Peter Lynn ARCHIVE
The first Stirling engine I ever saw was a Phillips 102C at the University of Canterbury in 1962 (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 powered domestic CHP (combined heat and power unit) had its 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, for a while, 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 Mondragon in Spain years ago when the lure of European green energy subsidies became irresistible, and in 2011, their remaining Christchurch based function (research and development) moved to Spain also (consequence of the Christchurch earthquakes).
Is anything still happening there? It doesn’t seem so.
Some complete engines and a residue of Whispertech equipment and components came back to my workshop in 2011 and having all this great stuff sitting around calling to me on a daily basis definitely kick-started various unfinished Stirling engine projects that had been floating around in my head (and workshop) for the previous 30 years or so.
By then I also had more free time and a measure of financial independence, so didn’t have to feel as guilty about wandering off into dreamland as I used to (not that this ever stopped me).
Specifically, I then developed a series of engines to see how much output I could get from a 2.5litre (swept volume) single cylinder unpressurised Stirling engine (with subsidiary goals of making it as compact as possible and easy/inexpensive to make). I sort of figured that nobody had done much work on larger unpressurised Stirling engine since the 19th century, so there could be some gains to be made.
I never planned for this to be anything mainstream or serious, (so as not to spoil the fun- or more probably so as not to be disappointed), but I did have particular applications in mind.
One was to provide an alternative to steam engines in replica 19th century gentleman's launches- and this has been successful. See Piwakawaka, it goes really well; 5kn with 4 people using a 2.5 litre swept volume unpressurised beta Stirling engine.
Another, more whimsical, was to apply one to an exercise machine, as a labour-saving device- heated by burning books- "Get Fit" books of course.
And a third was some sort of wheeled vehicle. I initially imagined a 'sulky' of the type that horses usually haul around. Instead of a horse there’d be a Stirling powered traction unit that would fit between the shafts- with rein 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 was hoping to get these engines up to – but haven’t yet, topping out at 400 watts so far.
Instead of the sulky I fitted one to a motorcycle and more recently have re-built this as a mobility scooter- in deference to my advancing years. It goes great.
I’ve also fitted one to a rocking chair- as a comment on the general usefulness of Stirling engines. Says it all really!
Peter Lynn, Ashburton, New Zealand, June 2025
