2/26/2010, last updated
This page describes the remaining parts associated with
the boiler and smoke box including:
|Smoke Box Front: The material for the smoke box
front was a 8" X 1.5" cast iron disk obtained form
McMaster-Carr. It was turned to match the design
drawing. The hinges and dogs will be added later. (I'm too
anxious to get steam up --- those details can be added next
Blower & Nozzle: The blower and nozzle were also made per
the design drawings except that the input line was changed from 1/4" OD
tube to 3/16" OD tube. The base plate is a scrap of the
tube used for the smoke box. The base is much wider than
absolutely necessary so that the two attachment screws can be accessed
easily. The blower line feeds through the smoke box wall via the angled 3/16" tube to female 1/8" NPT fitting
on the inside to a straight
3/16" tube to 1/8" male NPT fitting on the outside.
This photo also shows the screws that attach the smoke box to the
saddle. Most of those holes were drilled from the bottom up using
the saddle as a pattern. Those holes that couldn't be
drilled that way were marked using the holes in the saddle as a
Petticoat: When it came time to make the
petticoat, standard pipe fittings were found to be a close match to the
required dimensions. The photo above is from the boiler side
of the smoke box showing the fittings. The notch is the lower left
of the smoke box permits the smoke box to slide past the feed water
heater input fitting.
|The 2" to 1-1/4" reducing coupling and a 4" long 1-1/4"
nipple combination were used for the petticoat.
McMaster-Carr has drawings and CAD files for most plumbing
fittings on their website. The drawing on the right was
made by combining two CAD files downloaded from McMaster-Carr.
|This photo shows the bottom of the petticoat where most of
the hub on the coupling was turned off and the inside smoothed.
Note that the petticoat is supported by a bracket attached
to the smoke box front. The original plan was to support
the petticoat with a bracket to each side the smoke box.
This arrangement turned out to be simpler and has the advantage
that the petticoat is removed with the smoke box front.
The bracket is made from a scrap piece of 3" channel.
|Things are really tight in the smoke box. When I
first tried to push the smoke box front into position with the
petticoat attached a small interference between the top hub of
the coupling and the lower compression fitting on the pipe from
the throttle to the superheater input pipe was found. The photo shows how
a bit of grinding solved the interference.
Exhaust Pipe: The last piece of the Blower- Blast Nozzle
function is the exhaust pipe from the cylinder to the saddle. The
left side pipe is pictured above. The pipe is 3/4" OD tube
(5/8" pipe). The end that fits into the engine
exhaust manifold requires a custom fitting.
|This is that custom fitting at the cylinder end. The
brass elbow is for 3/8" NPT threaded pipe and was drilled out to 3/4" The
brass piece with the O-Rings was made from 1"
diameter brass bar stock; the shoulder next to the elbow was left
at 1" diameter. Both ends were turned to 3/4" diameter and
the grove made for #018 Viton O-Rings (7/8" OD-3/4" ID).
The WROT copper fitting is a street elbow. All these
pieces were silver soldered together. The screw was
made with a piece of 6-32 threaded stainless rod and and
stainless nut silver soldered on the end.
|The flange on this end was made at the same time as the
saddle. A short piece of the 3/4" OD tube was silver
soldered inside the flange. The pipes were
then fitted to the saddle and to the cylinder and the ends that
fit into the elbow marked and cut to the correct length. The
three pieces were assembled and the ends attached to the saddle
and to the cylinder. Once everything was found to fit
correctly the elbow was soldered while the ends were still
secured using 400 degree soft solder.
and feed water inputs are noted on this photo.
The safety valves
pictured on the right fit in 1/4" NPT holes in the steam dome
top. These particular valves are used in hydraulic
service. The setting is sensitive to the torque used to
tighten the valve so Teflon tape is used and the valves
tighten until just snug.
|The safeties relieve to the sides so the the defectors show
here were fabricated from aluminum bar stock. They are
1-3/16" OD, 15/16" ID and 1-3/8" high. The height may be
a little excessive; if so, they can be cut down later.
|Blow Down Valve: The blow down valve
connects to the middle front of the outside of the firebox, just above the mud ring
as shown on the right. The elbow and nipple are off-the-shelf 1/8" NPT fittings. That is a
compact high-pressure brass ball
valve, 1/8" NPT female X male, lever handle from
McMaster-Carr (#4112T13). A 1/8" nipple will be added to
the output side to get the discharge beyond the side of the
Water Input Valve and Check Valve: The photo
above shows the boiler water input valve and check valve near the front of
MRSR91. This input is fed from the left side injector.
This shows the water input valve and check valve on the model.
The input on the model will be from an electric pump located under the
oil tank rather than from an injector. The input pipe will
run along the top of the walkway into the front of the cab.
More detained information will be provided in the Water Plumbing
This wraps up the description of the construction of the boiler