That the engine works quite well and the "free" delivery option was surprisingly prompt from factory, but the design could do with tweaking.
The free delivery option was surprisingly fast - it took maybe 10 days from placing the order to having the box delivered to home in NZ. It was the demo Stirling cycle heat engine. Yes, it does run on the heat from my cup of coffee, for maybe 5 minutes or possibly more. Certainly, I was impressed with that result and very happy with my purchase. It does all that I wanted and expected it to do. I think that the engine could do with a little redesign, as ther flywheel does rub against the small cylinder while running. The nub of the problem is that the two supports for the main axle are slightly off vertical. A bit of judicious pushing sideways on them has helped. But simply moving the flywheel to one end of the axle, and/or enabling it to be slid 1-2mm along the axle, should fix this problem and remove the sensitivity to the fact that the axle supports are not quite at 90-degrees to the main cylinder. But overall, I am very happy with my purchase, it does work quite well regardless, and I would have given 4.5 stars if that option had been available.