The steam powered top floats on water, and a loop of copper tube passes down through the cork into the water below. The two ends of the copper tube are bent at 90 degrees, and face in opposite directions. When you light the candle, the top spins, powered simply by the heat of the candle!
This simple heat engine has no moving parts, and the top will spin as long as there is heat from the candle. How does it work? The mechanism is the same as the familiar ‘pop pop’ boats, which are propelled through the water simply by the heat of a little candle inside the boat.
In each case, the mechanism is the same. The copper tube must first be filled with water. You then light the candle, and the heat from the flame warms up the water inside the tube until it turns into steam, and expands, pushing water out of the end of the tube. This provides the force that spins the top. The steam then condenses, which draws water back into the tube, and the cycle continues indefinitely.
It might seem that the two actions of pushing water out and then drawing it back in again would cancel out. However when the water is pushed out of the tube it is much more directional, whereas when it is drawn in, the water can be drawn from all directions. In the same way you can blow out a candle from a foot away, but you cannot extinguish the candle by sucking air into your mouth from the same distance away.
The mechanism is attributed to various people, but a Frenchman called Thomas Piot filed a patent for a pop pop boat in the UK in 1891. However it seems this mechanism was known before that date.
Ideally you would use a larger bowl of water than we used for our video, since when the bowl is too small, there is a tendency for the top to stick to the wall.
The specially bent copper tube, and a metal rod which allows you to bend the copper tube are included, as well as the cork base. You will need to provide the candle. There are a couple of very simple steps required, in order to assemble the steam powered top.
