lego 6x6 banana gear turntable

[sammypants]

Hi yall, I'm working on making a mobile crane and am trying to design a turntable using the 15 tooth banana gears (part no 78442) and 1x1 round tiles but I cannot for the life of me figure out how to constrain the upper gear.

 

After all my searching, the best I've found is either this joint using the same idea of banana gears and 1x1 tiles,

or this turntable that doesn't appear to do anything about the gap made by using the 1x1 tiles as bearings

Both of those are also for the larger banana gears instead of the smaller ones and likely wouldn't work as well in a more space constrained space.

Any ideas?

[roeltheworld]

Check out the card tank: 

 

It uses train wheels in a frame between two 'banana gear circles', that are connected with a large turntable.

[sammypants]

53 minutes ago, roeltheworld said:

it uses train wheels

problem is, I don't have train wheels otherwise i probably would have tried that

[sammypants]

if I do want to get some of those, what part number are the wheels?

 

edit: they're part number 50254

Edited August 2, 2024 by sammypants

[Lego Tom]

Interesting build! Reminds me of the old carnival "Tilt and Whirl" aka "Tilt and Puke".

[ord]

It's an interesting problem @sammypants and one I have been scratching my head at too. Having built Akiyuki's design (first video), I think it's possibly the best solution - it runs smoothly and is the most rigid design that I've built.

The design in the second video is easier to build and remains in-grid, but doesn't have the upper gear form-locked below the lower gear, so is less rigid.

I'm not sure how either design would go with the smaller banana gears, but would be interested to see! 

[ord]

I built a bearing based on Akiyuki's design but with the smaller banana gears and it works well:

I even managed to pass two axles through it. I think I'll be incorporating this into my robot arm as it seems very rigid.

[aeh5040]

10 hours ago, ord said:

I built a bearing based on Akiyuki's design but with the smaller banana gears and it works well:

 

This looks really useful! It would be nice to have a version that works with the in-grid train wheel bearing (if that's even doable with the small bananas).

[ord]

7 hours ago, Vinceres said:

Thats insane, how did you figure out the programming to make it all move simultaneaously?

Again, I learnt from the great Akiyuki:

 

48 minutes ago, aeh5040 said:

This looks really useful! It would be nice to have a version that works with the in-grid train wheel bearing (if that's even doable with the small bananas).

I was looking into this last night. The train wheels don't stand up on their own so I think they need a carrier ring connecting them together. Maybe only four wheels could fit on such a ring, which might compromise performance. Also, the 1x1 tiles do a surprisingly good job at providing radial support, but the train wheels not as much, so the bearing might require extra support if using the train wheels. I will build one and see...

Edited August 15, 2024 by ord

[roeltheworld]

Here is the design of the ring from the aforementioned card tank:

https://www.mediafire.com/file/xgtux1ciluvp3gd/ringa_2.png/file

https://www.mediafire.com/file/0lzfd5po2ob4v9i/ring_bearing.io/file

It shows how the train wheels are suspended between the rings.

Hope it helps