3D printed alpha Stirling engine #2

by aeropic Mar 22, 2014
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Can you heat both cylinders? And if you could would it make a difference in performance?

no, it won't work...

I meant if you had a separate larger cold cylinder with both heard ones feeding to it

if you mean in a multi cylinders stirling, yes you have to heat each cylinder and keep cold each displacer !

IS it possible to modify it to become a 4cyl? i know i could construct it to work geometrically, but dont know if it would mechanically.

Yes, it would run very smoothly if you succeed to assemble 4 of them. Just introduce a phase shift of 90° at each motor (If the phase of the first motor crank is let's say p1, then p2 = p1 + 90°, p3 = p2 + 90, P4 = p3+ 90°)

Comments deleted.

Hi. Is there a way to use another thing instead of the glass syringes ?
Thank you!

Dude, hey, nice model.
Just one question, what's the separation from the syringes-holding part to the other one?
Should I just eye it? I want to print a base

Yes, just eye it... The idea is to leave around 5 mm of air when a piston is at the closest position to the tip of the syringe (where the needle plugs ...)

I can't get it to work :-(

I think I built everything according to spec. The angle between the two hands is 90 degrees. I heat the syringe to around 170 degrees Celsius. Nonetheless, it doesn't work.

Any ideas what I'm doing wrong? Should there be some minimal amount of air in each chamber?

(photos attached)

It should work ....
First try to remove the silicon tube and check that there is abolutely no friction when running the fly wheel, it shall turn by itself during more than 5 to 10 seconds...
I see you've installed just half the number of nuts into the holes of the flywheels, this reduces the inertia and is not good for a proper motion of the motor...

Thank you for your quick reply.

I added the nuts for the flywheels, but it still isn't working. I think I might have more friction than I should, since it only spins 3-4 seconds without the tube. I'll try to improve this.

Are there any requirements for the size of the air chamber in the hot or cold syringe?

the air chamber is not that critical, When the piston is close to the tip of the syringe (in direction of the silicon tube) just let 8 to 10 mm of air.

For friction, you might dismantle the syringes and clean the piston with dilluted bathroom cleaning cream. Once full of this soap, insert the piston in the cylinder and move it. Then rince under lots of fresh water, this will run in your pistons...

I wonder if someone made it workin with basic candle? I tried but mine didnt work, still feels like there is a bit of friction, gonna do some greaseing tmrw. Is WD40 good for that?

Aswell, I have little space(like 0,3 mm) between the 3 mm rod and ball bearings there, could that cause more friction?

Thanks alot

For the candel just have a look to the 'i made one' section somebody succeeded using aluminum reflector.

i see, i really struggle to make it work :( here is video with candel https://www.youtube.com/watch?v=Cb3clhtfw8U

without - https://www.youtube.com/watch?v=LZyZ6wr7biY

sry for ad quality, is there still too much friction? I used WD 40 on everything i could :D

edit: i even used sand paper for the plungers inside siringe, to make it smoother

Can be that issue, that the air is getting to syringe? So they are not tight enough? Because i used a bit of sandpaper to make them smoother, i am getting frustrated :D

I am afraid sand paper is too agressive... A proper running in should be done with dilluted copper est cleaning paste...

Just to make sure, there are 20xM6 nuts, 6xM3 with threaded bolts for the holes in stirling engine to hold siringes and wheels, 8xM3 bolts with sharp tip, to hold stirling support to the wood, right?

Thank you very much for your amazing work

Well, I have not counted the bolts, but you might be right ;-)
Thanks for your congratulations !

hi great file ! i have some problems with fitting the piston arms inside the heads is that a file problem or a tolerance issue of my printer?

you mean the flat printed arm into the printed part ? Or the head of the piston into the printed part ?

If the first option, then it could be indeed a problem of tolerance of your printer. If the second it is for sure the glass head of the piston which is too big !

I meant the flat printed arm!

hi great engine. I want to use cotton to block heat from hot syringe. is it work well ? I want to use pla

It should work, but do not use the engine too long if you do not want to melt the PLA !

Hello Aeropic. I have printed this engine and it looks flawless, but it doesn't run for some reason. Before placing the burner under the syringe, I am able to turn the wheel freely without much friction. After the syringe heats up however, the wheels will not turn. I feels as if a vacuum is created preventing the syringe from pushing in and out. I've spent weeks patiently gathering the right parts, thanks.

Maybe the syringes are too tight. I would advice some running in using bathroom diluted fluid cleaning paste or copper cleaning paste. Insert some between piston and cylinder move th episton in translation and rotation several times, then clean under tap water, dry and install back ... It should work !
Before placing any heat to the syringe try to disconnect the silicon tube and to make the engine turn. The pistons shall move very freeely and the engine shall rotate several seconds.

Hi aeropic. Thanks for sharing this very cool engine. I printed it, but it doesn't start to run. Is it ok if the syring is at 2ml when it's fully extended, or should there be more room?

Before placing any heat to the syringe try to disconnect the silicon tube and to make the engine turn. The pistons shall move very freeely and the engine shall rotate several seconds.
If not, if there is any friction between the piston and the cylinder, the motor will not start. You'll then have to run in the pistons using some abrasive bathroom cleaning paste diluted. After running in clean the syringe under lots of fresh water...

Hi Aeropic,

Thanks a lot for the share ! I wanted to make a stirling engine since a while !
I copied your model and add settings because i want to understand the process and find the optimal parameters.

I can modify the stroke, the angle and the play between the top of the piston and the bottom of the cylinder.

For first try i set everything as in your model, and it works well ! It turns really fast during one minute and then slow down and stop, the piston rub in the cylinder when hot (really smooth when cold). I'm using an alcohol burner and tried different distances from the flame.

Does your model turns indefinitely ? Any advice to fix this ?

Thanks in advance !

Hi, Nice setting including the silicone tubing in the color scheme is beautiful !
I never make it turn too long i often stop after 2 or 3 minutes... However if the piston ends stuck to the cylinder this is a sign of not enought clearence.
It might be useful to perform some running in using for instance bathroom cleaning product (use one which is creamy with some powder inside) dilute it and try to move the piston inside the cylinder. Then clean all this under lots of water.

If not already done, please post your make under the 'i made one. tableau !

Hi, thank you ! Here is the link for silicone tubing, you can choose the color ! https://www.ebay.co.uk/itm/391514668063

I spent hours on it last night and i think i solved it. I really need to evacuate heat in the rest of the cylinder so I had an aluminium foil on it and it works so fast for minutes ! But then my support started to smoke and melt, even printed in ABS and with O rings around the cylinder. So next step is to make a real heatsink with aluminium sheet !
When done i will play with settings and see what happens, for now i just increased the stroke to 7 mm instead of 6 and it works realy well !

I will post pictures and a video soon ! Also I can share 3d files if anybody want.

What is the diameter of the syringe in the Netherlands only 10 ml syringes are available. would that work to? I like this project very much! Thanks a lot for sharing!

The material list is in the description of the #1 motor.
The syringes are 5ml. I do not remember the diameter ...
I bought them on ebay in China !

The engine should work fine with 10ml syringes but you'll have to adapt the support to the proper diameter. (as it is openscad, everything is scripted are can be modified)

Thanks for the congratulations!

2x5ml glass syringes
20xM6 nuts
2xM3 bolts
one 3 mm rod axis
4 pieces of 2mm rod
4x2mm ball bearings
2x3mm ball bearings
several PLA meters !!!
2 pieces of wood
one candel
10 cm of 3mm ID silicon tubing

Thank you for the quick reply!

Hello, can you write me please the material list (except 3d printed parts) and how do I get it together and how much metres of 3mm filament does it take? Thank you very much


The material list is provided in the #1 motor description: https://www.thingiverse.com/thing:269119

For the length of the filament frankly speaking I don't know ! Just download all files, slice them and the slicer will give you an accurate length according to your settings ;-)

3D printed alpha Stirling engine
by aeropic

I always wanted to build a 3D printed working engine, this design comes very close and I realy like it!
I only have problems finding syringes, most of them have metal conntectors where the tube attaches. I guess that's not so good as the metal will transfer more heat into the silicon tubing maybe it will overheat?

In my mind I'm already a step further: What's about it's power? Might it be enough to drive a small ship?

There are plenty of them without the metal tip. For instance on ebay : http://www.ebay.fr/itm/1x-5ml-GLASS-SYRINGE-new-non-sterile-all-glass-syringe-/252939379494?hash=item3ae45ca326:g:4-YAAOSwEeFVDten

The power delivered by such a small engine is very low. I'm not sure it could drive a ship ...

how hot do the syringes get ???...great build by the way

As far as I know, the flame temperature is around 370°C which means that the syringe tip could be around 300°C or more ...

This looks like a great design. I've been re-watching the video of it running. So captivating. Can't wait to build this! Heading out tomorrow to get the components. Thanks for uploading this. :D

Thanks a lot, please post a picture or a video once running !

Will do, this engine is so awesome!

I would like to ask you!
What type of syringes did you use! What brand? If ypu could provide link it will be great!


Please see the information provided on #1 model.

What size syringes do you need

Please see the information provided on #1 model.

Do you have a Bill Of Materials type list for this engine? I really want to build it and it would really help if there was a description in the details of what is needed.

Hi Ridley,

I think you get all the details you need in the "things details" tab menu of the first 3D printed strinling here :
(see http://www.thingiverse.com/thing:269119)
You should read all the information in this first model and also in the second one. Please go through the comments also there are maybe also usefull indications.
Enjoy !

3D printed alpha Stirling engine
by aeropic

For the life of me I cannot find how long the M3 bolts need to be, I am sure I saw it somewhere.

Just print the parts then measure the length you need !
If fact you need "short" ones to fit in the wheels and tighten them on the axis ~1 cm , and "longer" ones, I would say 2 to 3cm to hold the syringes in place.
I just used a saw to cut the long ones to the right size of the short ones ...

Hello Aeropic

I was wondering what the largest component is(for determining how big of a printer I will need). Also, did you need to have a support structure for any of these parts or not? I am planning on building this at school and displaying it for an expo where elementary school students come and learn about engineering. If you have the overall dimensions of the finished product is, could you let me know please? Lastly, if you happened to know the overall volume of the printed objects, that would be very helpful.
Thank you so much!

Hi Mtown10,

The biggest component is 10cmx7cm. It is the syringes' support.
Everything is designed to be printed support less.
Overall length is about 20cmm including the syringes.

The source files of the pieces desgn are provided (.scad ones). You can easily donwload them, open in OpenSCAD (freeware) display a rule to get the dimensions and play with them.

For the volume of the printed objects, I don't know, but who cares ? ;-)

I would be very pleased if this engine could help for such an exhibition for education, thanks a lot

Thank you so much for all of your help! I'll have to download that program and try out what you are saying. Thank you again for your help, and hopefully I can start printing and assembling!

You'll see OpenScad is a really nice piece of software. The objects are coded in very simple yet powerfull script langage.

And all the pieces of this engine are very easy to print ==> success guaranted !!!

Hi I really like this model !
Do you know the name of the rods, bolts and ball bearings?
I don´t know how to get them :c


Bolts are M6 for the nuts and M3 for the rest
rods are silmply 2mm diameter pieces of metal. You can even cut them from a coat hanger

ball bearings (can be bought on ebay)
for the rods use a MR52-ZZ 2 X 5 X 2.5Mm at each tip
for the main axis I use MR83ZZ 3x8x3mm

Very nice, but it needs a lot of heat. May be you like this 3d printed solar stirling engine:


Thanks Andy.
Your 3D printed LTD is very nice. I know this concept as I built one years ago before 3D printers were invented !

This has been my first Striling starting a kind of collection that you can view here:


It is impossible to buy glass syrgine and cheap ball bearingshis fitt to this project in Poland./ Nie da się kupić w Polsce pasujących szklanych strzykawek ani tanich łożysk do tego projektu.

Try on eBay but I don't know if it is available from Poland?

Hii, great design. :) I dont get the rods and bearing for the axle from where I live... Do i need them to make this? or just replace them with longer screws?

Yes it is mandatory to get very low friction. For this ball bearings is a must...

Thanks a lot for ur reply.. I have managed to get them :) Printing in progress :) Awesome work i should Say:) And BTW how should the flywheels be aligned(to each other) with respect to the joint which connects to the connecting rod? is there any particular angle?

Yes it is important to set the two flywheels with the cranks at 90°. This gives the correct dephasing for the stirling cycle.
According to which wheel is "before" the other, the engine rotates in one direction or on the other.

What are the sizes of the screws used?

3mm in diameter (M3).length is not important 10mm to 15 mm would be OK...

Hello, I have a problem in getting it to work.
Without heat works perfectly, but when I put the flame doesn't work alone.
Do you have any advice?
Thanks, sorry for my bad english

When cold, you should feel the compression when running the engine. If you unplug the silicon tube, the engine shall run freely several seconds at least.

With the flame, if you have difficulties to make it turn (by hand) there is maybe some friction at the level of the syringes. You can solve this with some "running in" of the pistons using copper cleaning liquid or cream. remove the piston, start cleaning it between your fingers, rince under water. Put again some cream+water and insert inside the syrige cylinder. Gently insert the piston and turn it into the cylinder. Then clean everything under fresh water. Dry and install back...

Just tell me if it works?

Another idea is the position of the crancks there must be 90° between both...

Thanks for the advice

Now it works perfectly

I have a question, It is normal that It only turns in one direction (clockwise)?

You can heat the other syrige.... It may reverse direction...

Perfect !
Please post a picture in the "made one" section ;-)

Yes, it's normal.
If you want it turns in the other direction, just turn the cranks to orientate them at -90°

Hi Aeropic
My friend printed out the engine and had some difficulty getting it to work.
I have worked with various model Stirling engines and thought it would be interesting to try the glass syringe piston/cylinders.
I too found some difficulties, but have overcome some of them.
I have posted a You Tube video showing what I have found out.
Hopefully this will help others to get their engines working well.
Getting a Stirling engine to run is not always very easy!

thanks Thamesside for your video which gives usefull information (especially the running in of the syringe pistons...)
I think you should have left 1/2 cm or so of free space at the extremity of the piston when completely at the end of the "cold" stroke. This extra place acts as a margin of safety to avoid the piston to shock on the cylinder tip...

If you like stirling engines, please visit all my other videos on youtube you'll find half a dozen of machined stirlings all different (beta, gamma, ross yoke, LTD, thermoaccoustic and even a manson ...)
They're collected on a web page here: http://aeropic.free.fr/pages/stirling/stirling.htm

enjoy hot air engines


Thanks for your reply and your web page links
Also, apologies for my delay in responding

"More space between the end of the piston movement and the end of the syringe."
So far - I have yet to smash a piston or a cylinder!
I have set the gap at the end of the stroke as small as possible so as to minimise dead space.
Particularly on the hot side. Hot dead space seems to be a bigger problem than cold dead space.
Currently I use 1mm gaps

It could be that with less dead space I have got a bit more power and that is "tilting" the piston and causing me friction and seizing?

However - have a look at this video

Perhaps the design should be altered - to be upright - and have some heat shields to deflect the heat away from the silicon connecting tube?

Like you I have other videos recorded
They are on You Tube under channel MrAndrewHall
with titles like
Stirling Engine Boat Rally

I don't have a 3d printer. My friend Malcolm does.
Hopefully he will be evolving the design
And, like as not, I will be doing more video/thingiverse/You tube postings!

My hope for my activity is to get the engine to very easy and reliable for newcomers to Stirlings to just print one out and have it go well.


Wooahoo .. When vertical, the gain in speed is impressive... It might be the case you have a not fully round piston. Maybe try to polish them again to try to add play ?

I'm currently working on another 3D printed stirling project.. Stay tuned it should be available within a month or so !!!!
Meanwhile, Ask your friend Malcom to print the mendocino motor, http://www.thingiverse.com/thing:620961 . this was a cool Christmas project, I'm sure you will like this too ;-)

Tiny Mendocino solar motor
by aeropic

I have printed one of these but are having difficulty getting it to run.

I have been using 4mm id silicone tubing but it has been degrading under the heat of the flame and letting in air.

Has anyone encountered this problem and got any ideas as to a solution? I have just bought some 3mm id clear silicone tubing as per BOM - hoping that will fix it but any other advice is welcome.

Most probably the silicon tubing you used was not of good quality. On ebay some sellers provide us with so called "silicon" tubing that is definitely not silicon as it begins melting under a flame. Try to find silicon tubing from a RC plane shop: it should resist to such temperature.

i bought 50cm silicon tube for 8 euros!! very expensive ,but it is silicon

Nice, I've made my own Stirling Engine, similar to this one! :) It works almost the same way, but I use different sized nuts and bolts, different bearings and I have found different syringes! I have found two different versions, one completely glass and one glass tube syringe with a metal plunger/piston. The ones with the metal piston are about 10 times better than the glass ones.

What is the price of the metal piston syringes ?

Here, it's this one:

The contents are sadly only 2ml

I am seeing if I can convert my design to use these 2ml syringes, but I broke one when I was having a dress-up party with the medical theme so I would have to reorder the damn things.

Well priced ... I would have been afraid of differential dilatation between glass and metal piston, but if it works, it might be a good option.
Thank you for sharing this

No problem. I will reorder and let you know how it works/if it works.

Amazing!!! I have built some "stirling can engines" but this alternative is awesome!!! Congratullations!!!

What do you use M6 and M3 for?

M6 = the nuts inserted inside the wheels to increase inertia
M3 = bolts and nuts to connect everything (axes lockers, syringes holders ...)

What are the lengths of the 3mm and 2mm rods you use?

Humm, I have not measured... For the main axis, count 2 x wheel thickness + support thickness
for the 2mm, something around 2 cm is what you need !

What bearings do you use in this build?

for the rods use a MR52-ZZ 2 X 5 X 2.5Mm at each tip
for the main axis I used MR63-ZZ 3 X 6 X 2.5Mm but they are too small and fragile. I then switched to
MR83ZZ 3x8x3mm which are a bit bigger. I've just updated the support.scad and support.stl files to reflect this

Thanks! Im looking forward to making this, I ordered the syringes on ebay a few days ago.. Might as well order the rest now :-)
Im guessing that I can use just about anything as rods as long as its 2mm and 3mm?

yeap you can use any straight piece of steel you find in your garage ;-)
For the main axis, it must be straight... I found a piece of 3mm rectified rod inside an old CD ROM reader (the drawer's guide)
I'm looking forward to see one child of mine: I wish you great success. You'll see it's VERY simple to print as any piece is designed to be printed without raft or support, directly flat on the table !

I finally got my little stirling running :-) I will post a video soon. I had some problems with the syringes being really worn (Thats what you get from ordering "new" from china.. I got refurbished syringes - though they were listed as new, yum.)
But a new syringe fixed it.
The motor runs pretty fast. and the setup allows alot of tinkering and experimentation in what makes a stirling efficient (Like timing, pressure etc) I love it. your creation should be mandatory in every physics class room in elementary school!

Good news, I'm looking forward seeing the video.
Many thanks for your kind last sentence ;-)

Ever thought of rigging this up for something? Like maybe a generator or a toy car?

a simple generator with a magnet and a coil would for sure light a LED ...
Something else to print and build ;-) ...

cool thing. i want to build it. but were can i get these glas syringes?

I bought them on ebay (miyashop). Just make a search with "glass syringe 5ml". If you can find a temperature proof one, go for it. I can see a crack on the tip of my hot syringe which means it won't last forever ;-(

Thanks for uploading. Have you found the syringes that can handle the high temperatures better? Is http://r.ebay.com/cLZfIkhttp://r.ebay.com/cLZfIk a good one? it uses borosilicate.

Yes, this one with borosilicate should do the job.
Yours is 10ml, mine is only 5ml ... Both are OK but you'll need to adapt the syringe diameter in .scad before printing...

I printed the pied.stl part already, so i will buy the 5ml instead. http://r.ebay.com/1IeQbehttp://r.ebay.com/1IeQbe. I noticed the diameter of the holes in the pied.stl files are not the same. Is there a reason for this? Thanks

Yes, there is a major reason to have different diameters for the hole supporting the syringes. On the hot side, the hole is bigger to leave some room to insert a O ring made of silicon tubing. See instructions tab

Ok, are you planning on making a engine with 4,8, or whatever number of syringes? It can use the same wheel also.

I had not that in mind... However it would be very easy to buid a 4 syringes engine. Print a second support two other "bielles" and assemble all symetrically to the wheels supports usinf the same 2mm rods and that is !