The amazing Pringles Stirling engine · PDF fileThe amazing pringles Stirling engine, made from cardboard Pringles tube. When I saw this video by MarekSHayward I just had to have my

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The amazing Pringles Stirling engineby scraptopower on December 16, 2010

Table of Contents

The amazing Pringles Stirling engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro: The amazing Pringles Stirling engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1: The displacer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 2: Make the displacer cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Step 3: The shelf for the diaphragm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Step 4: The diaphragm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Step 5: The cranks and displacer rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Step 6: Make the top pringles tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Step 7: Seal the top tube in place . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Step 8: Connecting it all together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Step 9: Add a flywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Step 10: Make the candle holder and you're finished . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19


Author:scraptopower Scrap to powerAlways a brew in hand, I like to make stuff.

Intro: The amazing Pringles Stirling engineThe amazing pringles Stirling engine, made from cardboard Pringles tube. When I saw this video by MarekSHayward I just had to have my own! It impressed me seeinga Stirling engine made mostly out of cardboard, something which wouldn't normally be workable in an external combustion engine. This is a really easy to build Stirlingthat should be accessible to almost anyone.

How does it work ?

This engine uses air which is repeated heated and cooled. To allow the air to be heated and cooled the pringles tube contains a displacer which is like a loose piston thatcan move up and down forcing the air around the engine. When the air is heated it expands pushing the diaphragm (balloon) outward which turns the cranks. When thecranks turn they move the displacer down so that the air is near the top where it is cooled causing it to shrink and pull the cranks back, which of course moves thedisplacer upwards allowing the air to be heated at the bottom, this repeats over and over!

Materials :

4 x Pringles tubes, clean and dry1 x Balloon1 x Air freshener lid/ small aerosol lidCardboard from an old shipping boxSeveral plastic strawsGeneral purpose adhesiveHot melt glueFishing line (the creator of the original engine used cotton thread instead)Cotton wool

Tools :

ScissorsCompassDrill (with 2mm and 5mm drill bits)Mark penPencilRulerPliersBox cutterHot melt glue gun


Image Notes1. Give the gift of a Pringles Stirling this christmas!

Step 1: The displacerThe displacer is made from a cut down Pringles tube that is glued onto a few cardboard discs. I cut the cardboard disks out to about 6mm smaller than the diameter of thePringles tube, the cardboard I used was quite thin so I glued three disks together to make sure the Pringles tube was properly supported. The pringles tube is cut to about9cm and open at both ends.

The top set of discs has the fishing line threaded through it's centre. To stop the fishing line being pulled through the cardboard I tied and glued it onto a piece of a plasticdrinking straw . I also glued the knot to make sure that it couldn't come undone.

With that done, you can glue the cut down Pringles tube to the cardboard discs. You'll have to cut it down the side so you can make it into the smaller diameter.Glue thebottom cardboard disc down and then fill the space inside of the displacer with cotton wool to take up some of the dead air space.

Glue the top disc with the fishing line on and you're done.

Image Notes1. Marking the discs for the displacer.

Image Notes1. Cutting out the discs for the displacer cylinder.


Image Notes1. I cut out several, to ensure the Pringles tube was well supported.

Image Notes1. Gluing them together, three for the top and three for the bottom.

Image Notes1. Glued together

Image Notes1. Piercing a hole for the fishing line.

Image Notes1. Fishing line threaded through the cardboard and tied onto the straw.

Image Notes1. Cut down the side.


Image Notes1. The displacer filled with cotton wool to take up some of the dead air space.

Image Notes1. Apply plenty of glue.


Image Notes1. I taped it up whilst the glue set.

Image Notes1. Fishing line threaded through.

Step 2: Make the displacer cylinderThe displacer cylinder is just another Pringles tube cut down to about 14cm high. Drill a hole the same size as the drinking straw about a 1cm from the top.

Step 3: The shelf for the diaphragmMark out and cut out the cardboard parts for the shelf as shown in the diagram below. Fold them over and glue them together.

Drill a hole in the plastic lid the same size as the straw. Glue the lid onto the cardboard shelf. Make sure that the hole for the straw is pointing towards the Pringles tube.

Cut a piece of the straw about 1" long, long enough to connect between the lid and the displacer cylinder. Fit one end of the straw into the plastic lid. Now you can applyglue to the edge of the support for the shelf Align the other end of the straw with the hole in the displacer cylinder and push it through. I used an elastic band to holdeverything in place whilst the glue set.

Seal all around the straw using hot melt glue, apply plenty to be sure that you'll get an air tight seal. Make sure that the straw is flush with the side of the displacercylinder, or your displacer will catch on it.


Image Notes1. Use the lid to draw the curve.

Image Notes1. And the pringles tube to draw the other curve

Image Notes1. This will be the shelf

Image Notes1. This shows the shape of the shelf.2. Ignore the glue, I took this photo right before I was about to glue the aerosollid on.

Image Notes1. The triangular part that supports the shelf.

Image Notes1. You can lightly score the folds to make it easier to fold them.


Image Notes1. Glue tabs folded over

Image Notes1. I added these extra supports.

Image Notes1. Drill a hole near the bottom of the plastic lid. It should be the same size as theplastic straw.

Image Notes1. Test it will fit properly!

Image Notes1. Plastic lid glued in place! Note the position of the hole for the straw!

Image Notes1. Glued in place.


Image Notes1. Piece of straw for the air

Image Notes1. The straw should be flush with the side of the Pringles tube.

Image Notes1. More hot melt glue

Image Notes1. Apply plenty to seal it up.


Step 4: The diaphragmThe diaphragm is a straw glued to a cardboard disc, which is glued to a balloon. Cut out the cardboard disc and glue a straw down in the centre. I added some extrasupport pieces around the straw, but I don't (now) think that these are necessary.

Inflate a balloon and tie it off. You can now glue the cardboard disc and straw to the balloon.

When the glue has set, cut the neck off the balloon and stretch it over the plastic lid. It's should be tight, but not too loose either. You can always adjust it later .

Image Notes1. Marked out cardboard disc, about 2cm diameter.

Image Notes1. Cut it out.

Image Notes1. Straw.2. Cardboard disc.


Image Notes1. I added some little supports. Probably not necessary but I liked the idea....

Image Notes1. Blow up the balloon and tie it.

Image Notes1. Glue your space ship down, er I mean diaphragm connecting rod.

Image Notes1. Deflate the balloon and cut the neck off.

Image Notes1. This is the displacer cylinder and diaphragm finished.


Step 5: The cranks and displacer rodI made the cranks from 2mm galvanised wire - you could use almost any wire though so long as it's not too thin. I think the the minimum you could get away with is about1.2mm. The part of the cranks that the displacer is attached to needs to bent out about 20 - 24mm. The part that the diaphragm connects to should be bent out about 8 -12mm. The sizes don't need to be exact though. The diaphragm end of the cranks is rotated through about 90 degrees, this is really important so make sure you get itright. The starting piece of wire for the cranks should be around 20cm long.

Once you've formed the cranks, you can make the connecting rod for the displacer. It's just a piece of thin wire with a zig zag shape bent into it, and two hooks on eitherend . The purpose of the zig zag is so that you can adust the height of the displacer to prevent it from hitting the bottom of the displacer cylinder. This zig zag piece isfitted onto the displacer part of the cranks.

Image Notes1. Start with a piece of wire about 20cm long.

Image Notes1. First bend up for the diaphragm part of the cranks.

Image Notes1. The diaphragm part of the cranks.


Image Notes1. The displacer part of the cranks.

Image Notes1. The finished cranks should look something like this.2. Displacer part3. Diaphragm part.

Image Notes1. Zig zag

Image Notes1. Thread the zig zag onto the cranks, like this.


Step 6: Make the top pringles tubeThe top Pringles tube holds the cranks, and of course, seals up the displacer cylinder. This next part is the most important step in the building of this engine. You need topierce a tiny hole in the base of the top Pringles tube. This needs to be just big enough for the fishing line, if it's too big, it'll leak too much, and the engine won't work. Thefishing line should slide through the hole with any noticeable friction. A little patience here, will go a long way towards a working engine!

I marked the centre of the Pringles tube using a compass and then pierced the hole using a sewing needle held with pliers.

Once you've done that you can line the bottom of the top Pringles tube with the top of the bottom Pringles tube and mark the position for the bearing holes. These shouldbe marked on opposite sides of the Pringles tube and about an inch away from the top of the diaphragm straw.

Between the two bearing holes, mark and cut an archway, this is so that you can get to the cranks.

Image Notes1. Mark the centre.

Image Notes1. Sewing needle held in pliers.

Image Notes1. Finished hole for the fishing line.2. Fishing line.

Image Notes1. Line up the bearing holes, about an inch away from the end of the straw.


Image Notes1. Bearing hole marked

Image Notes1. The cut out so you can connect and see the cranks a displacer rod.

Image Notes1. Archway cut out.

Image Notes1. The displacer.

Step 7: Seal the top tube in placeThread the displacer fishing line through the hole you made in the previous step and put the displacer inside of the displacer cylinder. Now line the top can up with thedisplacer cylinder like you did to mark the bearings hole.

Double check the displacer is inside of it's cylinder :) Now seal away with copious amounts of hot melt glue. It must be airtight, so don't hesitate to go crazy with the glue !

Once the glue is set (cooled) you can test if it's airtight by pushing down on the diaphragm and holding it there for about a minute, if it quickly springs right back where itstarted, there's probably a large air leak somewhere. If it slowly returns to it's starting place, you're good to continue. The reason for this is because of the small air leakaround the fishing line, when you push down on the diaphragm, the air will slowly leak out, once you let go, it slowly pulls air back inside. If there's a big air leak, it canquickly return to where it started.


Image Notes1. Hot melt glue all around here, make sure you do EVERYWHERE around theseam, as it must be airtight.

Step 8: Connecting it all togetherNow you can thread the cranks through the bearing hole. It's a tight fit, but you should be able to squeeze them in. Turn the cranks to check the turn freely, if not makeadjustments to the bearings.

Stretch the zig zag displacer rod out by about 1". Make sure that the displacer is at the bottom of it's cylinder, then tie the end of the fishing line onto the end of the zigzag piece.

Adjust the position of the displacer so that it doesn't hit the bottom of it's cylinder by compressing the zig zag.

Line up the straw that is glued to the diaphragm and drill a 2mm (or whatever size wire you used for the cranks) through it and push the straw onto the cranks. push itonto the cranks.

Image Notes1. Cranks in place


Image Notes1. Tie it on here.

Image Notes1. Tie the displacer onto the free end of the zig zag.

Image Notes1. Use the zig zag to adust the displacer.

Image Notes1. Drill the diaphragm straw and connect it to the cranks.

Step 9: Add a flywheelMark 3 or four circles about 6" diameter for the flywheel, then glue them together. It's a good idea to thread a piece of wire through the centre to keep them in line whilstthe glue sets.

Once the glue has set, push the flywheel onto the cranks. Bend a right angle on the end of the cranks to secure the flywheel. This is to give the glue something to grip to.Glue the flywheel in place with more hot melt glue.

Once that's cooled, you can add some counterweights to counter balance the displacer. I found about 4p to be right, but you'll have to experiment.



Image Notes1. Displacer here2. Weights here to counter balance.

Step 10: Make the candle holder and you're finishedCut a Pringles tube down to about 2" high and cut a small slot into the side so the candle can get some oxygen.

It's finished now. Just light a candle and place it in the candle holder and place the engine on top of the candle holder. Leave it for about 2 minutes to heat up properly.Give the flywheel a flick, it should start turning away merrily.

If it doesn't work, there's either too much friction or an air leak, you'll have to look at those things.

Documents

The amazing Pringles Stirling engine · PDF fileThe amazing pringles Stirling engine, made from cardboard Pringles tube. When I saw this video by MarekSHayward I just had to have my