Stirlingengineforum.com

It is possable to make gapless cast iron rings, they are called Cluppart(spelling)rings, they are in the form of a ring that looks like a key ring, there is two turns of the ring. It has been used in full size, and in model steam engines. the important thing with the Stirling Engine is to get a good seal with the minimum of wall pressure.
Ian S C

Like this? I don't see how this works differently than piston rings in an auto engine.

Ah, I found a good cheap supplier for hBN. They give a really good description on how the stuff behaves. It is hygroscopic due to the 5 micron or less mesh, therefore care must be taking to remove humidity from the area or it will clump. Any open container must be used immediately or it will clump up later. Keep all packages sealed until ready to use because of this.
The smallest mesh they offer is .5 micron for 40% more in price. Here's the link: http://sandblastingabrasives.com/hexago ... e-781.html

I will definitely have to vacuum down the engine before I charge it with this fine powder. A source of dry air will have to be used, also. I think the computer keyboard sprayers look promising. Looks like I will have to coat the parts with my tumbler before I assemble them, also. This will be a bit of tricky work keeping things dry.

As to the video of the torch on the graphite......even they said it had lost mass. CO2. Gaseous compounds of any kind conduct heat poorly. Gaseous elements do it better. Check the chemistry. Graphite is tough, but not as tough as this stuff. hBN conducts heat better than graphite, that's why I want it floating about in the working fluid.
By the way, aviator, those rings would shatter or melt if subjected to the horrors of detonation. Automotive piston rings HAVE to leak some, or be destroyed when the engine knocks just once. Been there, challenged it once, and learned from my mistake.

Found a new seal. a WV-seal. like the vee seal, but W shaped, with less drag and more support. Here is what it looks like.
Here is the link: http://www.veepacking.com/

"WV Packings

While similar to Vee Packings, the WV style provides sealing properties that are largely independent of stack packing pressure. The WV is designed so that it will provide a multiple lip hydraulic seal in a fixed gland depth packing. Because of the design of the WV packing, te lips of each ring are free to flex when in a nested stack so each lip automatically reacts to fluid or air pressure, providing a better seal in a given packing space. There is no compression adjustment required during the seal life.

Since the WV Packing is a multiple lip hydraulic seal, it is recommended over a single lip seal for applications where side loading is a factor. The multiple lip also provides extra stability. If one seal fails, there will be another seal to serve as back-up.

There is an interference built into both the I.D. lips and the O.D. lips so that there will be sealing capabilities at low pressure.
American Seal & Packing stocks Center Ring and Flat Back WV packings in homogenous Buna 90 Durometer and fabric reinforced Buna.

WV Packing Installation Data

Since WV packings are designed to be free floating, it is not recommended that the rings be installed in a compressed state. Thus should be between .014” and .060” of area in the gland depth so that the rings are allowed to float. The amount of this free floating is determined by the ring cross section and the number of rings being installed. (See chart below).

For designs of medium to high pressure, it is recommended that fabric reinforced o-rings be utilized. The adjacent table is a guide to pressure rating of multiple rings. A homogeneous o-ring may be also used for sealing at low pressure. The homogeneous o-ring should not be included in calculating pressure rating."

I would have to see if they offered this ring in other materials.