Magnetics Business & Technology - March/April 2022 - 6

FEATURE ARTICLE
The Big Screen: Special Effects with the Aid of Absolute Draw-Wire Encoders
By Michaela Wassenberg, freelance journalist
Precise and authentic movements thanks to SIKO draw-wire encoders in the hydraulic cylinder: 12-meter boat deck in 'Fantastic Beasts'.
Draw-wire encoders from SIKO GmbH, a manufacturer of sensors
and positioning systems, are used by the British company
Absolute MoCo, which develops and builds hydraulic studio environments
for special effects in movie productions. Together with
his partner David Watkins, Special Effects Supervisor at Absolute
Effects, Andy Ryan wanted to be able to create movements
for special effects in the movie industry that are more accurate
and more authentic. For him, the technical effects available in
the UK for this purpose were outdated. The aim of Absolute
MoCo is to enable people to move more precisely and safely in
film scenes. " We specialize in creating the conditions for motion
control of certain motion sequences in movies with moving base
platforms and in sets. We act as a link between VFX and the
physical world and have developed a reliable HMI and software
package for movie production. For some filming we still use open
loop systems, but we mainly prefer systems with a closed control
circuit to guarantee positioning and reliability, which are crucial
in movie production today. Using absolute encoders from SIKO
gives us the opportunity to repeat takes as often as we like. This
means that we can work safely, stop safely and identify positions
at any time. This technology has catapulted the physical side of
special effects to a new level and is getting better all the time. "
Wire-actuated encoders integrated into the hydraulic cylinder
Hydraulic movements are a particular challenge if they are to appear
natural and still be safe to perform physically. Various SIKO
draw-wire encoders are used here to determine the position of
the hydraulic cylinders. All the encoder types have in common a
6 Magnetics Business & Technology * March/April 2022
design that is both robust and compact, making them suitable for
the smallest spaces. The SGH10 draw-wire encoder, which was
used, for example, in scenes for the Warner Brothers production
'Fantastic Beasts: The Crimes of Grindelwald', has a distinctive,
patented feature: it is integrated directly into the hydraulic cylinder
and measures the position - i.e. the extension of the cylinder
- directly. The advantages: the integrated design means that the
draw-wire encoder is protected from external factors. There is
also no need to drill out the piston to accommodate the drawwire
encoder, as is the case with other solutions such as those
with magnetostrictive sensors. An additional work step of this
kind is also a cost factor, which is avoided by using integrated
draw-wire encoders.
Detection of position and speed
During a rescue scene in
which a fully occupied boat
had to be tossed to and fro as
authentically as possible on
the high seas, three movement
axes were involved that
had to be hydraulically driven
(Trio Motion Technology),
plus a rotational movement as
a fourth, which was enabled
by the integrated SIKO drawwire
encoder. Andy Ryan:
The compact SG10 (orange), SGH10
and SG20 draw-wire encoders
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