?Chinese? Stirling Beam Engine

[klank]

My first post here - so hello to everyone.
I am very much a newbie to model engineering but have been "having a go at it" for the last 18 months.
I was retired early due to a back injury (Health and Safety rules) and decided to fulfill a boyhood dream of making something in metal and so bought my first lathe - never having had the opportunity to touch one before.
I have made a lot of mistakes but learned a great deal from reading what is posted on this site and others.

Anyway, I recently up-graded my lathe from a small Chester 7" (not a mini-lathe) to a larger Sieg C4 from a nearby machine tool supplier.
As part of the "deal" for the lathe, a "kit" of a Stirling engine was thrown in as a freebie. I have seen this kit advertised on Amazon and a couple of other places in the U.S., but never over here apart from the place I got the lathe from (not sure if you are allowed to "name names" on here).

Well, the comments on the Amazon site for this "kit" were not encouraging.
This is a "kit of materials" with detailed plans and some ?instructions? There is povided an Aluminium displacer piston and steel cylinder, plus a finished brass power piston. Everything else is Ally/Brass bar or hex stock, plus a length of stainless steel rod for the built up crankshaft.
To be fair, the materials are of good quality - each item individually labelled. The plans (one plan for each individual part) are excellent - over detailed in fact - showing tolerances etc.
The "instructions" are minimal in content and look as though they were translated from Chinese to Greek to Finnish and then to English. No instructions as to fitting, use of thread lock/silver solder or building up the crank and its main bearings.
Leaving their syntax aside, errors make them difficult to follow for a newbie - i.e. on one page it says the rotation from the "flying wheel" is clockwise, and on another it says it is anti clockwise. Go figure!

Anyhow, I finished it finally and after a lot of fettling/adjusting, got it to run freely.

Here is a pic. of the completed model - rigged up to a small ex. cassette recorder motor for "running in" purposes.




Has anyone else either seen this model or had any success in getting it to run?
Equally, if anybody has the kit and is struggling, I would be happy to pass on my trials and mods. in finishing it.

As at present, it does not run under heat - so trying a protracted "run-in" to see if it improves matters.

Just to add - I am amazed at the friendly nature that business is conducted here - I have gained so much from reading the posts. What a great site.

Best wishes to all

Peter

[Brass_Machine]

Hi Peter,

Welcome to the collective!    Glad you like it here.

That kit had me scratching my head as to where I had seen it before. I just figured it out:



That is the same kit that Little Machine Shop Offers. As I have never built a Stirling (yet!), I don't have much advice. What I do know is there should be as little friction as possible.

One of the others may chime up with some more info.

Eric

[bogstandard]

Welcome Peter,

So you have been going it alone, made a few mistake I suppose, and even then you still want to do more.

That is a sure sign of a wannabe model engineer.

Welcome to the bad back club, there are a few of us on here, but not of the type who can't get off it.

Even though this site looks like it is model engineering orientated, in fact it is for anyone who has some sort of project they either want to do, are doing, or just finding out about, so if you want to have a say in anything, just butt in. So really, as long as it is legal, we will discuss it.

I am amazed at the friendly nature that business is conducted here

We really do want it to stay that way, so we just go about business as though we were down the pub with our mates, discussing things, with a bit of joking and leg pulling as well. But do be aware, sometimes serious stuff must be discussed as well.

Just pull up a seat and bide awhile.


Bogs

[NickG]

I think a few companies seem to be stocking these models now. I know axminster and arc euro trade do them too.

I struggled for a while with my stirling. As well as the friction, ensure there are no leaks around the hot cap and the displacer rod gland.

If you get the friction down and the leaks down it'll work. It's achieving that that's the hard bit.

When I was having the problems with mine I spoke to many people including Jan Ridders, who nailed the problem down.

I think you can do the same thing on yours, or at least whittle potential issues down by the process of elimination.

Take your cylinder / hotcap / displacer / rod assembly off the rest of the engine, submerge it in a sink of water just with the power cylinder sticking out. Blow into the power cylinder. If there are any excessive bubbles around anywhere you need to seal these. There will be some around the displacer rod, unless you have a superb seal, in which case I could argue that it may be TOO tight. Bubbles from anywhere else are unacceptable!

The next thing to do is build the engine back together but take off the displacer cylinder to relieve any back pressure. With a flick of the flywheel it should rotate for at least 10 revolutions before coming to a stop. If it doesn't, something is too tight. Systematically take linkages off until you find the main contributer to friction, or start with just the flywheel in it's main bearings and gradually build up to the whole assembly.

Finally, make sure your displacement piston doesn't foul anywhere in the displacement cylinder or hot cap.

Another thing that improved the performance of mine dramatically was the wick believe it or not! I was using nylon shoe lace (couldn't find anything else) but then I changed to proper cotton wick and it ran at about 3 x the speed! Use some light oil such as sewing machine oil or 3 in 1.

Hope this helps, you will get it running, just persevere. The good thing about yours is that you know it's a tried and tested design so it will work if you can do the above. I was venturing into the unknown slightly with mine but got it working with a bit of theory and the above!

Nick

[sbwhart]

Welcome aboard Peter. 

Stirling engines are something I've shyed away from I'll have to have a go at one someday thare I go getting 

You'd better watch out as its catching

Have Fun

Stew

[klank]

Thank you gentlemen all for the kind welcomes and advice.

Nick - your advice is excellent - I shall have to get the bucket of water out and test as you say, then try to find/eliminate friction progressively. I am pretty sure I have air in the right place at the right time, but possibly not enough of it.
I built the meths burner (wick and collar supplied in the kit) and tried that, also in exasperation tried my gas torch (gently) - cannot get the beast to turn over more than two or three revs no matter how hot (or warm) the tube.

At least I got a bit more experience in lathe/bench work in the build - I learned that
1. when machining the finned items with a blade type parting tool, paraffin should be used copiously - even then the swarf can cut into the side of the slot being formed - I ended up with one free spinning ring of ally on the finned heat sink because of this - used wooden tooth picks/epoxy to "stick" it back in place.
2. almost impossible to put a "Z" bend accurately in a short length of 3mm brass rod (needed on both connecting rods).
3. when using white heat transfer goo (the type used in electrical components/heat sinks) - one drop escaping notice ends up on every conceivable surface - including walls/ceiling and eyebrows. Possibly the same characteristic when using engineer's blue?
4. you can turn a piece of round bar (Ally) to a cube in the 4 jaw chuck (thanks Circlip). Most satisfying to see it appear.

Respects and best wishes to all.

[NickG]

Peter,

I had exactly the same problem with mine. I had the hot cap glowing red with a butane torch and it still wouln't go. The first time I got it to run, I had ice cubes on the cold end of the displacer cylinder and it was running very slowly, but as soon as I did the water trick it revealed a massive leak around the hot cap interface (thread on mine).

Sounds like it was a good learning experience and you'll improve on your next project. But I still hold high hopes for this one, I'm convinced it'll run with a bit TLC. Then you really will be hooked, I can't think of anything much more satisfying than seeing your first engine run.

Good luck.

Nick

[Bernd]

Peter,

A quick welcome from the other side of the pond. We try our best to have fun here, so join in. And as Bogs says, it doesn't all have to be model engineering as long as it's interesting and legal.  .

Somewere along the line I'm sure you'll catch  . Also there is one requirement and that is  We like pictures because it gets a bit tiresome reading 1000 words.

So welcome to the collective.  You have been assimulated.   

Regards,
Bernd

[rleete]

We like pictures because it gets a bit tiresome reading 1000 words.

It wouldn't be so tiring if you didn't have to move your lips as you read along...   



Welcome aboard, Peter.  Nice first project; I'm sure you'll get it running soon.

[SPiN Racing]

Very cool engine!!!

And Another Sterling!!!  I am seriously going to have go get my rear out and do some research on them.. I want to make one some day.. but not yet. Too many other things in the fire!
 

Looks to be a really sweet engine! Im sure tracking down all the little details on the fine tuning will resolve into a awesome runner.

[Stilldrillin]

Hi Peter! Welcome to the forum / collective. 

Stirling engines are all "alchemy", but soo satisfying when they finally run reliably...... 

Good luck with yours. It will soon be sorted......

David D

[bogstandard]

Peter,

This was my first and only foray into building a sterling engine, this is a low temperature version.

After this vid was done, I duly did a fumble and dropped it onto the floor and bent the very thin crank, so it is gathering dust on a shelf awaiting rebuild 

Friction is the killer with these limited power engines, and lubrication isn't the answer, that usually stops them dead by causing too much friction.
On the type you have built, a think some sort of lubrication is allowed, maybe graphite powder. But smooth precision fits are the way to get them running at full wack.

It seems like Dr Sterling is due a lot of recognition, as designs on his engines are used on the space shuttle for refrigeration purposes, and the Japanese are looking at ways of using them in cars, they already have a solar powered prototype driving about. Third world countries are now using larger solar powered versions of them for water pumping and power generation. So not only is it a very old design you are mkaing, it is also maybe the saving of the planet by not relying on fossil fuels.

Keep at it, you will succeed in the end.

John

[NickG]

John,

As you said, oil is a definite no no on the low temperature differential versions. I found with my meths heated water cooled one, a drop of thin oil on the displacer rod and one on the power pistons just helps seal it. You're dead right though, sometimes I've added another drop of oil whilst running and physically seen the engine slow down!

I know you've had success with flame gulper type engines, in your opinion which is more difficult to get to run? I've often thought due to a flame gulper sucking in very hot gases in rather than just air heated by a flame in a stirling engine, there must be a greater scope to gain a bigger temperature differential in the gulper therefore more of an under pressure and more power? - although there is only 1 power stroke. Also, I gather that if the hot gases are quenched too quickly the underpressure is too short lived and atmospheric air forces its way in before the valve closes.

Nick

[klank]

John, Nick, David, Spin, Bernd and everyone - so kind of you all to take the trouble to post. Thank you all for the encouragement and good wishes.

State of play now:- I did the "blow in the hole" water test - no leaks apart from a bit around the displacer rod as expected.
I dis-assembled the "motion" and thoroughly cleaned everything.
The two con. rods connect to the crankshaft big end via two discs of brass, mounted eccentric/drilled and tapped on the thickness to receive the threaded ends of the rods. I polished their faces (they run close together side-by-side) but left them dry of lubricant - I think their flat faces would "drag" together if lubed too much.
The "bare" crank/discs revolves very freely in its plain brass bearings - one drop of clock oil on each.
One drop of oil on the displacer rod.
On linking up the displacer con. rod with piston attached and displacer cylinder sealed onto the block, sharp flick on flywheel - about 20 revs. No feel of binding anywhere.
The power piston drops like silk in the finned cylinder - I ran it in with a little powdered graphite. I made sure its gudgeon pin assembly inside the piston was free and sealed the screwed bit which projects through the piston crown.
Connected this up to the beam and the beam con. dod to the other disc. Same flick on flywheel - still about 20 revs.
All seems free.
Heated up the displacer cylinder end gently for a minute, flicked the wheel - 20 revs. I tried flicking the other way (just in case I'd got it wrong) and only 5 or 6 revs.
Eventually had the tube glowing on the end - same result!!!
One strange thing - when flicking the flywheel under heat, whilst it ran, there was a continuous singing/ringing sound as of a fairly small high pitched brass bell! (A bit like the sort on a Hotel desk if you know what I mean). Very odd.
?Resonance? of something?
The noise dies away if I flick it over as the tube cools.
The b***er still won't run.

John - that is a lovely little engine - so delicate. Is it like the one for which free plans were given in the ME a few months ago? Where do you get the plastic displacer materials? It is beautiful.

At our (local) club exhibition (Taunton) at the beginning of May, I was talking to someone who had a collection of Stirling engines running - he said Phillips had developed a commercial Stirling "type" engine which could deliver 900 b.h.p.!!!

[bogstandard]

That definitely sounds like something is catching as the engine warms up, or a pulse vibration that is telling you that the main bits are working as they should.
 
Get the engine hot, and super gently turn it over slowly by the flywheel and see if you can 'feel' anything catching or going stiff.
 
Really the only area on the engine that would cause that sort of resonating ringing are the cooling fins. the ones on the hot cap would be the main suspects. Either something is catching in there, or the air, as it is pulsing, is causing them to resonate at a certain frequency. If you want to stop the noise, try sticking a tiny ball of crumpled up bacofoil between each fin.

Jan Ridders is the man to get plans from. He is a very knowlegeable man, and we have had some good discussions about his engines. In fact he has started to use one of my ideas for vertical wicks on flame lickers because of the success I had with one of his designs.

http://heetgasmodelbouw.ridders.nu/tekening_overzicht/tekeningen_overzicht.htm

Plastic tubing is easily obtainable from fleabay, if you want the address, I will root it out for you. I made the eggcup clear cylinder out of a garden light unit that I no longer wanted.

http://www.homemodelenginemachinist.com/index.php?PHPSESSID=a90213aca8b938f0d06e41e921b100dc&topic=1424.0



John

[NickG]

Peter,

It sounds like the displacer is catching the hot cap to me when it's hot. What is the clearance like between the displacer and and hot cap? Mine has about 1/32" all around.

Another test, when everything is sealed up, as you turn the flywheel and the power piston is travelling towards the top of its stroke you should feel slight suction. Likewise, as it travels towards the bottom of it's stroke you should feel slight compression. If not there may be a leak in the system, as you've tested the rest, it points towards the fit of the power piston in it's cylinder. It may be too loose? I know it's a pain but you could try the 'pop' test. You would have to strip it back down, cover the displacer rod gland hole and the hot cap end and pull the piston out to see if it pops which tells you it's a good fit.

Other than this, I'm at a loss! 

How much of a leak was there around the displacer rod? Should only be a few small bubbles, you should still be able to build up a reasonable pressure in there.

Nick

[sbwhart]

Peter

Nick made a good point regarding the displacer catching when hot this could explain it running freely when cold but problems when hot there could not be enough clearance to allow for thermal expansion.

Good Luck

Stew

[klank]

John, Nick, Stew - thankyou all for the advice.

I turned it over super slowly when hot - no feel of binding or bottoming out anywhere.
I get loads of suck n blow from the top of the power cyl - with or without heat. - I put a little piece of cling film over it, held by an O ring. See it move in and out as it should.
Maybe I have too generous a clearance at the end of the hot end for the displacer piston - mine is over a 1/4" at the full extent of its stroke?
When I did the water test, there was a steady stream of quite small bubbles from the displacer rod bushing - ?possibly too much? - the rod moves freely, but with no slop.
Anyway, I have put the beast on a shelf to leer at me whilst I try and finish another project - to motorise the X axis of my Sieg X2 mill - lots of good stuff here about that.
Maybe I should post some pics/dimensions? - done mine with a wwm - but no need for complex clutch/linkeage.

With much respects and best wishes

Peter

[Darren]

whilst I try and finish another project - to motorise the X axis of my Sieg X2 mill - lots of good stuff here about that.
Maybe I should post some pics/dimensions? - done mine with a wwm - but no need for complex clutch/linkeage.

With much respects and best wishes

Peter

Maybe you should, 

[NickG]

Peter,

Sounds like you could be homing in on the issue with the stirling. 1/4" is much too big a clearance, mine is 1/32" at each end, the same as the radial clearance. Because of the 1/4" gap, you aren't efficiently displacing the air from the hot to the cold end ... even when the displacer piston is right in the hot end, there is still that volume of air being heated, counter acting the effect of the cooling on the other portion of air.

From everything else you've said, it should work once you get the clearances right on the displacer ... easiest way is to make a longer one and bigger diameter if that clearance is too large. The only thing you have to be wary of is making it too close a fit, then it can cause sort of viscous drag as the air has to get down the sides!

Nick

[klank]

Thank you very much Nick - you have nailed it (I hope).
I am toying with either lengthening the light Ally displacer piston a tad, or re-adjusting the brass rod frames to bring the whole crankshaft/motion a bit closer to the block (the 4 rods have washers under the threaded ends - take these out!). That maybe where I went wrong - in putting them in in the first place - I wanted to be sure the displacer did not touch the hot tube end internally.
I will let you know how it turns out.
Thanks for all your kind help.

Peter

[NickG]

Yeah, there are couple of ways of doing it. It really does want to be as close as poss without touching at both extremes of stroke.

[klank]

I appreciate this thread is a bit of an oldie now, but want to say thanks to Nick and Stew and Boggs and everyone else who offered help  - I have returned to do battle with this little sucker (not!!).

Following your advice, I re-set the stroke of the displacer piston such that it nearly touches the end cap of the tube at t.d.c. as it were and tried it again with some heat - made a heck of a difference - it almost "caught" - ticked over for a lot more revolutions before dying on me.
I noticed a bit of "smoke" emerging from the top end of the power piston - something not right.
Cut to the chase - made a better fitting power piston 0.08mm larger diameter - does a much better "plop" test and hardly sinks under its own weight when dropped in the top of the bore against a sealed up bottom end. The original piston was too sloppy a fit in the cylinder (my fault).
Now under heat it catches for even more of a bit longer - but still dies after a while.
I think the new power piston needs a bit more bedding in -a few rough spots to smooth off the bore - I have high hopes at last that I might get this thing to run. Going to put the electric motor back on it for a while.

[sbwhart]

Your getting close Peter  a little bit more fettling and she'll run all day.

Good luck

Stew

[klank]

Thanks Stew
Pleased to say I got it running at last.
The last bit of the puzzle was to firmly bolt the frame down - when trying to run it before, free standing on the bench, there was a bit too much vibration in the brass framing/built up crank. This seemed to "upset" the running.
Now it ticks over quite sweetly on a breath of clear flame from my propane torch.
I'm quite chuffed that it actually works!