Krxlion

Brushless motors in the lego world - general topic

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Well done @Krzychups. I am so happy that someone from my own country is doing so much stuff with Lego Technic and now I can see that you are also moving towards the dark side of 3rd party components, haha. :D From my experience A2212 motors are more than enough for Lego Technic usage, more power might simply not hold other Lego components (if we are talking about pure Technic model and only power source with electronic is the only 3rd party component). Regarding your gearbox I believe going with planetary setup might be better. Just look at MaxBrix YT video. He powered old PF XL motor case with even stronger motor than A2212:

This man is very close to ideal motor (at least for me) - 1200-2000 RPM, but those RPMs are build with a lot of torque. What we would need to even spice things up is ESC with possibility to slowly speed up the motor, so we could create also crawlers with brushless motors. @gyenesvi mention about that part in different topic. :)

I want to also highlight the great advantage of A2212 motors (or similar to those) - those are 14-poles motors, which means you have more precise control instead of 4-pole, like the one in film above or those ZENE is advertising. I don't say those are bad (I have two of those) but in precise control of maybe offroad vehicles it makes more sense to go with as many pole as you have.

PS The shaft on the A2212 can be reversed, although you would need to create that little groove to hold the motor housing. Nevertheless, sometimes I go without it.

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On 1/12/2024 at 7:26 PM, FriedlS said:

That is crazy. Maybe your geek servo is faulty.

Look here:

 

 

I tried 2geek servos  i bought them from aliexpress...

Your setup looks great. I am waiting for new receiver and brushless esc and motor i hope servos are not faulty 😅

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4 hours ago, Ryokeen said:

But you might consider making that mount as closable parts. So that the gears are sealed from the outside. That way you prevent stones/sand getting in and also make it possible to have some lube in those gears without it flying around.

Okay, I'll try to do that.

2 hours ago, Krxlion said:

This man is very close to ideal motor (at least for me) - 1200-2000 RPM, but those RPMs are build with a lot of torque. What we would need to even spice things up is ESC with possibility to slowly speed up the motor, so we could create also crawlers with brushless motors. @gyenesvi mention about that part in different topic. :)

 

I don't have XL PU motor. 1200-2000 rpm is too slow for me. That's why I have 2200 kv motor. The planetary gearbox is interesting but difficult to make and print (or not?). On aliexpress you can find metal planetary gearboxes, maybe something can be done with them. I also know that @Daniel-99 use planetary gearbox in his projects, I wonder what his opinion is. This is just the beginning, I'll see what I can do :) 

 

3 hours ago, Krxlion said:

PS The shaft on the A2212 can be reversed, although you would need to create that little groove to hold the motor housing. Nevertheless, sometimes I go without it.

Nice to know. But how do you "go wihout it"? 

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1 hour ago, Krzychups said:

Okay, I'll try to do that.

I don't have XL PU motor. 1200-2000 rpm is too slow for me. That's why I have 2200 kv motor. The planetary gearbox is interesting but difficult to make and print (or not?). On aliexpress you can find metal planetary gearboxes, maybe something can be done with them. I also know that @Daniel-99 use planetary gearbox in his projects, I wonder what his opinion is. This is just the beginning, I'll see what I can do :) 

 

Nice to know. But how do you "go wihout it"? 

Let's take 1200 RPM as example:
If you calculate that by with wheel diameter (107mm) you can get around 24km/h and this is just a beginning. With 2k RPM and using 3s batteries the speed would skyrocket.

Regarding "go without it", I meant that small metal brass that fill the grove so the motor case would not slide from the interior of A2212.

Edited by Krxlion
forgot to input wheel diameter

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Hello, at the moment it looks like this:

53489209295_f6d373d8f3_c.jpgphoto_2024-01-26_17-23-31 by Krzysztof Czech, on Flickr

53489098294_076a246f4e_c.jpgphoto_2024-01-26_17-23-25 by Krzysztof Czech, on Flickr

53487895787_0eb74d883a_c.jpgphoto_2024-01-26_17-23-18 by Krzysztof Czech, on Flickr

I haven't printed it yet. It's not possible to use 24:24 gear ratio.

On 1/21/2024 at 10:22 PM, Krxlion said:

Let's take 1200 RPM as example:
If you calculate that by with wheel diameter (107mm) you can get around 24km/h and this is just a beginning. With 2k RPM and using 3s batteries the speed would skyrocket.

Okay, I partially agree with you. I use smaller wheels :)

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26 minutes ago, Krzychups said:

Hello, at the moment it looks like this:

Can you explain how it's expected to be used? Where do you attach the motor (at the top?), what form factor fits, and where will be the output shaft (in the middle?) If the output is in the middle, is it going to be usable in AWD vehicles? (I'm afraid the shaft will be very high, not at the bottom, and it does not seem impossible to lower it)

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34 minutes ago, gyenesvi said:

Can you explain how it's expected to be used? Where do you attach the motor (at the top?), what form factor fits, and where will be the output shaft (in the middle?) If the output is in the middle, is it going to be usable in AWD vehicles? (I'm afraid the shaft will be very high, not at the bottom, and it does not seem impossible to lower it)

At the moment it's possible to use it when you use 11950 wheel hub or similar (the distance between the axle and the ground is 3L, look at the photo). It's possible to use 8:40 or 12:36 ratio. You can use it in AWD models. To fix the gear you have to use the @janssnet method.

53488928856_fb3fb1734d_c.jpg20240119_172050 by Krzysztof Czech, on Flickr 

53489344470_827205afdf_c.jpgmotor by Krzysztof Czech, on Flickr

Edited by Krzychups

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15 hours ago, Krzychups said:

At the moment it's possible to use it when you use 11950 wheel hub or similar (the distance between the axle and the ground is 3L, look at the photo). It's possible to use 8:40 or 12:36 ratio.

Oh, I see, thanks. I was afraid of this; it does not really work in live axle models, where that would mean a huge gear (and its protective housing) sticking out in the middle of the chassis (it's even sticking out quite a bit between that independent suspension). Such a down-gearing towards the bottom is kind of out of the question in such cases. Also, it's not even possible to raise the whole motor by two studs and gear the driveshaft two studs lower, because the huge gear is in the way for a lower shaft as well. It think for such models, planetary reduction is the way to go.

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So is it possible to solve the problem? Can you show it on photos? Its better to understand. I dont want to use a  planetary gearbox - its hard to find one that fits perfectly with the a2212 motor.

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5 hours ago, Krzychups said:

So is it possible to solve the problem? Can you show it on photos? Its better to understand. I dont want to use a  planetary gearbox - its hard to find one that fits perfectly with the a2212 motor.

Well I imagine something like Zene is doing (I guess you’ve seen that thread). Sure, that’s a different form factor for the motor (inrunner, not outrunner). But the end result fits into a 3x3 space (not considering the length), which means you can make any regularly spaced gearing downwards and route a drivetrain under the motor, which is the most straightforward way to build it.

But yes, I agree that a planetary gearbox is harder to find. I’ve seen someone experimenting with 3D printed one on instagram (also 3x3 form factor). Another option could be somehow reusig the housing and gearbox of an L or XL motor (get a cheap one from Ali). I have been thinking whether the front part of an XL housing could be attached to an A2212 motor somehow.. Or even better, to fit it entirely inside. I think the length (of a shorter one with lower kv) might even fit, the problem is more the attachment.. and also the cabling may be in the way

Edited by gyenesvi

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9 hours ago, gyenesvi said:

Well I imagine something like Zene is doing (I guess you’ve seen that thread). Sure, that’s a different form factor for the motor (inrunner, not outrunner). But the end result fits into a 3x3 space (not considering the length), which means you can make any regularly spaced gearing downwards and route a drivetrain under the motor, which is the most straightforward way to build it.

But yes, I agree that a planetary gearbox is harder to find. I’ve seen someone experimenting with 3D printed one on instagram (also 3x3 form factor). Another option could be somehow reusig the housing and gearbox of an L or XL motor (get a cheap one from Ali). I have been thinking whether the front part of an XL housing could be attached to an A2212 motor somehow.. Or even better, to fit it entirely inside. I think the length (of a shorter one with lower kv) might even fit, the problem is more the attachment.. and also the cabling may be in the way

I have tried fitting A2212 motor inside the XL PF motor. It could be done I believe, but there are few buts:
1. Ventilation of the motor (you would need to drill some holes in XL motor case)
2. Housing inside the XL motor case (it was kinda woobly for me, but it could use more work)

I could give it a second try, because I have some spare XL motors, which are third party, but I am afraid I would need some 3d printed parts inside to fit it in XL motor transmission correctly. ;)

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On 1/31/2024 at 8:30 AM, Krxlion said:

I have tried fitting A2212 motor inside the XL PF motor. It could be done I believe, but there are few buts:
1. Ventilation of the motor (you would need to drill some holes in XL motor case)
2. Housing inside the XL motor case (it was kinda woobly for me, but it could use more work)

I could give it a second try, because I have some spare XL motors, which are third party, but I am afraid I would need some 3d printed parts inside to fit it in XL motor transmission correctly. ;)

Yeah, I was considering exactly the same potential problems. I think that adding some 3d printed parts inside to fix the motor inside the case could be okay, I mean those 3d printed parts would not be visible, and they would only support the motor, so they don't need to be friction resistant or anything I guess. I'd even be okay with holes drilled on the side for ventilation. And I guess the cable routing would also need extra holes.

Another option is to 3d print the whole back section of the housing, in a way that it can accept the motor properly fixed, and with holes for ventilation / cable routing.. :) The important is to reuse the front section of the housing to obtain the planetary gears and to have good mounting points at the front. With a reprinted back section, even the rear mounting points may be improved.

Edited by gyenesvi

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Remember that the motor must have 2 mm shaft - a2212 has 3.17 mm.

My mouldking servo motor is glued so I can't take it apart. I don't know if other motors from aliexpress are glued.

Edited by Krzychups

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4 hours ago, Krzychups said:

Remember that the motor must have 2 mm shaft - a2212 has 3.17 mm.

My mouldking servo motor is glued so I can't take it apart. I don't know if other motors from aliexpress are glued.

It doesn't really matter, you can always drill slowly a bigger hole in the metal gear. I could fit it nicely in a A2212 shaft, but the motor is simply too big, no matter what I do I wouldn't fit it in the XL motor case. I would need to cut the back of the XL motor case like in the MaxBrix video. :/

It is weird that your motor is glued :O I have one servomotor from mouldkind and I could take it apart.

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Also, have you thought putting the motor housing in the center of the model rather on its rear axle?

Something like this

Screenshot%202024-02-01%20210304.jpg

Edited by Lixander

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1 hour ago, Lixander said:

Also, have you thought putting the motor housing in the center of the model rather on its rear axle?

Something like this

Screenshot%202024-02-01%20210304.jpg

Hi @Lixander,

I do not know if you are refering to my comment, but we were talking about fitting A2212 brushless motor inside XL motor case, including planetary transmission. Based on my experience it is pretty much impossible to do without cutting the back of it, but I would be more than happy to be wrong. :D

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23 minutes ago, Krxlion said:

Hi @Lixander,

I do not know if you are refering to my comment, but we were talking about fitting A2212 brushless motor inside XL motor case, including planetary transmission. Based on my experience it is pretty much impossible to do without cutting the back of it, but I would be more than happy to be wrong. :D

Sorry for not mentioning :/ ...............you have to modify a lot the XL to fit that drone motor, so you are not wrong ;)))
Also, I referred to the position and gearing of the motor housing that Krzychups, Gyenevsi and you were debating

And, as a kind of a side note - I thought some time ago to modify the buggy motor (cutting the area where the actual motor is and adding a RC motor with the help of some 3D parts; I would have used the ”usual” 540 or 550 brushed motors or their brushless brothers).

 

Edited by Lixander

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The idea to fit a A2212 motor in an XL housing is nice, but i'm not sure how well the gears will hold up in the long run.

Btw, as wheelhubs seem to be another problem i thought i share some of my findings.
So far some tamiya parts, mainly the wheelhubs fit quite well. They can be mounted by m3 screws and are about 1 1/2 studs wide at the mointing points. Also they are quite cheap.
IMG_20240124_170857.jpg
For the balljoints Amewi HSP 02038 fit well, their heads are 6mm along with a m3 screw at the bottom and give about the same range of motion as lego towballs.
IMG_20240124_171045.jpg
As an example, this is a tamiya front wheelhub from m-06 ra series(without the axle holder part), with the Amewi balljoints. I have some spacers in there as i would have to shorten the screw part of the balljoints.

IMG_20240131_162449%20-%20Kopie.jpg

So far the only thing missing is an dogbone to lego axle adapter, but for that i already have some rough cad designs and are just looking for a way to get them validated and manufactured.

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3 hours ago, Ryokeen said:

For the balljoints Amewi HSP 02038 fit well, their heads are 6mm along with a m3 screw at the bottom and give about the same range of motion as lego towballs.
IMG_20240124_171045.jpg

I never thought this will fit well. That's shock to me.

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I have an idea to make segments: steering on the front (camber adjustment and toe in, toe out, rc shocks) and rear of the car like in real rc cars and make adapters for lego bricks. It's hard to say if I'll succeed, I wonder if I'll go for a fully printed chassis. I need to ask people who have real rc cars if there is a chance to do the rear segment (if the parts will not be too expensive).

Possibly in the future I'll look into 4 wheel drive, although it's hard to say if I'll succeed. For now, this is just idea.

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@Krzychups if you go for the complete rear assembly, with the suspension arms and differential housing, you are very limited as you will have trouble changing the width of a vehicle or sometimes even the ride height. And at that point you might as well just use a full rc car chassis and just slab a brick body on it.
That's why i went for the hubs only so everything else can be done how i need it.
The adapter i need looks a bit like this :

2024-02-05%2015_46_32-Window.png

10mm pins can be exchanged as they are prone to wear.

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Hello, :classic:

This question is directed for @Ryokeen and @Daniel-99: which rc oil shock absorbers do you recommend? I know that I have to choose the suspension travel and the viscosity of the oil for the shock absorbers myself. I want shocks typically for buggies. With a 3d printer I've got a lot of options for attaching shock absorbers.

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@Krzychups I for myself can't recommend a specific brand. But i look for total width, so that it's max 2 studs wide, reviews about how likly they are to leak, a shaft of at least 3mm diameter and spring adjustments via a thread and not plastic spacers. Else maybe look it they are used as replacement parts in a similiar type or car that you want to build. Cause what often isn't stated or at least i never found it, is how big the holes in the shockabsorber are. You know the moving disc inside that builds the resistance against the oil. Cause i have some slim line shock absorbers that are pretty good, except that the holes are so small that even 100cps/cst oil is to thick for them to properly extend in less than 3 secs :D

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Posted (edited)

Hey everyone! Just wanted to mark the 1st year anniversary of this thread and share some thoughts at the same time! :pir-triumph:

I really appreciate y'all sharing your experiences with RC and Lego! I am currently in progress of building my own RC/Lego vehicle. I have purchased some wheel hubs from TF Engineering just like @vergogneless and @aFrInaTi0n did and might be getting some technic beams/frames with bearings (like what @Krzychups has designed) and some other similar parts to ones y'all have mentioned (like wheel hubs) from a Russian guy. I have a 3D printer of my own and have experience with Autodesk Inventor so I have designed my own parts and will be designing more similar to what y'all have already done. Also, I agree with you @gyenesvi, I think planetary reduction is going to be the name of the game here...

Edited by Fluwoeb

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Posted (edited)

I dont know if it is worth bothering you with a separate topic for my idea, so I will post it in here.

I want for some while to put a RC 550 brushed motor or its brushless counterpart in Lego off-road models but I never could achieved it because of the lack (in my opinion) of options for transmitting the power of a RC motor to the wheels, as the metal axles and other metal parts (excluding the universal joints) are expensive and modifying RC parts takes a lot of time and it is really hard.

So I thought of making a project which wants to offer 1x motor adapter, 2x metal-geared differentials, 1x central drive-shaft, 4x drive-shafts, 2x rear wheel-hubs and 2x front wheel-hubs. As I didnt managed to make a prototype, I dont know the approximate price.

The motor adapter is thought in fact to be a transmission with 3x outputs with ball-bearings, metal gear reduction and central differential. The drive-shafts (the central one being for the 4x4 drive-line and the other ones are for connecting the differentials to the wheel-hubs) are similar to the RC ones but more compact. The wheel hubs are basically modified 23801c01 for the front and 65766c01 for the rear with ball-bearings and custom connections with the center of the universal joint just at the exit of the wheel-hub.

I still need to find someone that can help me with finishing the design of all the parts and to also source all the parts I can from RC hobby-shops. Unfortunately, I hope that the prototype will start taking shape in the summer. 

Also, I made a short questionnaire for seeing the response to such an idea - https://docs.google.com/forms/d/e/1FAIpQLSfUfz95Xrt-eZBQqmmQ5n-T5FaI0tJ_LK-Sa5sWSxsIwK8qLA/viewform?usp=sf_link

Edited by Lixander

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