Boiler Smoke Box Fittings
Nelson Riedel Nelson@NelsonsLocomotive.com
Initial: 10/10/03 Last
The machining of the smoke
box related castings and fabrication of the smoke box fittings were done
while waiting for the boiler to arrive. The smoke box castings are the smokestack, smokestack base,
smoke box front and smoke box door. The other smoke box fittings
fabricated from stock are the petticoat, the blower and the engine exhaust
|Smokestack Base: The first casting to machine was the
smokestack base. This is the base for Cass No 10.
Kenneth's casting is similar except he provided only four attachment
bolts between the smokestack and the base. Maybe Kenneth has
the right idea since it appears only four nuts were used on Cass 10.
|The machining of the base is straightforward except for the radius
on the underside to match the smoke box radius.
The first step was to mount the casting in the 4- jaw chuck and
center the points between the little smokestack attachment
bosses. The upper surface was then turned to the correct
height and the inside drilled and bored. The chuck was
then transferred to the rotary table and the 4 smokestack attachment
holes and the 6 base attachment holes marked with a center drill as
shown on the right.
|There were two obvious ways to cut that 3.315" radius on the
underside; mount it to the lathe faceplate or to use a boring
bar/ fly cutter type tool in the mill. Friend Dan Staron said
he used a fly cutter.
A holder for a boring bore as shown on the right was made and
mounted in the mill. The base was mounted in the milling vise with
the finished side resting on a couple parallel spacers. The
vise and milling head were oriented such that the axis of the cut
was centered over the front and back mounting holes.
This turned out to be easy to setup.
The little Maximat V10 mill head originally had four speeds but
only two were working so care was take to make very small cuts on
the slowest speed --- that 3.3" lever produces a lot of
shock. After the job was about 80% done the last two
speeds on the mill disappeared. I'd been thinking that
the mill was just too light for live steam work
|So, had to use the lathe to finish the
job. The base was mounted to a scrap piece of 1/4"
thick angle using the smokestack mounting holes as shown on the
right. Care was taken when mounting the base to the angle so
that the axis of the cut was perpendicular to the base of the
angle. A centerline was scribed on the base. The
angle was then mounted to the faceplate on the bench and aligned so
that the centerline was in line with the center of the faceplate and
the position of the finished cut in the base would be 3.315"
from the center. This was much easier than expected --- of course,
this is not a precision cut and an error of a few thousands or more
will be undetectable.
|The finish cuts on the lathe went well --- again using low speeds
and a fine cuts. The angle and base were light enough and
speed slow enough that counterweights were not required.
The underside of the fished base is shown on the right.
The Mill: Now
back to the zero speed milling head. The gear box was opened and
three sets of gears found Each set (shaft) has two
gears, one steel and one fiber. Only one gear on each shaft is used
at a time and the arrangement is such that the meshing gears are always
steel - fiber, never steel-steel or fiber-fiber. The steel-fiber
interface may be to reduce noise. In any case, it's not a very
robust design. Two of the the fiber gears were toothless.
A call to the only know parts
distributor brought the expected news that replacement parts are no longer
available. Further study revealed that the damaged gears were
24 tooth and within a few thousands of 16DP 14.5 degree spur gears.
Replacements arrived in two days and three hours later
after boring, cutting off the boss, trimming the width and filing the teeth
a bit the mill was back online with all four speeds. It's now a bit noisier,
but these gears were always noisy anyway.
There is one fiber gear
remaining but it's much larger and probably less likely to
fail. On further reflection, failure was at least partially due to not
fully engaging the gears so that the load was carried
by only part of the width of the teeth. Must be more careful.
|Smokestack : The Cass 10 smokestack is very close to the
design that Kenneth used.
|The challenge with the smokestack is to find a way to mount it with
the casting centered --- there are no true edges. Also, the
lathe doesn't have a stead rest, but not sure how one word work on
the rough casting.
The thing that worked was to mount the large end on the 4-jaw
chuck and then adjust the chuck so that surfaces of the hub midway
between the little tabs (see photo on right) was as close to
centered as possible. Next, the inside of the end was
bored to a depth of about 3/8" using very small cuts. This
was continued until a smooth surface was obtained.
|Next, a brass disk was turned to match the bored inner surface of
the previous step. The disk was center drilled for the lathe
tailstock center. The setup is shown on the right. Next, the
4-jaw chuck was adjusted so that the end closest to the chuck was as
centered as possible --- see photo.
Once this was done, it was a simple matter to turn the base end
and then mount the base in the 3-jaw chuck to turn the taper on the
Friend Dan Staron had warned me that the outer crust of the
castings were very tough and hard to machine and it was best to grind the
surface. That turned out to be the case with the tapered
part. If one takes an initial cut of 0.020" or more,
there's not much trouble with the surface. However, very small
cuts sometimes dulls the tool nearly immediately. The tapered
part was lightly faced on the bench grinder which cured the tool
|Some voids were found in the base of the smokestack as shown on
the right. It almost looks like termite damage. The only area of concern was
under the ring and a small area above the ring. Those areas
filled with 550 degree solder and filed smooth ---- almost like lead
The base was then aligned on the stack and used as a drilling
fixture to drill the mounting holes in the stack. The
two pieces were joined and an air die grinder used to match the
ring and tabs on the stack with the mating surfaces on the
|Blower & Exhaust: The most difficult part of the
blower-exhaust system is the flange that attaches to the bottom of
the smoke box. Kenneth suggests that the flange be
made from the cutout for the boiler steam dome. I'm
having my boiler built by someone else so I didn't have the
cutout. A short piece of the 6" schedule 40
pipe was obtained from the local machine shop. The 0.28"
thickness seemed excess so I turned the thickness down to about
3/16" I then drilled a 1/2" hole in the middle
of what was to be the flange. This was done before cutting out
the flange to make sure the hole was perpendicular to the
flange. The flange was then rough cut from the section
of pipe. A piece of 1/2" rod was center
drilled on one end and the other end silver soldered into the
flange, making sure the rod was perpendicular. The
rod was then chucked in the lathe and the outside turned to
The photo shows the piece of pipe and the flange with
rod after the OD was turned.
|Next, the flange was chucked in the 4-jaw chuck. The end of
the rod centered with the tailstock center and the chuck adjusted
so that the rod close to the flange was also centered.
The chuck was then tightened and the rod cut off next to the flange (hacksaw).
The flange was then drilled/bored to ~ 0.975" to match with the OD of a
3/4" copper elbow.
|These are the components of the exhaust and blower system. The brass blower ring and exhaust were machined as per Kenneth's
drawings. The flange hole positions were changed from
the drawing; the two mounting holes closest to the
exhaust pipe were located away from the equal spacing position
slightly to give easier access to the screw heads. Update5/14/04:
Kenneth had specified four 1/32"
(0.032") holes for the blower working with his propane burner.
These holes plugged up several time using my oil burner. Bob
Reedy's design for his oil burning Three Truck Climax
(July/August 2003 Live Steam ) uses four #55 drill
(0.052") holes. Reedy's design was copied and the blower holes
were enlarged to 0.052" which fixed the problem End
|The finished blower and exhaust system after the parts were silver
soldered together. The 3/16"
nipple is to show the position of the blower input and will be
replaced with fittings connecting to the blower line.
This finishes the smoke box fittings. The installation of
these fittings will be presented in a separate page.
|Update 4/15/04 - New Dogs: I was unhappy with the clips
that held the smoke box door closed--- they seemed too large and way
out of scale. I replaced the clips with cast brass dogs from Railroad
Warehouse (the smaller dogs, part # DOG-01). The photo on
right shows the installed dogs on the freshly powder coated smoke
box front and door. The four shiny screws hold the front
to the smoke box --- these screws will be painted black at some
point. The powder coating sealed the door to the front casting
--- there are no plans to open the door; smoke box access is by
removing the door and front castings as a unit.