Bogie
A bogie comprises two or more wheelsets, in a frame, attached under a vehicle by a pivot. Bogies take various forms in various modes of transport. A bogie may remain normally attached or be quickly detachable. It may include suspension components within it, or be solid and in turn be suspended. It may be mounted on a swivel, as traditionally on a railway carriage or locomotive, additionally jointed and sprung, or held in place by other means.
Although bogie is the preferred spelling and first-listed variant in various dictionaries, bogey and bogy are also used.
Railway
A bogie in the UK, or a railroad truck, wheel truck, or simply truck in North America, is a structure underneath a railway vehicle to which axles are attached through bearings. In Indian English, bogie may also refer to an entire railway carriage. In South Africa, the term bogie is often alternatively used to refer to a freight or goods wagon.The bogie was invented independently in the UK and USA to solve different problems. The first locomotive with a bogie was built by UK engineer William Chapman in 1812. However there was no great demand because railroads in the UK at the time tended to be very straight which English engineers saw as the most efficient way get between two points. In the USA the terrain was more challenging and curved lines were a necessity. The bogie was first used in America for horse-drawn wagons on the Quincy Granite Railroad in 1829. The first successful locomotive with a bogie to guide the locomotive into curves while also supporting the smokebox was built by John B. Jervis in 1831. In 1834, the American Ross Winans independently patented a bogie configuration for the rail car, allowing cars that had no practical limit in length, since he had two bogies, each with two-axles, each mounted at opposite ends of the car, on a swivel attached to the undercarriage. This led to a whole new form of rail car that likes of which are recognizable today, they are long cars, not the short stagecoach cars which were initially required to keep the distance between axles short. These long cars carry more weight because the eight wheels distribute the load, smooth out the ride due to the independent suspension, and reduce friction on curves. The B&O railroad, who Winans contracted with, was the first to adopt bogie rail cars in the 1830s. It took a while for the "American" style car to catch on in England. The first use of bogie coaches in Britain was in 1872 by the Festiniog Railway. The first standard gauge British railway to build coaches with bogies, instead of rigidly mounted axles, was the Midland Railway in 1874.
Purpose
Bogies serve a number of purposes:- supporting the body of the rail vehicle
- running in a stable manner on both straight and curved track
- improving ride quality by absorbing vibration and minimizing the impact of centrifugal forces when the train runs on curves at high speed
- minimizing generation of track irregularities and rail abrasion.
Usually, two bogies are fitted to each carriage, wagon or locomotive, one at each end. Another configuration is often used in articulated vehicles, which places the bogies under the connection between the carriages or wagons.
Most bogies have two axles, but some cars designed for superior riding qualities or heavy loads have more axles per bogie. Heavy-duty cars may have more than two bogies using span bolsters to equalize the load and connect the bogies to the cars.
Usually, the train floor is at a level above the bogies, but the floor of the area between the bogies may be lowered to increase interior space while staying within height restrictions. Examples are container well cars, bi-level passenger cars or stepless-entry, low-floor cars on railways with near-ground-level platforms.
Components
Key components of a bogie include:- The bogie frame: This can be of inside frame type where the main frame and bearings are between the wheels, or of outside frame type where the main frame and bearings are outside the wheels.
- Suspension to absorb shocks between the bogie frame and the rail vehicle body. Common types are coil springs, leaf springs and rubber airbags.
- At least one wheelset, composed of an axle with bearings and a wheel at each end.
- The bolster, the main crossmember, connected to the bogie frame through the secondary suspension. The railway car is supported at the pivot point on the bolster.
- Axle box suspensions absorb shocks between the axle bearings and the bogie frame. The axle box suspension usually consists of a spring between the bogie frame and axle bearings to permit up-and-down movement, and sliders to prevent lateral movement. A more modern design uses solid rubber springs.
- Brake equipment: Two main types are used: brake shoes that are pressed against the tread of the wheel, and disc brakes and pads.
- In powered vehicles, some form of transmission, usually electrically powered traction motors with a single speed gearbox or a hydraulically powered torque converter.
Locomotives
Diesel and electric
Modern diesel and electric locomotives are mounted on bogies. Those commonly used in North America include Type A, Blomberg, HT-C and Flexicoil trucks.Steam
On a steam locomotive, the leading and trailing wheels may be mounted on bogies like Bissel trucks. Articulated locomotives have power bogies similar to those on diesel and electric locomotives.Rollbock
A rollbock is a specialized type of bogie that is inserted under the wheels of a rail wagon/car, usually to convert for another track gauge. Transporter wagons carry the same concept to the level of a flatcar specialized to take other cars as its load.Archbar bogies
In archbar or diamond frame bogies, the side frames are fabricated rather than cast.Tramway
Modern
bogies are much simpler in design because of their axle load, and the tighter curves found on tramways mean tram bogies almost never have more than two axles. Furthermore, some tramways have steeper gradients and vertical as well as horizontal curves, which means tram bogies often need to pivot on the horizontal axis, as well.Some articulated trams have bogies located under articulations, a setup referred to as a Jacobs bogie. Often, low-floor trams are fitted with nonpivoting bogies; many tramway enthusiasts see this as a retrograde step, as it leads to more wear of both track and wheels and also significantly reduces the speed at which a tram can round a curve.
Historic
In the past, many different types of bogie have been used under tramcars. A maximum traction truck has one driving axle with large wheels and one nondriving axle with smaller wheels. The bogie pivot is located off-centre, so more than half the weight rests on the driving axle.Hybrid systems
The retractable stadium roof on Toronto's Rogers Centre used modified off-the-shelf train bogies on a circular rail. The system was chosen for its proven reliability.Rubber-tyred metro trains use a specialised version of railway bogies. Special flanged steel wheels are behind the rubber-tired running wheels, with additional horizontal guide wheels in front of and behind the running wheels, as well. The unusually large flanges on the steel wheels guide the bogie through standard railroad switches, and in addition keep the train from derailing in case the tires deflate.
Variable gauge axles
To overcome breaks of gauge some bogies are being fitted with variable gauge axles so that they can operate on two different gauges. These include the SUW 2000 system from ZNTK Poznań.Radial steering truck
Radial-steering trucks, also known as radial bogies, allow the individual axles to align with curves in addition to the bogie frame as a whole pivoting. For non-radial bogies, the more axles in the assembly, the more difficulty it has negotiating curves, due to wheel flange to rail friction. For radial bogies, the wheel sets actively steer through curves, thus reducing wear at the wheel's flange-to-rail interface and improving adhesion.In the US, radial steering has been implemented in EMD and GE locomotives. The EMD version, designated HTCR, was made standard equipment for the SD70 series, first sold in 1993. The HTCR in operation had mixed results and relatively high purchase and maintenance costs. EMD subsequently introduced the HTSC truck, essentially the HTCR stripped of radial components. GE introduced their version in 1995 as a buyer option for the AC4400CW and later Evolution Series locomotives. However, it also met with limited acceptance because of its relatively high purchase and maintenance costs, and customers have generally chosen GE Hi-Ad standard trucks for newer and rebuilt locomotives.
File:Glenelg Railway Company clerestory-roofed, 30-window passenger car with Cleminson underframe.jpg|thumb|350px|An American-built broad-gauge passenger car in South Australia, one of six fitted with Cleminson self-steering axles; pictured in 1890, ten years after their purchase
A 19th century configuration of self-steering axles on rolling stock established the principle of radial steering. The Cleminson system involved three axles, each mounted on a frame that had a central pivot; the central axle could slide transversely. The three axles were connected by linkages that kept them parallel on the straight and moved the end ones radially on a curve, so that all three axles were continually at right angles to the rails. The configuration, invented by British engineer John James Davidge Cleminson, was first granted a patent in the UK in 1883. The system was widely used on British narrow-gauge rolling stock, such as on the Isle of Man and Manx Northern Railways. The Holdfast Bay Railway Company in South Australia, which later became the Glenelg Railway Company, purchased Cleminson-configured carriages in 1880 from the American Gilbert & Bush Company for its broad-gauge line.