Tuna Can And Some Other Trash Turned Into A Stirling Engine

Next time you’re making yourself a tunafish sandwich, try to figure out how to build a Stirling engine from the leftovers (translated). If you can pull it off as well as [Killerlot] did we’d say you’ve earned your hacker badge.

The can used in this project was actually sardines in tomato sauce, but the former contents are moot. The can serves as a steam chamber for the sterling engine. A cam rod, piston, and valve are all fashioned from paperclips, along with the support structure that holds them in place. Inside the can is a damp sponge. When an alcohol lamp is placed beneath the can it heats the water air inside, which creates pressure on the piston, pushing it up until the cam opens the valve, relieving pressure just in time for the cycle to start over again. Momentum is a necessary part of the mechanism and that’s where the CD fly-wheel comes in. See it chugging along in the clip after the break.

Update: Corrected spelling thanks to [Chris Muncy] and removed references to water/steam thanks to this comment from [Khordas].

[Thanks Mat]

35 thoughts on “Tuna Can And Some Other Trash Turned Into A Stirling Engine

  1. I think this should be called a steam engine. A sterling engine would be 2 pistons something like 90 degrees apart on the crank, with a tube between them. The heat source is on one side and a cool/radiator on the other. Heat expands the air in the hot side causing the crank to rotate, the rotation increases the total volume in the sealed tube, while moving the majority of the air to the cold side. This causes the air to contract and thus pull the crank around further while pushing the air back to the hot side. Wash rinse and repeat. A true sterling engine can also function as a heat pump if you drive it externally.

  2. What would make it even cooler is hackaday knew how a stirling engine worked. There’s no steam in this and no valve. The disk of sponge isn’t wet, and the heat doesn’t make steam. The disk of sponge displaces air from the hot end to the cold end of the can and back again as it goes up and down. When it’s at the hot end, the air expands and puffs up the baggie that’s acting as a piston. When the air is at the cold end, it contracts again and sucks the baggie back in.

  3. I tried to build one, but a cardboard piston doesn’t work at all, will definitely try again with a sponge piston. The thing is only good to look at, the torque is positive, but not usable in any practical application for this size.

    1. It looks like it has the scratch off area that is more likely a gift card… the kind where you scratch off the silver stuff and enter the code below to charge up an account.

      But I get your joke :)

  4. Hello,

    maybe i am wrong with this, but i think this (and each other) Sterling-Engine runns without water or isn’t it?

    Quote: “When an alcohol lamp is placed beneath the can it heats the water inside…”

    I think this is wrong, sorry.
    I have never heard about a Sterling-Engine with water or steam inside.

    Please tell me.

    Sorry for my bad english, i have not many times to use this langauge.

    best regards

  5. Actually, you missed a reference to “steam”. “The can serves as a steam chamber”.

    While cool, I really never have seen the use of these little models. It spins a little flywheel. I mean, if you hook up a record to that, you could make a sterling powered record player. That would actually be kinda cool, and come to think of it, I think I’ve seen one of those here before…

    But it’s damn rare to see one of these actually DOING anything besides spinning a flywheel. Wither it’s a scrap heap like this or a finely blown glass model. They just…spin.

    1. Of what use is a painting? It just hangs there and looks pretty.

      Of what use is a sculpture? It just sits there and looks pretty.

      Perhaps there’s more to determining a thing’s value than evaluating its utility…

  6. Stirling engines are hot air engines

    Not a steam engine

    Reverend Stirling invented them, because he was sick of his parishioners being injured by steam mishaps.

    Pressure is not relieved by a valve. Air is the working fluid in a typical stirling engine, and thermal work done heating and expanding the air is recovered as movement elsewhere in the device.

    More efficient Stirling engines are run with high pressures inside but the seals become tricky, making Stirling engines with four cylinders all running about 90 degrees out of phase and totally enclosed an attractive proposition.

    Stirling engines can achieve high efficiencies when compared to other heat engines and have applications in solar thermal power generation. The downside is low specific power, I.e. watts per unit volume.

    1. The displacer can be anything that will take up some space in the cylinder to displace the air from one end to the other. Some designs I’ve seen use a smaller can as a displacer. Foam is just nice because it’s lightweight, so it doesn’t take much force to move. This engine doesn’t have much spare torque to move heavy parts up and down.

  7. Hi, i have a doubt about this engine… Where is the air released? or it isn’t? i thought the air cooled down and then where heated again expanding but… well… i really liked the video but i cant understand how it works… the engine has a valve that controls the air escape or something? if so could somene tell me where is the air escaping? also if someone could explain it in a way an someone really slow minded would understand i would be pleased

    I am sorry by any mistakes i might have commited, my native language is Portuguese and even though i can understand pretty much i read i can’t write really well anyway thanks by the site it have pretty interesting stuff.

  8. There’s no air released, the Stirling cycle reuses the same volume of working gas for all phases. The displacer rises, air in the cilinder is moved to the hot side, the heat makes the air expand, the increased pressure pushes on the piston, which moves the cam forward. this makes the displacer fall, displacing air to the cold side. The air cools down, creating a vacuum that pulls on the piston, moving the cam forward… and the cycle repeats. An interesting feature is that you can use a stirling engine “in reverse”, to move heat from the cold to the hot side, by turning its axle. and the direction of rotation will determine which side is the hot one and which is the cold one. Stirling coolers are usually sealed and use Helium as working gas to achieve lower temperatures.

  9. Good work with tiny parts. Having tried 3 times to make a Stirling (and failing) I think that everyone who makes a working one is a fine fellow indeed.

    I found friction and air-tightness to be biggest problems.

  10. thanks by the explanation Brandano, by the way i thought that the sponge was pierced by the paper clip but if i understood correctly it is placed above the sponge so that the it pushes the sponge down making piston continue its movement (i actually liked this video so since i needed to do a project for my mecatronics class, it will be the first semester (first of 4) i think something like the stirling engine would be nice ^^ thats why i want to fully understand it)

    1. The “sponge” is acting as displacer. It is never squeezed, it just moves within the large cylinder up and down. As it moves up, the air that was in the upper portion of the cylinder is forced to move down, where it is warmer. The piece of foam that you call sponge could be solid, for example another smaller can, shorter in height than the outer one. It just needs to leave enough space around the edges to let the air move through, and it helps if it is light enough that the engine must not spend too much energy moving it around.

  11. Thank you for your wonderful “McGyver”;
    I am certain Richard Dean Anderson would be proud of your motor.
    I am always looking for new uses for CDr’s that never burned , failed,
    or just have obsolete data and music on them.

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