Second Grade Science Project: A Steam Engine


If you’re looking for a way to let the kids get hand-ons with science this is a perfect example of how to do it. [Erich] wanted to help out with his 7-year-old’s science project. They decided to build a working model of a steam engine but couldn’t find online instructions appropriate for the age group. So the two of them not only pulled off the build, but then they wrote a guide for others to follow. The thing about it is, you really have to understand a concept to teach it to someone else. So we think the write-up is equally important to having actually done the experiment.

Steam can scald you if you’re not careful. But you don’t really need steam to explore the concepts of a steam engine. The main reason to use steam is that it’s a fairly rudimentary way to build pressure which can be converted to motion. For this demonstration the blue balloon provides that pressure. It’s feeding a reservoir that connects to the valve built out of straws. A plastic piston inside pushes against the crank shaft, spinning the cardboard wheel on the left. When the piston travels past the valve opening it releases the air pressure until the machine makes a revolution and is in place for the next push. This is well demonstrated in the clip after the break.

30 thoughts on “Second Grade Science Project: A Steam Engine

  1. Heh, I never thought a steam engine assembly (ie, piston and such) could be made this easily out of such simple materials. Awesome write up! (am I the only person older than 18 that wants to make one of these myself now?)

  2. Just a little more explanation – the air is actually going from the balloon through the valve to the cylinder, then back out through the valve on the exhaust part of the stroke. The “plastic piston” in the explanation above is actually the valve plug, and although it does push on the crankshaft a little bit, the main source of power is from the yellow balloon which takes the place of a piston. There are probably lots of ways to make this more efficient, and certainly grownups can make a real piston, but we were pressed for time and stopped as soon as we had something strong enough to operate the valve. At the school science fair, this engine stood up to kids handling it the whole evening and kept running to the end with kids lining up to blow up balloons and try it.

      1. I second this idea, this tag would be extremely useful for all teachers. we all already search hackaday just to make sure something hasn’t been done better than we are trying, I’m sure teachers and parents would take advantage of this tag.

        1. Awesome idea! A kids tag would make it super easy to help get my kids interested in making things. maybe 2 (3-10) and kids (8-18).

          As an alternative…maybe a spinoff from the main page…Hack-A-Day 4 Kids?

          1. it was a joke about make magazine. a wonderful magazine and website about making things. We sometimes have an overlap of projects, but hackaday tends to do some dirtier stuff, or less kid friendly anyway.

  3. Thanks for the kind remarks. Just to clarify, the air goes from the blue balloon, through the valve to the cylinder/piston (the yellow balloon) and back out through the valve on the exhaust stroke. Those of you with better tools and abilities can make a better piston and make it double-acting, but we were pressed for time and stopped as soon as we had something strong enough to operate the valve. At the science fair, this engine stood up to handling and still worked after nearly two hours, with kids lining up all evening to blow up a ballon and try it themselves.

  4. the main reason to use steam is that when water is injected into a steam filled cylinder in a real steam engine, the steam condenses to water and creates a vacuum in the cylinder thereby causing the cylinder to pull back to the top of the cylinder. additionally, the steam is recovered as hot water and is able to be reused instead of just going out the stack. it significantly increases the efficiency.. just one more case of the HAD author not understanding the subject matter.

    1. Lets not forget the adiabatic expansion of steam, which also adds power to the stroke (something that air does not accomplish nearly as well under compression).

      If you look up designs for old steam engines, it is very easy to see how the design cycle progressed to modern gasoline engines.

      I really do wish the authors here would read up (even a little) before posting. What’s the rush when 15 minutes of extra work would save you a whole ration of ridicule! ;)

      1. You are clearly under the delusion that employer’s allow an extra 15 minutes to do a proper job. I can’t count the number of documentaries regarding scientific research projects where it is often stated, “we’re running out of time due to (insert obviously going to happen issue)”.

        Seriously, when setting deadlines, the only thing that determines when something is due is the cost. Never mind the fact that it more likely than not is not humanly possible to produce a quality product under such constraints.

        You need to address your complaint to the editors who set the deadlines, not the authors who do not have the authority to change the deadlines.

    2. Er, you may want to check history.
      What you are referring to (condensing steam to draw the piston under a partial vacuum) is an “atomspheric engine” (originally developed by Newcomen but greatly improved by Watt).
      This, however, is an example of a basic steam engine that existed before then and was driven purely by (low) pressure of the steam.
      Steam engines only started becoming popular after people like Watt [condensing improvements] and Trevithick [allowing for higher pressure] made better versions of the above engine.

    1. Sure, just plumb it in, and the vinegar/baking soda angle should work, too. We used air for convenience and safety. Also, we used a low-temperature glue gun rated at 250 °F, but I’m not sure what temperature the glue starts to soften at.

      1. hot glue is a fluid and as such, doesn’t have a melting point, but rather a temperature at which the viscosity when plotted against the temperature changes slope. other materials such as glass have the same characteristic.

  5. Help! My son and I built one of these and it won’t work. I’m not an engineer (not even close) but we tried to follow the directions and it looks pretty close. What are the critical parts of making this work? What are the areas I need to really look at?

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