in the UK, or a railroad truck
, wheel truck
, or simply truck
in North America, is a structure underneath a train to which axles (and, hence, wheels) are attached through bearing. In Indian English, bogie may also refer to an entire railway carriage.http://www.oxfordadvancedlearnersdictionary.com/dictionary/bogie
The first British railway to build coaches with bogies, instead of rigidly mounted axles, was the Midland Railway in 1874.
Bogies serve a number of purposes:
- Support of the rail vehicle body.
- Stability on both straight and curved track.
- Ensuring ride comfort 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. An alternate configuration often is used in articulated vehicles, which places the bogies (often jacobs bogies) under the connection between the carriages or wagons.
Most bogies have two axles, as this is the simplest design, but some cars designed for extremely heavy loads have been built with up to five 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 car may be lower between bogies, such as for a double decker train to increase interior space while staying within height restrictions, or in easy-access, stepless-entry, low-floor trains.
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 (more commonly) 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, or rubber airbags.
- At least one wheelset, composed of an axle with a bearing and wheel at each end
- 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 or a hydraulically powered torque converter
The connections of the bogie with the rail vehicle allow a certain degree of rotational movement around a vertical axis pivot (bolster), with side bearers preventing excessive movement. More modern, bolsterless bogie designs omit these features, instead taking advantage of the sideways movement of the suspension to permit rotational movement.
The British Railways Mark 1 coach brought into production in 1950 used the BR1 bogie, which was rated to run at . The wheels were cast as a one-piece item in a pair with their axle. The simple design involved the bogie resting on four leaf springs (one spring per wheel), which in turn were connected to the axles. The leaf springs were designed to absorb any movement or resonance and to have a damping effect to benefit ride quality.
Each spring was connected to the outermost edge of the axle by a roller bearing contained in oil-filled axle box. The oil had to be topped up at regular maintenance times to avoid the bearing running hot and seizing.
There was also a heavy-duty version designated BR2.
thumb|Commonwealth bogie as used on BR Mark 1 and CIE Park Royals
The Commonwealth bogie, manufactured by the English Steel Corporation under licence from the Commonwealth Rail Company in America. Fitted with SKF or Timken bearings, it was introduced in the late 1950s for all BR Mark 1 vehicles. It was a heavy, cast-steel design weighing about , with sealed roller bearings on the axle ends, avoiding the need to maintain axle box oil levels.
The leaf springs were replaced by coil springs (one per wheel) running vertically rather than horizontally. The advanced design gave a better ride quality than the BR1, being rated for .
The side frame of the bogie was usually of bar construction, with simple horn guides attached, allowing the axle boxes vertical movements between them. The axle boxes had a cast-steel equaliser beam or bar resting on them. The bar had two steel coil springs placed on it and the bogie frame rested on the springs. The effect was to allow the bar to act as a compensating lever between the two axles and to use both springs to soften shocks from either axle. The bogie had a conventional bolster suspension with swing links carrying a spring plank.
thumb|B4 bogie as used on BR Mark 2 and Irish Cravens
The B4 bogie was introduced in 1963. It was a fabricated steel design versus cast iron and was lighter than the Commonwealth, weighing in at . It also had a speed rating of .
Axle/spring connection was again with fitted roller bearings. However, now two coil springs rather than one were fitted per wheel. Unofficial West Somerset Railway website - Bogies
Only a very small number of Mark 1 stock was fitted with the B4 bogie from new, it being used on the Mark 1 only to replace worn BR1 bogies. The British Rail Mark 2 coach, however, carried the B4 bogies from new. A heavier-duty version, the B5, was standard on Southern Region Mk1-based EMUs from the 1960s onwards. Some Mark 1 catering cars had mixed bogies—a B5 under the kitchen end, and a B4 under the seating end. Some of the B4-fitted Mark 2s, as well as many B4-fitted Mark 1 BG were allowed to run at with extra maintenance, particularly of the wheel profile, and more frequent exams.
thumb|BT10 high-speed bogie as used on MK3
The BT10 bogie was introduced on the British Rail Mark 3 coach in the 1970s. Each wheel is separately connected to the bogie by a swing-arm axle.
There is dual suspension:
- primary suspension via a coil spring and damper mounted on each axle
- secondary suspension via two air springs mounted on the pivot plank, this is connected to the bogie by pendulum links. A constant coach height is maintained by air valves. Roger Barnett - British Rail’s InterCity 125 and 225
Diesel and electric
Most diesel locomotives and electric locomotives are carried on bogies (trucks - US). Trucks used in the USA include AAR type A switcher truck, Blomberg B, HT-C truck and Flexicoil.http://www.hosam.com/emd/emd6a.html
On a steam locomotive, the leading wheels and trailing wheels may be mounted on bogies. Articulated locomotives (e.g. the Fairlie) have power bogies
similar to those on diesel and electric locomotives.
thumb|Side view of a K-Car bogie]
Tram 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 and 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. The only 100% low-floor tram with pivoting bogies - Škoda ForCity - uses the Jacobs bogie.
In the past, many different types of bogie (truck) have been used under tramcars, e.g. "Brill", "Peckham" and "maximum traction". 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.
thumb| of the pneumatic bogie system of a MP 89 carriage used on the Meteor
metro, showing the two special wheelsets]
The retractable stadium roof on Toronto's Roger's 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 (VGA) so that they can operate on two different gauges. These include the SUW 2000 system from ZNTK Poznań.
The Cleminson system is not a true bogie, but serves a similar purpose. It was based on a patent of 1883 by James Cleminson,http://www.icevirtuallibrary.com/docserver/fulltext/imotp.1897.19461.pdf?expires=1315520526&id=id&accname=guest&checksum=AD521ED02561C3CF38D1772ECF1ACA2B and was once popular on narrow-gauge rolling stock, e.g. on the Isle of Man and Manx Northern Railways. The vehicle would have three axles and the outer two could pivot to adapt to curvature of the track. The pivoting was controlled by levers attached to the third (centre) axle, which could slide sideways.http://www.festipedia.org.uk/wiki/Cleminson_Flexible_Six-Wheeled_Waggon
Some tanks and other tracked vehicles have bogies as external suspension components (see armoured fighting vehicle suspension). This type of bogie usually has two or more road wheels and some type of sprung suspension to smooth the ride across rough terrain. Bogie suspensions keep much of their components on the outside of the vehicle, saving internal space. Although vulnerable to antitank fire, they can often be repaired or replaced in the field.
Articulated lorries (tractor-trailers)
In trucking, a bogie is the subassembly of axles and wheels that supports a semi-trailer, whether permanently attached to the frame (as on a single trailer) or making up the dolly that can be hitched and unhitched as needed when hitching up a second or third semi-trailer (as when pulling doubles or triples).
From Wikipedia, the free encyclopedia