Re: Nutating engine idea.
A nutating or wobbling disc in a close clearance housing is one of many different positive displacement devices all of which are theoretically capable of performing as heat engines. Most of us that live in urban or suburban areas have a quietly reliable device with such a mechanism close to us. It's in your water meter. It works as well as it does because it's bearings and sealing surfaces have to handle only tiny pressure gradients to extract the power needed to turn the meter dials. And this is the key to why this particular device was quickly rejected 50 years ago during the surge of interest in unconventional engine designs such as the Wankel. (Any of you ever heard of a Dynastar engine?) Most of those engine designs fell by the wayside because sealing the combustion chamber was too great an engineering hurdle to cross. The Wankel rotary was an exception and even that took a lot of work for the Mazda folks to get the seals right.
Take a look at a nutating disc:http://www.engineersedge.com/instrumentation/nutating_disk_displacment_meter.htm
and you'll see the problem of not only sealing but also bearing support for the rotor.
I suppose someone has some clever ideas for making an engine of high power output out of this device. Who knows? They might make it work. Materials and bearing technology has come a long ways in 50 years.
Fast forward a couple of Snell cycles and we may see one in a bike or something with Jack Costella's signature on it.