V Sharadha is a III year mechanical engineering student at Indian Institute of Technology, Chennai. This work was done when she was JNCASR summer fellow in 2003 at IISc.


Jaywant H Arakeri is Professor at Mechanical Engineering Department and in the Center for Product Development and Manufacture at Indian Institute of Science, Bangalore.  His research is mainly in instability and the turbulence in fluid flows. 

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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Address for Correspondence
V Sharadha
III Year
Mechanical Engineering Student
Indian Institute of Technology
Chennai 600 036
Jaywant H Arakeri
Mechanical Engineering Department
Indian Institute of Science
Bangalore 560 012, India.
Email: jaywant@mecheng.iisc.ernet.in