CE 515 Railroad Engineering

The Railroad Car and the TrainSource: Armstrong Ch 5 & 6,

AREMA Ch. 2.5

“Transportation exists to conquer space and time -”

The Railroad Car

• The essentials:– Car body– Bolsters– Suspension System– Bearings–Wheels

Photo: Cliff Cessna

Car Body

• This is the main part of the car that carries the cargo

• Many different types to carry different commodities

Photo: Cliff Cessna

Bolsters

• Car body rests on center plate on bolster

• Distribute weight evenly to springs on each side

Armstrong Fig. 5-3

Suspension System

• Heavy-duty springs are used for suspension

• Standard springs used with varying amounts of inner coils for heavier loads

• Springs compress 2½ to 4¼ inches when under load; more than this would affect couplings

Suspension System

Armstrong Fig. 5-4

Bearings and Wheels

• Springs are supported by a frame which connects directly to the axles

• Friction bearings used until 1963• Roller bearings replaced the friction

bearings– Reduced maintenance– Required for interchange service to other

railroads

• Wheels typically 33 or 36 in., based on weight (28 in. for some tall cars)

The Train – Putting It Together

• The essentials:– Power (previously discussed)– Couplers– Draft gear– Braking system

Couplers

• Federal Safety Appliance Act of 1893 required standardization for safety reasons

• Link-and-pin required going between cars

• Swinging-knuckle design chosen for standard

• Two types: E and F

Armstrong Fig. 6-1.

Draft Gear

• Used to cushion shock and strain on cars from movement

• Friction in system absorbs energy

• Most have a coupler travel of 5½ in., but some cars (mainly boxcars) have 9½ in. of give.

Armstrong Fig. 6-2

Braking System

• Most complex system on the train (and hardest to understand)

• Originally developed by George Westinghouse in 1872 (Westinghouse Air Brake Company or WABCO)

• Fail-safe system

Braking System

• Comprised of:– Brake pipe (connected by hoses

between cars)– ABDX valve (triple valve)– Auxiliary reservoir– Emergency reservoir– Brake cylinder

Braking System

• Brake pipe and system charged with air to 70-90 psi (110 psi on passenger trains)

• Once charged, all brake valves in “release” position

• Some leakage will occur such that each successive car will have less pressure

• This is called “brake pipe gradient” and must be less than 15 psi for entire train

• End-of-Train (EOT) device monitors brake pressure at the end of the train and radios information to locomotive cab

EOT/FRED

• Also called a FRED (Flashing Rear-End Device)

• If equipped with two-way communications, can be used to apply brakes from rear of train

From: www.translationdictionary.com

Applying Brakes

• Engineer reduces pressure in brake line

• Brakes apply on car next to locomotive

• Reduction in air pressure travels through train, one car to the next

• Can take several seconds for “signal” to reach end of train

Applying Brakes

• Assume train brake line has 70 psi• “Service application” – If the

engineer makes a 10 psi application:– Brake line pressure reduced to 60 psi– 10 psi of air flows from reservoir to

brake cylinder– Reservoir is 2.5 times larger than

cylinder– PV = nRT, so cylinder puts 25 psi on

brakes

Applying Brakes

- “Full Service Application” – Engineer makes a 20 psi application- Brake line pressure reduced to 50 psi- 20 psi x 2.5 = 50 psi in brake cylinder- Air pressure equalized, no further

reductions possible (valve on each car holds pressure on brakes until brake line pumped back up above 50 psi)

Other Trains

- Assuming brake line pressure of 90 psi- Full service application: 64.3 psi- Emergency application: 75 psi

- Assuming brake line pressure of 110 psi- Full service application: 78.6 psi- Emergency application: 91.7 psi

Emergency Application

- Engineer hits Emergency Brake (70 psi)- Opens release valve on locomotive fully- Sudden release of air recognized by

valve- Auxiliary and emergency reservoirs

dumped- Multiplier is now 5x- Do some math…- Pressure equalizes at 58.3 psi (vs. 50

psi)

Emergency Application

• Video: Amtrak in Michigan• Train was traveling at 70 mph at time

of impact• By my estimation on Google Maps,

the stopping distance is about ½ mile

New Ideas

• Distributed Power Units (DPUs)– Locomotives throughout train =

Release points throughout train = Faster application

– Assume 48 cars:1 - L------------------------------------------------½ - L------------------------*------------------------L1/3 - L----------------*----------------L----------------

New Ideas

• Electronically Controlled Pneumatic (ECP)Brakes– Electronic signal activates brakes on

each car nearly instantly (speed of light)– Flaw: Every car on the train must have

wiring and electronic controls

Questions?

Crash of Train 173, the Federal Express, January 14, 1953. From: wikipedia.org