Stirling Engines My first Stirling engine build

In spite of my video camera running out of battery during filming, I managed to get the first (and only) moments of my first Stirling engine running.

Tis a funny kind of beast running so slowly and deliberately.

I officially like Stirling engines. Mine looked like this...

It ran for a total of about a minute before the displacer fell to bits. It was sealed airtight, and as it got hot it just popped. It turns out there isnt really any need to make it air tight.

I think.

My displacer started life as a soft drink can.

I marked out a straight line to cut it down to size.

I took a guess as to what size it should be.

I scratched a series of arcs with a bent piece of sharp wire, each at different points, to find the centre, then punctured it with a drawing pin. 

I marked out another can, but this time much shorter.

Then squashed the big one over the little one after turning the little one upside down.

This gave me a sealed can again.

I glued it with super glue.

The gluing was what killed my brand new Stirling  engine after only 60 seconds. As the heat increased, so did the pressure inside the sealed displacer, and eventually it popped open.

I poked a straight length of fencing wire through both holes, then bent and super glued one end to stop it slipping through.

My wire originally had a slight loop at the other end, but I had to cut it off to remake the thing after I glued myself to it.

Dont do that.

And if you want to be really scared, use super glue, then adjust the dials and buttons on your new camera with the same fingers.

Anyway, the main thing is stick some wire through the displacer.

Next I took a tin can and smacked a hole in it with my familys trusty meat mallet.

This meat mallet used to be my mothers (it probably still is), and was used as the household hammer for as long as I can remember.

Here we see the entire family history of hammering.

Actually thats half the family history of hammering. The other half is of course, on the other side.







So then, I took the length of wire sticking out of the displacer (soft drink can thing), and threaded it through the bottom of the tin can.











Like this.

Its a bit difficult to see, but thats the soft drink can displacer thinggy under the tin can.









Next, I took another tin can and drilled a big hole in the side.










And sanded down a small plastic bottle so that its contour matched the tin cans.










Then cut a really big hole in the side of the small plastic bottle.

Something like a pill bottle would work.

All this, so I could glue the small plastic bottle on the side of the tin can with a big hole in the side. 

Next, I stretched a balloon over the entire little plastic bottle, and pulled the slack so that it was tight everywhere but the top.

I also glued a length of wire to the centre of the slack bit.

This, believe it or not, is something called a "power piston".

Ill explain what all this stuff does later.


Next I bent a crank shaft, and some mounting points for the wires coming from the displacer (through the bottom of the tin can), and the wire glued to the balloon (power piston)

The crankshaft has one offset bit (offset by around 8mm) to attach the displacers wire, and another to attach the power piston wire to.

The two offset, (bent out) bits, are at 90 degrees to each other.

So from the left...

straight, then down, then straight, then back up to the original.

That makes the first cranky bit.

Then continuing straight, then back, then straight, then forward back to the original plane.

That makes the next cranky bit.

If you look at the crankshaft end on, if one crank was at 12 oclock, the other would be at 3 oclock (or 9)

I found this almost impossible to get on camera (or to explain), but it looks like this.

Its probably best seen on the video.

The crankshaft is lightly held in place with two inverted U shaped bits of wire taped to the sides. (just visible near the top, left rim of the device)

I stuck a cardboard disk about the size of a CD onto the end of the shaft to act as a flywheel, and then added nuts and bolts with blu-tac until the thing was balanced.

To get them in the right spot, I put the disk in a random place, and if it rolled back to a different position, Id stick on a weight so it wouldnt.

I should have been able to do this with just one weight of the correct size, but for some reason it was beyond me.

So...

• The displacer is the soft drink can thing inside the bottom can. 
• The bottom can is sealed ([buy - EDIT  - note from the future-  Who makes errors like this?] by the top tin can) except for the small hole in its top that has the displacers wire poking through.
• The displacer travels up and down inside the bottom tin can with a total travel of around 1cm.
• The displacer gets very close to the top and bottom of its tin can container, but never actually touches.
• The displacers wire is connected to the crankshaft (between pink beads)
• The power piston (pink balloon) is floopy, and connects to the crankshaft 90 degrees offset from the displacers crank.
• The top tin can is there to hold up all the other kit, and as the top seal for the chamber holding the displacer (soft drink can thing)
• When the air inside the bottom tin can heats up it expands, forcing the power piston up. This turns the crank and gives the device its power.
• As the device rotates, and the displacer moves down, forcing the air up and away from the heat, so it cools and contracts. 
• When it contracts, the power piston is sucked down.

Thats pretty much it. Repeat as desired, or until something breaks. 

Some light oil can be added to any surfaces that have friction. (where the displacer wire moves up and down into the bottom tin is a high friction area)

==============>>> IMPORTANT!!! Note from the future - It turns out you probably shouldnt add oil to the point where the wire slides through the can. Theres a chance of explosion as the oil is heated to a gas. <<<================

120 things in 20 years - I made a Stirling engine!

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Thinking Vacant

Sometimes things conspire in such a way as to make you look blankly at walls for such a long time as to make other parts of you decide to wonder off and ignore those parts of you currently engaged in looking blankly at walls.

This is how we know its time to change the way we look at stuff.

Thats not to say we should actually look away from looking blankly at walls, but rather that we understand there are advantages to looking away.

What you do is up to you.

Its not necessary to look away, only that you should know there are better things to look at, and better things that might be revealed if you were to actually look away.

Currently, Im failing, but one day I hope to master new methods of looking...

Away...

blankly at walls.

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Winner! Attempt

I totally didnt win a 3D printer!

Sad face.

I really wanted to win a 3D printer.

But I guess everyone else did as well.

Oh well.

I actually voted for someone else.

Perhaps that was the problem.

This really cool barometer entry featured a glass jar with a balloon glued over the top, and a stick glued on top of that so that, when you place the device next to a wall, the stick would move up or down depending on the air pressure of the day.

Very cool.

Very minimalist.

Anyway, Ill just use my 2D printer, but Ill print a lot of copies so I gain some depth.

Or figure out a different way to win a 3D printer.

Or maybe just become a patissier.

Either way, its all good.

Perhaps I should have posted a link to vote for my entry or something.

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Stirling Engines My second attempt

I think I may have actually built something.

Or nearly built something.

It looks like this and almost works.

Most of that junk in the picture isnt part of it. The bits that are part of it are the bits that look like a Stirling engine.

Sometimes Stirling engines look like tin cans, and wire, and pink balloons. They also look like cardboard disks with blu-tac stuck weights all over the place to act as a flywheel.



I planned on posting a video of it working today, but it doesnt.

What it does do is spin around freely for a few seconds when you spin the flywheel. It also has a displacer and power piston that are configured in such a way as to do what they are meant to.

I think.

When I put it on the stove top, it nearly feels a bit like its trying to work, then smoke starts pouring out of the seals, so I take it off the heat before it catches fire.

Who knew tape might burn.

Yes. Thats right. I thought Id make my engine using gaffer tape for the seals.

It doesnt work so well.

Tomorrow, Ill buy some glue. I seem to remember hearing of someone who used two part epoxy on a real engine crankcase, so it should cope with the heat.

Maybe.

My next choice will be solder. Solder melts when you get it hot, so Im guessing that wont work so well either.

But the glue might.

If it works, Ill put up a big build post. If it doesnt Ill try something different.




120 Things in 20 years - Using a random evolutionary approach to building a Stirling engine. Chuck some bits in a bag, shake, then cull anything that doesnt work like a Stirling engine. Ill get there eventually.


[edit from the future - For anyone concerned that time may not be linear any more, this post was actually written two days ago, but for some reason didnt get posted. As a result the post after this one was actually two days after this one.]

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