Boxcar

Overview

The Boxcar is an enclosed railway freight car built to carry weather-sensitive general cargo such as paper, packaged goods, bagged commodities, machinery, and palletized freight. Unlike an open gondola or flatcar, a boxcar fully encloses its load behind steel walls and a sealed roof, so the lading is protected from rain, snow, sun, and wind throughout the trip. The car is built around a welded Underframe that carries an enclosed Body Shell shell, with one large Cargo Door System in each side wall for loading. Inside, a Lading Restraint System system braces the cargo against shifting. The car rolls on two Freight Bogie freight trucks, connects to the rest of the train through an AAR Coupler and Draft Gear, stops under a pneumatic Air Brake System, and carries the Safety Appliances crews need to climb and handle it. A typical 18.6 m car weighs around 29 tonnes empty and carries up to 100 tonnes of lading.

Underframe

The structural base is the Underframe, a welded steel frame that carries the body and transfers all train forces to the bogies. Its backbone is the Center Sill, a Z-section steel box running the full length of the car as the main draft and buff member, taking the pull of the train and the impact of shunting. Two Side Sill members run along the floor edges and support the body side posts. At each bogie position a cast Body Bolster carries the center plate that pivots on the truck. Across the frame, six Cross Bearer beams and a set of Floor Stringer longitudinals support the floor, while two reinforced Draft Sill sections form the coupler pockets at each end. The Car Floor is a nailable steel deck topped with laminated hardwood so forklifts and heavy pallets can work inside the car. A Fastener Set of rivets and structural bolts ties the frame together.

Body shell

The Body Shell is the enclosing weatherproof shell. Two Side Wall panels and two corrugated End Wall panels form the walls, stiffened by vertical Side Post members and tied at the corners by heavy Corner Post uprights. The corrugations in the end walls resist the longitudinal punch of lading that shifts forward during hard coupling. Overhead, the Roof Assembly assembly uses overlapping diagonal Roof Sheet panels carried on arched Roof Carline ribs and sealed at the eaves to shed water. Stamped Sheet Metal Panel sheets make up much of the wall and roof skin. A plywood Interior Lining protects the cargo from contact with the steel framing and from condensation that can drip off cold metal in transit.

Door system

Each side of the car carries one Cargo Door System, a wide sliding or plug door that opens the load space to forklift access. The Door Panel runs on a Door Track, suspended at the top by two Door Hanger roller brackets and guided at the bottom by Door Roller rollers. A plug door is pushed outward to clear the opening, then drawn back in and pressed tight by a cam Door Lock Gear gear, compressing a Door Gasket weather seal around the frame so the interior stays dry. The crew works the door with a Door Handle lever, and the same gear secures it against pilferage in transit. Door openings of around 3 m are common so that a standard pallet can pass through sideways.

Lading restraint

Because freight rides better when it cannot move, the Lading Restraint System system braces the load. Movable Load Divider bulkheads lock into Belt Rail anchor rails along the side walls, splitting the car into compartments and preventing the load from sliding lengthwise as the train accelerates and brakes. Tie-Down Strap webbing straps with ratchet tensioners run from the belt rails and from recessed Floor Anchor rings to hold pallets and crates down. Spring-loaded Dunnage Bar cross bars wedge between the walls to brace stacked freight at any height. Proper restraint keeps the cargo intact and keeps the car balanced so it tracks safely at speed.

Trucks and running gear

Each Freight Bogie is a three-piece freight truck. Two cast Truck Side Frame members are spanned by a single cast Truck Bolster that rests on a spring group and carries the car center plate. The truck holds two Wheelset wheelsets, each built from a forged Axle pressed with two monobloc Rail Wheel wheels turning on sealed Roller Bearing Cartridge cartridges. The spring group uses Coil Spring load springs, and a set of Friction Wedge wedges between the bolster and side frames damps the vertical motion so the car does not bounce or rock. Each truck also carries a Brake Beam that presses brake shoes onto the wheel treads.

Couplers, brakes, and safety

Cars are joined by the Coupler and Draft Gear, an AAR Type E knuckle coupler whose Coupler Head and pivoting Knuckle lock automatically when two cars are pushed together. The Coupler Shank runs back to a Draft Yoke and a Draft Gear unit that cushions the heavy buff and draft shocks of train handling, with the knuckle turning on a Knuckle Pin. Braking uses the Air Brake System system: a Control Valve watches the Brake Pipe trainline and, on a pressure drop, ports air from the Air Reservoir into the Brake Cylinder, which drives the Brake Rigging to clamp Brake Shoe shoes on the wheels. A Hand Brake holds the car when parked, and an O-Ring Set seals the pneumatics. Finally, the Safety Appliances make the car safe to handle: End Ladder ladders, Grab Iron hand-holds, Sill Step steps, and an Uncoupling Lever cut lever that lifts the knuckle pin from ground level. Together these subsystems let one boxcar carry up to 100 tonnes of dry, secured freight safely through a long-haul train.