Step 11: Thread the cranks through and attach displacer
You can thread the cranks through now, as you do, thread the displacer
rod connector onto the cranks. Don't worry if you widen the holes a
little, we'll be adding extra bearings in the next step.
happy with the cranks moving the displacer, you can bend the displacer
rod over a little more like a fish hook, to prevent the connecting rod
from slipping off.
Step 12: Steel bearing points
Because aluminium is so soft, the bearing points will wear out quite
quickly (mine lasted around 30mins!). To fix this, we'll add some steel
To make these, I drilled a 2mm hole in the side a flat
side tin can then I cut a square around this. Make two of these. Then
thread them onto the cranks and glue them in place using super glue. The
curve of the tin can should almost match the curve on the coke can.
Steel cut out for bearings
Step 13: The diaphragm
The diaphragm is a balloon with a bottle cap glued to it. The bottle cap
has a piece of 1.2mm steel threaded through it. I made the holes for
the steel wire using a drawing pin. To keep the diaphragm connecting rod
in the centre, you'll need to make two spacers by wrapping steel wire
around a piece of spoke. The spacers are around 1 cm long. Thread the
diaphragm connecting rod through the steel pin with a spacer either
Cut the neck off a balloon, and stretch the main part of
the balloon over the end of a coke can. Then glue the bottle lid to the
balloon using super glue.
Step 14: Fit the balloon onto the paste lid
The balloon is fitted over the paste lid. It should be a little bit
loose. You might need to use an elastic band to hold the balloon in
place. You can connect the other end of the diaphragms push rod to the
cranks now. You'll need to add another screw block to the end of the
cranks to stop this coming off.
Screw block holding the diaphragm rod
Step 15: Firebox/candle holder
Cut a coke can down to about 45mm tall, and push another coke can into
it, this is just to widen the top of the can as it'll be weak once you
cut the hole for the candle.
Next cut a slot in the front of
this can, about 50-60mm wide for the candle to fit in. Use your pliers
to flatten the bottom of the can, so that you can fit the bottom of
another can in there upside down for the candle holder.
bottom of a can right around the bottom edge. This is just to hold the
Step 16: Building a fan
The fan is really easy to make. Essentially it's squares of paper glued
onto BBQ skewers, which are epoxied to a cardboard disk.
by cutting a cardboard disk out about 70mm diameter, before you cut it,
mark 8 sections using a protractor or similar. Cut 8 lengths of BBQ
skewers at around 10cm long.
The paper is folded along it length,
the folded again. Please look at the photo's, as it's hard to explain.
Then it's cut along the previous fold and cut again in the middle. This
should give you 8 little gift tag sized pieces of paper. These are
folded over the ends of the BBQ skewers, tape the loose ends over and
glue the paper to the skewers.
Tape each of the blades to the
cardboard, along the 8 lines that you marked. Raise your cardboard disk
up about an inch using any random object, and epoxy the blades near the
centre. Raising the cardboard makes all of the blades sit at the same
Step 17: Attach the fan
The fan is attached on the opposite side that the diaphragm connects to.
Push the fan onto the shaft and bend a hook on the crank shaft. The
hook is pressed into the cap so that the crankshaft can grip it.
With the fan attached, tape on a 2p coin on the opposite side to where
the displacer is connected. This is to counterbalance the displacer
Fan hook bent
Blades hooked in
Step 18: It's finished now!
Hopefully, it'll work first time, unlike mine which needed some
tweaking. You'll most likely have to adjust the diaphragm connecting rod
until the engine turns smoothly. There's not much to wrong in this
engine, other than too much friction, or air leaks. So if your engine
doesn't work, check those things.
The next few steps are
additions you can add to make the engine better, such as a fan, heat
sink and "super stylish" red trim.
Step 19: [OPTIONAL] A heatsink
I made a simple heat sink out of a coke can, by cutting the top and
bottom off. I cut fins down the sides of the can leaving out a space for
the fan. It's glued to the wooden block using super glue.
Step 20: [OPTIONAL] Add some trim
I added some trim to the edges of the cans in the same way as I did in
my other Stirling engine instructable.
Take some electrical wire and cut it down the side, this can then be
pushed and glued onto the edges of the engine.