Interesting development- I wonder when we'll see production, how much they will cost, and what horsepower they will develop.

I've never heard of Revgine before - is this a startup as well? If so, it bucks the recent trend of alternative technology firms partnering with larger, existing manufacturers (for example A123 with DeWalt, Firefly with Husqvarna, etc)

I found a news clip which has footage of the engine actually running:

http://www.youtube.com/watch?v=ja-h7ti4VRQ

The sound of the pistons would be best described as a "gurgle" sound, with a slight whine from the combustion chamber mixed in.

For what it's worth, I think they play the biofuel card a bit too hard at this company. But I admire them nonetheless.

Revgine inc??? Can't find it in the yellow pages and in search engines it only appears with the CYPW article.
Anybody ever heard of the company?

Looks like any multi piston radial with cylinder fins possibly hollow to take heat in No schematic of the valveing mechanism, wich would be the key to understanding. The pictures from the earlier post links
showed rough machined castings.
Apears that the main advantage claims are the ability to use any(liquid) fuel available(including gas), Does this imply also any external heat source? Solar, Wood ,Thermochemical? Nuclear in Some distant incarnation??
I can't see people giving up their lawnmowers very easily unfortunately, but versitile heat engines are going to find a place in many applicaions for some time to come. What sort of thermal efficiencies can be hoped for I wonder.

Arnold, I've been following Cyclone's progress for a couple of years now. The Cyclone engines are best considered as modern steam engines. No fins on the cylinders by the way... they are insulated from the inside through a ceramic cylinder coating. Engines are totally water lubricated (by the working fluid itself, i.e. water).

All of their piston engines are uniflow where steam is exhausted through ports in the cylinder wall uncovered by the piston during operation, much like 2 stoke internal combustion engines. So, each cylinder has a single inlet valve. Some of their smaller engines use piston operated valves where a projection on the piston head actuates the steam inlet valve. The automotive engines use cam operated needle valves. I'm still unclear on the waste heat engine valving, but I do know that the exhaust is through the piston face itself.

The system is hermetically sealed, so no fluid changes ever. The design is remarkably simple and production costs are expected to be very low. The automotive engines operate at 30-35% thermal efficiency, while the smaller engines for lawn equipment and such operate at 25-30% thermal efficiency.

Any heat source can power the engine provided the high temperatures can be met. 1200F steam temperature for the automotive engines, and 1000F steam temp for the smaller engines. However, their "waste heat engine" operates at far lower temperatures (400F) and sees impressive efficiency for such low temps (12-15%)... it is suitable for solar, biomass, and other lower temperature heat sources.

I suppose I am biased as a steam enthusiast, but I've held the view for many years now that once we reach the point where steam engines can do away with oil lubrication at high temps and we see highly efficient and cost effective condensing systems, then small and medium power steam engines will supplant internal combustion in many applications including automotive and lawn equipment. It's just a matter of the engineering catching up with the physics.

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