In an eye-catching TV advertisement, Sony has turned to one of the oldest moving picture technologies – the zoetrope – to promote one of the latest – flatscreen TVs. An unusual drive mechanism was chosen to spin the 3,000kg carousel up to peripheral speeds of 44km/h.
When Sony was looking for a spectacular way to promote its latest flatscreen TV technology, it turned to one of the earliest forms of moving picture technology, the zoetrope.
This device, invented in 1834 by the British mathematician William Homer, gives the illusion of motion when a series of still images on a rotating drum are viewed through vertical slits.
Sony’s 200Hz MotionFlow television technology is designed to create extremely smooth movement by displaying four times more images per second than standard TVs operating at 50Hz. To promote the technology, Sony decided to build the world’s biggest zoetrope and to use it to animate a sequence of images of the Brazilian footballer, Kaká performing a trick.
The London-based special effects company Artem was brought in to build the zoetrope. To produce just over 2.5 seconds of animation at 25 frames per second would require 64 images of Kaká in a sequence of slightly differing poses.
The 3,000kg Zoetrope would need to rotate at 23.4 rpm, producing speeds of up to 44km/h at the edge of the 10mdiameter structure.
To make the images appear large and clear, Aretm moved the image plane close to the slit plane by integrating both planes
in a single structure. It built a small test model, followed by a 1:10 scale model to assess the functionality and quality of the image. This became a test-bed for the construction methods and design ideas. The design went through several stages before a final version was approved. This consisted of a torus assembly with the image slits supported from above by a carrousel arrangement of spokes. The entire 3m-high structure is contained inside a clear safety barrier that echoes the design of the torus. Artem prepared
detailed CAD drawings from which more than 1,000 laser-cut steel parts were ordered, welded and assembled to produce the finished structure.
For specialist motion engineering assistance, Artem brought in London-based Mercury Bearings, which supplied bearings and pneumatics for the project. Mercury, in turn, approached Amir Power Transmission (APT), based in Hemel Hempstead, to help design the drive system.
After performing various calculations, APT recommended a slewing drive consisting of an 11kW Parker Hannifin SBC eddy current variator and a Bonfiglioli epicyclic gearbox.
An eddy current drive consists of a fixedspeed
clutch containing fixed- and variablespeed rotors separated by a small air gap.
Varying a DC-controlled magnetic field changes the torque transmitted between the rotors, and thus controls the speed.
There were several reasons for choosing this technology instead of a conventional inverter drive for the zoetrope. Eddy current drives can produce a 300% starting torque and are not

susceptible to regenerative voltages on the deceleration cycle. With an inverter, it would have been necessary to dump this regenerated energy using braking resistors.
Although an eddy current drive costs more than inverter system, this cost was outweighed by the benefits of the high starting torque, the simple control electronics, and the absence of braking resistors. Unlike inverter and DC drives, control cards for eddy current drives are the same size from 0.37–22kW, reducing
the cost disadvantage for larger drives.
Furthermore, because the torque is transmitted magnetically via an eddy current variator, there are no mechanical moving parts to wear. And with the motor rotating constantly at 2,750 rpm and only the output speed changing, the variator provides full ventilation throughout its speed range.
The zoetrope was built in Artem’s London workshops and trucked to Italy, where it was assembled in three days in the town square of Venaria, near Turin, ready to be filmed for the TV advert that has aired in recent months.