On his "Engineering with ABS" website http://www.engineeringwithabs.ch/ , Swiss AFOL Beat Felber has a clever design for "A version of a large turntable that works without a standard Technic turntable. Track links are used instead to build a gear ring." Go to his "Building Hints" page to see it. Here is the description and pictures in their entirety:

"This second version of a heavy duty turntable I developed with the goal of not using a standard Technic turntable. The functionality should be the same than in the first version but there had to be a big hole in its center to let wires and other things pass through it. The whole thing consists of four main parts - the gear ring, the king pin, the upper part and a roller ring. The gear ring is made of 72 old chain links, connected to a circle. To achieve a strong shape, there is a 1 x 2 Technic brick with two 1 x 1 plates attached to every second link. This structure is connected to the lower structure of whatever you are building - in the case of this prototype a simple base plate holds all the parts.

"The king pin is made of eight arched bricks resulting in a perfect circle. This circle is in the center of the turntable and is needed to guide the upper part. The upper part features four pins, forming a rectangle, which perfectly fits in the circular shape of the king pin. This way the upper structure is hold in place and allows just a rotational movement. To propel this movement, old 9 teeth gears can be attached to the upper part. These gears grab into the gear ring, which is made of old chain links. Therefore the whole thing works perfectly together. In my prototype I used just two gears but it is possible to attach as many as needed. The gear ratio is 9 theeth to 72 chain links which equals 1 to 8.

"The roller ring is not shown on this model. But it can easily be built following the instructions given on the page of the first version of a heavy duty turntable. This time it has to have bigger diameters - at least 32 studs for the inner one. When using a roller ring, be sure that the weight of the upper structure is supported by this ring and not by the king pin or the gear ring. Otherwise the whole thing whould have too much friction and would not work well.

"Possible applications of this turntable could be dragline models where a large turntable is needed, models of stripping shovels where an elevator passes the king pin or bucket wheel excavators where the coal passes the turntable before it is forwarded to the spreader. Another possibility is to use this construction for large crane models like offshore or twin ring cranes."

The red gear he used is the g9 Technic, Gear Expert Builder 9 Tooth. There are downloadable Building Instructions ( http://www.engineeringwithabs.ch/download/turntabl.zip ) and LDRAW file ( http://www.engineeringwithabs.ch/download/turntabl.mpd ).

Note that the diameter of the turntable can be changed by using his Circle Template -- "Use [the link to] this drawing to build circles out of LEGO bricks with a diameter from 4 up to 40 studs."

I remember seeing this years ago, but I'd forgotten about it. I think Jennifer Clark considered using a version of it for her mobile crane. I actually happen to have a couple of those 9t gears from a garage sale, but I only have a few of those chain links.

That's really clever, could of done with that a few months ago

I like how the top half of the turntable is secured in horizontal direction, but what (except from the red gears) prevents the top half of the turntable from just falling off?

I'm not convinced by this turntable.

To have a similar result, the use of a hailfire wheel may work perfectly. :)

I like how the top half of the turntable is secured in horizontal direction, but what (except from the red gears) prevents the top half of the turntable from just falling off?

It's really just useful for the slewing mechanism of very large cranes and such. The weight of the superstructure is more than enough to hold the turntable together. It's not like you would use this for applications where the turntable would be in any position other than horizontal. I don't think it can take very much horizontal stress anyways.

I'm not convinced by this turntable.

To have a similar result, the use of a hailfire wheel may work perfectly. :)

Hailfire droid wheels are REALLY expensive, though. And I'm not sure they existed when Beat Felber came up with this design.

Edited August 9, 201014 yr by Silcantar

I'm not convinced by this turntable.

Considering that he used this turntable for his massive Moutaineer excavator, I think we can conclude that it is a viable design.

I think the primary reason he came up with it is that he wanted a minifig elevator to pass through the center of the turntable which can't be done with a central axis or one of the standard smaller turntables.

Seem to remember a esign using the hailfire wheels and LEGO footballs... can't find the picture though.

It's really just useful for the slewing mechanism of very large cranes and such. The weight of the superstructure is more than enough to hold the turntable together. It's not like you would use this for applications where the turntable would be in any position other than horizontal.

The point is, that this won't work if the superstructure is not balanced. For example, on large cranes, when you're lifting stuff the center of gravity changes.

Also, there seems to be no way of reducing friction. Or does the superstructure have a few sets of wheels underneath that will roll over some tiled surface below the turntable? This is of course possible if there's room for that. As I see here, http://www.engineeringwithabs.ch/mturntab.htm the way he has done this is very clever.

Edited August 10, 201014 yr by Erik Leppen

With the hailfire wheels, how do they attach the wheels to the structure? I do not have any of the wheels, but from what I've seen there doesn't seem to be anything on the sides where you can connect them to anything.

With the hailfire wheels, how do they attach the wheels to the structure? I do not have any of the wheels, but from what I've seen there doesn't seem to be anything on the sides where you can connect them to anything.

Check out some pictures of the 4481 hailfire droid ;)

or just search for 'hailfire' on brickshelf:

Sariel used Hailfire Droid wheels in his Bucket Excavator project: http://sariel.pl/2009/11/big-bucket-wheel-excavator-cancelled/ . The wheels were mounted vertically to hold the scoops:

Of note is the cab's turntable that uses 16 rollers and is 21 studs in diameter. You'll have to visit the webpage above to see the picture and description of it.

Seem to remember a esign using the hailfire wheels and LEGO footballs... can't find the picture though.

Guess you was thinking about this video from Sariel, Jetro.