My Jeroen Jonkman’s Stirling 60 brass Stirling engine build

After building my first model (a simple, single action wobbler) I started searching on-line for my next build. When I came across the beautiful brass Stirling engine designed by Jeroen Jonkman, and found out that he had posted free plans for it, I knew I had found it.

So, I converted the drawings from metric, ordered the materials I needed and got to work. First thing I did was cut the Pyrex test tube to length. I ended up using my Noga mister to keep the tube from thermal cracking. For the machining, I started with the flywheel. I drew it up in Fusion 360 so I could make drawings for the offset positions for the slots. I set it up on my rotary table and used those offsets and moves along with the rotations of the table to cut the slots. Boy, was this a lot easier with my new DRO! Also, using Fusion was a lot easier than doing all the Trig to calculate the offsets and moves.

I haven’t worked much with such small parts. For example, some of the pins were only 0.047” in diameter. Most of my experience is with parts that if I drop them on the floor I’ve got at least a chance of finding them. And, my equipment is geared towards larger work, as well as my work holding devices. I’m sure that after building a few more models I will have built up a better supply of small work holding equipment. I also ordered and used a pair of Optivisors!

I made piece after piece until it was time for polishing. I ordered some buffing wheels and compounds from Caswell. These did a great job of shining things up. For me, I got to the point where I just had to say enough is enough, because you can drive yourself crazy polishing parts… The more you polish, the more those tiny little scratches show up!

I made the wood platforms out of walnut, because I thought that would look nice against the polished brass.

There can be no friction or air leaks or these little guys won’t run. So, great care must be taken there.

This project certainly came with its’ challenges… but that’s why we build this stuff, isn’t it?

So, what’s my next project? Well, to start with, I’m going to make two more of these brass Stirlings! One for each of my boys!

Ted



The raw materials...



Used a Dremel type diamond cut off wheel to cut the Pyrex test tube to the required length.



Some fun with the rotary table.



One of the first things I did was make this plate to hold some of these small parts.



These adjustable parallels were just the right size to add some support.



Cut these 0.047" diameter pins by taking a heavy, single cut.



You lose a little stock finding the correct depth of cut, but once you find it they will come out right on size!



Had to hold some of the parts with hemastates with aluminum shim stock (to keep from marring it) so I could buff them up nice.



Used my tiny Albrecht chuck as a pin vise to hold the tiny pins so I could file them to the proper length.



I love these Albrecht chucks!



The finished main components (before buffing).

Here's a YouTube link to see it running if you're interested...

 

Ted, are there any drawings on the 2 long linkage arms connecting to the cam? They are missing from your prints?

 

Ted, are there any drawings on the 2 long linkage arms connecting to the cam? They are missing from your prints?

There is an updated set which includes the arms. I don't know the link off the top of my head but I'm sure if you Google you will find them.

Ted

 

Here's the complete drawing.

Ted

 

Awesome work, absolutely gorgeous.

 

Hello Technical Ted!
I finally made my engine!
I mention that I replaced the displacer piston with a glass test tube.
In the first tests the engine turns, but only when I give it a lot of temperature. The rehearsal ended when glass drops fell
The biggest problem I have, as you can imagine, is friction. Mostly on the displacer hub, made of cast steel.
My question: can this bushing be made of bronze? (The displacer is made of steel)
Thank you very much
--------
Hola Technical Ted!
Finalmente hice mi motor!.
Le comento que reemplacé el pistón desplazador por un tubo de ensayo de vidrio.
En las primeras pruebas el motor gira, pero solo cuando le doy mucha temperatura. En ensayo concluyó cuando cayeron gotas de vidrio
El problema mayor que tengo, como imaginarás, son las fricciones. Mayormente en el buje del desplazador, de fundición de acero.
Mi pregunta: se podrá hacer este buje de bronce? (El desplazador es de acero)
Muchas gracias a ti

 

Hello Technical Ted!
I finally made my engine!
I mention that I replaced the displacer piston with a glass test tube.
In the first tests the engine turns, but only when I give it a lot of temperature. The rehearsal ended when glass drops fell
The biggest problem I have, as you can imagine, is friction. Mostly on the displacer hub, made of cast steel.
My question: can this bushing be made of bronze? (The displacer is made of steel)
Thank you very much
--------
Hola Technical Ted!
Finalmente hice mi motor!.
Le comento que reemplacé el pistón desplazador por un tubo de ensayo de vidrio.
En las primeras pruebas el motor gira, pero solo cuando le doy mucha temperatura. En ensayo concluyó cuando cayeron gotas de vidrio
El problema mayor que tengo, como imaginarás, son las fricciones. Mayormente en el buje del desplazador, de fundición de acero.
Mi pregunta: se podrá hacer este buje de bronce? (El desplazador es de acero)
Muchas gracias a ti

Please keep in mind I am not the designer of this engine so take my advice as someone who has had to struggle through the problems with this engine myself.

Not sure about using brass/bronze for the bearing... you want to use whatever material will hold up to the heat and also offer the least resistance/friction. I think this is why cast iron was used by design. It is self lubricating to an extent. But, I certainly don't see where trying different materials is going to hurt anything...

On all 3 that I built, the bearing was the biggest source of trouble... the hole through it has to be perfectly centered and concentric with the OD. The tiny drill I used to drill these ALWAYS wondered off enough to cause big problems. The only way I could get a nice straight hole was to mount one of my small Albrecht chucks in my tool post block and use a dial indicator to get it perfectly centered. This worked, although I think now there is a better way. I would make the bearing with a slightly oversized OD. Then, machine a stubby mandrel in my lathe that I could super glue the bore of the bearing to. Then, turn the OD of the bearing to final size. Heat or acetone will release the super glue.

Also, I would think that glass might weigh too much for the displacer, since you want this as light as possible. If you don't want to make it out of very thin machined brass then I would try aluminum, although it probably won't look as nice. The heavier the displacer tube is, the more the shaft will bind in the bearing.

A thought that I've had if I make another one of these is to tweak the design a little so I could make the cast iron bearing a little longer. My thinking is that being longer would give more bearing surface and help to keep the shaft from cantilevering and binding up. It would be a little more drag because of the longer surface contact, but should help the shaft from binding up because of the unbalanced weight on the shaft as it moves back and forth.

Also, make sure to get all the linkages in perfect alignment when mounting the posts/assemblies. Did you de-grease the ball bearings for the fly wheel? The assembly should turn over VERY freely.

Good luck,
Ted

 

One can use ball bearing from computer fan maybe?

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

One can use ball bearing from computer fan maybe?

Sent from my SAMSUNG-SM-G930A using Tapatalk

Maybe? I guess any bearings that are the correct size and type will work, but removing all grease is recommended to reduce the force required to rotate the flywheel. You want it to turn as freely as possible and grease will add restriction. The ones I used were shielded, but the grease was easily removed by letting them soak in brake cleaner, multiple times, and blowing them out with compressed air.

Ted

 

Please keep in mind I am not the designer of this engine so take my advice as someone who has had to struggle through the problems with this engine myself.

Not sure about using brass/bronze for the bearing... you want to use whatever material will hold up to the heat and also offer the least resistance/friction. I think this is why cast iron was used by design. It is self lubricating to an extent. But, I certainly don't see where trying different materials is going to hurt anything...

On all 3 that I built, the bearing was the biggest source of trouble... the hole through it has to be perfectly centered and concentric with the OD. The tiny drill I used to drill these ALWAYS wondered off enough to cause big problems. The only way I could get a nice straight hole was to mount one of my small Albrecht chucks in my tool post block and use a dial indicator to get it perfectly centered. This worked, although I think now there is a better way. I would make the bearing with a slightly oversized OD. Then, machine a stubby mandrel in my lathe that I could super glue the bore of the bearing to. Then, turn the OD of the bearing to final size. Heat or acetone will release the super glue.

Also, I would think that glass might weigh too much for the displacer, since you want this as light as possible. If you don't want to make it out of very thin machined brass then I would try aluminum, although it probably won't look as nice. The heavier the displacer tube is, the more the shaft will bind in the bearing.

A thought that I've had if I make another one of these is to tweak the design a little so I could make the cast iron bearing a little longer. My thinking is that being longer would give more bearing surface and help to keep the shaft from cantilevering and binding up. It would be a little more drag because of the longer surface contact, but should help the shaft from binding up because of the unbalanced weight on the shaft as it moves back and forth.

Also, make sure to get all the linkages in perfect alignment when mounting the posts/assemblies. Did you de-grease the ball bearings for the fly wheel? The assembly should turn over VERY freely.

Good luck,
Ted

Thank you very much for your answer!
I will take into account your advice

 

Please keep in mind I am not the designer of this engine so take my advice as someone who has had to struggle through the problems with this engine myself.

Not sure about using brass/bronze for the bearing... you want to use whatever material will hold up to the heat and also offer the least resistance/friction. I think this is why cast iron was used by design. It is self lubricating to an extent. But, I certainly don't see where trying different materials is going to hurt anything...

On all 3 that I built, the bearing was the biggest source of trouble... the hole through it has to be perfectly centered and concentric with the OD. The tiny drill I used to drill these ALWAYS wondered off enough to cause big problems. The only way I could get a nice straight hole was to mount one of my small Albrecht chucks in my tool post block and use a dial indicator to get it perfectly centered. This worked, although I think now there is a better way. I would make the bearing with a slightly oversized OD. Then, machine a stubby mandrel in my lathe that I could super glue the bore of the bearing to. Then, turn the OD of the bearing to final size. Heat or acetone will release the super glue.

Also, I would think that glass might weigh too much for the displacer, since you want this as light as possible. If you don't want to make it out of very thin machined brass then I would try aluminum, although it probably won't look as nice. The heavier the displacer tube is, the more the shaft will bind in the bearing.

A thought that I've had if I make another one of these is to tweak the design a little so I could make the cast iron bearing a little longer. My thinking is that being longer would give more bearing surface and help to keep the shaft from cantilevering and binding up. It would be a little more drag because of the longer surface contact, but should help the shaft from binding up because of the unbalanced weight on the shaft as it moves back and forth.

Also, make sure to get all the linkages in perfect alignment when mounting the posts/assemblies. Did you de-grease the ball bearings for the fly wheel? The assembly should turn over VERY freely.

Good luck,
Ted

Hello!
I agree to lengthen the bearing. I'm going to make a small modification to make it as long as possible. You may be able to lengthen it by 2-3 mm. I'm going to try to make it out of bronze.
Yes, I removed all the lubricant from the ball bearings.
I liked the alternative to get the hole to be centered.
I will tell you about the results I get.
I tell you that I did a pendulum clock and it was also a fight against friction.
Thank you very much again and my apologies for my Google English