[Concept] In Search of the Ultimate Portal Hub Design

[gyenesvi]

12 minutes ago, N1K0L4 said:

No need for cutting. All ends of all axles are rounded off, which is not represented in digital programs.

I wasn't talking about cutting the axle, indeed that's rounded anyway in reality and the situation is even better than on the renders. Rather, I was talking about having an axle hole at the top where the bottom corner of the surrounding material is chipped off, like in the images. Which, when designing a new special piece, is a viable option :)

[N1K0L4]

2 hours ago, gyenesvi said:

I wasn't talking about cutting the axle, indeed that's rounded anyway in reality and the situation is even better than on the renders. Rather, I was talking about having an axle hole at the top where the bottom corner of the surrounding material is chipped off, like in the images. Which, when designing a new special piece, is a viable option :)

Ohh..., that makes more sense. :)

[SAM_KTM_304]

lego definitely should make this 

[Aurorasaurus]

As some people mentioned earlier, a version of this hub with bearings would be even better. The original might work with injection moulded parts but 3d printing them at home just wasnt an option for using this concept in an actual model. So I've started designing one with bearings. I'm using a 25x37x7 (25mm id) bearing to go around the "insert" part, so that it isn't hanging in the air or leaning too much on one side of a further back bearing. Then I'm using 5x8x2.5mm bearings for all the axle and gear parts. As Zerobricks suggested earlier, I've combined the insert and the lower gear part, for simplicity and strength. I'm also using a 12:20 ratio instead of 8:24, because as we all know, 8t gears are much too weak.

The big bearing will drop into the main housing, then the insert goes in. Then, from another direction, because it would otherwise collide with the main bearing when you try put that in, a separate part with the 5x8x2.5 bearings drops in. Maybe I will have that get fixed in place with a clip or something, not sure yet. Then you put the 12t gear in, then axles, and finally the wheel.

Here's a video of the whole process in reverse. (easier to make the animation in reverse)

I can upload CAD files but this is very WIP so I haven't as of posting. Roughly sketched in black is roughly how I will do the rest of this thing, simply more parts joining onto that front ring to hold everything else, but at this stage many things can change.
I'd love some feedback, am I going in the right direction here? Is anybody else working on this/made it already?

[gyenesvi]

Nice idea, curious what comes out of it!

On 3/28/2025 at 5:06 AM, Aurorasaurus said:

I'm also using a 12:20 ratio instead of 8:24, because as we all know, 8t gears are much too weak.

I think it would be great to retain the possibility of the 8:24 ratio. For one, we often need more down-gearing for off-roaders (both to slow things down and to have more torque). Second, don't forget that only 1/4th of the whole power goes to each wheel, so those 8T gears don't need to take that much.

Also, I think the solid connectivity of the big ring and the other side is important!

[efferman]

6 hours ago, gyenesvi said:

only 1/4th of the whole power goes to each wheel, so those 8T gears don't need to take that much.

When the diffs are locked, and only one wheel has grip, this is maybe not correct.

[gyenesvi]

10 hours ago, efferman said:

When the diffs are locked, and only one wheel has grip, this is maybe not correct.

Indeed, that's true, but most of the time..

[efferman]

It really depends on the carried weight. I guess for really heavy things there is more neccessary than 3:1, or even 5:1.

[Igor1]

On 1/16/2025 at 9:13 AM, SAM_KTM_304 said:

lego definitely should make this 

Today we can finally write that Lego really did it!

[Aurorasaurus]

Finally, after many tries, I have a completely working prototype with bearings!

So, lets talk about what changed from my initial plan.

Main bearing
Initially, I wanted the big bearing to be able to be removed from the hub easily. But it just proved too difficult to design, and not worth the far increased complexity. So, I went with the option to put the bearing inside a part that holds it while 3d printing, so that it becomes trapped inside. This part will be strong enough. It takes drifting on pavement with a brushless model to break a smaller amount of plastic. This will be plenty strong for slow models. How do you do it? Once you put the parts into your slicer and slice it, use the layer preview slider to go to the last layer before you can no longer drop the bearing in. Then add a pause, once you print the printer will stop automatically and you can drop the bearing in place! Then just continue the print and everything will work fine.

The main body of the hub looks really scary to print, but at least on my printer it was super easy! I let my slicer auto orient it and it turned out perfectly. The holes for the small bearings are not as deep as the bearings so they stick out to ensure the gears never rub against the walls.

The insert part has changed a bit since the original plan too. Now, it has 22 teeth, for a higher gear ratio and an astounding 1mm of extra ground clearance! Wow! The slicer thinks it should print with support, but it doesn't need it at all.

And finally, a video of the hub and how it all goes together.

STL files: https://bricksafe.com/pages/Aurorasaurus/miscellaneous/ultimate-portal-hubs-/with-bearings/first-successful-version

[N1K0L4]

Awesome work! Interesting to see from what it evolved :)

What material did you print it in?

[2GodBDGlory]

That's super cool, and looks well thought-out! I look forward to seeing what you build with it

[Aurorasaurus]

10 minutes ago, N1K0L4 said:

Awesome work! Interesting to see from what it evolved :)

What material did you print it in?

Thank you, its been a bit of a rollercoaster, getting overwhelmed with it and such. Its just printed in PLA+

7 minutes ago, 2GodBDGlory said:

That's super cool, and looks well thought-out! I look forward to seeing what you build with it

Thank you! I'm thinking a land rover... but we'll see.

[Zerobricks]

Amazing concept @gyenesvi what I would do is simpy integrate towball into the hub and increase the hole to accept the larger, stronger CV joint. You can also use LOTR rings or bushes on 3,2 mm axles for bearings. 

[gyenesvi]

2 minutes ago, Zerobricks said:

Amazing concept @gyenesvi what I would do is simpy integrate towball into the hub and increase the hole to accept the larger, stronger CV joint. You can also use LOTR rings or bushes on 3,2 mm axles for bearings. 

Which version do you mean? The original design or the ball bearing variant of @Aurorasaurus?

Great progress @Aurorasaurus! I like the way it's made up of those parts and bearings, looks solid enough. Maybe the mounting points could be moved around a bit, for example the lower one could be lowered, so that it joins the axle from below, that way it could be more stable, and the axle itself could have more ground clearance.

Curious how it behaves in an RC model!

[Zerobricks]

1 hour ago, gyenesvi said:

Which version do you mean? The original design or the ball bearing variant of @Aurorasaurus?

Was lookind at the deisgn from October.

Edited April 5 by Zerobricks

[gyenesvi]

4 hours ago, Zerobricks said:

Was lookind at the deisgn from October.

Then I guess you are talking about the second, simplified version, which is more similar to the currently existing Lego portal hub (because the primary design had the towball integrated and accepts a large CV joint too). So indeed, it would be possible to make the second design as well as it is in the first one, but the key idea there was to keep the option to use towball-axle or axle-pin at the top, so that a solid axle can also be built compactly, without needing to use towball socket liftarms, which need more space in the axle and are more complicated to integrate.