Not just for the bathtub admiral.
This intriguing little steam boat is a
good opportunity to understand the
physical principle of the pulsed motor.
It is not a speed boat, nor is it up to the
rigours of the open ocean. The key
parts of the motor, which does very
nicely without pistons, valves or
wheels, are a brass coil and a tea candle.
In order to prime it, the coil is filled
with water with the aid of the pipette.
When the tea candle is ignited part of
the water in the coil boils, turning it
promptly into steam and expelling it.
That creates a vacuum in the coil,
which sucks in a fresh charge of water.
Since the expulsion of the water is
stronger than the subsequent sucking
in of fresh water, the boat moves
slowly, but steadily forward. The boat is
made of cork, which floats better and is
propelled a tiny bit faster. The pulsed
motor can be rotated to change the
direction of travel. The boat is made in