Tis a funny kind of beast running so slowly and deliberately.
I officially like Stirling engines. Mine looked like this...
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 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.
Don't 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 family's trusty meat mallet.
This meat mallet used to be my mother's (it probably still is), and was used as the household hammer for as long as I can remember.
Actually that's 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.
It's a bit difficult to see, but that's 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 it's contour matched the tin can's.
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.
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".
I'll 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 displacer's 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 o'clock, the other would be at 3 o'clock (or 9)
It's 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)
To get them in the right spot, I put the disk in a random place, and if it rolled back to a different position, I'd stick on a weight so it wouldn't.
I should have been able to do this with just one weight of the correct size, but for some reason it was beyond me.
- 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 it's 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 it's 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 displacer's 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.
That's 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 shouldn't add oil to the point where the wire slides through the can. There's a chance of explosion as the oil is heated to a gas. <<<================
120 things in 20 years - I made a Stirling engine!