johnsmachines

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"

Category: Stirling cycle

October 18, 2018

Model Engines on Steam

It is Geelong Show time again.  It is actually titled the Royal Geelong Show, but having had more than a gutful of royal non-entities visitors being adored by unthinking cringers, flocking around Harry and Meaghan Kardashian, Windsor, and being a committed republican, I refuse to bother with the “Royal” handle.  (they are probably very nice people, I just cannot stomach the hoo-ha).

More importantly, it gives us steam junkies a chance to run our small engines on real hot steam.

For a treat, I am sharing four short clips taken today.

The first is a small beam engine, made by Swen Pettig.

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The next two engines you have probably seen before.  My beam engine, and the triple expansion engine.

The small engine to the right is a Stirling engine which is running on the heat from the exhausted steam from the beam engine.

The triple is leaking a bit more than it should, although it is running amazingly smoothly on 25-30 psi.  The valve glands need repacking.

And finally, a model IC engine, the really odd Atkinson.  A 100+ year old design.  2 stroke. Made by Rudi vanderElst

 

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July 1, 2017

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.

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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.

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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.

 

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October 1, 2015

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.

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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.

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September 27, 2015

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.

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100mm flywheel.

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

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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.

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