the tubes into the tubeplates
using a commercial tube expander, but its bulky head prevented its use
around the edges, especially the tubes near the crown sheet. I made
up a tapered drift from bright mild steel about 10" long. 6" is tapered
and 4" parallel for a handle. The smallest diameter of the taper is
about 20 thou smaller than the tube ID. The major diameter is about
1 thou per inch diameter bigger than the hole-diameter-less-twice-the-wall-thickness-of-the-tube.
I made the major diameter parallel for a length about 1-1/2 times the
thickness of the front tube plate. Make sure you allow enough metal
to get to the major diameter while achieving a highly polished finish.
The dimension of the minor diameter is not critical. The transition
point where the taper meets parallel should be radiused.
Anneal both ends of each tube before you start and make sure that excessive
force is NEVER used to expand the tubes into the tubeplates!
on the original design of the drift would be a length of steel rod (about
5/16" dia. up to 3/4"dia tubes, and correspondingly larger for the larger
dia. tubes) screwed in to the minor dia. end of the drift. The rod would
be long enough to extend past the end of the tubes before the tubes
have been expanded. You then make a stepped collar with a hole to fit
loosley on the drift rod and mount the collar on the opposite end of
the tube you are working on. As you operate the drift, it is kept parallel
to the tube by the rod passing through the guide collar at the other
Keeping the drift rod diameter fairly large will allow you to use it
to tap the drift back out of the hole after expanding the tube. Make
sure the exposed end of the rod is chamfered to reduce the mushrooming
effect of prolonged tapping during the extraction process.
Make sure the tube doesn't slip along while expanding! It's hard to
fix if it locks in the tubeplate after it moves out of position.
Once the tubes are secure in the tubeplates you can flare the front
edges. I simply tapped the back end of a lathe dead centre with a wooden
mallett to gently tap the tube end to a 60 deg flare. Stop when you
see that the tube end is in the correct shape and you feel just the
slightest increase in resistance to the flaring process. If your tube
diameter is larger than your lathe centre you will need to make a larger
"centre" to suit. Don't forget to polish the contact surface to prevent
damage to the tubes and make it easy to slide in during the process.
If you bash the centre too hard you can easily shear off the end of
the tube flush with the tubeplate and that would be disasterous! You'll
have to replace the damaged tube!
This part is a little harder to accomplish than the front end. However,
I used a similar technique as used when securing eyelets. I made up
two more tools. Start with a piece of steel about a millimeter larger
diameter than the flattened end of the tube will finish at.
Tool No.1 has a stub end about 15mm long that fits neatly inside
the tube as a guide. The face of the shoulder is radiused like an eyelet
tool. The purpose of this tool is to GENTLY roll the end of the tube
over to 90 degrees and up against the back tubeplate.
Tool No.2 is similar but without the radius on the shoulder face.
Its job is to GENTLY bead the end of the tube (created by tool 1) against
the tubeplate. Use a wooden mallett on the ends of both tools and keep
the tapping light. The aim is to form a seal and it takes very little
force on the tubes to achieve that aim.
sealed well and have never needed "touching up". The tapered drift,
flaring and beading tools are very easy and cheap to make.
care of a steel boiler
several theories about how to care for a steel boiler. I guess they
all work to varying degrees, but my method of steel boiler care is a
bit different to all of the other methods! You can make up your own
difference of my method is that I leave the water in the boiler between
runs. I usually blow it down "half a glass" a couple of times during
the session, but never empty it until inspection time. Before you reach
for the back button, I'll tell you that after ten years of operation,
the boiler interior in still in excellent condition. There are no pitting
or corrosion marks at all due to the protective tannin lining on all
When you leave the water in the boiler, it is important to make
sure that it is totally full of water with no air spaces inside (see
After the run for more details).
If you decide
to empty your boiler after each run, you must open some plugs etc to
allow air to circulate inside the shell to prevent condensation forming.
You could also rig up a 25W light bulb in the firebox to keep the shell
operation of the boiler I use a chemical produced by Maxwell Chemicals
called Nu Wood Boiler Disincrustant as a dose in the water tanks. Nu
Wood is a concentrate that is mixed 5ml per litre of water. I use a
10 litre plastic jerry can to dilute the concentrate and take with me
to running days or visits to other clubs. Over ten years of use, I have
barely used 1/2 a litre of the 5 litres of concentrate I originally
purchased. The 10 litre jerry can of water with 50ml of Nu Wood can
last about a year, because I only use about 1/2 a litre of diluted chemical
has a tannin base so it looks like black tea in concentrate form, mild
tea in mixed form, and very weak tea by the time it is in the boiler.
A dose in the tender or water tank at the start of the session is usually
enough to keep you going for the day. If the water in the boiler gets
to dark, just skip a dose to weaken the mix.
drop the fire and leave the loco as it is! I have an axle pump on my
loco, and one day I accidentally discovered that if I leave the by-pass
valve closed after a run, the vacuum created in the boiler as it cools,
draws the water from the tank into the boiler to fill up void (the vacuum
also helps remove oxygen from the water). If you don't have an axle
pump, you'll have to manually pump the water in to fill it up. You will
also need some way to allow air to escape from the highest point on
your boiler as you pump in the water.
thing that works in my favour is the whistle mounted on top of the steam
dome. After the boiler has cooled down, I simply open the whistle valve
and give the loco a shake to get any trapped air to the top and then
pump in a small amout of water via the hand pump until the water flows
out of the whistle. The whistle valve is closed and the boiler given
another pump to put a small amount of pressure on the gauge (about 20KPa)
to squeeze out some more oxygen. This process is called water wedging.
is left in this condition until the next run.
at the track for the next run, you simply open the blowdown valve to
release some water to half-glass. You may need to open the blower valve
to let some air in so the water flows out better. Then proceed with
lighting up as usual.
I leave the water in the boiler
can include many other ingredients besides H2O...
(Al), Iron (Fe), Manganese (Mn), Mineral Elements,
Naturally occurring elements which can enter the water from the catchments.
A naturally occurring element which can enter the water from the
catchments. It may also be added to water in the treatment process to
reduce the acidity levels.
The application of chlorine to drinking water, waste water, or industrial
waste to kill bacteria or to oxidise undesirable compounds.
A chemical containing iron. Used in the water filtration process
to settle contaminants.
A chemical which encourages heavy contaminants to gather together
and settle from water more quickly in the treatment process.
Small amounts of fluoride are added for dental health reasons in
accordance with legislation.
A naturally occurring element which can enter the water from the
catchments. Is used by plants as a nutrient.
A measure of the alkalinity or acidity of water expressed on a scale
from 1 to 14: 1 is most acidic, 7 neutral and 14 most alkaline.
A by-product of chlorine which has been used to treat water.
feedwater for a boiler, there are three basic items we are trying to
prevent. These are: Scale, corrosion, and foaming. All of these problems
can cause boiler and engine damage.
Chiefly, calcium and magnesium salts, dissolved in boiler water,
deposit on tube surfaces as deposits and/or scale when water evaporates.
This reduces heat transfer, increases tube metal temperature, and leads
to ruptured boiler tubes; and an increase in fuel consumption.
Scale formation is prevented by removal of these hardness salts. This
is done by chemicals to turn these salts into a soft sludge which can
be removed by blowdown. The least expensive and most reliable method
is by means of water softeners with the addition of boiler treatment
Boilers become corroded for several reasons. Low pH water and the
presence of dissolved gases such as carbon dioxide and oxygen can all
cause corrosion, such as pitting of the boiler tubes and shell. To prevent
this, the pH of boiler water is maintained in the alkaline range. The
dissolved gases can be removed by corrosion inhibitors to protect surfaces
of steam and return lines.
Foaming (called Carryover in the US) is boiler water leaving the boiler
with the steam. These slugs of water in the steam line can cause mechanical
damage. Several things can cause this: Alkalinity too high, poor boiler
design, oil in the water, over firing, and others (apart from pumping
too much water into the boiler). Foaming is controlled by the addition
of anti-foam agents. It is also controlled by boiler blowdown.
elements are floating about in the boiler as "solids" and remain in
suspension. While still in suspension, the Nu Wood chemical in the boiler
helps keep the solids as a sludge to prevent them from baking on the
heated surfaces like the crown sheet and girder stays as well as the
boiler tubes. Blowing down the boiler a couple of times during a running
session helps reduce the amount of suspended solids in the water as
well as the effects of foaming.
wedging after the run helps reduce the oxygen content of the water for
If no chemicals
are used and the boiler is drained after each run, the solids are deposited
on the horizontal surfaces of the boiler interior as the water level
drops. The residual heat of the boiler cooks the solids on to the boiler
surfaces and eventually builds up a crusty coating on the tubes etc.
that will eventually reduce the heat transfer and reduce the boiler's
efficiencey. All is not lost though because chemical cleaning with something
like Phosphoric Acid can clear away the crust.
To me, the
downside of draining the boiler after each run is having to unscrew
fittings each time for air circulation which could lead to premature
wear and failure of the threads/bolts etc.
The residual heat in the boiler can bake o-rings hard as a rock and
reduce their sealing efficiency. The forming of scale on the interior
surface means the addition of an ACID in the boiler to clean it! If
you warm the shell with a light bulb in the firebox, you are using electricity
you have to pay for!
you have it. With simple care, a steel boiler will give you great service
and will last for your lifetime and beyond!!!
to get the Nu Wood
Boiler Disincrustant is available from ECOLAB at 6 Hudson St. Castle
Hill, NSW, Australia. Phone (02) 9680 5444. The current availability
(January 2000) is a 25 litre container for AUD$134.09 (including tax).
The 25 Litre container is a bit much for individual use, so a group
or club could divide the cost and decant the concentrate into smaller
In a 10 Litre container, add 50ml of Nu Wood and 10 Litres of water.
I also add 1/2 a teaspoon of Calgon (the brand name of a domestic water
softener) to help maintain the water in the alkaline range of pH.
from the 10 litre container is poured into the tender or tanks in small
doses to maintain a very weak tea colour of the boiler water. The colour
should be barely noticable.
to get the AMBSC Code books
Association of Live Steamers (AALS) Operating Codes of
Australian Miniature Boiler Safety Committee (AMBSC) Boiler Codes
Part 1 (Copper boilers) and Part 2 (Steel boilers - Briggs and Wet-back)