896gerard

[NEW PART] ≥3 drive axles through a Lego Technic turntable | The fin

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Only two axles through a Lego turntable (the 48452cx1) has always irritated the more experienced Technic builders, stimulating them to work out many different solutions. Actually, some really clever solutions have been found, but most of them cause too much friction or require too much space. I have succesfully tried to do an attempt too, thanks to 3D printing and a good friend, he designed the CAD model of my solution. I can say that my solution has low friction and consumes much less space in comparison to the existing solutions. More of the story and some more pictures can be found at http://mocpages.com/moc.php/419288

I have made an elaborate video about the problem and the process, but I think it will be 6 well-spent minutes. At the end of the video, there is another big surprise... Something that never was possible, is possible with the new parts!

http://youtu.be/1OsSGkDsgXs

To get a better idea of the part, you can find some photos here:

All photo's can be found on: http://mocpages.com/moc.php/419288 in a higher resolution.

turntable896gerard.png

The CAD drawing assembly:

thepart.png

This design is extenable to bigger versions, I think that up to 5 or 6 axles would fit through the turntable. The only problem is connecting all gears in a robust way: to 'get to the gears', the outer gears have to get a bigger diameter and the problem of space-consumivity is back. I found that the three axle design really was a good optimization between robustness, way of accessing the gears and maximum transported torque through them.

It is my hope that the Lego group takes over this idea and starts producing it, because especially the three-axle option ore the two-axles through the small turntable could be very useful in an upcoming Lego flagship. So, if you happen know someone at the Lego Technic department, please give him/her a good impression of the idea!

Edited by 896gerard

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I was literally watching this video while you were posting it. I LOVE THIS!!! Great design, and very compact. Nice job

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I noticed on the initial demonstrator that the outer items rotated when the turntable did, but I couldn't tell if that was still occurring on the crane with the additional resistance. In other words, was the boom extending or the hook lowering just because the turntable was rotating?

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I noticed on the initial demonstrator that the outer items rotated when the turntable did, but I couldn't tell if that was still occurring on the crane with the additional resistance. In other words, was the boom extending or the hook lowering just because the turntable was rotating?

That happens by definition, when the turntable makes one rotation and the drive axles are at standstill, the two drive axles that go through the 16t gears have to make one rotation too. However, if the drive axle is slowed down enough, the effect of one rotation is barely noticeable, as you can see with the crane.

Edited by 896gerard

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Really great design! Love the simplicity. Have you made this available on any site like Shapeways yet?

Yes, it looks simple, but like all things that look simple also this design required a lot of thinking.

No, it is not my idea to 3D print it on a massive scale. it should be done by the Lego Group.

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Great presentation. The idea with the small turntable is just great. Non the less, it's basically the same part Alasdair Ryan came up with about 3 three years ago. He sold a couple of those via BrickLink for testing purposes.

Edit:

Here the Topic:

http://www.eurobrick...+driving +rings

I developed my idea entirely independent of him. In fact, this is the first time I saw the part! It is NOT basically the same part, as the part of Alasdair Ryan still has the delays (because of the standard clutch gear fittings) ánd it fills all space in the turntable completely, not allowing for any more axles. My design allows for more axles.

IMAG0034_zpsc29161b8.jpg

To be fair, this design looks as if it can have way less torque than my solution. Especially the 20t-12t gear connection will not be able to handle a lot of torque without slipping. My solution has the real 16t gears with long teeth.

In my design, the outer shaft connects through 16t gears. In the video you can see how much torque even that shaft could transfer: it drove the crane's heaviest function, lifting the boom, without problems.

Edited by 896gerard

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@ 896gerard

My apologies - i didn't intend to offend you nor sound rude nor play down your efforts. It's a great prototype. I was just thinking that i saw something like you part before.

Both solutions seems to have their advantages: Alasdair Ryan's driving ring is a "1-Part"-Solution, allowing the use of the driving ring extenders.

Your solution has far less backlash and fits through a small turntable.

Could you show us your solution with a fourth axle? I'm curious. Won't it get to flimsy, especially when it comes to bracing the gear connections?

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That happens by definition, when the turntable makes one rotation and the drive axles are at standstill, the two drive axles that go through the 16t gears have to make one rotation too. However, if the drive axle is slowed down enough, the effect of one rotation is barely noticeable, as you can see with the crane.

If you want the peripheral gears not to need to rotate with the turntable then this is one way to do it:

technic1_m_bellis_us8096106.jpg

The tan cog on the right is the reference in the rotating frame, relative to the frame that is static.

The yellow cog on the left is where the pitch change motor would be.

The pitch of the 2x6 plate "propeller blade" remains constant as the tan cog rotates, until the yellow cog rotates to change it.

When the yellow cog rotates it moves an idler gear around the left turntable, relocating the chain on it and stepping the peripheral drive relative to the rotating frame reference.

During this time the parallelogram flexes to accommodate the chain movement. Other methods are explained in the patent US8096106.

In effect the propeller blade pitch has a stepped position control.

On this model the worm provides a no-back mechanism to take propeller pitch force off the mechanism.

It would be easy enough to add several more blades around the circumference to make a full propeller.

The small mechanism at the top is the prior art - the state of the art before I moved it forward.

An essential novel element of the patent is the continuous rotation of the chain with the rotating frame of reference.

Mark

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If you want the peripheral gears not to need to rotate with the turntable then this is one way to do it:

technic1_m_bellis_us8096106.jpg

The tan cog on the right is the reference in the rotating frame, relative to the frame that is static.

The yellow cog on the left is where the pitch change motor would be.

The pitch of the 2x6 plate "propeller blade" remains constant as the tan cog rotates, until the yellow cog rotates to change it.

When the yellow cog rotates it moves an idler gear around the left turntable, relocating the chain on it and stepping the peripheral drive relative to the rotating frame reference.

During this time the parallelogram flexes to accommodate the chain movement. Other methods are explained in the patent US8096106.

In effect the propeller blade pitch has a stepped position control.

On this model the worm provides a no-back mechanism to take propeller pitch force off the mechanism.

It would be easy enough to add several more blades around the circumference to make a full propeller.

The small mechanism at the top is the prior art - the state of the art before I moved it forward.

An essential novel element of the patent is the continuous rotation of the chain with the rotating frame of reference.

Mark

Good greif, how do you design this stuff? My head hurts just looking at it.

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@ 896gerard

My apologies - i didn't intend to offend you nor sound rude nor play down your efforts. It's a great prototype. I was just thinking that i saw something like you part before.

Both solutions seems to have their advantages: Alasdair Ryan's driving ring is a "1-Part"-Solution, allowing the use of the driving ring extenders.

Your solution has far less backlash and fits through a small turntable.

Could you show us your solution with a fourth axle? I'm curious. Won't it get to flimsy, especially when it comes to bracing the gear connections?

A Youtuber, Senti Josef, saw my idea and created the four axle solution in about 1 evening. That shows how scalable the idea is:

throughturntable2.jpg

throughturntable1.jpg

As you can see, the 4-axle solution has an even better quality than my own parts! Because the gears are so tight together, I think the solution is not flimsy. In the video, I show you how the 4 axles can be accessed. If this is done with 90 degrees difference for each gear, there is enough space to mount the 16t gear properly. With this solution, we need 3 16t gears around it (the 4th axle goes through it and is directly accessible), so a 5-axle solution would use 4x90 degrees, filling all the orthogonal space. That means that for a 6-axle solution, bigger gears need to be used for the outer shaft or the gears that access the part have to be 20t gears.

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