Stirlingengineforum.com

Since a few years, I have been 'inventing' new types of hot air machines. Recently I came to a design that seemed to have interesting properties, and I thought I had made a complete new invention.
...Until I found a 90 year old (1919) patent of Elliott J. Stoddard, who had patented almost exactly the same engine that I had invented. (See f.i. http://en.wikipedia.org/wiki/Stoddard_cycle )

So then I was interested if I could find more information about this machine. Would it really work? Or was it no success and is the idea discarded? Did Stoddard or anyone else ever build a real Stoddard engine?
I could not find a trace of a real existing one.

Is there anyone on this forum who can tell me more about this fascinating concept?

Erik Wannee
Apeldoorn, the Netherlands

There have been ideas posted here in the past about Stirling's using reed type valves but I have yet to see anything that functions. It would seem that a flexible rubber reed valve would do little in the way of air flow restriction and should improve efficiency in the right design, there must be something either over-looked or it just doesn't work. I think all the design examples I've seen have been "gama" engine bases though. This Stoddard engine looks more "alpha". Have you seen this? http://www.proepowersystems.com/

Cartech wrote:There have been ideas posted here in the past about Stirling's using reed type valves but I have yet to see anything that functions. It would seem that a flexible rubber reed valve would do little in the way of air flow restriction and should improve efficiency in the right design, there must be something either over-looked or it just doesn't work. I think all the design examples I've seen have been "gama" engine bases though. This Stoddard engine looks more "alpha". Have you seen this? http://www.proepowersystems.com/

The 1919 Stoddard engine is different from Stirling engines. It is certainly not an alpha stirling.
In a Stirling engine, air flows there and back, while air in a Stoddard engine always flows in one direction. That way, the 'hot' part can theoretically be a relative long distance away from the 'cold' part.
Another essence of the Stoddard principle is that it has two pistons of different size. With the same pressure, the force on the big piston is bigger than the force on the smaller one. That way, the pressure pushes the big piston away and it lets the small piston come against the pressure.

I hope someone knows a hot air engine that works with two different valve sizes and air that flows only in one direction.

Btw: The Proe power systems engine is interesting, but it is completely different from the Stoddard principle.

I took some time to look at the original design again, your right, not an alpha with valves. I too would like to see a working model. If you attempt to build one, please let us know how it works out. I'm currently working on a rotary gamma that will feature port valves just for kicks. Not sure if the port valves will do anything but my design will need ports anyway and I will attempt to "time" them rather than provide an open port.