Heavy Duty Turntables #1


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(Click on any image to enlarge it)

Introduction

Turntable, complete

The turntable I will present here, I developped for a dragline model. My goal was to build a P&H 9020 Dragline but I had not enough parts. Nevertheless the turntable is useful for other models too.
It is a heavy duty version with a base, rollers and an upper ring. On the circular base lies a ring with rollers and on the rollers a flat ring. The upper structure of the model is connected to the upper ring. A Technic turntable is attached upside down to the base. This allows the motors for the revolution to be in the upper structure. You need two at least - it is best to use the newer 9V ones because they need less space and they feature already reduced speed. The Technic turntable is needed to hold the whole thing in place and doesn't have to support weight of the upper structure. It all lies on the rollers.
Have a look at the building instructions to get an idea how to build it.


The Base

Turntable, base

The base of the turntable is a circular structure with a flat ring to allow the rollers to lie on. A Technic turntable is mounted upside down as a king pin and is needed for the revolving mechanism because of the gear-ring.
The base is 24 studs in diameter and the flat ring, made of tiles, is 22. Go to the Download section to get a drawing which helps you to build circles with LEGO bricks.
Of course this turntable can just be used for a dragline because it is built that the model stands on the base of it. If you like to use it in another model, you have to insert a ring, to run the rollers on, into the chassis of whatever you are building. The Technic turntable can then be mounted in normal position to have the revolving motors in the lower structure or, as mentioned above, upside down to move the motors in the upper structure.

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The Rollers

Turntable, rollers

The turntable shown here features 24 rollers. It is possible to build bigger ones but they have to have a number of rollers which can be divided by eight. Less than 24 rollers will be too small to place a Technic turntable in the middle.
The ring with the rollers I made of 24 1' x 2' x 1' Technic bricks which I connected with flat hinges to a circle. But a structure with 24 sides won't stay in the desired shape when using it. Therefore I made an octagonal structure with 8 sides with 1' by 6' Technic plates with holes at the ends. This structure is absolutely stiff. Every third side of the ring I then connected with an edge of the octagonal structure. Now the whole thing is strong enough to withstand the forces of a heavy model.
On every of the 24 sides I attached a roller which is made of a 2' x 2' x 1' rounded brick with an axle through it.

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The Ring

Turntable, ring

On the rollers lies a ring which is connected to the upper structure. The ring is made of two layers of plates and has a circular shape. Go to the Download section to get a drawing which helps you to build circles with LEGO bricks.
The ring doesn't have to be very strong when the upper structure is stiff enough.

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