Brushless motors in the lego world - general topic

[gyenesvi]

Interesting idea, I'd like to see that problem solved. But there are some details in your plans that I don't understand.

12 minutes ago, Lixander said:

1x central drive-shaft, 4x drive-shafts

I guess I kind of get where these would fit, and what they would connect, but not exactly how. What is their length? Fixed or variable (swappable)? Do they include joints on the ends? Or is that separate?

12 minutes ago, Lixander said:

The motor adapter is thought in fact to be a transmission with 3x outputs with ball-bearings, metal gear reduction and central differential.

Why are the 3 outputs required? And why is a central differential required? We practically never build that in lego (RC) cars (just makes it worse offroad), and I think most RC cars don't have that either (many 4x4 offroaders don't even have axle differentials either, just locked).

12 minutes ago, Lixander said:

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 think we have already concluded in some thread that that's not possible physically due to lack of space; the U-joint would collide with the pinholes on the hub when the joint is articulated up/down. Only CV-joint would fit in there as for that the female part remains stationary and so it does not collide with the pinholes.

12 minutes ago, Lixander said:

I hope that the prototype will start taking shape in the summer. 

Unfortunately, before seeing some prototypes, it is hard to say anything more concrete, as the devil is in the details.

And I guess you'd use ball beared diff frames and beams as well but you consider those available already.

[Lixander]

1 hour ago, gyenesvi said:

I guess I kind of get where these would fit, and what they would connect, but not exactly how. What is their length? Fixed or variable (swappable)? Do they include joints on the ends? Or is that separate?

The way I thought the drive-shafts should have a variable length and  come with the joints at each end.

1 hour ago, gyenesvi said:

Why are the 3 outputs required? And why is a central differential required? We practically never build that in lego (RC) cars (just makes it worse offroad), and I think most RC cars don't have that either (many 4x4 offroaders don't even have axle differentials either, just locked).

I thought the pack more for short-course trucks, but I guess it will be easier and more convenient for everyone if there is no central differential.

1 hour ago, gyenesvi said:

I think we have already concluded in some thread that that's not possible physically due to lack of space; the U-joint would collide with the pinholes on the hub when the joint is articulated up/down. Only CV-joint would fit in there as for that the female part remains stationary and so it does not collide with the pinholes.

I am not sure we are speaking exactly of the same thing.......what pin-holes the joint would hit? And also, I will see what they will look to prevent anything grinding or hitting.

1 hour ago, gyenesvi said:

Unfortunately, before seeing some prototypes, it is hard to say anything more concrete, as the devil is in the details.

And I guess you'd use ball beared diff frames and beams as well but you consider those available already.

Yup :/

And the differentials will come in a case with pin-holes something like Zene did.

I will post later during the day a Bricksafe link to a PDF with some drawings and some explanations I did some days ago.

Edited March 21 by Lixander

[gyenesvi]

1 hour ago, Lixander said:

I am not sure we are speaking exactly of the same thing.......what pin-holes the joint would hit?

That pinholes on the top/bottom of the hub you use to mount them. If the U-joint has the flex point right in between the two pinholes (where it has to be to steer and articulate properly), then as it must tilt upwards for an independent suspension, it will collide with the pin you insert in there (and the support structure to hold the pin). You can try it in Studio.

[Lixander]

4 hours ago, gyenesvi said:

That pinholes on the top/bottom of the hub you use to mount them. If the U-joint has the flex point right in between the two pinholes (where it has to be to steer and articulate properly), then as it must tilt upwards for an independent suspension, it will collide with the pin you insert in there (and the support structure to hold the pin). You can try it in Studio.

I think I can see what you mean.

I thought the design of this type of wheel-hub is the same with the one which has the axle holes.

But anyway, thanks!

 

[Ryokeen]

So in an attempt to get a proper AWD into my next project i designed(with some help) an adapter and the machined parts today arrived. So far it all fits and should work with any RC hub that uses dogbones with an end diameter of 6mm and 2mm thick pins.

This is the adapter part(pins will be inserted later as they tend to wear out). The it can be directly connected to any lego axle hole, means axle connectors, u-joints and so on.


This is how it fit's into RC wheel axles/hubs:
 

Spoiler

And some small testbuild for a driven and steered axle:

Spoiler

P.S.
if anyone wants to have the cad file and specs i can upload them.

Edited March 23 by Ryokeen

[2GodBDGlory]

Cool project!

[gyenesvi]

11 hours ago, Ryokeen said:

And some small testbuild for a driven and steered axle:

Interesting to see that the steering pivot is not aligned with the suspension pivot in that RC wheel hub (the steering pivot being one stud further out). Is that common in RC hubs? Can RC driveshafts follow the change in length during articulation (can the axle slide in and out somewhere)?

[Ryokeen]

6 hours ago, gyenesvi said:

Interesting to see that the steering pivot is not aligned with the suspension pivot in that RC wheel hub (the steering pivot being one stud further out). Is that common in RC hubs? Can RC driveshafts follow the change in length during articulation (can the axle slide in and out somewhere)?

Yep a lot of RC 1:10 models have hubs made this way. I assume they try to avoid balljoints on those parts(some larger 6s models do use balljoints but they are big enough for that). The dogbone shaft that are normally used to have play in it to move a bit in and out. Normally there are small O-rings in the pan part so account for that.

[Bensch55]

On 3/24/2024 at 9:03 AM, gyenesvi said:

Interesting to see that the steering pivot is not aligned with the suspension pivot

Not really something new, that is a way to achieve Ackermann steering geometry, even present in your real car. It's often easy to implement in MOC's too, but for some reason Lego fears advanced suspension/steering setups.

[gyenesvi]

1 hour ago, Bensch55 said:

Not really something new, that is a way to achieve Ackermann steering geometry, even present in your real car. It's often easy to implement in MOC's too, but for some reason Lego fears advanced suspension/steering setups.

I don't get how the suspension pivot has anything to do with Ackermann geometry; they rotate in orthogonal planes. I think you misunderstood what I'm talking about (the kingpin is further out than where the suspension is hinged).

[2GodBDGlory]

3 minutes ago, gyenesvi said:

I don't get how the suspension pivot has anything to do with Ackermann geometry; they rotate in orthogonal planes. I think you misunderstood what I'm talking about (the kingpin is further out than where the suspension is hinged).

I think the idea is that you can then mount the steering link joint inline with the suspension pivot, and simultaneously mount it inboard of the steering pivot. You want to have the link pivot inside of the steering pivot to get the Ackermann geometry, and you want it to be inline with the suspension joint to avoid bump steer, so by separating the steering and suspension pivots in this way, you can have the best of both worlds

[gyenesvi]

9 minutes ago, 2GodBDGlory said:

I think the idea is that you can then mount the steering link joint inline with the suspension pivot, and simultaneously mount it inboard of the steering pivot. You want to have the link pivot inside of the steering pivot to get the Ackermann geometry, and you want it to be inline with the suspension joint to avoid bump steer, so by separating the steering and suspension pivots in this way, you can have the best of both worlds

Okay, I get what you mean, but then the Ackermann geometry is not caused by the fact that the kingpin is further out, but that the steering link pivot is inboard of the kingpin, which can be done even if the kingpin coincides with the suspension link pivot. And even though it's a nice trick to eliminate bump steer, that can simply be eliminated by moving your inner suspension pivot inboard the same amount as the outer one is moved in from the kingpin (that's what lego models do usually).

Anyway, thanks for the explanation, it is an interesting trickery. Wonder if this could be reproduced in lego, the driveshaft would have to be able to shorten in this case, which is harder to do as it means you need to leave space for the shortening, which also means that axles have space to fall out of their place..

[Aurorasaurus]

3 hours ago, gyenesvi said:

Wonder if this could be reproduced in lego, the driveshaft would have to be able to shorten in this case, which is harder to do as it means you need to leave space for the shortening, which also means that axles have space to fall out of their place..

You can use a small pen spring and a 5.5m axle with the new extendable cv on one end, so the pen spring pushes against the extendable cv and the circular part on the 5.5m axle. This applies a bit of force to keep the axle falling out. So it's doable, at least in regards to the driveshaft.

Edited March 25 by Aurorasaurus

[gyenesvi]

28 minutes ago, Aurorasaurus said:

new extendable cv on one end

Do you mean the 5L heavy duty one? With that the driveshaft will be something 10L (5L + 3L for the other joint, + at least 2L for the spring part), so the total axle with would become around 27 wide, which sounds huge..

[Aurorasaurus]

4 hours ago, gyenesvi said:

Do you mean the 5L heavy duty one? With that the driveshaft will be something 10L (5L + 3L for the other joint, + at least 2L for the spring part), so the total axle with would become around 27 wide, which sounds huge..

Its big, yes. You could cut down the pieces but then it kinda defeats the point...

[Stereo]

If the axle's the same length as the upper/lower control arms, shouldn't it work fine? The 3 joints won't be in line with each other at either end, but they move in parallel.

[Bensch55]

21 hours ago, gyenesvi said:

I don't get how the suspension pivot has anything to do with Ackermann geometry

You are right, I misunderstood you in the previous comment. It looks like they offset it just for ease of assembly, as it would be more difficult to have the horizontal pivot axis intersect the vertical pivot axis.

[gyenesvi]

16 hours ago, Stereo said:

If the axle's the same length as the upper/lower control arms, shouldn't it work fine? The 3 joints won't be in line with each other at either end, but they move in parallel.

If they can be made the same length then it can work indeed. But they are definitely not the same length on the posted picture, the axle is about 2 studs longer than the suspension arms (about 1 stud offset on both ends in the opposite direction). It would have to be brought outwards on the diff end to make it the same length.

[Ryokeen]

As said, it was just a quick test build to see if the parts fit propery. Ofc the driveshaft is to long(but will always be about 1 stud longer) but even with the setup as in the picture there is a solid 3 stud suspension travel. Unlike lego cv-joints dogbones don't click or stay in position so they can move freely in and out of the axle in the wheelhub, together with an small o-ring that gives enough play.
Once i get the needed pins and some other parts i can say more on how it performs, but for street cars or ralley ones it should work quite well and most parts are easy to replace if they break

[Ryokeen]

So finally the last parts for a proper prototype arrive and so far it all fits nicely(except that i couldn't find 35mm m3 screws :D)
So apart from the custom made adapter parts everything now can be replaced for little money. Ball bearings can be changed if worn out(Zene glues them), wheels are secured with a proper nut and almost 0 play in steering. Toe in/out and chamber(i think) can be easily adjusted but for me the biggest advantage is more wheels are and more narrow wheels. Everything with 12 hex fits. Also the pivot piont is better(not perfect) and is just on the edge of the wheel.

So far, front driven and steered(lacks servo attachement yet) axle:

How the tamiya parts are attached to lego parts. The spring adds some tension as the driveshaft needs some play. The adapter part can be seen in the wheel hub and attached to the axle connector. The axle connector is there so that different suspension arms lenghts can be used also together with the 2 3/4 axle it serves as a weak cheap link in case of an accident that can break.

Edited March 31 by Ryokeen

[killerfrost]

@Ryokeen I would like to see the specs of the metal cv joint. I’m using 1/8 wheel hubs that @ZENE has and trying to make an awd car.

https://www.zenebricks.com/collections/technics-super-speed-rc/products/lego-rc-accessories-bearing-drive-axle-compatible

id drill out the center and slide that cv setup you have in

Edited 17 hours ago by killerfrost

[Ryokeen]

@killerfrost I'm afraid that it won't work that way. The part i designed is the male part of a "cv" joint that is supposed to fit into 1:10 and 1:8 scale RC axles with the matching female part. And the female rc axle parts are 10mm in diameter with 6mm diameter space in it where the ballhead of my part fits in. That won't fit in the Zene parts as they have max 8mm of space

[killerfrost]

I’m not above modifying parts that are already aftermarket to make something work. I’ve already been able to fit the diff cup into the wheel hub. I can post pictures when I get home from work.

this is the part I got to fit with minimal modification.

https://a.co/d/7XBGO4E

Edited 10 hours ago by killerfrost

[Ryokeen]

@killerfrostIf the inner Diameter is 6mm it might fit. Send you a pm