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My take on a Ringbom engine (posted in 2010)

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Well I've decided to start my next build. It is a Ringbom Stirling engine that I modeled and drafted up.
I've decided to build 4 this time. One for me one for my father-in-law and the other 2 may be sold for some funds for our local Humane Society. I'm a bit of an animal person and they could always use some funds.
Anyway here is what I started with.
First thing to go is the flywheels. I started with some 1018 steel just slightly longer that 2 flywheels and a saw blade width.

Turned hub and inside half of the under cut.

Trepanned rest of material to finish undercut.
Did this on both ends.

Both ends done ready to be cut into to pieces.

Here they are separated and ready to turn back side.

Loaded in a 5c collet and back side turned same process as used on front side.

Next I'll build a little holding jig to help mill out the spokes they will be 5 spoke fly wheels.
Until then.

Tomorrow last day of real work then I hope to concentrate a little more on fun stuff.
I do still need to wrap up my father-in-laws fan I built for him for Christmas.
If I don't make any more posts before Christmas here is wishing everyone a Merry Christmas and hope Santa brings you lots of goodies!


Got to work some out in the shop today worked the fly wheels'

Use a little jig to drill holes in all corners and used same jig for milling out the spokes.

Jig is mounted to a sub plate with a stripper bolt on center of flywheel hub. Allowing me to swing radius between spokes. I use 2 clamps to set stops at radial distance to swing between spokes.

Ready for deburing and mount back in lathe after cleanup and drill crank hole into hub.

Started turning up the cold cylinder. Bored the ID and single pointed threads and parted off

Turned up a mandrel to turn outside

Turn shoulder on back side.

Turn radius with a corner round.

I'll be using the same mandrel to cut cooling fins next.


Well set up my spin fixture with mandrel and commence cutting cooling slots into cold cylinder.

Started by taking .050 depth of cut.

Ahhh one down only 3 to go!

And only one mistake darn it any way I'll have to turn down the od to get rid of it its only about .01 deep.

Ahh 2 down increased depth of cut to .100 per pass.

Ahh slots done went full depth on last 2 worked fine 3/16 port hole next.

Ok hole done cylinders complete.

Next I think I'll work on the displacer piston.


Well this morning between looking at the snow fly and smelling turkey in the oven I turned up the displacer pistons.

started by drill ID under sized just riffed in and then finishing the OD

Then applied masking tape to the OD to help in finishing the ID.

Parts completed.

Next the caps back out to the shop need to wear of some of this turkey.
Even though it feels like nap time.

The tape will stop the ringing while boring help stop chatter and when doing thin wall turning help support material.

Well there's nothing like a full belly some butt kickin music and some fun work to do in the shop. Oh yah a compressor that works helps too.

Worked the displacer caps.

turned center boss.

Treepan material out of undercut.

Bore ID

One down 3 to go.

Completed parts.

Now I think I'll go back to the shop and work on the power cylinders Right after I get another bite of Turkey.

Well started power cylinders.

Bore the inside diameter.

Turn up the OD of shoulder this dia mounts into main plate.

Grabbed a 5c collet stop. Need come up with a different stop rod.

Used a carriage bolt had to tun down head slightly.

Ready to face length ah turn shoulder to mount cylinder capp.

Turn shoulder to mount cylinder cap.

Power cylinder blanks done on lathe ready for milling cooling slots. Before cleaning up lathe and moving to mill will turn up power cylinder caps.

Turn up top spud and turn a corner radius on OD and part off.

First side done ready for back side.

Bored 3/16 dia hole .330 depth used a 3/16 end mill.

Bore cap ID to a slip fit on power cylinder will be loctited in place.

Blanks ready for mill work. Clean up lathe and move to the mill.


Moved to the mill after making a mandrel to hole parts for cutting fins.

Cutting fins in spin fixture.


With cap on.

Next to finish the cap need to drill top cross hole and press in a nipple tube.


Well got all the snow moved and a couple hours of shop time.

I set up and drilled the nipple holes into the power cylinder caps.

Finding center of cap.

Used an 3/16 end mill to drill hole straightness of hole more important than the size of the hole.

Completed parts

Turn up nipples used some 3/16 aluminum rivets I just happened to have should work good.

Parts inventory so far. Shouldn't be to much longer and I'll have enough parts to start putting some thins together.

I think next time in the shop I'll work on the crank shaft.


Well here is what I accomplished this after noon wasn't a whole lot.

Grabbed some scrap material I had laying around for the main plate.

Boring holes for cylinder mounts.

Used end mill to cut reference radius to blend to when cutting end width.

Cutting width need to blend to radius cuts made previously.

Parts with width cut.

If you followed my previous builds you recognize the littl fixture here. I turned up a plug for these parts to fit. This little jig I cobbed together has worked pretty good for me in the past.

Part loaded and milling end radius. Conventional cutting only here!

I'll be painting these parts with high temp black paint so I ran them through some grit blast.
Next will be the pillers. I had a piece of 1/4 thick 7075 t7 so I'll use this.

Laid out width needed.

Cut off end.

Parts roughed out ready for tomorrow.

Started with the pillars.

Dial in center of pillar to drill 4-40 hole in ends.

Tapping 4-40 holes in ends with my thumb tap wrench.

Holes drilled and slot in sides cut completed.

Drill and ream 5/16 dia crank bearing housing hole.

Holes all drilled.

Mill slots in ends.

Slots completed.

Mill side cuts.


Single point threads on hot tube 3/4-32.

Check fit with matting part.

Next time I'll continue with the hot tube cylinders.


Well I did get the 4th hot tube cylinder done this afternoon.
I also grabbed a small 1 dia piece of stock (never throw those little drop end pieces away) and made up a spacer sleeve to chuck up the hot tubes and face off the tubes to length.

Load with sleeve into a 1 inch 5c and face ends.


Tomorrow I will start the bases for them.
Still feel a little under the weather but a lot better than Monday!


Been a good day so far haven't made any major errors so far today (knock on wood).

Sized up some stock and cut to length.

Scribed out the bottom legs.

Made first cut to depth. Not moving -y- axis after picking up scribe line.

Rotated parts 180 degrees and made next cut.

Now rotated 90 degrees made 3rd cut.

And again rotated 180 degrees and made 4th cut unfortunately cutter size didn't clean up the center.
Needed to adjust -y- and finish.

Picked up back jaw and picked up stop basic the corner of the 1-2-3 block and zeroed dials.

Drilled hole pastern for standards and also lamp hole.

Flip part to bottom side adjust table to the lamp hole and use a 3/4 end mill plunge in to proper depth

Now plunge in using a undersized 1inch end mill for a counter bore for the bottom lamp chamber cover.

Counter bored holes for the standard screws.
Parts are complete for now. I may come back and do some thing with the top edge chamfer radius or some thing we will see.

Grab a bite to eat and go work on the crank disks.


Now for this afternoons progress.

Using some stainless turned up dia and drill crank shaft hole and faced off and asjusted over .007 and feft a .188 dia to ride against center of bearing.

bearing side complete ready to face backside to proper width.

Now to the mill mounted in a 5c collet block drill and tap 2-56 UNC 2b rod journal mounting hole.

Drill counter balance holes.

Disks completed.

Next part of and face to length some .125 drill rod for crank shafts.

Crank assembly.

Grabbed some 1/4 brass and turned up end and parted off for lamp tubes.

Face parts to length turn shoulder to press into base and drill the wick hole.

Put one into base just to see how it looks.

All 4 done.

Couldn't resist putting some parts together temporarily to see what we have.
I'm liking what I see.

Tomorrow I'll start with the power cylinder mount collar till then.
Was a pretty good day! No broken tools all fingers still in place and no major errors can't beat that.


Turned up some collars that will be pressed into the main mounting plate to help mount and hold power cylinders in position.

Collar pressed into position

Ok parts completed now for the connecting rods.

Cut up some .062 aluminum stock to width.

Setting parts in vise to mill lengths.
Note most of you more than likely already know but I'll mention anyway.
If you look at the left side of vise you will see a spacer block you always need to have something on the opposite side of vise close to the same size that you are clamping. Other wise the movable vise jaw will kick out at an angle and essentially you will only be clamping on the corners of whatever you are clamping. I've seen people do this and then clamp the hell out of the vise to try and get their part to stay and not move while milling. (just though I would mention it)

Suppose to be 1.803,
1.804 close enough for me.

Drilling journal holes and lightening holes.

All hole drilled.

Setup for milling the taper in rod.

Part completed going to call it a day.

I believe I only have 4 major parts left power piston displacer rod and bushing and finish up the fly wheels.
Cool I should be able to have them running next week end. 

Well I didn't make it out to the shop all week finally this morning got some much needed shop time (actually my unwind from my real job time). Here is what I accomplished so far today.

I started out by turning up some graphite plugs for the bushings in the cold cylinder for the displacer rod.
I'll press them into place and turn the inside diameters of the bushings while they are in place.

parting off first plug.

Since I was turning graphite I decided to turn up the power pistons also.

Turned the OD and bored the skirt diameter.

Chucked up piston in 5c collet to cut slot for connecting rod.

Without removing piston from collet laid collet block on it's side and drilled .046 dia wrist pin hole.

Slot and wrist pin hole completed.

Turn up a wrist pin from some 1/8 dia brass.

Ready to assemble

First one assembled 3 to go.

chuck foster:
thanks for the pictures and the write up, you sure do some nice work  :ThumbsUp:

how did they get the name ringbom was that the inventors name?



Here are a few pictures from Sunday's work in the shop.

4 power cylinders and piston and connecting rod assemblies ready to go.

Displacer cylinder with displacer bushing pressed in place getting ID drilled and bored to size.

Number 1 engine getting put together.

Number 1 test run !


Now to get the other 3 cleaned up and painted and put together.

Here is a video of 3 of the 4 running.


--- Quote from: chuck foster on July 28, 2012, 04:13:52 AM ---thanks for the pictures and the write up, you sure do some nice work  :ThumbsUp:

how did they get the name ringbom was that the inventors name?


--- End quote ---

The name is the style engine that they are not sure if the inventor I would venture to say yes that he named them.
These engines were a fun little build.


This is similar enough to the James Senft design I built and can't get to run. I think I probably have leakage at the displacer rod bushing, which I have remade three times.

Yours run beautifully.

By the way, yes they are named after the inventor Ossian Ringbom US patent 856,102 (year 1907).



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