Check valve

[Mark]

http://www.billsroom.com/pcfs/products/ ... ysdesc.htm[/quote]
Seems to me like something you could use right up close to a piston engine crankcase, but not right up close to a pulsejet chamber! Of course, that wouldn't keep you from using it, you'd just have to isolate it from the chamber tap via a long, thin pipe. This sounds like a very logical answer to the desire for pressurization.
L Cottrill[/quote]

Yea, I had mulled that over Larry. I can think back to my silicone fuel line attached to a brass fitting with a 1/8 " thread at one end and a notched or ribbed staulk at the other end. I screwed this into the tip of my Logan bell head and the silicone lasted for the short runs not getting too hot. But yes, I too think heat is a consideration to watch out for with the check valves being to close to the fire. And as Mike suggests if I read him right, you can only go so far before your line pressure drops, in the same way, my simple silicone tube filled with fuel would only feed into the side port via a very thin copper tube if I didn't make it too long or too fat. Once a portion of the fuel in the tubing is sprayed into the side port, there forms an air pocket that just grows in the tubing and eventually becomes too spongy to function or push any remaining fuel.
So I am aiming to keep the fuel tank and duckbill valve as close to the engine as is safely possible to maximize a "fuel pump effect."
I'm hoping the duckbill is a tiny metal reed and not a synthetic reed. I might take one apart to see if I can match it. I have some .002ths blue tempered spring steel that might do as well.
As an aside or tip of the day, the 1/8th inch NPT fittings are kind of nice because the CM-6 NGK spark plug will also screw into such a fitting. Sometimes I would take out the spark plug in the tip of my Logan and screw in a brass hose adapter. Some of my tiny bells only necked down to the 1/4 inch size but that is OK too, because you can by sleeves that screw into the 1/4 inch hole to make it a 1/8th inch thread.
On my piglet tank there are two 1/8th inch female attachment points on the sides of the tank, I can screw in a CM-6, a brass hose line adapter, or if I just want to seal it off, I can screw in a tiny 1/8th inch plug.
I also have a 1 inch diameter pipe pulsejet that accepts a spark plug or a 1/4 inch NPT nipple. I wonder what mm that spark plug is offhand? I threaded the hole in the side of the combustion chamber but now I have forgotten.
Mark
PS
Here's my crude methanol fuel feed system, you have to imagine the sound, but if you look closely you can see a faint blue fire as it was doing it's thing when the picture was taken.

[Mark]

PSS The monstrosity, no not the squid, the ungainly device ahold of the pulsejet is a fly tying clamp holding the tiny copper tubing in place at the side intake.
Mark

[larry cottrill]

Mark, I still always chuckle when I see your "Project Squid" lurking in the background.

L Cottrill