What is Rack Railway
In case of steep gradient, a system or an arrangement, known as the rack or sometimes it is called a rack and pinion, which is provided to haul a train along such steep gradients. Therefore, this allows the trains to run above 10% on steep grades.
In this system, the track consists of three rails, two running rails and a third toothed rack rail usually, adopted between two running rails.
The train is provided with a toothed pinion-wheel, the teeth of which fit into the teeth of the central toothed rail.
There are various systems of rack and pinion for railways such as fell system, Marsh system, Riggenbach, Strub system and Abt system.
Marsh system was the first successful invention of the rack railway system. This system was invented by Sylvester Marsh in 1861.
Today, the most popular and usable system is abt system. This system was invented by a Swiss engineer Dr. roman abt in 1885.
Rack system reduces the speed limit of the trains. But on very steep gradients, the use of rack is essential. It is surprising to know that a gradient, as steep as 1 in 2, is adopted with the help of this system.
In India, a distance from Kullar to Coonoor around 19 km on Nilgiri Mountain Railway, is constructed and operated by using abt system, and the gradient on this track is 1 in 12.5. The maximum allowable speed on this track is 13 km/h.