Heisler Truck Construction III
Nelson Riedel, Nelson@NelsonsLocomotive.com
1/30/2010, last updated 02/10/2010

The fabrication of the part of the brake system mounted on the trucks is described in this page.

Brakes Shoes:  The HM220 Brake Shoes are difficult to machine because of the combination of rectangular and round surfaces.   To simplify the process two shoes were fabricated from a 3" length of 0.688" X 1.25" aluminum bar as shown in the drawing on the right.  The first step was to mill the sides to form the 0.433" part as shown in the drawing above.  Next, the holes shown in red on the right were drilled.  Some of these holes remove material where slots will be milled.  Some of the holes are in corners of future saw cuts.   The countersunk holes in the corners are for 1/4" FH screws that will secure the bar when the curved surfaces are machined.
This photo shows using the milling table to accurately locate the position of the holes.
The holes located.......
The piece was returned to the mill where the slots were machined.
The piece was transferred to the drill press for drilling the vertical hole where the screw through the brake beam fits.
The same piece of aluminum that was used to hold the reversing link for machining was put back on the rotary table.  Holes were then located for the hold-down screws at the ends of the  aluminum bar with the two shoes.   These holes were tapped 1/4-28.
Once the bar was secured to the rotary table, the curve at one side of the back of the bar was milled by rotating the table.   The bar was then unfastened and reversed end-to-end and the radius turned on the other side.
Next, the curvature was milled on the front side of the pair of shoes.   The back side of the shoe is not as thick as the front.  A shim was placed under the back to make the bar level during this machining.  The shim is visible in the right side of this photo.
Two pair of shoes are shown in this photo.  This photo was taken right after the machining on the rotary table.
The next step was to saw off the excess material on the back side of the shoes and then cut them in half.   The back side was then cleaned by milling and filling.  The photo shows using the mill to clean up the slot at the top of a shoe.
This photo shows a pair of completed shoes with the hanger attached.
Adjuster: The photo on the right shows a male and female adjuster.   They were machined per the drawings in the design section except for the threaded part of the male adjuster.   The threaded part is a piece of stainless steel threaded rod which was screwed into the clevis part and secured by Loctite.
Brake Cylinder Mount Spacer:  The photo shows one of the spacers installed on an Axel Bearing Cap.  That is a nyloc nut just above the spacer.
Gear System Swivel Shaft:  The bottom of the Swivel Shaft had to be trimmed slightly as shown in the photo to give clearance for the brake beam.

Cylinder Drain:  The plan is to run the brakes off both air and steam.   Steam condenses and the cylinders will eventually fill with water.   Arrangements must be made to drain off the condensate to avoid freezing if the locomotive is stored in an unheated place.     Photo above shows installation of the drain under the cylinder mount.  (A 1/8" NPT to 3/16" -40 bushing is screwed into the supply port of the cylinder.  This bushng was made of the NPT end of a 3/16" compression tube to  1/8" NPT fitting.  The NPT end was shorted and a NPT thread die was run backwards over the treads to make for a better fit in the cylinder port.  Thread sealant will be required.)  The 3/16" fittings are then connected to the bushing as shown in the photo above.  A globe valve is used as a drain cock with the handle above the cylinder mount.  Note that several notches were cut in the cylinder mount for the plumbing fixtures.  Also note that the end of the globe valve was cut off --- this allows the free end of the cylinder to move side-to-side to match the variations in brake linkages.   The air/steam supply will be via 1/8" hose fitted to a hose barb that will screw into the open end of the tee.     The plumbing on the under side of the cylinder mount is covered with a ~4" length of 2" X 1/2" X 1/8" channel attached with four 6-32 screws and nuts.       

Photo above shows all the brake components for the tender truck.  About 1/4" was cut off the threaded end of the cylinder rod to provide clearance between the rod and the truck lower cross.   Note that the guard over the cylinder plumbing has been installed in this photo.  The handle of the drain valve can be accessed by reaching under the frame.  

Photo above shows the tender truck with the brake hardware installed.   Note the brake drain valve handle beside the brake cylinder.

Bottom view of the tender truck shown above.   Note that the cover has been installed over the brake drain plumbing.

This warps up the truck construction.   The brake valve and associated plumbing will be described in the brake section.