This small and simple steam powered boat is an exciting little project. It is a hot invention that uses the power of steam to generate movement.
Caution: This activity involves a candle flame to heat up copper tube. Do not touch tube when hot and look out for any potential fire dangers. Be careful using the scissors. Have an adult present when doing this activity.
What you need
A milk carton (we used 1L size)
Scissors
A tea-light candle
60cm of 3mm diameter soft copper tubing (try a hardware or plumbing shop). The exact amount depends on the size of your bottle; try and get the hardware to cut it to size for you
Sticky tape
Blu-tak or plasticine
A large tub, sink, bath or pond of water
What to do
Gently and slowly wind the tubing around a thick pen (like an permanent marker) one-and-a-half times, to form a coil in the centre. The two ends should lead off from the coil next to each other (see picture).
Bend both ends of the copper tubing so the looped end sits up and the other ends are down.
Cut your milk carton lengthwise in two, then cut a little off the top so the bottom part is the largest – this is your boat.
Make two holes around 2cm apart in the carton's end and stick the ends of your copper tubing through, so the two tubes stick out downwards from the boat (you may need to adjust the bends).
Seal the holes so they are waterproof. We used Blu-tak, but plasticine would work as well.
Place the tea-light candle under the loop in the copper tube. Fix the candle in place using sticky tape.
Fill the copper tube with water. You can do this a few ways. 1. Suck at one end with the other end in a bottle of water, place your finger over the end to keep the water in and then put your boat on the water. Clean the tube first and avoid getting water in your mouth if you use this method. 2. Use a syringe to squirt water into the copper tubing. 3. Suck water through with a clean plastic tube if it fits nicely over the copper pipe. This lets you fill the tube whilst the boat is in the water and you are not.
Light the candle! After a short while your boat should start to move forwards and will keep moving as long as the candle burns. We found that we needed two candles to get some speed as the copper tube we had was quite thick.
What's happening?
What force is powering this little superb steam engine you ask? Well, the engine here is only copper tubing, water and a candle. As the candle heats the water inside the tube, it expands. As the water expands, it pushes out of the tube.
As the water is pushed out of the tube backwards, it pushes the boat forwards as Newton's Third Law tells us every action has an equal and opposite reaction – watch it go! Put your fingers behind your boat you'll even feel the little pulses of water coming out of the tube ends.
The expanding water above the candle soon reaches a cooler part of the tube and returns back to its normal cool water size. This creates a vacuum in the tube that sucks water in from the outside.
Applications
The first steam turbine was first built in the 16 th century by an Arab philosopher, Taqi al-Din from Ottoman Egypt. He came up with the perfect way to make a spit roast by turning the meat with a steam turbine – nice work, we approve.
Steam boats were built and used in the 19 th century and usually used a paddlewheel powered by a steam engine to move forward.
Modern day steam turbines are still used to make a large proportion of our electricity. The main form of energy production in Australia currently is burning coal to heat water to create steam which rushes upwards to drive a turbine which creates electricity. The problem with this form of energy production is it produces huge amounts of carbon dioxide, the world's most produced greenhouse gas. Time to get re-inventing!
