Slide 1
CANDLE POWERED PUT PUT STEAM BOATHow it worksA putt putt boat is
powered by a very simple heat engine. This engine consists of a
small boiler, which is connected to an exhaust tube. When heat is
applied to the boiler, water in the boiler flashes into steam. The
expanding steam pushes some of the water in the exhaust tube,
propelling the boat forward. The steam bubble then condenses,
creating a vacuum which draws water back in through the exhaust
tube. The cooled water that is brought back into the boiler is then
heated and flashed into steam, and the cycle repeats. This constant
flashing and cooling cycle of the engine creates the distinctive
putt putt" noise for which the boat is named.
MaterialsSoda CanStraws Milk CartonSeal All glueBlue stik
puttyTapePaintTrayCandleWaterProcedureCut apart the soda can for
the boiler
2. Start folding the aluminum "pocket. to make boiler
3. Measure and mark the straws.
4. Insert the straws into the end of the boiler
5. Form a convex top and flat bottom in the boiler.
6. Start sealing the boiler.
7. Cut out the boat body
8. Mount the engine into the boat
9. Wet, paint and test the boat
Steam Boiler
How the boat movesWater expands a lot when it turns to steam.
Steam can occupy more than a thousand times more volume than the
water it came from.
If you put a spoonful of water in a ziplock bag and heat it in a
microwave oven, you can see how the steam occupies many times more
volume than the water it came from.Once the aluminum boiler is
heated, even the tiny candle can flash boil those small droplets of
water almost instantly, and they expand enough to run the engine.
Two things happen as the droplets flash explosively into steam: The
bottom of the boiler pushes out with a ping. And the water in the
straws is pushed out.
The fast-moving water columns in the straws has momentum. That
momentum tends to make the water want to charge ahead even when the
boiler is no longer pushing it. That's good! It gives the engine an
instability that keeps the cycles repeating over and over.
Sir Isaac Newton's Third Law of Motion is the familiar, "For
every action there is an equal and opposite reaction."
So, when the water jets backward out of the straws (action) the
boat jumps forward (reaction).
