Heisler Brake Plumbing
Nelson Riedel, Nelson@NelsonsLocomotive.com
3/28/2010, last updated 03/28/2010

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.

Vinyl Hose: 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.
Hose Barb:  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.
Adjustable Elbow:  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 Electric Wiring.
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 snifter valve.

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 channel.

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 Compressor. 

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 handle. 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 line hose.

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 10-32.

This wraps up the brake system which has been fun.