Heavy Duty Turntables #2

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Turntable 2, picture 1

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.

Turntable 2, picture 2

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.

Turntable 2, picture 3

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.

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