Stirlingengineforum.com

Here is my water bottle Stirling engine I've been building. It's a work in progress,
any suggestions welcome. The alternator is to be replaced with a permanent magnet
axial flux type soon.

You tube video here: http://www.youtube.com/watch?v=J15Al2b-Aa4

The displacer cylinder is a SS drinks bottle, inside runs the displacer which is made from
fine steel wire wool. The wire wool wasn't actually all that fine though, so I think there's
some room for improvement there. The displacer rod is 1.57mm running in a 2.38mm brass
tube, this gives a sliding fit that's airtight enough.
I cast a diaphragm from RTV silicone as an experiment, it's seems to be holding up fine, but
it looks a bit rough!


The cranks are bent from 3mm stainless rod with ball bearings on all of the bearing points.
Flywheel is from a large tin can lid.

The rest of the engine is plywood and threaded rod.

Did you manage to get the bends OK on the crankshaft, I never seem to get bends like that just spot on, I machine My crankshafts, that way you can get a more compact design. I must look into the water bottle idea. Ian S C

I got them working, but they're a long way from what I'd planned. Really hard to bend them into the shape you
want. Approtechies cranks seem to be much neater, but I don't know what his secret is :)

Good torque output on the motor. The fly approves. How upset does it get when you short the generator leads together?

you could make the crank webs out of flat metal, say 1/4" thick, drilledin pairs the diameter of the shaft. Feed the long shaftright throughan the crank pinwith the bearing in place, and maybe the conrod to. Loctite the shaft as is, and when cured saw the bit out of the main shaft between the webs. No lathe needed, just needs accurate drilling. Ian S C

Ian S C wrote:you could make the crank webs out of flat metal, say 1/4" thick, drilledin pairs the diameter of the shaft. Feed the long shaftright throughan the crank pinwith the bearing in place, and maybe the conrod to. Loctite the shaft as is, and when cured saw the bit out of the main shaft between the webs. No lathe needed, just needs accurate drilling. Ian S C

I use a similar technique, but prefer solder to glue.
You can make crank webs from plated shorting bars used on DIN rail terminal blocks, these already have accurate holes drilled.
I solder them to brass rods as this allows several tries to get good alignment before cutting away the unwanted sections.
Not all shorting bars can be soldered though, the shiny ones work well, the dull ones are aluminium and don't solder.

Another source of crank webs is to use coins - the Euro one, two and five cent coins all solder easily after cleaning them with sandpaper.

I agree with you Carnot, I was looking at a simple way of doing it without heat, and your idea of using predrilled bar is a good one, the idea is to use whatever you can find. I suppose you could use the aluminium bar with glue, could be worth a try if nothing else was available.
There are many ways of assembling a crankshaft, press fit, heat ie., shrink fit, brazing, or soldering, and loctite glue. My favoured method of making crankshafts is to machine it out of solid, but you need the tols to do the job, and not every one has, it also can require quite a large lump of metal to start with. Ian S C

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