Building Pop Pop Steam Boats by John Howard Green

Pop Pop steam powered boats are available readymade manufactured in India

and China and hand-made quality from Rose Boats of South Africa .

So to learn about pop pop steam boats I read up on information on the internet.

Interestingly there are differing opinions on how the engine works.

Alan Raubenheimer of Rose Boats describes the steam engine as a cyclic flush

action.

Another more detailed description :

The boat works because the water in the boiler turns to steam from the heat of the flame. The steam expands and jets down both pipes, propelling the boat forward. When the hot steam reaches the end of the pipes, It condenses, causing a vacuum, which sucks water up from both pipes back into the boiler.

This process is repeated as fast as you can hear it beating the pop pop sound. This cycle is repeated over and over keeping the boat moving forward. The boat will chug along for a least 15 minutes, using a small candle or a few spoons of coconut or olive oil.

It sounds simple enough, but the more detailed scientific explanation is even more difficult. Even after well over 100 years since their invention, much about the pop pop boats remain a mystery. Some scientists, over the last few years, have been trying to calibrate and measure the heat and water temperature and sizes of tubes etc., in order to try and build a larger size boat and engine, So far they have not succeeded. ( Extracted from Daves website Poppopman UK)

The above example of a simple steam powered boat designed by Slater Harrison

see http://www.sciencetoymaker.org was built by myself from the excellent

instructions and plans on the website.

The stand is my own design.

This steam powered pop pop boat will work very well first time if you follow the

instructions step by step and it has a nice loud engine with good speed.

The boat is built from recycled milk or juice cartons and the engine from a used

Soda can and flexi straws plus epoxy and hot melt glue.

Highly recommended as a first pop pop boat build.

My first attempt at a steam powered boat was based on the concave bottom of a

soda can with top made from soda can metal soldered using 50/50 plumbers solid

solder and flux with 4mm copper for the water intake/exit.

The boiler was fired / heated with a candle after priming the intake tubes with

water and went well at first then the boiler split at the soldered seams and

despite a number of repairs and pressure tests keeps on failing.

My next attempt will use thin brass for the diaphragm and I will make it fit into

the top of the soda pop bottom so all solder will be on top of the engine. I note

that the better made engine have crimped on diaphragms for strength.

I have also had a go at building a coil type pop pop steam engine having just

completed a tube bending jig.

The above photo shows the tube bending jig ( a piece of wood about 150mm by

50mm). The round dowel (a sawn off wooden broomstick) is 20 mm in diameter

and is spaced from the brass wood screw the diameter of the brass pipe being

bent in my case 3mm.

The wood screw was positioned on the centre line from the bottom of the dowel.

The line across the bending jig is 95mm from the bottom of the dowel and gives

the start point for your tubing being wound into a coil. Position the brass tubing

between the dowel and brass screw with its end on the bending jig at the 95mm

mark and start to wind around the dowel keeping the turns close together.

The black rigid plastic tubing of about 200mm is slipped over the brass tubing and

used to assist in the bending around the dowel. It is important to keep the black

tubing about 20mm away from the dowel while bending the coil and make the 4

coil turns in one go ie do not stop as I found that when I stopped winding and

resumed later the tubing wanted to flatten a bit.

The brass 3mm diam. coil mounted in the foam test boat has only 3 coils as it was

a test piece made from the cut off bit of brass tubing. The coil lying loose in the

test boat has 4 coils the recommended number and runs better than the 3 coil

engine which tends to cut out after a while.

The heat source used was a T candle and a cut down birthday candle wrapped in

some aluminum foil. I also tried some solid fuel tablets (like Esbit or Mamod) but

they tend to be too hot and the fuel tablet holder started to melt the foam, hence

the aluminum shield.

Here is the four coil pop pop steam boat. A success! ran the first time for 15 min

continuously until the solid fuel was all burnt up and a good performer.

Note the blackened aluminum fuel holder from the heat and the four layers of foil

to protect the fuel holder from melting into the foam

To make the simple foam four coil pop pop boat you need :

Brass or copper tubing 3mm (1/8 “) about 500mm long

Wind into four coils using the bending jig as described above remember to keep

your rigid plastic winding tube about 20mm from the jig dowel and wind all four

coils at one go.

Foam tray from meat or confectionery

Cut try to boat shape, do not make the boat narrow as the coil is heavy and makes

the boat top heavy .

Chunk of foam to mount the coil at a height for the burner used

Aluminum foil as a heat shield for under your burner tray

Burner tray made from coffee tin top or very heavy foil or an aluminum soda can.

Fuel solid tablet best ie Esbit or Mamod or other camping stove fuel

You can also make a alcohol or methylated spirits burner with side mounted wick

from an Altoids tin or similar.

Hot melt glue and gun to glue the engine in the foam boat and make a stand for

your boat.

When mounting your engine in the boat before glueing check the burner

clearance is correct and that the pipes are about 6mm (1/4”) below the

waterline.