The Mill Creek Central Logging Line is about 1/2 mile long and climbs about 60 feet for an average grade of about 2.3% with the grade over some short stretches exceeding 6%. I have two locomotives, a Shay and a Heisler. Both have considerable instantaneous power but are limited by their ability to generate steam. The shay can climb the logging line pulling three cars and two adult passengers without having to stop to build steam. The Heisler (which is bigger than the Shay) can pull 5 cars and 4 adult passengers up the grade. So, I'm not going to worry about 20 car trains, etc. The Shay has steam powered brakes and the Heisler has air powered brakes. Both locomotives were able to stop the loads indicated with little or no trouble. However, after the last run I used the Heisler to drag the Shay and two cars to the loading facilities. That time the Heisler brakes could not stop the train ---- the train became a roller coaster. I was able to stop the locomotive with the Heisler hand operated park brake. Later investigation revealed that the Heisler brakes needed adjustment. Early in the log car project I'd designed brakes for the trucks, primarily for appearance. After loosing the locomotive brakes I decided to install operational brakes on several of the cars as a backup for the locomotive brakes.
One of the first cars I made using the fabricated trucks was a flat car with a large tool box --- I called it a utility car. The tool box was a convenient place to carry all the stuff needed to start and operate the locomotives. The utility car worked great. However, the toolbox I selected was about 20% too big. While discussing a possible remake of the utility car Mike Green suggested I check out the logging cabooses used by Rayonier in the northwest. These cabooses were essentially half cabooses on flat cars. The half the flat car exposed was used to carry logging equipment such as chains, etc. These cabooses were often placed directly behind the locomotive. I decided to build such a caboose to replace the utility car. The caboose could haul the required tools and also a battery plus air compressor for car brakes. The caboose could be arranged with one seat for a "brakeman". The brake control could be equipped with a long cord so that it could be operated by the locomotive engineer if there was no brakeman. It isn't necessary for all cars to have brakes --- I decided to put brakes on the caboose and one or two skeleton log cars. That's the plan.
Many folks make the brake assembly with cylinder(s) mounted on each truck. I chose to follow the prototype and use a single cylinder per car and use linkages to connect the cylinder to the brake assemblies shoes on the trucks.
The outer brake bar in drawing is a piece of 1/4" diameter CFS bar with the ends turned to 5/32". It has only one function -- to control the separation (gauge) of the shoes. The small holes in the ends of the bar are 1/16' diameter for 3/64" cotter pins. The ends of the bars go through the middle hole on the shoes. The inner brake bar made from a piece of 5/16" diameter CFS bar also serves to hold the shoes to the proper gauge. The levers that are silver soldered to the inner bar serve to transfer the brake force from the brake cylinder to the shoes.
Photo above shows the top view an assembled brake unit for a truck. This unit has been on a truck for several months and has accumulated considerable dirt. The U shaped bars on the ends are hanger brackets for the shoes. The bottom of the U screws into the bottom of the lower spring plank.
This photo shows the bottom view of the brake assembly. The hex bar with threaded rods in the ends is the brake adjuster. The adjuster connects between the short lever on the inner bar and the lower hole on the outer shoe. When the brakes are applied the longer lever on the inner bar is pulled towards the center of the car causing the short levers to rotate towards the rear and via the adjuster force the shoes apart and against the wheels.
Brake Cylinder & Linkage:
Photo above shows a brake cylinder mounted on the underside of a skeleton log car. The cylinder is 7/8" diameter with 1" throw -- Clippard USR-14-1. It has an internal spring which retracts the piston when no air pressure is applied. This cylinder should lock the brakes with less than 50 psi pressure. The clevis on the left end of the cylinder is Clippard RC-1281.
The drawing above shows the dimensions of the brake link levers. The levers are made from 1/8" X 1/2" CFS bar stock. The right lever has a forked end that fits over the cylinder universal mount. The lever pivots are 1/4"diameter rod with the ends threaded 1/4-28. The pivots were silver soldered into holes in a mounting plate made from a length of 1/4" X 1/2" bar stock. The mounting plate was attached to the car frame tube with a couple 8-32 screws. The levers are retained on the pivots with lock nuts.
Photo above shows the top view of the cylinder. The brake line (hose) is Clippard 1/8" ID Polyurethane Hose #URH1-804. Clippard barb fittings are used to connect the hose. The hose is secured to the car frame with cable ties.
The linkage from the levers in the center of the car to the long lever on the truck brake assembly is 5/32" rod (drill rod) and turnbuckles identical to those used on the skeleton log car truss rods.
The brake line connector is through the car sill to the right of the coupler (the safety chain eye is on the opposite side of the coupler). The fittings are Clippard MQC-3 quick connect and 11752-1 hose barb.
Photo above shows the fittings in more detail. The 11752-1 hose barb is on the left and all the other parts are the MQC-3 quick connect. The sill has a 1/4" deep hole threaded 5/16-24 . The hole to the inside of the threaded part is 3/8" diameter. The hose barb is threaded into the stud using thread sealant on the joint. The stud is screwed into the sill from the inside until it bottoms and then secured with the nut and lock washer. The remaining part with knurled end and hose barb is the connector for the hose that runs between the cars. The stud is equipped with a Schrader type valve which seals the brake line if there is no inter car hose connected.