Thorax 98a
consists of a brass cylindrical body with
springs (302 stainless steel, 2.5mm long,
0.229mm wire
diameter, 1.14mm spring diameter, 11 turns)
mounted on the sides. On the springs
were mounted brass wings (7mm long, 5mm maximum chord;
later steel wings, 10mm in length,
100 microns thick, were also available using
the EDM process). The wings were driven
using voice
coil actuators (VCA) coupled to the springs through
connector rods.