Instead of being underneath a piece of rolling stock, Jacobs bogies are placed between two carriages. The weight of each carriage is spread across the Jacobs bogie.[1] This arrangement provides the smooth ride of bogie carriages without the additional weight and drag.
Talgo trains use modified Jacobs bogies, that only use two wheels, and the wheels are allowed to spin independently of each other, eliminating hunting oscillation.
Background
Jakobs bogie of the Pioneer Zephyr (CB&Q 9900, Budd 1934)
The first fast train using this type of bogie was the German Fliegender Hamburger in 1932. In the United States, such configurations were used throughout the twentieth century with some success on early streamlined passenger trainsets, such as the Pioneer Zephyr in 1934, various Southern Pacific Daylight articulated cars, and Union Pacific Railroad's M-10000. Dallas Area Rapid Transit rail trains originally used a center bogie in a two-car unit but these have been modified to add a lower center section for handicapped level entry making a 3-car unit with two Jacobs bogies.
In Australia, Jacobs bogies were first used in 1984–85 on B class Melbourne trams, which were designed to run on two former suburban railways which had been converted to light rail operation.
Some triple-bogied two-section electric locomotives such as the NZR EW class have an articulated body supported on the centre bogie. Other types of Bo-Bo-Bo locomotives instead use a body shell that has enough allowance for sideplay in the central bogie.
Tram (streetcar)
The Jacobs bogie can be found in trams (streetcars) such as the Tatra K2 and Oslo's SL79. The first 100% low floor tram with pivoting bogies, the Škoda ForCity, also uses modified Jacobs bogies.
On this crossover between the tram (streetcar) and the high-speed train, Jacobs bogies occurred on the latest equipment of any significance, the two Electroliner trains (1941–1976). They were suited for streets with tight curves, the Chicago El and running through the countryside at approximately 140 km/h (87 mph). They served the Chicago–Milwaukee line and later the Philadelphia area.
Advantages
Safety, because the trains are less prone to collapse like an accordion after derailing. A Eurostar train has been recorded as having derailed at a speed close to 300 km/h with no resultant loss of life or severe injuries among its passengers.[4]
Lower weight and simpler and cheaper construction because bogies are heavy, expensive, and complex structures.
Less rail squeal and other wheel-to-rail noise because of fewer bogies.
Disadvantages
The cars of the vehicle/unit are semi-permanently coupled and can only be separated in the workshop. However, some flexibility may be achieved by coupling two or three units together into one train.
Fewer bogies and fewer wheelsets mean greater axle loads – if everything else is equal.
