Stirling engine with 3d printed half rhombic drive and details of development and optimisation

[@Chrisworkshop]

Nice job as always Ralf. I use 3D printing for my Stirlings but to mold aluminum parts. I am trying 3D printed lost wax to mold my next parts.

[@myengines2443]

Hi Chris, casting with 3D printed Wax sound very interesting, please make a Video and please in english. I surely watch all your amazing videos but my french is not so good. Merci beaucoup et à bientôt Ralf

[@serena8540]

im always thirsty for some stirling content and your channel is a bliss to me, keep up the good work!

[@etonetonovich5340]

Hello! You have not been seen for a long time. Great job!

[@myengines2443]

Hi Eton, thanks for your interest. Unfortunately I have not much time to make many videos because of my other hobbies ;-) But as soon as (in my eyes) something interesting is to report I will do. Stirling development is much work and to get presentable results you have many flops and this takes time. Best wishes Ralf

[@barumman]

Excellent work Ralf, very interesting. :)

[@kadettipanema9259]

Great job, best regards from Brazil friend.

Amazing work! Thank you for sharing this.

[@christophercridlebaugh8965]

Your work is amazing 👏 I would buy one of your builds think about it

[@myengines2443]

Thanks

[@christophercridlebaugh8965]

@@myengines2443 how much for a finish engine. Also is this based off the Philips design

[@myengines2443]

@@christophercridlebaugh8965 the engine is still in the experimental phase and not for sale. It is not based on an Philips design because it has an HALF rhombic drive what was not used (as far as I know) by Philips.

[@adrianlevy7841]

Hi Ralf Good to see a some great use of 3D printing in a (non-toy) Stirling engine. We just need affordable 3D metal printing for the top end now, so that the heating into the working gas can be optimised. Regarding pressurisation, I'm sure the shape of the crankcase can be improved and ribs added to help achieve higher pressures - obviously with great care. Keep up the good work.

[@myengines2443]

Hi Adrian, I worked with some 3D printed parts of copper, they were expensive and not absolutely ait-tight. I think metal 3D printing has to get much cheaper and better (tightness) to use in engines. Good to hear of you and with best wishes Ralf

[@GiesbertNijhuis]

Great progress! If there would be an afordable good quality stirling engine on the market (±300W electric output) I would buy one. Printing reduces the prince of one, but I things large scale production is the way to go: make & sell millions of units.

[@myengines2443]

Hi Giesbert, thanks for your interest and high expectations. Maby if the engine proves as useful I am dreaming of a small mini series of up to ten engines. Then it would be interesting to 3D print. As soon I can make use of metal casting it would be far better but not for prototypes. This would be very costly or another hobby of its own. Many greetings Ralf

[@edvogel56]

Beautiful!

[@soeft]

Nice job! Do You consider to use water cooling?

[@myengines2443]

Yes, as the durability and strength of the printed parts is not good enough I again use my old water cooling of the original rhombic engine. Greetings Ralf

[@mehmettufan7914]

Have you gain some progress?

[@IronGoober]

Wonderful work as always. I'm pleased to see you making use of 3d printing. Will the crankcase handle pressurization being plastic? It would be amazing if it did. I'm also wondering if you have plans to 3d print the heat exchangers and have them cast (i.e. lost wax) and use something like a copper alloy because of the high melting point compared to aluminium, maybe CuNi alloys? (I'm not sure if that could handle pressurization) Just some ideas. I love your videos. Please be encouraged to make more.

[@myengines2443]

Hi IronGoober, surely the printed crankcase will withstand only low pressures, no way of 10 bar. When the development is finished and power and reliability are satisfying the metal casting of the crankcase and the heat exchangers is the only way of cost effective mini production. Many thanks for your interest and your kind suggestions. Greetings Ralf

[@sierraecho884]

You can also replace the air with helium, helium can be bought in "birthday and carneval stores" in small pressurized bottles. You would have to add 2 one way valves to exchange the gas inside but this should improve efficiency further and might be just a small change as an add on. You also improve combustion by using the same compressed air you use to cool the engine to feed into the burner. Examples of this can be seen with thr Philips stirling engine.

[@myengines2443]

Yes, thanks I already made some experiments with helium but have to test it more. Combustion air preheating is important for good efficiency and I will do that when the engine reaches target power. Thanks for your hints

[@018_sajil3]

Can you provide me the design of it? Solid works or cad model? I need this for my project.

[@treydonnell2871]

So how difficult would this be to convert into a ten horse power design with a constant input temp of 1050° and if a ten horse power design couldn't be done is it possible to do anything 2 hp or above?

[@myengines2443]

Hi Trey, sure this is possible but I find it hard enough to produce a reliable 300 watt engine. It is much more work than it looks like and experimenting with more powerful prototypes will make it much more expensive as you have to build much bigger or use higher pressure. Greetings Ralf

[@nirodper]

what are the benefits of a rhombic or half rhombic system compared to the pistons being 90° out of phase? what is the motion like?

[@myengines2443]

Hi Nicolas, these crank drives give the possibility for a beta inline Stirling which may give better performance and efficiency for small engines.When you look on the piston position diagram in the video you can see that the fluid distribution of the working gas is very good for the Stirling cycle. Greetings Ralf

[@LPdotLP]

Have you tested this engine for life? Is a liquid lubricant used or is the tribological polymer run dry?

[@myengines2443]

Hi, I have made the experience that printed parts are not durable enough and made all parts in metal now. Soon as I am ready with my EDM project I will make a video about it. The polymer runs completly dry, thats its advantage. Greetings Ralf

[@LPdotLP]

@@myengines2443 Thanks for the answer! Good luck with this project!

[@danielreborn4707]

Great Job I think You channel is underrated -subscribed to help a bit

[@myengines2443]

Thanks alot. Ralf

[@sergiygumenyuk2670]

Hi Ralf, your engine with half-rhombic drive looks beautiful and, the same time, very simple. I know that this is just the look but I believe these are two the most important factors to describe good idea. I've been reading about Stirling engines and want to start experimenting by myself (mostly different materials and heat exchangers) but there is not much real drawings in the internet to start with (simple, no power producing engines or people who didn't make any measurements not counted). Do you have any drawings that you can shear? Or at least dimensions of the components? Link to STL files below is no longer valid. Thank you very much and good luck with your inventions, Sergiy

[@myengines2443]

Hi Sergiy, nice that you also want to build Stirling engines it is a lot of work but very satisfying when an engine runns well. Look for the book "Making Stirling engines by Andy Ross" it is free in the internet and very good. Also a good choice is "The Stirling engine Manual 1 and 2" by James Rizzo. I have no proper plans but if you serch a bit you will find the basic design parameters in the internet. Its best to design your engine from scratch then you can build it to match your workshop skills. Greetings Ralf

[@sergiygumenyuk2670]

@@myengines2443 Hi Ralf, thank you very much for the books. I went through Andy Ross's book about a week ago and now I try to get my hands on "The stirling engine manual". Have a nice day and thank you very much for your videos! Sergiy

[@Viper54K]

Very Very cool!

[@Lechoslowianin]

very careful workmanship

[@myengines2443]

Thanks and many greetings Ralf

[@pratikmane8824]

Greetings from India. I'm just surprised with your work. Great job indeed. I'm a student and working on Stirling Engine project. But since I'm just student, couldn't find basics to design a Stirling Engine. So can you give me tips and some designs, drawings or plans of this engine? It will be a great help to me.

[@sierraecho884]

Instead of cutting all the parts wh not use MLS (metal laser sintering) to 3D print the metal parts with all the channels in place, this way the whole part with the regenerator can be optimized and printed as one part which would make the welding and slotting process obsolete. I know it´s more expensive to print the part but if you value your time and you want to mass produce the part some day this is the way to go to reduce complexity. Also you don´t want to create additional "dead space" that´s why it´s called dead space, but you want a regenerator.

[@Negyo]

So, did you get at least 100 Watt?

[@myengines2443]

Hi, the last few months I was optimizing my workshop and didn't experimented with the half rhombic further. But now I will start to work on the Stirling engine again and report as soon as I get some reasonable results. As I now use the complex heat exchangers of the original rhombic stirling which delivers 300+ Watts I think that I will get much more than 100 Watt. But unfortunaly not with the 3D printed parts, they are not strong enough. I replaced them with metal parts an get very promising results in first test runs. The half rhombic drive will only be a success when the power will be in the range of the original rhombic (300 Watt), the vibration will be acceptable and piston side loads low. Greetings Ralf

[@andrewhall2702]

Ralf - As ever - your work is just way out in front! A question. How were you cutting internal fins in the s/s hot cap? Was that via the thrust head? Or wire erosion? Andrew

[@myengines2443]

Hi Andrew, yes I cutted both fins for the heater and the cooler with the self made thrust head. In an older video you can see it in detail. Nice to hear of you and with best wishes and greetings Ralf

[@FrenchStirlingFablab]

Nice job

[@myengines2443]

Thanks and best wishes Ralf

[@tkmotors991]

But what would be the price just to get an idea 🙃

[@myengines2443]

Hi Tristan, the original rhombic is so complex that the price would be so high that it just might be interesting for someone who wants to experiment with it or for academic use. Absolut unreasonable for a generator or micro CHP. You want to hear a number so I just say several thousend dollars for just the rhombic Stirling engine without the accessories. This is ridiculous for a 300 watt engine. This is why I try to make it more easy to maybe make it possible to use it as a generator or micro CHP. Many greetings Ralf

[@primaryairsoft2315]

I want one!

[@andrewhunter2520]

can you post the stl files or a diagram

[@myengines2443]

Hi Andrew, here you can find the STL file: www.mediafire.com/file/hd064wjey6dajlc/Crankcase.zip/file Greetings Ralf

[@FirstName-nf4fx]

​@myengines2443 hello its 3 years later and I'm also hoping to see the files, can you share again?

[@EstebanGonzalezaraya]

great!

[@paulmaydaynight9925]

is this a never ending fun tweaking/optimising project to collect spreadsheet data or does the machine have a practical diy purpose? ,diy *cryocooler* engine for over night hydrogen production & *dense liquefication* etc, i.e something diy cant normally do on demand at home without an expensive commercial ready made unit. feed stock to operate room temp 'Tesla Turbine COLD STEAM Testing, Medium RPM low temperature, 61280 RPM' then use the expended -small bubbled trompe reservoir- atmospheric temperature gas + oxygen, nitrogen etc to -sand tube- heat the garden patio greenhouse -direct under water pool heater/burner ^_~- etc

[@sierraecho884]

It´s not a rhombic sterling engine it´s an beta sterling engine with a rhombic drive. You can increase efficiency and cerease part count and complecity further by completely removing the linkages and replacing them trough a "free piston" design".

[@tkmotors991]

Outstanding excellent work what do you think about Thermoacoustics ? Wouldn’t it be a better approach as there’s only one moving part iv had som pretty good results with my primitive engine that I’ve designed I could imagine you would do a much better job than me😂check it out

[@myengines2443]

Hi Tristan, the thermoacoustic is a very nice concept but has there ever been an engine with more power than a few watts? I thought it is just for very small engines in special requirements or am I wrong? Thanks for your interest and with best wishes Ralf

[@tkmotors991]

On the contrary they actually produce multiple kw at half the size and are a lot more efficient due to that reason thirmoacoustics are the fundamentals of a good stirling engine 🤗but a good Thermoacoustic engine doesn’t need all of those moving parts The Sterling engine is actually a clumsy way of utilising thermoacoustics which is the heart of the power

[@jansendwan1221]

Hey man I am here because I am into the idea of building a thermoacoustically driven thermoacoustic refrigerator. (Yeah I kinda fell down the rabbit hole). Is yours designed to produce electric work or mechanical?

[@tkmotors991]

Jansen Dwan Either either that’s the thing with these engines I haven’t done A frost test yet i would have to make a empg to power it or another engine to pressurise together one hot one cold 🤙

[@myengines2443]

Hi Jansen Dwan, I dont find your original post so I answer here. Yes you are right I am from Germany but it is better to write in english because then everyone can understand and discuss with us. I bought all all my machines used and very cheap on auctionplatforms like ebay. You have to look very carefully and a long time because there is a lot of scrap for high prices. I also made the cnc - conversions as cheap as possible so I just paid a few hundred dollars for each machine. The machines are mostly used for my Stirling engines but sometimes I build some fun stuff with/for my kids (thats the alibi for my wife ;-) ) Greetings Ralf