Amateur Workshop Magazine Stirling Engine

[mnay]

I will try this again the correct section of the forum.

I have wanted to build a Stirling engine with enough power to do more than turn it's own flywheel. I came across this small engine and asked the forum if anyone has built it. Some were aware of the engine, but no one responded about constructing one. It was also pointed out to me that the Amateur Work Magazines were free domain on the internet.
http://chestofbooks.com/crafts/popular-mechanics/Amateur-Work-3/A-Hot-Air-Engine.html

The following will be a description of my version with a few changes and using materials I have available. Hopefully I will have success. I have only built models so far from proven plans. We will see how this goes.

Comments and suggestions are appreciated.

Mike

 

[mnay]

I started with the displacement cylinder. Instead of threading the pipe and cut grooves. I also found a piece of alloy tubing to use for the displacement piston.

My version is going to have a water jacket, so I burned out a couple of rings for the water jacket.

After grooving the displacement cylinder, I welded on the rings for the water jacket on the cool end.

More to come

 

[mnay]

On the previous post I had also welded a fitting to tie into the power cylinder.

I rolled a piece of sheet metal for the water jacket and welded it on.
I used the TIG welding method with 309 stainless filler. It seems to be more forgiving and I have fewer pin holes on mild steel than with the steel fillers.

I welded on a fitting top and bottom to circulate the water through the jacket.

I then pressure tested it for leaks to avoid problems down the road.

 

[mklotz]

Given your desire to perhaps power something with the engine, be aware that, with that design, neither end of the crankshaft is available to attach a power take off pulley (or whatever). You would need to run a captive belt off the flywheel circumference.

Are you planning a pump for the waterjacket or will you use a static water tower?

 

[mnay]

I plan to run a water pump for the jacket and hope to have room for a small drive belt or chain. I am designing as I still stay within the basic specifications for an operating stirling engine.

Mike

 

[mnay]

After the water jacket passed the test, I welded the front flange on.

to be continued

 

[mnay]

For a break from the displacer cylinder, I found in my junk box an 8" cast iron hand wheel. I decided to true it up and use it as the flywheel on this engine.

 

[mnay]

Here is the displacer cylinder with the head end flange which will also be used as a mounting bracket

 

[mnay]

Next part to complete in the displacer piston. I had already finished the boring the tubing to .050 wall and the OD was already to size. I faced the end and parted of 1/8 short to allow the two end caps to stick out 1/16 per side.

I soft soldered the 1/8 material for cap opposite the rod end to be able to finish it in one set up.

I then machined the rod end cap from 1/2 plate and reamed for a close fit on the rod. I put it in the angle vise to drill and tap a hole for the set screw to hole the rod in

to be continued

 

[mnay]

The ends were then silver soldered on. Note that I left a tapped hole to be later filled with a set screw so let the hot air escape while the soldering was done.

A little bit of clean up and the piston is done.

Next I will need to machine the piston rod and a head for the displacement cylinder.

 

[mnay]

I have finally gotten back to work on this project.
I machined the linkage for the displacer side and the bearing pedestal, but as I suspected the displacer piston rod was too small and it vibrated and chattered and the piston stroked.
To correct the problem, I threaded the head and machined a graphite bushing to support an new through rod, that extends through the displacer piston.

 

[mnay]

Here is the graphite bushing installed in the head. I moved it around to find the "sweet spot" so it stroked smoothly, then I clamped it and welded the head on.

 

[mnay]

You can see the power cylinder and power piston setting in the background.

I am ready to start on the linkage for that side of the engine.

Hope it runs

 

[techonehundred]

Really looks like it is coming together. Waiting to see more.

 

[mnay]

Made a little more progress. I built the head for the power cylinder, (just have to drill and tap) and the power connecting rod and power side crank. Just a few hours from testing. If it runs good I will build a good fire box and fancy it up.

Mike

 

[mnay]

I finally got the stirling put together far enough that I could test run it. I put water in the water jacket, checked everything for free movement and oiled her up. I heated the hot end by hand with a propane torch but the darn thing would not quite run. I experimented with the timing, but still not quite.

I believe I know a couple of the problems. The flywheel could be a little heavier to help it roll through it’s stroke, but that is not the main real problem. I finally disconnected the power connecting rod from the crank so that I could roll the displacer and flywheel by hand with the heat on and see how much it would move the power piston without it being connected. To my dismay it only attempts to move about half of the 3” stroke. I am going to move the drive pin down on the crank to cut the power stroke in half and see if it will run. If it does I will make some modifications to it so it will at least run. I double checked the math for the displacement in the displacement side and the power side and the calculations seem to be close enough to run.

 

[mnay]

With a night to sleep on the problems, I tackled the solutions last night. As I mentioned before, when I could not make the engine run, I disconnected the Power piston from the crank and with the diplacer heated I turned it over by hand to see how much movement I would get out of the power piston.
For whatever reason, and these things are a mystery sometimes, I was only getting about half of the stroke in movement. I drilled and tapped a couple more holes in the power crank to be able to adjust the stroke, not worrying about the dead space I would have in front of the piston. With the stroke cut almost exactly in half it runs pretty good.

I will next make a longer connecting rod to eliminate the dead space and if that works out I can shorten the piston and cylinder if I decide to. Anyway I feel better about this project after spending so much time on it.
It seems like it will have enough power to at least run a small water pump to circulate the water in the cooling jacket.

I will also need to build some type of stove cover over the hot end to heat the cylinder evenly. I didn’t take much heat to make it run and it ran for a long time after I removed the heat.

Anyway, onward and upward……

 

[mnay]

For some reason this photo didn't post
Here is a photo of my variable stroke crank to experiment with

 

[mnay]

A tiny bit more progress. I got the stove section welded up and slid on.
I experimented with a couple of alcohol burners. It will run, but not quite enough heat. I will need to fix up some type of propane burner. When I blow my propane torch in the bottom it runs real well.

 

[mnay]

opps wrong photo
here is the correct one