Lego Automata: Two hand rude gesture

An automata, or a kinetic sculpture, is usually a decorative item which moves in some way. Popularized some hundreds of years ago with clockwork like mechanisms, they can more easily be made today using Lego Technic bricks.

Here is a kinetic sculpture which shows the somewhat rude two hand gesture, where the index finger of one hand is passed in and out of a loop formed by the thumb and index finger of the other, suggesting coitus.

At the same time, the whole contraption also rotates, as you can see in this video:



The hand itself is made mostly out of fairly common bricks and plates:

The most used special plate is the 1x2 plate with handle (60478). Each finger uses three of them:

I got these parts mostly from the Mixels Busto set, which has six of them each. The hand can be posed in a fairly realistic way:

Not so visible in the video, but the base of the contraption is made with rubber wheels as "feet", to make it more stable. The motor powers both the rotation and the contraction of the yellow arms. The motor output is geared down 1:8 using a worm gear and a z8, and the 8:56 as the z8 (8 teeth cog) meshes with the outside of the big turntable:

LEGO Technic useless machine

In popular mechanics, a "useless machine" is one that does nothing beyond turning itself off again. When made in LEGO, you will often find them powered by a motor, by gravity, or by some other means. When I saw the new wind up motor in the LEGO Technic sets 42033 and 42034, I knew it could be used to power a "useless machine".

The only disadvantage of using a wind up motor, is that it runs very fast. It easily reaches a high speed, as long as the friction is low. To overcome this problem, I put a clockwork escapement mechanism into the machine, to limit the speed of the motor when the device is running. Here is the result:

Geneva drive in Lego Technic

The Geneva drive is a mechanical device that transform a smooth rotation into an intermittent rotary motion. Traditionally, this has had applications within watch making.

The Lego mechanism showcased here transfers one rotation of the drive axle into 1/4 rotation of the output axle. Here are the basic movements explained.

The driving axle (to the right) locks the output axle, due to the black half circle shape.

Helicopter rotor with cyclic control

In 2012, LEGO released the 9396 Helicopter model. While this is a good set, with realistic looking helicopter blades, the blade operation is still far from realistic.



The model includes collective pitch adjustment for the rotor blades. The word collective in this case refers to the fact that the pitch of all the blades change at the same time, collectively. This is all well, however, not really anything new, since this feature was also included in the 852 Helicopter model from 1977!

The key to the success of the helicopter is the cyclic rotor pitch adjustment, usually operated through the pilot's stick. This involves having a swashplate below the rotor, to which there are rods connected to the rotor blades. The rods control the pitch of the blades. As the swashplate is tilted, the pitch of the rotor blades change cyclically through the rotation. This animated GIF explains how the a tilted swash plate affects the cyclic blade pitch:

Animation made by Richard Wheeler (Zephyris) for use in Wikipedia, and uploaded using the GNU Free Documentation License

In the animation, the disc below the rotor is the swashplate.

Lego Technic 4x4 skid steer loader

Here is a video demonstrating the model. In the rest of the article, I will describe the design choices and design challenges with this model.