Stirling Fan

[doc1955]

Decided to build a Stirling Fan.
I also decided to make it a double build as I did with my last build.
The second one will again be a gift.

This is the first part the hot cap.
Here I start with a piece of stock long enough
For 2 parts plus enough to allow for parting tool.

Here are the 2 parts one end has been cut with the
End slots to help capture the heat during operation

I cut the slots using a hexagon collet block
Here I depart from the drawings this should be sufficient and easier to accomplish.

After finishing both ends I part into 2 pieces.

Here the 2 parts are split now load each and
Bring them to the proper length.

Face to length and rough drill inside diameter and finish bore.

Here I turned up a spud to slide part over the spud is a nice snug fit. I then turn down the under cut section of the hot cap. This section helps keep the heat at the end of the cylinder. I used the tail stock and a small scrap piece to pinch the material to turn.

 

[Deanofid]

These look nice, Doc. Is this one of Jerry Howell's projects?

You sure keeping in good with the family. Anyone would be thrilled to be on your "gift list"!

This should be another great build!

Dean

 

[doc1955]

Dean yes its Jerry's super Stirling I purchased the plans awhile back.

He's still showing all his friends the other engines I've built for him. He is fun to build things for. He gets so excited about them.

 

[doc1955]

Here are both part finished.

Next I worked on the displacer cylinder.

Picked out a scrap drop end piece of 7075 t6 aluminum.

Cut piece in half and layed out to rough mill out outside profile.

Rough milling part profile.

Pieces are cut to size.

Laid out the center and bore to aid centering in 4jaw on lathe.

Centering in lathe with dial indicator.

Parts have holes bored and ready to have cut cooling fins cut.


Next time turn up a mandrel to cut fins.

 

[Deanofid]

You're going at it, Doc. Double the parts count doesn't seem to slow you down much!

Dean

 

[SAM in LA]

Doc,

Looking good.

If I tried to make two engines at a time, I would scrap twice as many parts. :big:

SAM

 

[Maryak]

Doc,

Looking good.

If I tried to make two engines at a time, I would scrap twice as many parts. :big:

SAM

ME TOO

Best Regards
Bob

 

[doc1955]

Well got some time in the shop.
Turned up a mandrel to turn cooling fins everything went well during process.

Here is the mandrel noting special just fits snug slip fit to the bore in part and screw in end pinches it.

I used a part off blade with a full radius ground on the end and extended from holder just far enough to reach proper depth and clear the corners of the stock.

Here they are next the hole pattern for the hot cap and the power cylinder.


That will be next time.

 

[Deanofid]

Nice slim fins on these cylinders, Doc. Nicely spaced, too. That's something I always worry
about screwing up when I do fins.

Dean

 

[doc1955]

If you look closely you'll notice I did mess up the last fin isn't suppose to be there a .031 mistake. But the thing is it isn't the fins I messed up on but actually the base thickness. So after doing the fins on the first one I had to make the second the same. That's ok I'll adjust and it'll be ok.
What spooks me is the first few cuts with the part off blade keep picturing it grabbing the fin and ripping it off but honestly it has never happened (Knock on wood) but I have ruined a cylinder once when a parting tool grabbed and sucked in that happened in a 3 jaw. After that I take my time and make a mandrel and put it in a 5c collet.

Thanks for the comments Dean!

 

[doc1955]

Well started putting hole pattern in. I decided t change the cross hole to the power cylinder and drill it from the side and plug the access hole in the side.

This part went ok then set up to do pattern in bottom.

This didn't go so good had a math error in the hole pattern so I ended up rotating the pattern 10 degrees to get the correct pattern in. Why is it when you do something like this right after you drill the last hole in the pattern you go hey wait thats not right! Well things were going smooth.

Then hole pattern in top.

Well at least you won't even see it once the hot end is bolted in place but I'll know it's there.

Now on to the displacer, didn't have any round stock the right dia. so grabbed a drop end block and comenced to make it round.

Next time finish the displacers hope things go better with them.

 

[Deanofid]

Darn holes!

"you won't even see it once the hot end is bolted in place but I'll know it's there."

Well, yer Paw-in-Law won't. That's consolation for you, Doc. Sorry for your troubles.
I ended up doing the displacer can on my current one three times before I got it right.
Couldn't measure the shaft for it to same my life! I'm sure you'll do much better.

Did you get the bearings and graphite for these from Howell?

Thanks for the update.

Dean

 

[ksouers]

Doc,
Glad to see you on another project. I'm surprised it's so quickly on the heels of the beam engines.

I'll be watching closely.

 

[doc1955]

Didn't get out into the shop today.

Dean I had plenty of small precision ball bearings on hand I did order some graphite I had some on hand but not large enough I had .500 and it runs about .003 undersized I was going to leave the bore for the power cylinder u/s but have decided to just go ahead and order some .625 stock so I ordered 6 pieces to have some on hand.

Ksouers
I can't seem to leave my mill and lathe sit for more than a day or two. (funny how its a blast when I'm working at home)

 

[doc1955]

Got the displaces turned up. I turned the OD to finished size.
Then rough drilled ID to proper depth.

I set drill off end to get to the right depth.

Then I bored the finished dia to the proper depth. Notice I wrapped masking tap around the OD on the end to keep wall from flexing.

Finished parts next the end pieces that slip and get loctited into the ends.

 

[Deanofid]

Good idea with the masking tape for the displacer cans, Doc. Those things are about as thin as they can be without just being air, aren't they? One of those 99.9% swarf jobs.

They look good, and the Noid sure seems happy about it.

Dean

 

[doc1955]

Thanks Dean!

I've done thin wall turning 2 ways with tape on the out side or the other way is to turn the ID first and make a snug plug and then turn the out side. I've had good luck both ways but these were pushing the limit due to the length of them.

Dean I sure like your build it has been super! I hope these turn out half as good. I've been trying to think of an easy way of constructing the fan blades.

Thanks again for checking in on my build and congrats on yours!

 

[Deanofid]

Doc, I don't know how the prints show to make the fan blades, but I saw what I thought was a kind of
nifty way to do it somewhere.

The hub was turned to size, left on the parent stock, and then slots were cut with a slitting saw on a
diagonal to the axis of the hub bore. The diagonal slots make the pitch for the blades.

The blades were just cut out of sheet, sandwiched together, and the rough edges files smooth, making them all the same shape. To bend the blades, they were just rolled over a piece of round stock of a suitable diameter. Then soldered into the slots on the hub. Voilá! Fan, (or propeller, screw, ect).

Well, that's one way to do it, I suppose. This happens to be fresh to my mind because it's how I plan
to make the small cooling fan for the finned cylinder on the engine in my project thread.

Something to think about, maybe.

Dean

 

[b.lindsey]

doc,

This is a fine looking project and these little sterling fans are such fun to watch. I haven't made Jerry's Super Sterling Fan but did make his smaller one. A friend here at work is currently working on the larger one as well, so I am aware that the blades are more contoured than those on the smaller fan. As for blanking them out though, the method Dean suggests is what I used. I sandwiched four pieces of .015" brass together and held them together with 3M Super77 spray contact adhesive, then pasted the template on top of the sandwich as a guide for cutting, sanding and finally filing to shape so they were all identical. Once the balnks are done they can be separated easily by soaking the sandwich in lacquer thinner and using the same to clean of the residual contact cement from each blade. Just one warning...especialy when sanding...if the sandwich gets too hot the contact cement will loosen its grip some, so take the sanding in small steps and allow to cool often.

There should be a couple of pics here: http://www.homemodelenginemachinist.com/index.php?topic=3366.msg33423#msg33423

The hub was also done much as Dean suggests but due to the thinner brass stock I used a dremel cut off disc to make the slots since I didn't have a suitable slotting saw. I used JB Weld to attach the blades to the hub which in the end made for a nice clean result which has held up well. More traditional soft soldering is also an option.

Great thread so far and I am looking forward to more.

Regards,
Bill

 

[idahoan]

Hi Guys

I have a soft spot for hot air fans: I have close to a 1/2 dozen of them. I built 3 Moriya fans quite a few years ago and decided for something a little different I would go with wood blades. I made one with Walnut (dad's) one with Cherry (brother's) and mine with Maple. I pretty much used the same approach; drill the holes sandwich all the blades between 2 pieces of aluminum and cut, sand, and file the profile. The wood blades required a lot of individual work to smooth and round over all the edges by hand.

Move ahead quite a few years and I built my Essex Hot air fan (3 summers ago) from a Myers casting kit. What I did on this one was to design the blades in AutoCAD and have a local shop cut them out on their waterjet machine. I formed the blades over a piece of pipe to the the curvature.

I also have a Paki. KyKo from around 1945 that I have fully restored. I made a new set of blades and hub for this one also based on the Moriya design only scaled up to fit the full sized fan.

I show my fans throughout the summer and thoroughly enjoy them.

Dave