Introduction: Water Cooled Chinese LTD Stirling Engine.

Picture of Water Cooled Chinese LTD Stirling Engine.
==============================  UPDATE  ==============================
This high speed run combined with a 13 hour endurance run at approx 250rpm has caused the plating to wear off the displacer rod and now the engine barely run at all even on the hot plate, the displacer tube is cracked and when I removed it to inspect it i found it was so badly warped that I think it is no longer air tight.   These engines where never designed to run this fast and at the temperatures that I have used here, I am surprised it actually lasted as long as it did.  


Yes, I have indeed water cooled a Chinese made LTD Stirling engine. Why?....  curiosity mainly, and simply because It was not all that difficult to do.

I was counting the clicks of the piston between each tick of my overly loud clock to give me approximate rpm speeds, it now goes to fast for me to count, I will do a video giving the real numbers once I replace the acrylic displacer tube with glass.

The water tank is a large pear tin, its base knocked together from bits and bobs I had at hand in the shed ie. a pine plate i had turned for practice and some scarp dowel I found on the floor of the shed.

the cooler is made up of scraps of 15mm copper pipe and 90* bends i picked up in the bargain bin of B&Q with 2 reducers to 10mm to fit the PVC tube. It is soldered to a hard drive platter using solder paste(find it on eBay, they say it don't keep well, but's they be lying).

The water pump is a 5-12V DC brushless submersible water pump I picked up for £11.00 on eBay, at 12V it draws 1 amp and shifts 500 ltrs per hour. I run it on 6v as that's more than enough for this job. I should have done the maths before testing the water pump, I had to dry the laptop out when i tested it with no lid on the bucket, it pumps approx 138 ml per second and the 1 second burst on a 12v battery send a column of water about 4 feet in the air and it naturally all hit the laptop.

8mm PVC tube was used to join it all together with some 1/2" tubing used to join the outlet of the water tank to the inlet of the pump.

This test run managed to get a temperature differential of 78*c approx, I didn't push it any further as the displacer tube is seriously distressed now due to way to much heat, I am waiting on a G2 bottle cutter to arrive so i can replace it with glass any then turn the heat right up. 

I can also use Ice water in the tank and use thermal grease between all the surfaces to coax the last few RPM out of this thing.  I will make a video of the high speed destruction run, a friend has both laser tachograph and thermometer and also a HD camera I think so stay tuned as we will most likely find out at what temperature the displacer fails at or the CA glue holding it to the displacer rod melts, either way it should be interesting.

Thanks for looking.


WirelessGuyN (author)2016-11-20

While this is a nice project I'm not totally sure about overall efficiency here.

You might be better off just building a top with fins, like a heat sink, and blowing a fan across it than the amount of energy required to run the entire pump setup. I'd actually be curious to see both as a comparison. That would be some good scientific tinkering.

GinaG5 (author)2015-05-16

I'm more of a thinker than a practical with my hand type of person, but would a stirling engine be able to run as a compressor, ie. would it be able to use the heat from a solar hot water heater to compress gas in an air conditioner or refrigerator directly without being converted to electricity first. If that was possible 70% of worlds energy demands could be solved instantly.

Sanctus (author)2013-04-15

Dr Qui (author), after reading the comment (and finding some very useful ones) I feel distracted by personal explanations on linguistics in this international community, somehow expressing ourselves in English. I don't write a lot of comments on instructables, though I admire the good work or effort put in conceiving the idea or realising the object itself. Why I comment on yours - I like Stirlings and what you were trying to do, and as well how did you answer to the comments. The best thing to do with the comments that don't follow the topic - IGNORE. As I will not continue any discussion on communication, please read and obstain of commenting on that. Apart of that, good instructable ;)

gaiatechnician (author)2013-02-04

Easy way to find the rpm is to pop it into a video program or record it on an mp3 player or use the sound directly in playback as a track in audacity. You will see the peaks and valleys on the second scale.

Dr Qui (author)gaiatechnician2013-02-04

Sounds like to much hassle, anyway it's dead now from over exertion, was not designed to run at 300rpm, the endurance test I did to see how long 1 fill of the spirit burner would last (12hours 50 minutes) killed it, the plating on the displacer rod wore off and there is just to much friction so it barely runs with a 70* temperature differential.

rimar2000 (author)2012-07-05

The idea is good, but I get the impression that your improvement contradicts the simplicity and economy of the Stirling engine. It is only another point of view...

Dr Qui (author)rimar20002012-07-05

Exactly! You got it right, this is total overkill, pointless stupidity just for the sake of it!  Learning by play.

LTD Stirling engines look simple but break it down and you have maybe 50+ individual parts. a cooling system improves your economy. But I know what you mean, it is a little bit to much.

The Stirling engines "throttle" is the temperature differential between the top and bottom plates, this managed 78*c approximately, with the use of ice water, thermal grease and a glass displacer I think i can get the differential to about 120*c before the glass either cracks or the displacer or CA glue melt.  I'm experimenting as how to get the largest differential which gives maximum power.

If you check out marshon's Ible he tests such a beautiful engine to destruction, why? to find out limitations he is up against before he tries to build a big Stirling engine.

But by doing this tinkering to the engine I am also learning about Stirling engines, the limits of the materials used and where the weaknesses are likely to be before I start work on a real engine.  The water pump was bought for use with a large Stirling cooling system, this setup was to see how affective it would be.

To be honest once I change the displacer to glass and do a high speed run to get the maximum rpm possible the cooling jacket gets shelved and the engine will go back to to an display piece.

I have 2 engines in the design stage, a small decorative Alpha and a large Gama with a 18" flywheel to run on a wood stove.

rimar2000 (author)Dr Qui2012-07-06

WOW, it is awesome all your study and experiment with Stirling engines. Thanks for sharing it.

"My" design have a rotary displacer, that at same time has a crank actuated by the plunger. I did, 2 years ago, a first try but it did not worked. The chamber was an aerosol can, it is to say longer than thicker. Now I want to do a new one, with a very short chamber, maybe 1 inch, but large diameter, maybe 5 or 6 inches.

Dr Qui (author)rimar20002012-07-06

Make one like this, you could run it on your Chulengo

I just had the thought that if you had a good Stirling engine you could run through a reduction gearbox and have a roasting spit powered by the hot embers. Thats your excuse to build one now.

rimar2000 (author)Dr Qui2012-07-07

My design has a chamber like that, horizontal and flat, but the displacer rotates. The crank has only one connecting rod, and the hot and cold areas are horizontally separate. Do you see it?

I think it is simpler than other designs, but I must to make all parts, it is not easy use existing parts.

Dr Qui (author)rimar20002012-07-07

I found a video of one of these rotary Stirling engines on you-tube I might have a go at one of these as it looks quite simple, I found plans for one here.

rimar2000 (author)Dr Qui2012-07-08

Wow, thanks but I never seen that. It is precisely my idea. Although I thought the chamber horizontal, not vertical. My first attempt was horizontal, longer than thick.

Yesterday I started to make the chamber of my model.

Dr Qui (author)rimar20002012-07-08

I have been thinking of how to build a horizontal rotary Stirling too. The biggest problem is how to stop thermal transfer from the hot to the cold side. I would also extend the axle out of the chamber and add a flywheel

rimar2000 (author)Dr Qui2012-07-09

My solution to this was to make both sides of the chamber in two parts each. I sticked the parts with a strip of an old bicycle rubber. With the perimeter I will do the same. It is not perfect, but avoids the rapid heat transfer. The flywheel in my case will be the displacer. All the chamber will be black, inner and outer, but using an indelible marker, to avoid the thick coat of paint.

Think that any heat engine is a heat transfer pump. The thinner the walls, better result, but that is limited by the mechanic requirements.

The displacer will be white, precisely to avoid (diminish) it interacts thermally.

Dr Qui (author)rimar20002012-07-09

I was thinking of splitting a large diameter aluminum tube and using either acrylic or glass as a thermal insulator.   The rotary Stirling has got me interested enough to make on that can run on my hot plate.  An aluminium base could be screwed to the bottom section and heat sinks screwed to the top section with some thermal compound to improve the thermal transfer.

What diameter of cylinder are you using and how long is it?

I was thinking of adding a flywheel as the displacer is off balance, a counter wight could be added to the flywheel to improve the balance.

rimar2000 (author)Dr Qui2012-07-10

My cylinder (chamber) has 27.5 cm inner diameter. It is made in relatively thick galvanized iron sheet. The displacer will be carefully counterweighted, within my means.

An interesting improvement to such motor would be a speed regulator, that drive the amplitude of the crank: more speed, less amplitude. But that device would be difficult to make, it requires precission.

As dissipators I think to use thin L sheets soldered with tin. They can go only in the cold part of the motor, because tin could melt with the heat.

Dr Qui (author)rimar20002012-07-06

You're welcome Rimar, I post things to share what I have learned with anyone who is interested.

The rotary displace sounds very complicated, I have not seen one of those on you-tubes I like the marble displacer Stirling engines. I so want to make one.

You should try a LTD to start with, try using a silicon baking tray to make a diaphragm rather than a power piston, that is the best info I have picked up from you-tubes recently. I'm going to try that on my first ornamental Stirling engine. this LTD engine is a great design using scavenged parts. this one uses a diaphragm rather than a power piston, looks looks a film canister.  I cant wait to see what you make.

When i showed the little engine to my father he told me that he and my grandfather tried to repair an old water pumping Stirling engine some time back in the 1940's, he says my grandfather never gave up trying to get it to work even casting a new power piston but could never get a good enough seal on it as the power tube and piston had seized with rust and was to badly damaged to be air tight.  This must be why I find them so interesting too.

rimar2000 (author)Dr Qui2012-07-07

No, the rotary displacer is very simple, it is the only mobile part of the motor. See it rotating horizontal, no vertical. The crank, vertical of course, is actuated by the piston or diaphragm. The cold and hot areas are each a semicircular half of the chamber.

It is not easy I make it this year, I have too many "portfolio projects" to deviate my time in a new one.

At home in Entre Ríos was a beautiful Stirling Motor fan. But the rust was ruined it. At that time I was very intrigued about how it could work. Never I seen it working.

Old Nubbins (author)2012-07-06

This is neat! I bet you could write a great instructable on how to seek attention and then pedanticaly dismiss it once given.

Wait for it.... Wait..... for........ it..............

Dr Qui (author)Old Nubbins2012-07-06

You're OK thanks, ill leave that for you to do as you first instructable, The comments section is a forum after all so we can discuss and debate the finer details of our work.

OK so mrmath comment irritated me while I was having a bad day and I snapped, but don't we all sometimes. we have had our disagreement and moved on.  ilpug's chindogu comment was an insult in a most pedantic way, he has now dug himself into a hole with his last reply.

As for my conversations with Rimar2000, that is us just having a normal conversation where we discuss details not covered in the Ibles, Rimar speaks only Spanish so I must use very good grammar as he uses Google translate, so I cant really start talkin like I is from da street.... init. I cant use any of the Ulster Scots dialect words from my own vocabulary in my instructables and even more so when i speak with Rimar so things don't get lost in translation.  I have the utmost respect for Rimar who is not only some 20 years my senior but has uploaded 86 Ibles to my 57 and your 0, but has done it in both Spanish and English

mrmath (author)2012-07-05

It's very steampunkish, which is kind of cool. Now if you could just harness the power of the flywheel to run the water pump, you'd have a self-water-cooling Chinese Sterling Engine.

Dr Qui (author)mrmath2012-07-05

Its not at all steampunk, copper pipes do not equal steampunk, if I wanted steampunk it would be sprayed copper and have 2kg of dysfunctional brass and copper scrap hot glued to it. The copper pipes here are functional, the design just happened to be symmetrical.

The design style if any is more along the Art Deco style and Industrial style, If you look at the engine the design is obviously industrial.  By moving out of the 1800's and up into the 1920's you get to play with Aluminium, stainless steel, industry standard parts and plastics.

This is a toy, it does not have the power to pump its own water even with the tiny impeller from a screen washer pump. The flywheel is to light and has no room for additional weight without snagging the mechanism.  To have useful power this engine would require a total rebuild to the point where I would have built a new engine.

Should have done the maths mrmath.

mrmath (author)Dr Qui2012-07-05

I meant the steampunk comment as a compliment, not an insult. I think the copy pipes, all fit at rounded right angles, lying on the horizontal plane with the "giant" wheel on a vertical plane give it a steampunk look. And while I'm not a fan of much of what counts as steampunk, I do like the look of this.

Dr Qui (author)mrmath2012-07-05

Firstly you called it steampunkish. The be nice policy prevents me from explaining the irritation of you using ish. 

Secondly a steampunk purist would say that aluminium although available in Victorian times would have been the most expensive metal on the planet at the time the amount of aluminium that I have used in the hotplate would be seen as tacky and wasteful as having gold leaf toilet paper, the fact that the hard drive platters used are aluminium coated in a microscopic layer of platinum makes it even worse.   It would also not use, acrylic, stainless steel or high density foam but be of materials of the era and highly ornate rather than drab and industrial.

To use the word steam to describe a Stirling engine is just wrong on so many levels, the Stirling engine was developed to be a safer, more efficient and quieter replacement for the steam engine, it also can run on a wider range of fuels and even of waste heat.  In 1816 the power was limited due to the limitations of materials of that era and was mainly used for water pumping until the 1940 when the Phillips company took it to a whole new level using modern materials and technology.  Modern day improvements in materials have allowed the use of pressurized hydrogen gas to optimize the preference.

Even if i close one eye, tilt my head, stand on one leg and squint at the "giant" 3" diameter wheel I still don't see any trace of steampunk in the design

mrmath (author)Dr Qui2012-07-06

I thought there was. I was trying to be nice. Sorry I ever brought it up.

Dr Qui (author)mrmath2012-07-06

No worries, you just pushed the wrong buttons on one of the bad days with the first comment on this post.  I like steampunk, the real artisan stuff not the arts and craft hot glue and sequins stuff we see to much of

I knew this one would draw heat no pun intended because it has crossed the line into the realms of silliness, but done in the name of research for a future project.  There are 3 schools of sterling engine on the net, the school science project the tin cans, coat hangers and bubblegum kind, fun to play with but no practical use.  Then there is the highly engineered LTD, beautiful to look at but again no practical use. Then there is the very rare larger Stirling engines that has been highly engineered and is capable of powering a boat or generating electricity.
This series of Ibles are all ground work for a engine that can do some real work. If you check them in order you will see how I first pushed the limits of the engine, then discovered I had over pushed it and had to make improvements to dial things back, the third one alone trebled the out of the box performance of the engine.

Don't take some of my reply's as out of hand, this is a forum of sorts after all and I will debate a subject quite strongly if needed. you unfortunately drew some of the flack that ilpug's insulting chindogu comment created , he effectively called my work a chocolate teapot or ash tray on a motor bike, in his reply to my rebuttal he has now managed to contradict his original statement and dug the hole deeper, so keep watching you might get a laugh.

ilpug (author)2012-07-05

Make a super-efficent cooling system and you have a Chindogu...

Dr Qui (author)ilpug2012-07-06

Funny, I almost laughed... keep playing with the toy guns and Leave the engineering to the auld fellas.

Chindōgu (珍道具?) is the Japanese art of inventing ingenious everyday gadgets that, on the face of it, seem like an ideal solution to a particular problem. However, chindōgu has a distinctive feature: anyone actually attempting to use one of these inventions would find that it causes so many new problems, or such significant social embarrassment, that effectively it has no utility whatsoever. Thus, chindōgu are sometimes described as "unuseless" – that is, they cannot be regarded as 'useless' in an absolute sense, since they do actually solve a problem; however, in practical terms, they cannot positively be called "useful."

In the UK we use the term Grot.

This is not pointless as it does work improves performance and if you had read my reply to rimar2000 you would see that this cooling system was just to test a pump I purchased for use in a future engine build.

ilpug (author)Dr Qui2012-07-06

Woah, holster your guns man! I know that your build is something that improves the engine, and is quite a nice addition. Sterling Engines are pretty awesome machines, and anything that improves their efficiency just makes them better.

I was merely commenting, very clumsily, on the irony of putting a cooling mechanism on a heat-powered engine. It's obviously BS, but if you could put something on a heat engine that would cool it more than the fuel heated it, you would have something that solves the problem of heat inefficiency, while causing a problem, namely that the engine won't work. Something that solves a problem but at the same time renders itself completely impractical sounds like a Chindogu to me, or however it's supposed to be spelled.

I do in fact play with toy guns, as is shown by my various builds, but there is actually a fair amount of engineering that goes into them.

Nice build. Could you either make some heat sinks or grab some off old electronics and incorporate that into the build? Possibly pierce the copper rod around the area to be cooled with some heat-sinking metal pins, so one end of the pin is in the water flow, and the other end is very close to what you need to cool?

Dr Qui (author)ilpug2012-07-06

"I was merely commenting, very clumsily, on the irony of putting a cooling mechanism on a heat-powered engine. It's obviously BS, but if you could put something on a heat engine that would cool it more than the fuel heated it, you would have something that solves the problem of heat inefficiency, while causing a problem, namely that the engine won't work.  Something that solves a problem but at the same time renders itself completely impractical sounds like a Chindogu to me, or however it's supposed to be spelled. " You did spell it right the ō symbol didn't paste properly, ill give you that much. The errors in this statement only adds to the insult of the chindogu remark of your first comment.

The irony is that you don't seem to understand the function of the water cooling system or how in fact a Stirling cycle works.

If you had goggled Stirling engines you would find that the hotter you get the hot zone and colder you get the cold zone the higher a temperature differential you achieve and the power increases. The sterling cycle transfers heat from the hot zone to the cold zone with each cycle, without cooling the cold zone eventually heats up and you loose performance. Therefore the cooling system works perfectly enhancing the performance without any secondary problem occurring.

In high temp Stirling you would run the stainless steel hot end at red hot heat pushing it as close to failure point as possible while trying to cool the cold zone to as close to freezing as you can get it.

I already have made a heat sink, the aluminium hard drive platter the copper pipe is soldered to is the heat sink, because it is water cooled it does not require fins but it does require it to be touching not just close to the object , for better affect thermal compound should be used.

Can you explain to me what you mean by "the problem of heat inefficiency"? and how this will now cause a secondary problem, "namely that the engine will not work"? I really want to know what this secondary problem is and how I missed it when doing the test run.

Please do explain "the irony of putting a cooling system on a heat engine" The internal combustion engine is also a heat engine that requires a cooling system, check it out and see how many and varied types of heat engine there are.

About This Instructable



Bio: Learning to live with Fibromyalgia brought on be numerous injuries some old some quite recent. Currently under no fixed agenda, just going with the flow ... More »
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