To see all the parts of an internal combustion engine,
exploded views are often used. This idea is to display an
actual disassembled engine in such a way that the parts can
actually rotate, rock, pivot and move as if the engine were
This is done by having all the parts attached
to clear lucite
mounts that are themselves moved by hidden mechanisms.
For instance, you'd have a steel gear mounted in the center
of a clear lucite disk that fits in a slot in the base of the
display where a hidden motor rotates the entire assembly.
The way the lucite support parts are hidden is by filling the
display with water or clear oil rendering them virtually
invisible. You can see this effect by dipping a glass rod into
a glass of water. As bigsleep pointed out, when one
material is dipped in another with the same refractive
index, it completely disappears. So
a disk with a gear mounted in the middle is turning, it
appears that the gear is floating in space and turning
being attached to anything.
This would make an eye catching display and allow a unique
view of an actual engine's individual parts moving in
Great for turbine engines too.