journal of science
Propulsion of the Putt-Putt Boat – I
The putt-putt boat is a little toy that has fascinated everyone from
children to physicists for over a hundred years now. This boat is
powered, not by a conventional heat engine, but by a motor that can be
termed a pulsating water jet engine.
The propulsion mechanism that drives the putt-putt boat uses simple
physical principles in an ingenious way. It basically consists of a
small shallow chamber, covered by a thin copper diaphragm. This is
connected to the water astern of the boat by two pipes of 3mm bore (See
Figure 1). The two pipes are initially primed with water and the base
of the chamber heated, using a candle. The diaphragm begins to vibrate
and the boat moves forward making the characteristic putt-putt sound.
The boat works as long as the flame glows.
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