Jan Ridders’ New LTD Stirling Engine

I am a big fan and admirer of Jan Ridders.  He is a talented and prolific designer of Stirling, flame-eater and internal combustion engines that are both beautiful to look at and fascinating to watch operate. Jan generously shares his plans for free and you can also frequently find him answering questions on the Yahoo Barstockengine discussion group, a group that I highly recommend if are interesting in building one of Jan’s designs or some other engine that doesn’t require castings.

I have not built one of his engines yet, but I have been gathering the materials needed to build his Coffee Cup Stirling and I have made some practice parts.  That engine, like most of Jan’s designs, has some features that almost make it a work of art, like the spoked flywheel, the finned power cylinder and the connecting rods with decorative holes. It also uses bearings and a lot of brass.  These features require extra time and skill to make and they increase the cost of the materials and effort needed to obtain them.

Jan Ridder Stirling PlansJan just designed a new easier-to-build version of that engine.  Instead of a spoked flywheel it uses two CDs mounted on an easy-to-make hub.  Balancing the engine should be easier because a small weight is added to the flywheel instead of drilling small holes in it and slowly enlarging them as needed.  Silicon sealant is used to attach the top and bottom plates of the displacer cylinder instead of six machined brass spacers that need to be tapped and then used with screws that are countersunk.  The new engine also does not use any ball bearings.  Instead it uses “point bearings” that do not look hard to make.

A glass tube is used for the power cylinder and the piston is made of graphite.  Graphite is also used to make bearings for the crankshaft.  I am sure that Jan chose these materials to minimize friction, which is absolutely critical when building a low temperature differential Stirling engine.  I was initially concerned that it might be difficult to obtain them in the right sizes and then fabricate the parts, but it doesn’t look like that is going to be a problem. I easily found numerous sources on the Internet and learned that it is apparently not that hard to cut a piece of glass tubing to length, even if it is made of borosilicate or Pyrex.  Using glass is also an inexpensive way to make a cylinder. The working cylinder for the Coffee Cup Stirling is made from a piece of 30mm (1.2-inch) diameter brass, which could be costly to buy.

I would say that the biggest obstacle to building one of Jan’s LTD Stirlings might be finding an affordable large-diameter transparent tube for making the displacement cylinder.  That is what has been holding up construction of my engine because you need to know the dimensions of the tube in order to make the top and bottom cylinder plates.  Jan suggests looking for a suitable piece of packaging to use.  I did find a wholesale-club size package of Slim-Jim snacks that was almost the perfect size but I am reluctant to use it because it looks cheap and would detract from the appearance of the engine.  I know others have had the same problem and there was a recent discussion about it on the Barstockengine group.  I plan to pass along some of the suggestions that were made at another time.

The plans are written in Dutch and English.  The units are metric but I don’t think you are going to have any problems converting them to English units and using standard size metal stock if that is your preference.

Jan usually asks that you to send him an email request if you would like a set of his plans but he has kindly given me permission to make them available for download here (PDF, 2.9 MB).  As I said, Jan gives his plans away for free, but I do know that he’ll accept a small donation via PayPal “only if you are very satisfied and feel called upon.”

Related Links

Jan Ridders’ Web Site (in Dutch & English)

14 thoughts on “Jan Ridders’ New LTD Stirling Engine”

  1. Hi Rob, thanks for your excellent write-ups. I’ve also got a Stirling engine on my list of thing-to-build-with-my-lathe. I will probably use a clear plastic case from blank CDs or DVDs. Although they are not perfect cylinders, the taper that I measured is very small, and I don’t believe that this is super-critical for the displacement cylinder, since the piston does not fit air-tight. I guess I’ll find out…

    When assembling the displacement cylinder, I’d like to avoid using silicone sealant to attach everything. I’d rather have something that can be disassembled if needed. Maybe some kind of nylon spacers, with a thin gasket for sealing the plastic tube to the covers?

    I’m also going to use that friction method for rounding the top and bottom covers.

    Bye for now…

  2. Thanks for letting me know. I don’t know what happened but I replaced the file and it should be OK now. Please let me know if you have any more problems.

  3. Hi Jan , Thank you for the drawings of the LTD sterling engine , I was wondering what kind of black finnish you are using on the standards and bottom plate? it looks pretty sharp.

  4. Hi Folks,
    I ve just build my 1st stirling ltd based on some other plans. I had also bring my small contribution and new tips to finalize it since i had also a few problems with airtight at the begining like anyone.Relative to the “o” ring question, one must find several tricks to achieve it. You may depending the size u want get different materials ie for small ones a coca cola bottle (very strong) plastic ring.You can also use some Rhodid bands easy tu cut. Mine has been specially shaped into a 2 mmm polyglas (172 mm diameter)but is more tricky and takes longer to be perfectly manufactured. My first idea was to fix the 2 aluminium plates with some nylon screw with 2 silicon joins assuming airtight with a possibility to access again the inside motor to prevent maintenance of the displacer. Possible but difficult, further considering that any screw will create thermic bridges affecting the engine efficiency. Silicon sealing only, with a thiner as possible “O” ring despite u keep some efficient rigidity of the ensemble will give u the best result. I’ll be glad to further help on any other question since i ve been first helped on my side. Good Work…

  5. Re Jan Ridders coffee cup engine. I have just finished mine and are doing some minor tweeks to get it to run better. Re the displacer cylinder I bought a plastic biscuit jar (the ones with the compressable clip for sealing)NZ$5.00. The softening temperature appears to be about 150degC so dont overheat the bottom plate to coax it into life like I did. It is near enough to 100 mm dia but slightly tapered. Just need to machine the top and bottom plate grooves to an appropriate dia. I used silicon gasket sealer (the red one from the motor car spares dept.) From memory it has about a 300degC operating temperature. I basically cast my own rectangular “O” rings in the plates using this goo. The cylinder does not adhere to the plates using this method.
    Murray T

  6. I just wanted to say that I run my LTD sterling engines on a Peltier CPU cooling module I got from Electronic Goldmine. It is powered from a 6 volt power source. I was going to use the cool side but after a while the cool side warms up due to no colling air on the hot side heatsink. So I use the hot side. I set the engine on the heatsink and it works great.

  7. I am in my final semester in advanced machining technology.The Sterling engine is as present our current project.Some parts were made on a Haas cnc mill but most are being made on manual machines.We are making 6 of these machines,one for each student,one for our showcase and one for our advisor.We have been brainstorming on how to increase the horse power.This is a very interesting project.

    • David,

      I have a suggestion for improving performance. I’ve been building a low-temperature-differential Stirling and it seems to me that you could greatly increase heat transfer to or from the air inside the displacement cylinder by adding fins on the inside of the cylinder plates. Even if the fins were very small they would still greatly increase the amount of surface area in contact with the air and therefore the rate of heat transfer.

      Simple fins could be manually machined without much difficulty. And if you have access to CNC equipment you could easily make much fancier and more effective ones (even artistic looking fins).

      Most high temperature Stirlings have external cooling fins on the cold side but I don’t know if I’ve ever seen a LTD Stirling with some. Whether they would help much on the hot side would depend I think on what kind of heat source it was designed to use.

      Rob R. (Editor)

  8. Hi

    I think one way to improve performance would be to include heat recuperator between the top and bottom of the cylinder. This needs a high thermal gradiant and resistance to work.

    I think this could be implemented by wrapping fine copper wire around the edge of the displacer piston. Copper is a very good conductor. Wrapping the wire as a coil around the edge would provide high thermal resistance between the top and bottom edges of the piston. I would wind the copper wire over a thin layer of glue and alongside a fine fishing line to achieve separation and even spacing. I would then unwind the fishing line.

    As the air flowed around the edges of the displacer piston, the air would transfer heat to and from the copper. The use of fine wire would minimise added weight. This addition should improve power and efficiency.

    The use of a heat recuperator is not my idea. I believe that winding copper wire around the edge of the displacer piston is an original idea.

    I haven’t built an engine yet, but it is next on my list of things to do.


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