machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most. n.b. There is a list of my first 800 posts in my post of 17 June 2021, titled "800 Posts"

Tag: Coffee cup engine

Koffiekop Modification

I have been considering this modification for some time, and today I located the aluminium heat sink-radiator material which I needed, and which I knew was somewhere in my stuff.

The Koffiekop Sirling engine requires differential temperatures between the top and bottom plates.  I wondered if installing some heat shedding plates on the top plate might increase the running time on a cup of coffee.


The heat sink material is glued to the top plate with a heat transmitting electronic silicone glue.

Afterwards I ran a test with a cup of hot water.

The engine ran for 26 minutes!  That is an improvement of about 25% on the best previous runs.  Success!

The Horizontal Mill Engine (HME) is assembled and ready for the D valve to be timed.  This is how it looks.  I wont get to it for a couple of weeks now.


I did squirt some compressed air into the valve chest, but minimal movement.  Not surprising, considering the position of the eccentric was just a guess.  When I get it going there will be a video.  That crankshaft pin is temporary.  It is a 3mm cap screw going through a 4mm cap screw.  go figure.


KoffieKop Engine Working!

I assembled the engine today.  The flywheel was required to be balanced, but I decided to give the engine a run in its unbalanced state, and was quite amazed to see it start up, hesitatingly at first, but then got into its stride, and ran for 13 minutes.

Quite excited at this point, I spent some time balancing the system.  That required the base to be removed, then multiple holes, 7 in all, drilled in the flywheel, to balance the mechanical components.

Then another run.   14 minutes.  Then another, 19 minutes.  Then the best run at 21 minutes.  Very exciting.

So I took it home, and showed SWMBO.   Hmmm.   But what does it do???  She asks.

It just goes…..   It is like an architectural folly.   Just interesting in its own right.   OK?

So this is what you have been spending your spare time on for the last 2 weeks?   Yes.

A bit of a credibility gap here.

The engine, sitting on a cup of hot water, running at about 100rpm.

The engine, sitting on a cup of hot water, running at about 100rpm.


Best run…. 21 minutes.

Koffiekop Engine

I have been busy for the past week or so making a Stirling cycle engine.  It is the Coffee Cup engine designed by Jan Ridders.  It is powered by the heat from a coffee cup of hot fluid.  Or an ice cube sitting on the top plate!


Page one of five of Jan Ridders excellent plans.

Page one of five of Jan Ridders’ excellent plans.

Most of the components of the coffee cup engine.

Most of the components of the coffee cup engine.


100mm flywheel.


Possible alternative flywheel, roughed out, I will see how it appears with a bit more finishing. Looks interesting?


An experiment with engine turning on an aluminium surface, using a “Brownells Engine Turning Kit”, kindly loaned to me by Stuart.   The pattern is made with the spring loaded wire brush seen in the picture. I used this on the upper plate of the displacement cylinder.

Lots of tiny fiddly bits.

Lots of tiny fiddly bits.

The piston is made from graphite.  An interesting material to turn.  Surprisingly tough, accepting a 3mm internal thread.  And presumably self lubricating. Machining it produces black, pervasive dust.  SWMBO is not impressed, since my CNC lathe sits in our living room.   I might get marching orders for the lathe as a result of this one.

Triple Rest

I have put the triple expansion steam engine build to one side for a while.  There are many parts made over the past year, but still a few to go, and I am taking a rest from it.

My modelling club is conducting a competition to build a Stirling cycle engine, and I have decided to make an entry.  It is the coffee cup engine by Jan Ridders.  It is an annual Stirling cycle competition.  I made an entry last year, but I couldn’t get it to work.  So I am determined to make this one work.

I am also using the Koffiekop engine project to become more familiar with the CNC machining processes.  So I am making as many components as possible using CNC.  For simple parts this often takes longer than using a manual process, but my CNCing is definitely becoming faster and easier, and crashes and tooling breakages are now rare.

The Koffiekop is progressing well, and I will post some pics and maybe a video when I get it working.