Flash steam

[Al_Messer]

Is it possible for a scale model locomotive with Cast Iron cylinder liners and valves to handle the pressure and temperatures of a "Flash Steam" generator? Benson & Rayman in their book stated that one model experimenter had recorded pressures in the range of 4,000 psi, with temperatures associated with these pressures.

[Craig]

The first thing comes to mind if you are talking about slide values and currently available steam oil the answer is no it will destory the values and cups out the cylinder of the values.
I have destoryed slide values with improper lubrication within 20 miles in a Stanley steam car running 400 to 600 psi.
The railroads went to piston values in the 1920's once they exceeded about 225 psi. because of the drag wear and tear on values, and linkages.
Why do you want to run 4,000 psi?
This is out of my experience, but I would guess these high pressure are only suited to steam turbines.

[Rolly]

Al
The answer is yes.
Piston valves would be my choice. Temperature of the steam should be held to no more then 700 F You can control this if necessary with a de-super heater. Oil for my choice would be Mobil one Synthetic SHC 634 or TK1500.
Cylinders. Valves, piping & fittings would have to be designed for the pressure.
But why would you do it.
Rolly

[Al_Messer]

Craig, I didn't say I wanted to run at 4,000 psi, I just stated that some early experimenters had recorded reaching those pressures. Personally, I'd be happy to run at 100 psi and about 340 degrees F.

[Craig]

Al
I should read closer, I misunderstood. Sorry!!
Craig

[Al_Messer]

I suppose I should expand upon my question. With all the hullaboo about miniature boilers and building codes, inspections, certificates, etc., it seemed logical to me that a single length of tubing would not only be safer but subject to less hassle that the historic scale model boiler. The exterior could be made to conform to scale and to looks as well. That is the thinking behind my questions. Plus, it would be simpler for a beginner to construct: winding tubing around a form is much less demanding than forming, riveting, and Silver Soldering/brazing plates and stays.

[Rolly]

Al
They did a lot of that kind of work in the twenties and thirties on steam powered hydroplanes. The feed water pump and the engine volume need to be calculated very close. Some of my old book showed photos of burned out coils and blown engines. 10,000. RPM engines, single acting. Very high pressure and temperature.
But you spoke of scale model locomotive.
There is no need to run a mono tube boiler at such a high pressure for a scale model locomotive. It will work just the same at 100 PSI as 4000. You will need a very good control system. Pressure regulated control for the burner and water control to match the engine's use.
Rolly

[Al_Messer]

I was thinking of using a Coles' pressure regulator or a similar control on the propane fuel, and somehow using it or another on the water by pass valve as my control system. I want to keep it as simple as possible. White Steamers had a good control system but I don't think it could be successfully scaled down to model size. I could be wrong about that, though.

[Rolly]

Al
The control system would needs to work very fast. My Stanley car is all mechanical and is very slow, delayed reaction. I keep my fingers crossed the water will come up in time. Electrical control work much better. Water pumping all the time and bypassed with a solenoid valve. You could mount a small micro switch on a pressure gauge to turn a burner on and off. I use commercial ones on my large boat. A thermal couple and small commercial controller would be even better.
Rolly

[Craig]

The mention of a White steam car, their control systems were great when everything worked right. When they did not major headaches.
The poor old Stanley a much simplier system, and when some things did not work properly you could still limp down the highway. Many of the times no one even knew you had a problem.
I understand where you are coming from now. I personally would go with the standard locomotive boiler. If I remember the boiler used in Australia with I think a water pipe or two in the firebox. Sorry I do not remember how they are build, I have seen several run and they fire great. if you want an engine that will fairly trouble free.
If you want to experiment with the other, then more power to you. You might get it right the first time & we could all learn something. It is fun to try something different.
Good luck
Craig

[kap]

Briggs boilers have been written up in me, and live steam.
They use coils, or vertical tubes instead of a loco type firebox.
The front of the boiler is a firetube boiler.
They are popular down under.
kap

[Phill]

I hate to tell you kap, but most o us Aussies don't like Briggs boilers at all. They are a waste of time and effort, in my oppinion. The ONLY advantage that they have over conventional loco boilers is that they are easier to make. In every other area they fall well behind the conventional loco boiler.
Did you know...In full size..... The greatest quantity of steam produced per square inch, is the first 6 inches of your tubes? Followed by the fire box. If you remove most of your firebox, as in a Briggs boiler, you loose a lot of your steam production.
The risers do not recover any more than 65% of the radiant heat lost due to the removal of the water leg. And then only for that particular wall that the riser is replacing.

Monotube boilers can be very dangerous if not properly controlled. The use of thermo-couples for regulating the steam temp is critical. If this is not done, than the boiler cannot be considered safe. The pressure fluctuations can go to extremes, and when coupled to the corresponding temperatures, can become lethal. I have seen too many failures to consider them safe.

Cheers,

Phill.
Cheers,

Phill.