Alasdair Ryan

ideas on 3 axle functions going though turntable?

70 posts in this topic

is there a way to get 3 axle functions though a turntable which will still allow for continuous 360 spin?

i have got some great ideas for a pneumatic excavator which i hope to biuld later this year :grin:

i have ordered new wheels for my skip truck (£50 that cost me for 10 wheels) :laugh:

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yes there is. I built it, and it would work with seven, but that would take tons of space..

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yes there is. I built it, and it would work with seven, but that would take tons of space..

How did you made it? Do you have pictures or something?

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yes there is. I built it, and it would work with seven, but that would take tons of space..

Pics or it didn't happen ;)

Because I don't see how one could do this, so if you claim to have done this, I'm very very curious and I'd very very much like to see how you did it. :)

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i see in normal sized turntables no posibilities for three functions. But if blueshinyapple shows us pics from his solution, i will call him a genius.

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It's possible in my head. If you let the third function(gears) come in on top of the turntable, and connect it to the central axle after the first function has been led to a side. Not a very practical solution though. Maybe I'll try it once. :tongue:

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It's possible in my head. If you let the third function(gears) come in on top of the turntable, and connect it to the central axle after the first function has been led to a side. Not a very practical solution though. Maybe I'll try it once. :tongue:

I don't think that would work. The arm which is connected to the third axle on top of the turntable should be able to rotate around the whole turntable, and it can only do that if the arm completely surrounds the whole model.

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If the functions are really low torque, you could use a flex cable through a flex tube through a driving ring. But I'm guessing this is not what you want :classic:

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I don't think that would work. The arm which is connected to the third axle on top of the turntable should be able to rotate around the whole turntable, and it can only do that if the arm completely surrounds the whole model.

I'm not sure if I get what you're thinking of, but the arm used to get the third funcion onto the central axis will be fixed to the chassis. You would have to place the superstructure above the entire installation. This means a very tall and therefore impractial solution, but I still think it's theoretically possible.

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The only way to run mechanical functions through a rotating turntable is to have them be coaxial. With present LEGO parts, you can only manage 2 coaxial functions using an axle as the central function and a series of driving rings as the annular function. There is no space inside the turntable ring gear for anything else. However, the ring gear itself could theoretically also be used to power a function, though that function would be slaved to the rotation of the ring gear.

There is a way to get an unlimited number of mechanical functions above a turntable. Use the central axis for driven power. Use the drive rings to power a second function which is a switching function for a transmission which is above the turntable. As long as the transmission is above, you can shift it from below and drive as many functions as the transmission has gears. This means you'll need quite a bit of space available above your turntable, but at least it can be done. You'll need a sequential transmission to really be able to shift more than 2 functions though. I'd love to see someone do it!

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It is also possible to do it with an "old" diff (in set 8421 for example ; well, not so old actually) in the middle of the turntable.

This way, it is also possible to include a gear down or a gear up (depending on how the diff is used).

Edited by Anio

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It is possible with up to 7 functions:

7-functions-2.jpg

Here is a view of the 8t gears and axles. The red pieces rotate individually. The blue pieces are stationary with respect to the superstructure.

7-functions-1.jpg

BlueShinyApple's solution may have been similar.

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It is possible with up to 7 functions:

Here is a view of the 8t gears and axles. The red pieces rotate individually. The blue pieces are stationary with respect to the superstructure.

*huh* That's simple enough to draw in CAD, but the amount of friction in the turntables and the amount of twist in the long axles would be huge. Also, with no lateral support the little pinion gears would just push out toward the center and not engage the ring gears.

Cool concept though.

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Having said 7 is the maximum number, it is 'possible' to have many more than 7 using hoses instead of axles.

Also, the top turntable is not necessary. Two functions can be passed through a turntable even when only 1 is in the center.

*huh* That's simple enough to draw in CAD, but the amount of friction in the turntables and the amount of twist in the long axles would be huge. Also, with no lateral support the little pinion gears would just push out toward the center and not engage the ring gears.

Cool concept though.

The 6 other axles could be supported at the top, and some 2L beams could keep the axles at the correct spacing. Axle joiners could also be used between the turntables. I know, it still won't work!

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It is possible with up to 7 functions:

7-functions-2.jpg

Here is a view of the 8t gears and axles. The red pieces rotate individually. The blue pieces are stationary with respect to the superstructure.

BlueShinyApple's solution may have been similar.

*oh2* I fear that I might not be able to squeeze this construction into my next MOC.

I guess the Large Hadron Collider started with a drawing like this...

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I assume that you want three rotare function and for them all to be operated either individually or simultainiously as desired. like drive both tracks at the same time. Am I right? Or is there any consession you could make, ie is it possible that one of the functions be a linear movement?

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On his website, Sariel showed his Liebherr R996 with TWO axles running through the center of a single Lego Technic Turntable; how is there room for any more?

7.png

Edited by DLuders

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I assume that you want three rotare function and for them all to be operated either individually or simultainiously as desired. like drive both tracks at the same time. Am I right? Or is there any consession you could make, ie is it possible that one of the functions be a linear movement?

i was thinking of two axles for tracks which can be made together and then another one for something else :wink:

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There is no practically useful way to do this as far as I know. This is actually something people have tried to do for decades and there have been many discussions about it on Lugnet in the past. The best solution is as Blakbird said, to have a switching mechanism on the turntable. If you have two independent geartrains, you can in principle get arbitrarily many functions out of them.

The turntable idea is pretty cool, but I think it would only be realistic for a stack of 2 or 3 of them. The studless turntables may also have too much friction for it to work smoothly. It would work better with the old studded turntables.

If the functions are really low torque, you could use a flex cable through a flex tube through a driving ring.

I used this once a long time ago. It works but it limits the turntable's range of movement to a 90 degree arc or so, before the flex cables get caught up in the center axle. You can also do something similar with the flexible Znap axles.

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BlueShinyApple's solution may have been similar.

yeah kinda'

Here's how to do it:

get as many freely spinning axles through the turntable, then one ofter another get into the centre then lead them away to their functions:

post-12306-129693527722.jpg

hope you understand :classic:

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i will give it a go :thumbup: there are 3 functions that can be moterised in this design?

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I had actually thought of the 'yellow' and 'green' functions before, but hadn't figured out a way of getting the 3rd function accessible by another gear. Anyway, you found a proper solution! :wink: (although using modified parts EDIT: never mind!)

Here is the way I thought of getting 2 functions through without driving rings (basically the same as your yellow function):

7-functions-3.png

The 3rd function could have come through the left, and then returned to center with another '16t with clutch' gear higher up. But the problem is that if this is done the blue function cannot go anywhere:

7-functions-4.png

Because of this, I don't think it is possible to do more than 3 without using more than 1 turntable.

Edited by fmmjqtft

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yeah kinda'

Here's how to do it:

get as many freely spinning axles through the turntable, then one ofter another get into the centre then lead them away to their functions:

post-12306-129693527722.jpg

This actually looks a great idea, although I think the gray liftarms need to be more firmly attached to the 36t gears for this to work well. I like how you made the gearing symmetric on both sides of the turntable, which allows the 36t gears to spin without affecting the other geartrains at all (if there is enough friction on both sides).

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