3/28/2010, last updated
This page describes the interconnection of the Steam
Air Compressor, Electric Air Compressor, Air tank, Brake Valve, Brake
Cylinders and Brake Gauges. The water plumbing and nearly all of
the fuel plumbing is on the left side of the locomotive. The Brake
plumbing is nearly exclusively on the right side of the locomotive.
The diagram above shows the interconnection of the
air brake components. The air generation is at the top with
the steam powered compressor on the right and the electric compressor on
the left. The steam compressor is the main unit with the electric
compressor a backup. There are piston type check valves between
each compressor and the main air supply line to prevent a leak through a
faulty valve in either compressor.
The Brake Valve is the connection between the
air supply line at the top and the brake line at the bottom.
Note that there are gauges on both the air supply and the brake line
sides of the system. Also note that there are drain valves on the
air tank and both brake cylinders to drain off condensate.
The hard plumbing is with 1/4" copper tube and scale
fittings on the air supply side and 3/16" hard copper tube with scale
fittings on the brake line side. Clippard 1/8" ID hose is
used to the brake cylinders, brake valve, pressure switch and brake line
gauge. Clippard fittings are used to interconnect the hose to the
hard copper tube.
The following provides more detail on the specific
fittings used. Consult the Clippard online catalogue for more
information on the hundreds of available fittings.
The hose I used was Clippard
#3814-1. That number has been changed and I think the
current number for that same hose is VYH1-0804-050 as shown on
the right. The 050 on the end means a 50 ft roll.
The 11752-1 hose barb is
the easy way to transition from 3/16" scale pipe fittings to the
Clippard vinyl hose. One of the standard Clippard
interconnections is via the 10-32 thread. They use a thin
rubber washer to seal the joint. Pipe joint compound can
also be used. I rethread the scale pipe fittings to 10-32 to
mate with the Clippard fittings and use joint compound.
This is a really neat fitting in that it can be rotated to the exact position
desired and then tightened in place via the screw.
|Adjustable Tee: This is another
fitting that can be rotated to the desired position and
then tightened in place.
|Hose Tee: This is simply a
small tee fitting for the hose.
|Pressure Switch: The pressure switch is
used in conjunction with the electric compressor to turn on the
compressor when the tank pressure is low and turn off the
compressor when the desired tank pressure is reached.
Details on the compressor wiring are at
|Quick Connect: These quick connects contain
a Schrader valve which shuts off the port when the hose is
disconnected. This is particularly useful when one is
stringing brake line through a number of cars with quick
connects at each end of each car.
The photo above shows the steam air compressor
located at the right front of the locomotive. This is a good place
to start the description of the brake plumbing. The various
pipes are identified on the photo. The air tank is located
inside the frame side under the boiler.
This photo taken from above shows the routing of the
steam exhaust from the compressor. It shares a vent pipe with the
This photo gives a better view of the air tank and
check valve. Note the drain valve on the air tank
|Photo on right shows the front part of the air tank --- the
right side engine exhaust pipe has been removed. The air
tank is made of an 8" length of 2" OD 1/8" wall steel tube.
The end on the rear is bronze silver soldered in place.
The front also initially had an identical bronze end.
Unfortunately it leaked and after resoldering it several times I
plugged the leak with slime tire sealer. The slime worked
in that the end blew out --- and then really leaked. The next step was to make a
steel plug shown in the photo and secure it with a dozen #2
drive screws and sealing with slime. I'll make the
next tank this way if I'm interested a scale tank. (Dick McCloy uses spent propane cylinders for his tanks. )
The three brake pipes run along the side of the
boiler on top of the walkway as seen in the photo above. The steam
supply pipe to the steam compressor and the air supply line from the air
tank are both 1/4" tube. The brake line is 3/16" tube. The hose
from the brake line pipe to the brake pressure gauge has the 11752-1
hose barbs on each end. The gauges are McMaster #38105K51, 160 psi
for the air supply and 100 psi for the brake line.
This photo shows the same stuff as the previous photo
but from a different angle. Note the valve from the steam manifold to the
steam powered compressor. The oil line is from the lubricator
which supplies steam oil to the steam side of the compressor.
The air side of the compressor receives a couple drops of oil
periodically via the air input line (remove the air filter).
|Once inside the cab the air supply and brake lines drop down
and run inside the frame side channel. The hose for
the brake line goes to the output side of the brake valve.
The air supply hose goes to the input side of the regulator via
a UT0-4004 adjustable Tee on the pressure switch.
Note the check valve for the electric compressor is beside the
This photo shows the electric air compressor which is
located on the right side of the electrical compartment under the oil
tank. The pressure switch is attached to the under side of the
compressor mounting plate. Additional photos of the these
components are at Electric
Wiring and Electric Air
|This photo shows the brake valve located at the top of the
electric compartment bulge. It also gives a perspective of the
various gauges. The throttle will be above the brake valve
Note the use of the hose barb on the input
tot he brake valveand the adjustable L with hose barb on the
brake line side.
|This shows the brake hoses before most of the electrical
stuff was installed. Note the use of the tee in the brake
The photo above shows the quick connect fitting in
the front brake line.
|Photo above shows the quick connect fitting for the
brake line to the tender truck. The fitting is located
under the rear sill to the left of center. It was
put on the left side so it and the water line from the
tender are both on the same side.
The photo on the right
shows the quick connect with a scale 3/16" street elbow and hose
barb on the input side. The scale fitting was rethreaded
This wraps up the brake system which has been fun.