Model Steam Engine

An engine is a machine that turns energy into motion.  Here we give instructions on how to make your own model steam engine from inexpensive materials.

Read on for detailed instructions on building the steam engine and on how steam engines work.

How A Steam Engine Works

A steam engine works by heating water in a pipe, turning the water to steam.  As the steam heats the gases expand creating pressure.  The pressure can be used to move parts.

In this diagram below you can see that water is run through pipes above a very hot chamber.  The water is turned to steam as it heats then the steam is heated even further as it runs through more pipes.  Finally the steam escapes with great force out a pipe (number 5) where it is used to create motion for an engine.

1. Bilge; 2. Combustion Air; 3. Fuel atomizer; 4. Super heater header; 5. Super heated steam to engine room; 6. Saturated steam take-off; 7. Steam drum; 8. Feed water inlet; 9. Steam bubbles forming; 10. Steam being super heated; 11. Boiler seating.   Image by Shakki, CC licence, Wikimedia

A steam engine is an external combustion engine.  This means the heated combustion chamber is in a different compartment than the fluid that is expanding.  In this diagram, above, the water is contained in pipes and never is in the same chamber as the fire, or combustion.

How To Build Your Own Model Steam Engine

To build a model steam engine you will need

  • soda pop can
  • tin snips to cut the can
  • pliers to bend down the edge of the can so no one gets cut
  • nail to punch holes in the can
  • soft copper tubing, 1/8″ diameter and about 12″ (30 cm) long (we found copper tubing at the automotive store, it’s called “Oil Pressure Copper Tubing Kit” and cost just a few dollars)
  • tea light candle (small short candle that comes in a little metal dish) and lighter to light it with
  • bowl of water

how to build a model steam engine

Here’s what you do

  1. First cut the can down 2.5 inches (6.5 cm) from the bottom with the tin snips.  Then bend the edge of the can down all around the edge so no one gets cut on the can.  Be careful with this step.  It is sharp!
  2. Punch two holes in the can just under the rim using a nail and exactly opposite to one another.  Flatten the bottom of the can as much as possible so the tea light will sit in the center.
  3. Bend your copper tubing around a marker, your thumb, or another round object so you have three coils in the center with two long ends extending from either side.
  4. Insert the ends of the copper tubing through the holes on either side of the can so the coil is in the center of the can.  Bend the two ends of the copper pipe so that they are facing in opposite directions parallel to the can.  The idea is that you are directing the water/steam so that the can will turn in a circle in a bowl of water.
  5. Place a tea light candle in the bottom of the can under the coil.  It can help to drop some hot wax under where the candle will sit or secure to candle with a bit of hot glue.
  6. Get your bowl of water ready and get some water into your copper pipe.  You can just suck a bit of water through to get it started.  Then set your pop can engine on the surface of the water and light your candle.

Instructions on how to build a model steam engine with your kids.

The candle will heat the water in the pipe, turning it to steam.  The steam will force its way out of one end of the pipe and at the same time more water will be sucked into the pipe so your engine will keep running as long as the heat source and supply of water remains.

Instructions on how to build a model steam engine with your kids.

History of the Steam Engine

The first practical steam engines were used to pump water out of mines in Cornwall, England, which had recently been delved deeply enough to begin filling with water.  They were invented in 1698 by Thomas Savery, an inventor and engineer.  The water was heated, steam expanded, and then was cooled so that a vacuum was created and water was sucked up a pipe.  This engine, with some improvements, was manufactured and used for nearly a hundred years.

This is the Savery engine. Public domain, Wikimedia.

In 1712 Thomas Newcomen improved on the design and created an engine that could pump water with a piston.  The engine could only perform that one motion, the pumping motion.

This is the Newcomen Engine, the first useful steam engine. Image by Emoscopes, CC license, Wikimedia.

In 1758 a repairman who worked for the University of Glasgow in Scotland, James Watt, discovered the university had a small model Newcomen engine.  He was fascinated and began experimenting to improve the efficiency and design.  He spent his whole life immersed in the problem of creating a more efficient steam engine.  After decades of work he was wildly successful and started a company selling upgrades to the engines already being used at mines.  Watt’s improved designs made steam engines cost efficient enough for many industries to begin to use steam to power their factories.

This painting is titled “James Watt and the Steam Engine: The Dawn of the Nineteenth Century” (1855) and is by James Eckford Lauder.  Public Domain, Wikimedia.

Eventually Watt improved his engine to the point that it moved smoothly enough to turn a drive shaft, which made it possible to do work that the limits of the pumping motion could not do.

In the late 1700’s experiments were done for powered vehicles like ships and trains. But these applications meant a smaller boiler and greater pressure were required.  But the technology to make sufficiently strong boilers, to prevent explosions, was not quite there yet.  In 1800 Richard Trevithick, a British engineer, developed the first high pressure tank for steam.  He then went on to place the engine on wheels and power a coal train in Wales.

This is a replica of  Trevithick’s 1804 steam locomotive.  Image by chris55, CC license, Wikimedia.

The 1800’s became the century of steam.

Additional Layers

  • In this experiment the chemical energy in the candle is turned into the energy of motion, kinetic energy.  Can you trace the path of energy?
  • Today steam is not used very often to create motion, but it is used in reverse to create energy all the time.  Power plants, whether they use coal or nuclear or another form of heat energy, use steam to turn a turbine to produce electrical energy.  Find out more about how energy is produced from steam.
  • Steam was replaced by the internal combustion engine and by electrical power from the grid because steam was less efficient and more polluting than the newer forms.  But technology has come a long way since 1900 when steam was being phased out.  New steam technology is being developed today in a movement called “Modern Steam”.  Find out more.
  • It’s easy to look at the bare facts of a life like James Watt’s and focus on his success.  It is tempting to think that he was just lucky.  But to create that “luck” he worked for decades with no guarantee that anything would ever come of his work.  He didn’t know if he would ever really improve the steam engine.  He didn’t know that if he did fix the problems he would ever receive any rewards of money or fame for his work.  But he did it anyway.  The work always precedes the “luck”.  Reading about successful people helps us learn how to be successful people.  Part of your children’s curriculum ought to be biographies of achievers.
  • Make the model steam engine, add a poster about the history of the steam engine and one about how steam engines work and you have a great science project.

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