Model Forum / Radio Controlled / Water Models / January 2005

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Hi
Two questions and two answers! Yes and No.
All the boilers, i use in my steambotats, are calculated and made by
myself. My profession is mechanical engineer and so is there no
problem. The steps you have to do, is first, to calculate the steam-
consumption of your engine. Considering the volume of one stroke, the
number of the cylinders, the avereage pressure, the speed of
revolutions, the efficiency etc. Everything is shown in Harri's book.
Next, after knowing the result, you are able to calculate the boiler
dimensions, the needed size of the heat transfer surface, the water
volume, the thickness of the pipes and of the jacket and the bottoms
on each end, according the local rules (may be ASME) i think. The
general way is just as shown in Harri's book. Respect the allowed
strength of the used  materials  i.e. copper, brass or perhaps
stainless steel.
Here in germany the rules say, that you have to make finally a
performance test with a testing pressure 30% higher than the nominal
pressure and not much higher. It ist not allowed to use compressed
air for this test. Only could water is allowed to perform this test.
The reason for limiting the testing pressure is, that otherwise there
may arise little micro cracks especially in the silver soldered
connection seams. Dont forget! 30% higher is enough (according our
geman rules) I dont know if modellboilers with a product from total
volume multiplied with the noiminal pressure are a category which
must be checked according ASME. I think you will be able to find it
out. May be, that there in your area are steam enthusiats which will
give some assistance to you. If you are not experienced in silver
soldering or you have not the tools to do this work, then visit your
local plumber and let him do the work. Dont forget connection flanges
for all important parts. man steam valve, security valve, feed
checkvalve, wistle, water gauge,filling plough, manometer etc.
After all dont forget an good thermal insulation.

bye and have a lot of fun
- -
eddy

Cheddar models do materials and drawing kits for model boat boilers and
in fact the Pegasus Boiler is quite large. See:-

HTTP://www.Modelsteam.co.uk

For further info

Cheers.