Gravity railroad
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- For theoretical Gravity railroads of the future, see Gravity train
A Gravity railroad (US) or Gravity railway (UK) is a railroad on a slope that allow cars carrying minerals or passengers to coast down the slope by the force of gravity alone. The cars are then hauled back up the slope using animal power or a stationary engine and a cable, chain or one or more wide, flat iron bands. The speed of the cars is controlled by braking mechanism on one or more cars on the train. The typical amusement park roller coaster is designed from gravity railroad technology.
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[edit] Types of gravity railroad
Some gravity railroads were designed to allow the weight of the descending loaded cars to lift the empty cars back up to the top, using a cable looped around a pulley at the top for a portion of the line. A later revision designed by John B. Jervis, used two separate tracks known as the loaded or heavy track going down hill, and the light track, used to haul the empty cars back to the top. This method allowed cars to travel in one direction without the need for passing sidings. A stationary steam engine and a looping cable, chain or iron bands were used to raise the empty cars up the lift planes. The cars then coasted down a slight grade to the next lift plane. When cars reversed direction at the ends of the line on a switch or turnout, the railroad was known as a switchback gravity railroad.
[edit] Switchback gravity railroad
The term "switchback gravity railroad" was also sometimes applied to gravity railroads that used special self-acting (momentum-driven) Y-shaped switches known as switchbacks to automatically reverse a car's direction at certain points during normal travel along the line, rather than at the line's end. For example, if two such switches were used, an overhead view of that section of the line could resemble the letter Z. Several implementations of this system existed at various times on the Mauch Chunk Switchback Gravity Railroad, and were very popular with the passengers. This railroad hauled coal and passengers from 1827 until 1933, and might possibly be restored.
[edit] Self-acting incline
In the UK, a self-acting incline is one in which the loaded wagons going down pull, via a cable and drum, the empty wagons going up. There might be two separate tracks, or a single track with a passing loop. This system was widely used on slate railways in Wales.
A variation on this system is the cliff railway for passengers. Both passenger cars are equipped with water tanks and, at the start, both tanks are full. Water is then let out of the tank on the lower car until the difference in weight between the two cars causes them to move.
[edit] Examples
[edit] United Kingdom
The Ffestiniog Railway in Gwynedd, northwest Wales, was built in 1832 to carry slate from quarries high in the hills to the sea at Porthmadog. The line was laid out for the wagons to descend by gravity, while horses were originally used to haul the empty wagons up the hill. On the downward journey the horses travelled in a Dandy waggon at the rear of the train. Later on, steam haulage was adopted. This narrow gauge railway is still operational but all trains are now locomotive-hauled.
[edit] United States
In the United States, The Delaware and Hudson Canal Company operated extensive gravity railroad system from 1828 until 1898. With 22 separate lift planes, the 55-mile (88 km) Pennsylvania Coal Company Gravity Railroad, was the longest and operated until 1885. A portion of the railroad was purchased in 1886 by the recently constructed, 1882, Shohola Glen Summer Resort and used until 1907.
[edit] Other inclined railroads
A funicular is not a true gravity railroad, as cars never coast freely and are always connected to a cable. A rack-and-pinion railway or rack railway is also not a true gravity railroad for similar reasons.
