Fueling is a huge variable, and not well done by most enthusiasts on those big Lockwoods. Not that I'm doing it perfectly on mine, but I'm also not going over 3" dia! Nor can I advise as to the proper fueling of a Lockwood; but most methods I've seen are fairly crude (no insult intended, just most are of the "git 'er dun" variety.)pulsejetter wrote:I would say that the 1.2lbs per inch squared of combustion chamber diameter sounds about right as many people haven't really achieved the 55lbs of thrust that the design is claiming. So 40lbs sounds more realistic/ the types of figure many are getting.
I would've thought that the combustion chamber includes the cone sections too, but then the combustion takes place sometimes quite far from the combustion chamber.
When i ran mine i noticed the combustion chamber was glowing a cherry red on idle but so was the u- bend.
Eric Beck did probably the most fueling and general experimentation of anyone I know. His TP180-70 had an honest (as far as I know) 70 lb thrust from a 6.37" CC diameter. If you punch that into the Kentfield limit equation (cc" ^2.5 x .62), he's getting 76% of theoretical max, and 2.2 lb/in^2.
So, we can make a general bounding statement:
Use 1.2 lb/in^2 CC for a good straight pipe exhaust, or a so-so, not so great expanded tail with questionable fueling.
Add a pound per inch^2 for a nicely evolved, nicely fueled, optimized expanded tail, which I have not done yet myself.
...and don't feel bad if you are under these numbers! I made a lot of one pounders, too.