Materials List for Jan Ridders’ Simple LTD Stirling Engine

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Here is a list of the materials you will need to build Jan Ridders‘ new simple low temperature differential Stirling Engine.  You can download the plans here (PDF).

I was going to build his Coffee Cup Stirling but I have started building this one instead because it will take a lot less time.  I have not been able to spend much time in my workshop lately, which is typical during the warm weather months, and I would like start a project I can finish within a reasonable amount of time.

I know I get a lot of visitors looking for information about Jan’s Stirling engines, so I am posting this with the hope that someone will find it useful.  I usually hate studying plans to determine what materials and tooling I’ll need to buy.  I’m always worried I’m going to miss something and the project will grind to a halt while I place an order and pay a huge shipping fee for just one item.  I’m not too fond of ordering stuff either.

Fortunately, I already have almost everything I will need.  I just have to buy the graphite, a glass tube for the power piston cylinder and a suitable plastic tube for the displacement cylinder.  I did some checking last week and I think the glass and graphite will be easy to obtain.  Finding a 4-inch clear plastic tube has been a problem.  You really can’t make the top and bottom plates until you know dimensions of your tube.

Jan’s plans are in Metric units and I’m in the US, so I am going to have to convert them to English units.  I have not built this engine yet, so consider the fractional English sizes I listed to be just suggestions for now.  Stayed tuned because I’ll start posting some construction photos and notes soon.

Aluminum

  • 18 mm [.70 ~ 11/16-inch] round – Countra weight (Counterweight) – Sheet 6
  • 20 mm [.78 ~ 3/4-inch] round – Displacer kernel (Hub) – Sheet 5
  • 32 mm [1.26 ~ 1-1/4-inch] round – CD kernal (Hub) – Sheet 6
  • Material to make two 112 mm [4.41-inch] diameter disks for the top and bottom plates of the displacement cylinder.  One needs to be 5 mm [.20-inch] thick and the other 8 mm [.31-inch] thick.

You have a couple of options here.  One is to start with a couple of disks cut from a 112 mm or bigger round bar.  This could be very expensive if you have to buy a length of it.

A cheaper alternative is to make them out of a flat plate by following Bogstandard’s excellent tutorial.  You also have some choices if you do it this way.  You can buy your aluminum plates in the two thicknesses you’ll need or use the same thickness for both cylinder plates, which should look and work fine.  You can also mill the metal down to the thicknesses you’ll need.

Brass

  • 5 mm [.20 ~ 3/16-inch] round – Fork (2) – Sheets 5 & 6
  • 11 mm [.43 ~ 7/16-inch] round – Crank webs (4) – Sheet 7
  • 1 mm thick x 6 mm wide flat stock [.04 x .24 ~ 1/32 x 1/4-inch] – Displacer & Piston Rods – Sheets 5 & 6

Steel

  • 2 mm [.08 ~ 1/16-inch] round – Fork/Clevis pins – Sheets 5 & 6
  • 2.5 mm [.10 ~ 3/32-inch] round – Crankshaft parts – Sheet 7
    I recommend using .0940 (3/32)-inch W-1 drill rod for these parts.  I like drill rod because it is ground to close tolerances, polishes nicely and resists rust well.
  • 12 mm [.47 ~ 1/2-inch] round  – Point Bearing Holders (2) – Sheet 7

Graphite

  • 6 mm [.23 ~ 1/4-inch] round – Bushings – Sheet 6
  • 8 mm [.31 ~ 5/16-inch] round – Displacer Shaft Bearing (Seal) – Sheet 5
  • 14 mm [.55 ~ 9/16-inch] round – Power Piston – Sheet 6
    (depends on the inside diameter of the glass tube used for power cylinder)
Jan says “You can make the piston from brass as well.  It works as good as graphite. The only thing is that the brass will oxidize somewhat, but it will take months before the friction will cause some problems. In that case you can easily take out the piston and polish it again and the engine will run as before. Graphite doesn’t need that kind of (small) maintenance.”
Someone on the Barstock engine group suggested using EDM graphite.

Fasteners & Threads

  • Machine or set screw for flywheel hub & tap: M2 x 0.4 [40-4] – Sheet 6
  • Displacer shaft, fork and hub: M2.5 x 0.45 (tap & die) – Sheet 5
  • Piston fork: M3 x 0.5 (tap and die) – Sheet 6
  • Point bearings (2): M4 x 0.7 machine screws or threaded sections to make the point bearings, plus two stop nuts and a tap – Sheet 7
I’ve only suggested one English equivalent because I’m not ready to suggest any others right now.

Miscellaneous

  • Balsa Wood – to make a 100 mm [3.93-inch] diameter x 5 mm [.20 ~ 3/16-inch] thick disk for the displacer on sheet 5.  The exact diameter will depend on the inside diameter of your plastic displacement cylinder.
There needs to be a small amount of space (2mm / .08 inch?) between the displacer and cylinder wall so air can flow around it. Thickness is not critical but the lighter the displacer the better the engine’s performance.  I’ve heard that you should make it by gluing up 1/16-inch thick balsa wood with the grain going in different directions to prevent warping.
  • Compact Discs (2) – Used for the flywheel – Sheet 6
  • Glass Tube – 16 mm [.63 ~ 5/8-inch] outside diameter / 14  mm [.55 ~ 9/16-inch] inside diameter – used for the power cylinder on Sheet 6.I found some test tubes that were the correct diameter and here is how I cut them to the correct length.
  • Silicon Adhesive (clear) – Used to attach the top and bottom plates to the displacement cylinder and also the glass power cylinder to the top plate.
  • Glue – To glue the two CDs together and to the flywheel hub.

This is the first time I’ve made up a materials list like this and it probably won’t be the last.  I would appreciate any suggestion you may have for doing it better the next time.  Unfortunately, I can’t put it in a table because WordPress doesn’t really support them.

I would like to know if you have any questions or find any mistakes.

5 thoughts on “Materials List for Jan Ridders’ Simple LTD Stirling Engine”

  2. Just found this article. I have both glass tubes (test tubes) and graphite you can have if you ever get back to making this. I also still have that section of 4″ plexi tube you gave me – I never did get around to cutting a piece off!

    I have plans for at least 4 LTD Stirling engines, and I will be using ideas from all of them to create my own Frankenstein design. Now that the weather is turning colder, I’ll be getting more shop time.

    Reply

  3. I got some parts made for mine until I ran into a couple of problems. I found the test tubes I bought had a slight internal taper that could cause friction or leakage problems. So I considered either buying an airpot or making a brass cylinder instead. Then warm weather arrived and I got so busy with other things I pretty much forgot about it. I’d still like to finish it. Maybe we can combine our efforts if your FrankenDesign isn’t going to be too different.

    Reply

  4. Malkeet: It was difficult finding some of the non-metal materials for this engine. I think I found the graphite on eBay. McMaster-Carr was the best place to buy a 4-inch inside diameter acrylic tube and Hobby-Lobby had test tubes that were the right size. Most of the other materials I bought from Enco. Sorry, but I can’t help you much more than that.

    Reply

  5. Hello , sir ,I am Nitin. i want to produce stirling engine . so please , help me . send me a material required for it . can it work.

    Reply

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