The threaded axles are very weak. Although they are a theoretical solution to your problem, I think that structurally they are not adequate which is why they were produced for such a brief time. The cross section available to carry tension is only the core since the flanges are cut away by threads.

Out of interest would you say that if you did a nut then two half bushes then another nut on a threaded axle,would this be stronger?

I do have some in my own collection,but have never used them for such a application.

I suspect if you just pile on a few half bushes onto a '8' axle like I should in my example it should improve things.

Although my design is small Daniel's design is much stronger still but does take up a lot more room.

Edited July 25, 201311 yr by Alasdair Ryan

Out of interest would you say that if you did a nut then two half bushes then another nut on a threaded axle,would this be stronger?

No, that won't make any difference. It would have to be something that prevented the threaded axle from getting longer (pulling apart), but if you had something that did that then you wouldn't need the threaded axle in the first place.

@Blakbird, how well do you think the last solution I posted will work in practice?

tim

@Blakbird, how well do you think the last solution I posted will work in practice?

It's strong but it only works over a portion of the rotation angle. I think it will fall apart when the top and bottom are 90 deg out of phase, and I think the "rollers" will have trouble re-engaging when coming back into alignment.

The truth is that these turntables are only intended to be used as radial guides carrying compression load (weight) and not tension. They are especially ill suited for bending which is what you get from an unbalanced load. This mean you either need to brace the turntable mechanically or balance your load.

Except the time it takes to dissemble, rebuild and test over again.

In my testing, I discovered that the dual turntable technique required too much space, and I need a smaller solution. While messing around I came up with this idea to keep the turntable halves together.

I tested it myself, and the two halves stay together, obviously only when the two sides match up. I would have to keep the other two ends of it open so I could run the wires through the middle. What do you all think about this solution?

tim

This is exactly what i meant. If only i could remember where i saw this used. BTW can't you just add another plate on the sides to complete the square? Using a studless turntable would work too if mounted in one of those frames or open back liftarm as bricklink calls them.

Tim, that may work, but I think you will need plates all the way around. If you need wires going through the center, I'm not sure that is doable.

Here are several more ideas:

The one in the center is a bit more compact, and I think is more similar to what efferman used. The other two designs allow for an axle to pass through the center. The one on the left uses four 6L links with the ball pins, and the one on the right uses the 5L links with regular pins.

I'm not sure the 5L links will work, and I don't have any of those links to test it. I'm wondering if there is sufficient clearance between the link and the teeth on the inside of the turntable. I think there will be, but I'm not sure.

Edited July 25, 201311 yr by dhc6twinotter

@Blakbird: I see what you are saying, it probably will have trouble realligning after the 90 degree rotation.

@ dhc6twinotter: Thank you for all these different designs, but having two turntables really will not fit with the model.

@EyesOnly: No, I need some space for the wires to go through .

I will keep trying!

tim

Do you are a purist? If yes, forget this answer if not listen :D Going back to the idea of the threaded axle you can just buy some non-lego ones. They come in one meter lenghs and are very cheap. If you take the 5M ones they will fit a standard one stud hole perfectly. It wold be the perfect solution for your problem I think.

But how well will the underlying bricks or beams hold up for that. A washer would be needed to spread out the forces involved. But it is a good idea.

lovely one !

Recently I built some POCs (Proof of Concept) for Mobile Crane ideas and I "invented" double turntables as an idea for sturdier support of crane superstructure.

Of course we all know that a crane superstructure needs a counterweight in order to be able to lift any kind of load.

Still, there are many situations where a counterweight is not, or is not the only, solution. Difficult to balance weight according to load and so on.

We also have other machines with turntables, diggers and such.

However, having said that, which is, I know that counterweight is always the answer(!) I came up with this idea for a more stable turntable, which will never snap and which adds a lot of strength and balance to superstructure and turntable

'nuff said, here are the pics, I have built it as well. This is my first creation in LDD

Just a concept, not the Nobel prize!

Gentlemen, start your opinions!

not a opinion, a fact: it works

not a opinion, a fact: it works

Brilliant! I am on the right track. Yeah, the machine gets a lot tougher, but counterweight is still needed for proper build.

As a matter of fact, heavy lifting with my crane bends the entire substructure of truck as well, but turntable stays together..

We had a discussion about this a while back, and it's nice to see that both you and efferman have had good results with this.

Using two turntables like this is something I plan on doing on my forwarder project, if I ever get around to finishing it.

Edited October 13, 201410 yr by dhc6twinotter

We had a discussion about this a while back, and it's nice to see that both you and efferman have had good results with this.

Found it! Good discussion and nice options.

http://www.eurobrick...8

And here I was thinking I had invented something new for the world

It works indeed. I have used a similar construction in my LTM11200, but than with a big and a small turntable.

However the tilt-resistance of the turn table is still quite bad. So even if it doesn't pop apart it still sags a lot if the load is not properly balanced.

I used an extra ring of wheels to widen the base of the turntable to tolerate more uneven loads without excessive sag.

Found it! Good discussion and nice options.

http://www.eurobrick...8

And here I was thinking I had invented something new for the world

I will merge both topics.

not a opinion, a fact: it works

Just out of curiosity, what is the red car in the picture?

this was a try of a small 4x4 dune bug, but i had massive problems with the shape

this was a try of a small 4x4 dune bug, but i had massive problems with the shape

Do you have any more pictures of the car? I actually think the parts of the body that are there look quite nice.

not really, when i hooked it on the crane the bug was already a rejected project.

not really, when i hooked it on the crane the bug was already a rejected project.

Oh, ok.

I thought , a bit of time ago, about increase the surface area, but I never thought about double turntable, it will be very useful for future!!

Lol I thought about it many years ago (I was not even into Technic but in system LEGO) but I never said it because I thought it would not work and I didn't had two turntables... Your idea to build it is very good I will try it.