STIRLING ENGINES, DAMN THEM!


Philips 102C Stirling generator
Philips 102C Stirling generator
The first Stirling engine I ever saw was a Philips 102c at the University of Canterbury in 1961 ( when I was an impressionable 15 year old wannabe physicist).
I took to it like a duckling takes to a gumboot (in the absence of anything more mother-like) and have as yet been unable to shake the bond.
Unfortunately, or fortunately, I wasn't smart enough to be a physicist, so became an engineer instead, and then one thing led to another.
Somehow in the middle of a more than challenging enough career trying to understand why kites fly- and getting them to pull boats, boards, buggies and ski's around- a project to design and develop a Stirling engine driven domestic CHP (combined heat and power unit) had it's genesis in my workshop in 1987.
This eventually became Whispertech Ltd, and developed, under the very able leadership of our next door neighbour's kid (now Dr Donald Clucas) to become, by 2012, the world's leading manufacturer of CHP's.
I had very little to do with any of this- and don't have much understanding of the technical minutiae of the WhisperGen design either, but have followed the saga with interest and hope.
Whispertech production moved to Spain a few years ago (I guess the lure of European green energy subsidies was pretty much irresistible), and last year, their remaining Christchurch based function (research and development) moved to Spain also (consequence of the Christchurch earthquakes).
Some complete engines and a residue of their equipment and components have now come back to my workshop, and having all this great stuff sitting around calling to me on a daily basis has definitely kick-started various unfinished Stirling engine projects that have been floating around in my head (and workshop) for the last 30 years or so.
Plus, I now have more free time and adequate financial independence, so don't have to feel as guilty about wandering off into dreamland as I used to (not that this ever stopped me).
Specifically I'm developing a series of engines to see how much output I can get from a 2.5litre (swept volume) single cylinder unpressurised beta style Stirling engine (with subsidiary goals of making it as compact as possible and easy/inexpensive to make). I sort of figure that nobody much has had a serious try at a purely atmospheric Stirling engine since the 19th century (Philips' 1937 18cc/17watt prototype excepted), so there should be some gains to be made.
I'm not planning anything mainstream or serious, (so as not to spoil the fun- or more probably so I won't be disappointed), but do have a few particular applications in mind.
One is to replace steam engines in replica 19th century gentleman's launches- and I have one working in this role now. See Piwakawaka, it's going great; 5kn with 4 people using LSM14 (was fitted with LSM12 until a few weeks ago).
Another, more whimsical, is to apply one of them to my wife's abandoned exercise machine (she's become so trim and fit in the last 2 years that it's now redundant- yes really!), heated by burning books- "Get Fit" books of course.
And a third might be to make some sort of wheeled vehicle. I'm rather thinking of a 'sulky' of the type that horses usually haul around. Instead of a horse I'd make a Stirling powered traction unit that would fit between the shafts- with reign steering of course. Then, hopefully, people would ask me how much power it had and I could reply "one horsepower of course"- and that's what I'm hoping to get them up to after a few more versions.
So far I've made 4 engines in this series; LSM 11, LSM 12, LSM 13 and LSM 14. Ideas for LSM 15 are taking shape and I've started collecting materials for it.
Watch this space!
Peter Lynn, Ashburton, New Zealand, March 2012

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