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: Jan Ridders

Stirling Engine Failure. Now Successful!!

The Ridders “Bobber” Stirling engine which I made in 2014, and which defied all attempts to make it work, is now functioning beautifully!

After I completed the Koffiekop engine, and saw it working, I realised that I had not been adequately  particular with some of the machining aspects of the Bobber.

So I took the Bobber off the shelf, took it apart, and remachined the bore, made a new piston, and a new connecting rod bush.  Then I polished the bore using Gumption (see old post about Gumption) on a wooden dowel which was turned precisely to the correct diameter.  I was not concerned about some splits in the wood, as they acted as reservoirs for the Gumption.  After cleaning out the Gumption residue the bore was ultra smooth and shiny.   The piston slid easily on its own (miniscule) weight, and the sliding ceased when the top end was blocked with a finger tip.

I experimented with fuels (olive oil too much carbon deposition, but methylated spirits fine), number of ceramic ball bearings (three specified in the plans, but two seemed to work better), and most importantly, and serendipitously (that one’s for you John), reversed the direction of the flywheel.

See the video below for the result.


Photo of the operating Bobber engine.  The white balls are ceramic bearings.  The piston is now made of graphite rather than the original steel, and I was particularly particular about the polish of the cylinder bore and the fit of the piston.

Video of the operating Bobber engine.

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.