1000 to 3000 psi................now this is interesting.
can you tell us more about this project you are working on ???
chuck 
Chuck,
Its sort of a long story, but the condensed version goes:
Circlip and RipSlider are sitting in a pub, and Circlip tells RipSlider ( who likes model boats and is pestering Circlip about using diesel engines to make a racing boat to do 100mph ) about model boats in the 1950's which did 100mph with ease, using a fabulous sounding system called "flash Steam".
RipSlider goes and reads books ( Of which there are only about 2 ), e-mails people and generally gabbles away until he finds out more about said subject. RipSlider is struck by the fact that the 100mph+ boats of the 1950's have nothing in the way of the hull design, prop design or any other goodness of a modern racing model boat. This makes RipSlider wonder what happens if you mix an ultra fast powerplant from the 1950's with an ultra-modern hull, trans-cavitating propellor and all the other goodies that are in todays model boat world.
The 1950's boats - up to 40" long - were using props 8" (!!!) in dia, and were sometimes developing so much torque that 5/16ths steel prop shafts were being bent 90 degrees. some of the plants were rated at 4 and even 6 bhp.
So - cunning plan - build flash steam power plant. Build fast hull. Graft two together.
Flash steam is one of those things that seems very easy, but rapidly ( I'm finding ) gets complex. At it's most basic, you get 30 foot of copper pipe and wrap it into a helix 2" in diameter. Then get your propane torch, set it burning down the centre of the helix and force water down the tube.
If you shove "pellets" of water into the tube, then the water will "flash" into steam, and then super-heat to very high levels. You then get super-heated steam out of the end of the pipe. Keep shovong in "pellets" of water, and you get masses of lovely superheated steam. To give an idea of efficiency, a 5" gauge model loco using an ultra-efficient boiler such as a Yarrow would be considered to be working fantastically if it was consuming 2.5lb of water a minute. Some Boswell pattern boilers have pushed towards 4lb a minute at a good super-heat.
A flash plant of the 1950's build by the experts would start to be considered "useful" by consuming 15lb of water a minute, and were considered "good" if they were converting 20lb a minute.
So, the traditionally "hard" bit of steam engines, the boiler, is actually really easy in flash steam, the problems come from the mechanicals.
If your flash steam boiler is producing steam at 2000psi - about average - then you need a water pump ( and one way valve system ) which can work in EXCESS of 2000psi, in order to be able to get the water into the tube in the first place.
Then you need an engine that can work at that sort of pressure. So that's piston valves basically - no slide valves, and probably not poppet valves either. But the thing will be wanting to run faster than the springs on the valves can close - a lot of the plants were running at 12,000rpm+. So then your either into desomdronic valve gear, or something simpler, but "off the beaten path", which you have to work out for yourself. I'm looking at the Wilkinson quick return gear.
The other thing is the burner - you need to be putting 800 degrees plus onto the tubes - which is easy enough you could just use a propane torch if it was still - but when the boat is doing 100mph, then that will just blow itself out - so it's a parrafin burner and a clever system of flame holders.
And you have to get all that kit in a boat 40" long and weighing no more than 8lb.
The thing which fascinates me about flash steam is that each of the individual components - apart from the engine - SEEM really simple. Oil system, pump system, burner, boiler - all of it is something you can fiddle with in the garage without investing a lot in either time or money. It's the putting it all together which is the challenge.
So, rather than tackle it all at once, I am looking at two area's first. Firstly is making the tubing for the boiler, which I think I want to be about 60 foot long.
The second is the burner, which is a fairly simple thing to make - it's making it run well in high winds that is the fiddly bit.
Then I'll do the main engine, then the ancilleries, such as pumps, oil etc. For testing I am using an electric pump.
As soon as I have something of interest I will post it.
Steve
