large spindle.stl

small spindle https://bricksafe.com/files/Killerfrost/truck/new-project/small spindle.stl

 

 

Edited April 16 by killerfrost

[Krzychups]

On 4/15/2025 at 1:51 PM, Tup4n said:

With the summer is comming my brushless RC McLaren P1 is ready to get back on the road!

Cool! 

@killerfrost, does your wheel hub for metal cv joint have any offset? If so, the pivot point won't be aligned. Anyway, good work.

On 4/15/2025 at 11:19 PM, killerfrost said:

I would like the file to be able to print this.

Well, I've printed 3 versions of the diff housing and nothing of them work properly. When I screw the housing to the 5x7 frame, the diff doesn't turn. Probably wrong tolerances. Now looks like this:

[Aurorasaurus]

16 hours ago, Krzychups said:

I've printed 3 versions of the diff housing and nothing of them work properly. When I screw the housing to the 5x7 frame, the diff doesn't turn. Probably wrong tolerances. Now looks like this:

Looks even more promising though, if just the tolerances are wrong then soon it should be easy to get working. How is the experience printing nylon? Or are you just using PLA for prototyping at the moment?

Edited April 17 by Aurorasaurus
spelling error

[killerfrost]

8 hours ago, Krzychups said:

Cool! 

@killerfrost, does your wheel hub for metal cv joint have any offset? If so, the pivot point won't be aligned. Anyway, good work.

Well, I've printed 3 versions of the diff housing and nothing of them work properly. When I screw the housing to the 5x7 frame, the diff doesn't turn. Probably wrong tolerances. Now looks like this:

Very nice, the metal cv axle is .5mm off the wheel bearing because of the snap ring inside the hub but has the same pivot angle as the newer cv part lego makes.

[Krzychups]

13 hours ago, Aurorasaurus said:

How is the experience printing nylong? Or are you just using PLA for prototyping at the moment?

For prototyping nylon doesn't make sense. It's quite a hard material to print. At the beginning I had a problem with adhesion. You need to have good adhesion, no air movement (closed enclosure is recomended), direct extruder which can reach high temperature (250-270 degrees Celsius). I'll probably print only adapters to the axles from nylon. Nylon is very durable and heat resistance itself. Polycarbonate is an alternative, but I don't have knowledge of it, it's also a hard material to print. I don't say that it's a must-have, you can use other materials.

Edited April 17 by Krzychups

[Krzychups]

Today I was in a forest with my crawler. Here are some photos and films. 

It has live axle suspension with the Panhard rod at the rear and 98 mm diameter tires The final reduction is about 1:48,5. I use my custom reduction for the A2212 motor (this one is 1400 kv) and a transfer case. It has no diffs. The RC servo is used for the steering instead of the geekservo. I decided to use this one because I had had some problems as skipping gear on the gear rack and the whole steering was placed low so the ground clearance wasn't good. I've modified one of HorcikDesigns' live axle part to mount it. For the hardware parts I use a 3S battery and the AM32 40A ESC. I really like how it performs, it does serious offroad. 

 

Unfortunately, I've melted one axle by trying to climb that steep hill in the photo above :/

In conclusion, a lot of 3D printed parts and fun! 

PS. I'm sorry that I haven't finished the differential case yet.

Edited June 3 by Krzychups
added wheel diameter

[Aurorasaurus]

2 hours ago, Krzychups said:

In conclusion, a lot of 3D printed parts and fun! 

Wow! I was surprised by the performance, it seemed get up really slippery surfaces with relative ease. I feel sorry for you having to clean it now, ouch...

[Krxlion]

Looks like a fun model to drive around @Krzychups. Are you planning to put some kind of car body on it, or is it called "finished" in this state? I feel like the suspension could be little bit more softer, or the model should weight more. It is also little bit hard to catch from that camera angle how hard are the obstacles your model try to overcome.

Other than that, I can see that you dived more into "dark side", but as long as you come up with new neat solutions, I am happy with it. :)

[HorcikDesigns]

@Krzychups  Wow, nice to see my diff housings in action (hope I am not wrong). Do you have the version with ball bearings and diff lock, or without? Do you use sone lubricant in them? 

Edited June 4 by HorcikDesigns

[Krzychups]

1 hour ago, Krxlion said:

I feel like the suspension could be little bit more softer, or the model should weight more. It is also little bit hard to catch from that camera angle how hard are the obstacles your model try to overcome.

I agree that the suspenion is too stiff. So far these are the softest springs I have. Maybe with a bodywork this problem will be less noticeable. And yes, it is not always easy to see how hard is the terrain to drive.

1 hour ago, Krxlion said:

Are you planning to put some kind of car body on it, or is it called "finished" in this state?

I'd say that the chassis is finished and the bodywork is in progress. It's all about 3D printing a few panels as I don't want to buy them.

6 minutes ago, HorcikDesigns said:

Do you have the version with ball bearings and diff lock, or without? Do you use sone lubricant in them? 

Yep, they're the with ball bearings and for diff lock, but I don't have diff lock since my idea with the SG90 servo to lock them haven't worked. Gears were skipping and it's plastic so it can break and you drive it with a thought in mind that it will soon break. I've showed my idea on this forum in this topic before.

[vergogneless]

17 hours ago, Krzychups said:

Today I was in a forest with my crawler. Here are some photos and films. 

It has live axle suspension with the Panhard rod at the rear and 98 mm diameter tires The final reduction is about 1:48,5. I use my custom reduction for the A2212 motor (this one is 1400 kv) and a transfer case. It has no diffs. The RC servo is used for the steering instead of the geekservo. I decided to use this one because I had had some problems as skipping gear on the gear rack and the whole steering was placed low so the ground clearance wasn't good. I've modified one of HorcikDesigns' live axle part to mount it. For the hardware parts I use a 3S battery and the AM32 40A ESC. I really like how it performs, it does serious offroad. 

 

Unfortunately, I've melted one axle by trying to climb that steep hill in the photo above :/

In conclusion, a lot of 3D printed parts and fun! 

PS. I'm sorry that I haven't finished the differential case yet.

Really impressive! It looks very performant, and despite the camera angle, I think I can see that these slopes are really steep. 

As a big fan of modifications and alternative parts, it's a treat to see a project like this and it makes me want to move to larger scales indeed 

No metal parts here? Maybe carbon fiber axles? How much does this beast weigh? 

And I wonder if there's a way to get your custom reduction for the A2212 motor? Have you thought about reproducing and selling it?

[Lixander]

Sooo......in the next month, I am planning to test a new model with about the same hobby-grade electronics (1x Geekservo, 1x SkyRC Leopard V2 3650 3.300KV brushless motor + 60A ESC, powered by a 2S 2.200mAh Li-Po) that I used in my past Skunkworks models (the fairly successful RC mod of Apachaihapachai`s Sprite retro buggy, the  RC-E buggy, the RC-E REVii buggy and the Sprite EVO buggy).

The new model uses the experience I had with the other Skunkworks models, as it is designed to have metal U-joints instead of the new CV-joints (that proved to be also weak for the brushless power) and to have a fairly large gear ratio without using the planetary wheel-hubs (which also proved to be a bad choice when used with a hobby-grade motor; anyway, the gear ratio is around 11:1 and it is made by 2x pairs of 12/40t gears).

While it reuses most of the front-axle of the RC mod Sprite retro buggy and has about the same suspension arms as the Sprite EVO buggy, I went with a new approach for keeping the front suspension arms in place and also made a completely new rear-axle.

As for the independent suspension and the weight, the model uses 2x hard 6.5L shocks for each axle (so 4x in total), but for the rear, the small shocks might be too soft for the 765 g / 1.7 lbs of the model (without the electronics).

Also, for the aesthetics, I went with modified versions of the detachable bodywork and wing found in my RC-E EVO buggy.

Moreover, if everything goes as intended, I might go for the power of a 3S 3.200mAh or 5.000 mAh Li-Po and switch the motor with a Robitronic Razer ten G2 3652 4.000KV motor + 60A ESC.

Edited June 15 by Lixander