A small Stirling

MuellerNick · Jan 29, 2013

Hi!

Today, I cleaned this Stirling engine that I have built many winters ago. It was just collecting dust in dark box.
As I didn't like the flywheel, I also turned and milled a new one, that better fits the overall appearance.

Looks like I have to re-read the camera's manual re "white balance".

Base is 200 * 60 mm.
I'll put that back into the dark corner

Nick

ShopShoe · Jan 29, 2013

Nick,

Thanks for showing that.

Such Simple Elegance.

I like the the way you did the flywheel in the picture, Don't know if I've seen one like that before.

Also like the two metals on the cylinder

--ShopShoe

MuellerNick · Jan 29, 2013

I like the the way you did the flywheel in the picture, Don't know if I've seen one like that before.

I invented that yesterday. I guess.

Here's a better picture showing the detail how it was made:

I cut off a disk ø90 mm that was faced on both sides. Then it went into the 3 jaw chuck on the mill and 3 pockets a bit more than half the disk's thickness deep were milled. Flipped it over and rotated it about 30° (I wanted to avoid that I do have to rotate it exactly 60°). Milled the same 3 pockets again and … voila!

Also like the two metals on the cylinder

That's copper - steel - copper (under the fins) to improve and reduce heat transfer.

Nick

MuellerNick · Jan 29, 2013

Made and uploaded (unlisted) a video of it:
[ame="http://www.youtube.com/watch?v=dyZRyPp9ZCY"]Stirling engine[/ame]

Nick

borna · Jan 30, 2013

This looks awsome. As far as skills, what is the hardest part of this engine?
How long it took you build this?

Borna

MuellerNick · Jan 31, 2013

I have built it from plans in a booklet. In the meantime, I have sold that booklet, Stirlings are no longer my interest.

I have changed the shape of the outer parts to my like. There were no really complicated parts to make. Only the working cylinder and piston do require attention for a good sealing fit with no sticking. All was done on manual machinery.
Except the flywheel that I now remade and CNC-milled. But it could be made on an RT.

Nick

MuellerNick · Jan 31, 2013

How long it took you build this?

Forgot to answer this.
Well, that depends on your skills.

Something in the range of 20 hours maybe?
Required skills: precise boring to scribed lines, milling, turning, filing, silver soldering.
Takes two different reamers (axle and boring the guide for the displacement plunger + one for the working cylinder). A few taps and counter sinkers and that's it. Nothing too fancy or expensive.
Just bar stock, no castings or unobtanium.

Stirlings at this size are a bit tricky to get them running. As soon as you oil the rod for the displacement plunger or the piston, it won't work. Oil it and wipe it off. That's enough lubrication.

It is a gamma-Stirling. If you take any plans as a basis, the end result might look similar. Just leave out any ornamental crap and reduce to the max[tm].

Again, I no longer have the plans.

Nick

robcas631 · Jan 31, 2013

Beautiful engine!

aarggh · Jan 31, 2013

Nick,
Absolutely beautiful engine. the wheels especially look great! Can I ask how you constructed the copper - steel - copper section? And the piston appears to look like it's made of nylon or similar white material? If it is, I thought nylon suffers high temperature expansion rates which can cause it to bind?

cheers,
Ian

MuellerNick · Jan 31, 2013

Making the copper-steel-copper section is not complicated.
I started with a copper tube that I cut off two suitable pieces. Then, at one end of each, I turned a recess of maybe 2 mm deep. The diameter so that the wall thickness was halved. Turned a matching tube out of steel (from solid bar). The steel tube obviously had a recess at both ends "the other way round". Pushed the 3 parts together and silver soldered them at the seal.

The reason for the copper-steel-copper mix is:
In the displacement cylinder, you want to have two separate zones. One hot and one cool. Copper does conduct heat well. So the heat would transfer from the hot to the cold part through the copper tube. Steel is a less good heat conductor, so it went in between as an "isolator". Stainless steel would work better.

And the piston appears to look like it's made of nylon or similar white material?

I'm sorry, piston? If you mean the cylinder with the cooling ribs, it is aluminium. If you see part of the piston of the working cylinder, that one too is out of aluminium.

Nick

aarggh · Feb 1, 2013

Great, thanks for explaining that Nick, very helpful. The aluminium in the photo seemed very white to my eyes which is why I queeried nylon being used, but it must have been lighting just making it brighter.

Cheers, Ian

steli · Feb 7, 2013

MuellerNick said:
Hi!

Today, I cleaned this Stirling engine that I have built many winters ago. It was just collecting dust in dark box.
As I didn't like the flywheel, I also turned and milled a new one, that better fits the overall appearance.

View attachment 60055

View attachment 60056

View attachment 60057

View attachment 60058

View attachment 60059

Looks like I have to re-read the camera's manual re "white balance".

Base is 200 * 60 mm.
I'll put that back into the dark corner

Nick

Hi Nice work look like factory made

A small Stirling

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