Water bottle Stirling engine made from aluminium water bottle. Uses wire wool displacer, bike hub and ball bearings. It's running around 450rpm in the video, I've had it upto 600 on max heat, but that seems to be about the limit. I haven't managed to achieve high RPMs but it's still a good engine. As apportechie found, the aluminium is too conductive so it limits the speed a bit. It feels quite powerful. Yes I know the electric water pump uses electricity, I couldn't get the thermosyphon to work properly .
Keep an eye on my website