Stirling Engine

[John KinmanParticipant @johnkinman36462]

I have purchased a Maidstone SE-02 MX Stirling engine and would like the various parts explained to me please.Firstly the displacer .Is that the glass bulb ?…and secondly what is going on inside the cylinder……I have a rough idea but would like a detailed explanation as to what is happening inside it please.If someone could do a diagram of working I would be very happy.I see the valve action in and out of the cylinder but dont know if this is displacer or piston .I know it is all about hot and cold air (expansion and contraction) but am finding it difficult to relate to the model……….ie when glass heats up it forces piston into cylinder …how does hot air get into cylinder to cool ??….I would like to see whats inside cylinder …Thanks in advance

[John KinmanParticipant @johnkinman36462]

Basics

[russellParticipant @russell]

you could have a look here.

.. http://www.animatedengines.com/ltdstirling.html

there are other stirling configurations on this site. google is your friend…

[Ian S CParticipant @iansc]

There is quite a bit on google, including one site called? zobobo, it has a vidio by Tubal Cain on the workings of the hot air engine,(I'm on dail up about 12,000 miles away, and could'nt get it properly). Have a look at The site suggested by russell, they do'nt actually show the GAMMA type of motor that yours is, but go back to the single cylinder example, just imagine the piston (r/h one in the diagram ) is in another cylinder. 'Fraid I build 'em but I'm not that great in writing a description of the workings.

The glass part is the displacer cylinder, the displacer is the bit inside that moves, when it is in the foreward position (leaving an open bit visable in the tube), the air gets heated, it expands, increasing the internal pressure, this pushes the power piston down, the displacer moves back, filling the hot space, and opening the cold end where the air cools, the pressure drops, and the atmospheric pressure pushes the piston back up the cylinder ready to start all over again.  There are no valves in a Stirling Engine, the air stays in the engine, it's just heated and cooled as the displacer shuttles from one end to the other.

he animations the first one you see is actually the same type as yours, except it opperates at low temperature, usually hot water, but some have been built that will run on the heat of your hand.

These motors can be adictive, I'v got 17 working ones that I'v built, and ideas for a few more I would like to try.

Ian S C

Edited By Ian S C on 26/03/2012 08:28:15

[SpringbokParticipant @springbok]

Hi

Could I reccomend this book by Roy Darlington and Keith Strong. Roy shows Stirling's at most ME Exhibitions. Look at

http://www.stirlingengineer.com

He is one of the most knowledgeable people I know on this subject

Goog Luck

Bob

[John KinmanParticipant @johnkinman36462]

Yes thanks I have seen many articles on web but cant see any for my model …….Im not sure what is displacer and what is power piston…….Once I know that I will die a happy man……My model is SE-02 MX……..Its this one………http://www.youtube.com/watch?v=3erBMzk5r5s

I would like to know that when glass is heated and draws piston in does it allow hot air to escape around sides into cylinder where it cools and contracts and what is happening inside cylinder with the valve type mechanism.Is that dislpacer or power piston………Many thanks…….Its irritating me because I would like to explain workings to Grandchildren.

[Ian S CParticipant @iansc]

John, there is a good vidio on youtube

http://www.youtube.com/watch?v=DkfXd8364WY Principles of the Stirling Engine by Tubalcain (this is not the Tubal Cain of Model Engineer fame.

The displacer in the glass tube is driven by the power piston, the air is displaced from hot to cold,and back again by the displacer, there are NO valves involved it the Stirling Engine. The vidio is 7 miniutes long, I'm on dial up, so I did not look at all of it (life's not long enough), but you maybe faster, watch it two or three times, look, and listen. Ian S C  tried the site, it says not available, it is you might just have to look for it.

Edited By Ian S C on 26/03/2012 12:15:44

[Ian S CParticipant @iansc]

edited

Edited By Ian S C on 26/03/2012 12:13:53

[TerrydParticipant @terryd72465]

Hi John,

The Stirling cycle works simply because gas expands and contracts when heated and cooled. If you had a simple cylinder with one end closed and a close fitting piston with a fixed amount of air behind it and you heated the air it expands and the piston would be pushed towards the free end of the cylinder. If you then cooled it, the air contracts and would pull the piston back.

The displacer chamber is simply an extension of the cylinder volume. The system is closed with a fixed volume of air. There are no valves, it is a very simple sytem. When the displacer piston is at the 'cold' end of it's chamber, the air at the hot end is heated, expands past the displacer (hence the gap) and pushes the power piston which rotates the flywheel. This moves the displacer to the hot end displacing the gas to the cold end, it cools, contracts and pulls the piston back, which rotates the flywheel causing the displacer to move to the cold end, gas is now at hot end and expands again etc etc etc

Once you get the idea that it is simply a fixed volume of gas expanding and contracting in a closed system you will understand.

Best Regards

Terry

[Sub MandrelParticipant @submandrel]

The power piston is the one that's a close fit in it's cylinder – it changes the volume. the Displacer is a loose fit in a cylinder heated at one end and cooled (or in open air) at the other and as it moves back and forth it 'displaces' air from the hot to the cold end.

Neil

[John KinmanParticipant @johnkinman36462]

Posted by russell on 26/03/2012 02:50:26:

you could have a look here.

.. http://www.animatedengines.com/ltdstirling.html

there are other stirling configurations on this site. google is your friend…

Thankyou for explanation …..I was confusing displacer with power piston…..Thanks once again……Diagram is clear.

[John KinmanParticipant @johnkinman36462]

Posted by Terryd on 26/03/2012 15:26:39:

Hi John,

The Stirling cycle works simply because gas expands and contracts when heated and cooled. If you had a simple cylinder with one end closed and a close fitting piston with a fixed amount of air behind it and you heated the air it expands and the piston would be pushed towards the free end of the cylinder. If you then cooled it, the air contracts and would pull the piston back.

The displacer chamber is simply an extension of the cylinder volume. The system is closed with a fixed volume of air. There are no valves, it is a very simple sytem. When the displacer piston is at the 'cold' end of it's chamber, the air at the hot end is heated, expands past the displacer (hence the gap) and pushes the power piston which rotates the flywheel. This moves the displacer to the hot end displacing the gas to the cold end, it cools, contracts and pulls the piston back, which rotates the flywheel causing the displacer to move to the cold end, gas is now at hot end and expands again etc etc etc

Once you get the idea that it is simply a fixed volume of gas expanding and contracting in a closed system you will understand.

Best Regards

Terry

Thanks Terry ….I understand now i was confusing displacer with power piston……John

[John KinmanParticipant @johnkinman36462]

Thanks everybody for your help .One thing I am surprised at is that the air cools so fast on the contraction cycle after taking a while to warm up on the expansion cycle………I guess thats something to do with cooling fins on cylinder ?

[John KinmanParticipant @johnkinman36462]

Im thinking of buying a model steam stationary engine with a view to running on compressed air or steam . Can anybody suggest which is best Mamod or Wilesco ?….Or other manufacturer…please ?

Which is better build quality ??

.

[Ian S CParticipant @iansc]

Hi John, yes it still amazes me the speed of change of heat, whether it's my biggest engine with a 2 1/4" bore, or my smallest with a 3/8" bore.

I'v had a Mamod SE-2 (I think) since my Grandfather gave it to me for Christmas about 55 years ago, it's in a box in the workshop, but just needs water, and meths, and it would be up and going. Since then I have built some similar size, and style engines, also one V twin, and one with a bore of 3 mm and stroke of 6 mm, that one went into a boat, and sailed on the pond at the local park.

don't know of the quality of other steam engines, I find my own are the best ones. Ian S C

[John KinmanParticipant @johnkinman36462]

Hi Ian after looking at the animated working of the Stirling Engine I have one other question …It appears

the linkages play an important part in the movement of both the piston and dsplayer…….Does this have an overriding effect of the air pressure changes ie hot and cold .It looks as if the linkages and air pressure changes work together.If so would I be right in saying the engins would not work entirely on just the pressure change principle without the linkages…………Sorry to be a Geek its just that much is made of the basic pressure changes but little of the part of linkages to carry the cycle through.My question is would the engine work without the linkages………I suspect no.

[Ady1Participant @ady1]

There's a 400+ page thread on stirling engines in here

Hot air and Stirling Engines

They're pretty popular

[Ady1Participant @ady1]

Youtube has dozens of variants and is good for different ideas

 

This one is pretty hilarious

 

This lamina flow one has a piston, no apparent displacer and runs at 700 rpm

 

Edited By Ady1 on 28/03/2012 10:12:38

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi John ,

Movement of the displacer has to be in advance of movement of the piston and this is what the linkage does . The exact amount in advance depends on the specific design of the engine but is often about 90 degrees . Put more simply if the engine simply had two cranks – one each for power cylinder and displacer – then the displacer cylinder crank would be 90 degrees ahead of the power cylinder crank . The angle between the cranks is usually known (not quite correctly) as the phase angle .

The 90 degree cranks described above are for an engine which has both cylinders side by side . Some engines have the cylinders at right angles running on one crank and this give the 90 degree setting intrinsically .

I've simplified the explanation a little to make it clear . In an actual engine the detail arangement of the cranks (or any other mechanisms serving same purpose ) depends on many things such as :

Direction of rotation , which way the power and displacement cylinders are placed relative to one another and which way round the displacer cylinder is (which is hot/cold end) .

More subtle things are whether the engine is regenerative and/or pressurised , the working fluid and whether engine is intended for slow or fast running .

Michael Williams .

Edited By MICHAEL WILLIAMS on 28/03/2012 10:35:47

[1Participant @1]

Hi John

To respond to your question about purchasing a stationary engine. I started down the road of model engineering a couple of years ago by buying and assembling a Mamod traction engine, which I have steamed. The engine part is an oscillating cylinder and assembly of the whole thing took me about half an hour, 10 minutes of which was spent searching for a miniature Allen key. I followed this with a Wilesco traction engine which is a world away from the Mamod having a double acting valve controlled motor and a more complex chassis. I spread assembly over a couple of hours and I have not steamed it because I didn't want to spoil the polished brass finish on the boiler but I have run it on air. Both these projects are little more than tinplate toys.

For an insight into how a steam engine functions and to allow some experimentation with valve timings I would suggest something like my third project, a Stuart Models ready to assemble kit, (I built a 10H), or something similar from Cotswold Heritage or the like. Having built one of those I was encouraged to get my workshop up and running, make an oscillator from stock material and I'm now machining a Stuart 10V from the castings kit.

I haven't yet got a boiler, a project for later, so I run my engines on air. This gives me the satisfaction of seeing them working but I understand that there's nothing as good as water and heat to bring an engine to life so ultimately that's what I will use.

Jim

[John KinmanParticipant @johnkinman36462]

Posted by MICHAEL WILLIAMS on 28/03/2012 10:07:16:

Hi John ,

Movement of the displacer has to be in advance of movement of the piston and this is what the linkage does . The exact amount in advance depends on the specific design of the engine but is often about 90 degrees . Put more simply if the engine simply had two cranks – one each for power cylinder and displacer – then the displacer cylinder crank would be 90 degrees ahead of the power cylinder crank . The angle between the cranks is usually known (not quite correctly) as the phase angle .

The 90 degree cranks described above are for an engine which has both cylinders side by side . Some engines have the cylinders at right angles running on one crank and this give the 90 degree setting intrinsically .

I've simplified the explanation a little to make it clear . In an actual engine the detail arangement of the cranks (or any other mechanisms serving same purpose ) depends on many things such as :

Direction of rotation , which way the power and displacement cylinders are placed relative to one another and which way round the displacer cylinder is (which is hot/cold end) .

More subtle things are whether the engine is regenerative and/or pressurised , the working fluid and whether engine is intended for slow or fast running .

Michael Williams .

Edited By MICHAEL WILLIAMS on 28/03/2012 10:35:47

Yes there was as I suspected more going on then just hot and cold spots …the flywheel and linkage are just as important …….In most explanations the hot and cold areas are not enough to drive engine alone.

[John KinmanParticipant @johnkinman36462]

Thankyou for taking time to explain……..It appears as I thought that it is not as simple a principle as is normally explained .There is a lot more going on then just expansion and contraction of air.But seeing the animated drawing from Ian S C I can equate to my model……..Thanks for help

[John KinmanParticipant @johnkinman36462]

Posted by Im Indoors. on 28/03/2012 10:58:12:

Hi John

To respond to your question about purchasing a stationary engine. I started down the road of model engineering a couple of years ago by buying and assembling a Mamod traction engine, which I have steamed. The engine part is an oscillating cylinder and assembly of the whole thing took me about half an hour, 10 minutes of which was spent searching for a miniature Allen key. I followed this with a Wilesco traction engine which is a world away from the Mamod having a double acting valve controlled motor and a more complex chassis. I spread assembly over a couple of hours and I have not steamed it because I didn't want to spoil the polished brass finish on the boiler but I have run it on air. Both these projects are little more than tinplate toys.

For an insight into how a steam engine functions and to allow some experimentation with valve timings I would suggest something like my third project, a Stuart Models ready to assemble kit, (I built a 10H), or something similar from Cotswold Heritage or the like. Having built one of those I was encouraged to get my workshop up and running, make an oscillator from stock material and I'm now machining a Stuart 10V from the castings kit.

I haven't yet got a boiler, a project for later, so I run my engines on air. This gives me the satisfaction of seeing them working but I understand that there's nothing as good as water and heat to bring an engine to life so ultimately that's what I will use.

Jim

Thanks I have purchased a Wilesco D16 on ebay and awaiting deleivery…..I would like to switch between running on steam and compressed air…….is there an easy option or does it involve pipework being altered ?…….Thanks

[John KinmanParticipant @johnkinman36462]

I see on the internet one person is running a D18 on compressed air by modyifing the water filler intake on the boiler with a screw fit connection for compressed air hose .Is there an off the shelf connector available please .Or can someone make one for me for price please ?

[TerrydParticipant @terryd72465]

Hi Jim,

It sounds as if the person you are referring to is using compressed air to pressurise the boiler. I personally would no way contemplate that. It would be very easy to over pressurise the boiler with catastrophic failure using a compressor. When generating steam in the boiler the pressure is raised steadily and the safety valve operates if the pressure exceeds it's working level. By connecting a source of compressed air, especially from a pre pressurised receiver it is al too easy to fill at a higher pressure than the safety level of the boiler due to the speed of the transfer the safety valve, designed for steam, would not be able to spill air quickly enough. Do You know the safe working pressure of the boiler? To run engines on compressed air you should connect directly to the engine. I may be wrong but I wouldn't risk it.

Why not steam it?

Terry

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