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: Bobber

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.


As you can see from the picture, the Ridders “bobber” is quite a pretty engine.
If it works perfectly it develops just enough power to revolve, but not enough to do any work or to overcome any perceptible internal friction.
Unfortunately, my Ridders does not even turn over with the heat applied. It revolves freely by hand, so I do not see where the problem is. In any case, now that I know how powerless these machines are, I have lost interest in spending more time on it, and I am returning to paint and finish the beam engine.
The pictures are for interest only.

(ps.  Note made April 2017.   About a year after I originally posted this, I returned to the Bobber.  I made a new piston from graphite, replaced the 3 steel balls with ceramic balls and retried it.   It still did not work.  Then I tried varying the number of ceramic balls.   With 2 balls, it ran perfectly!   Smooth and fast.  There is a video of the feat in a later post.)

This is the first engine which I have made which does not function.

Almost fully machined Ridder “bobber” heat engine.
With heat applied.
Unfortunately it does not work.



I have heard that the castings for the triple expansion marine engine will be arriving in the next week or so. That is good news after waiting since the order was placed in January.
In the meantime, I have bought some castings and partly made components for a Burrell Traction Engine. It is 1.5″ scale, and I obtained some 1.5″ plans from EJ Winter for the Burrell. Unfortunately, one mans’ 1.5″ is anothers’ 1.45″ and the plans are not exactly correct for the castings! What would have been a difficult build, has turned into a very difficult build. So I have put it aside and will tackle it gradually. The plans will be some use, but as well as the difference in scale, there are differences in the designs. So I will have to make it up as I go, to a considerable extent.
My metal working club has promoted a competition for 2014, and it appeared to be a fairly simple build, so that is what I am currently machining. See the progress in the photos below. It is a Stirling heat engine, designed by J Ridders. You can see one working on the Ridders web site




Almost finished stand for the cylinder fork.

Almost finished stand for the cylinder fork.


Components made so far

Components made so far

The spirit burner, almost finished.  Copper and brass,  silver soldered.

The spirit burner, almost finished. Copper and brass, silver soldered.

Stirling "Bobber" plans

Stirling “Bobber” plans