Bogie

A bogie in the UK, or a railroad truck, wheel truck, or truck in North America, is a structure underneath a railway vehicle (wagon, coach, or locomotive) to which axles (hence, wheels) 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 (shortened from bogie wagon). The bogie was independently invented in the UK and the USA to address different problems. The first locomotive with a bogie was built by UK engineer William Chapman in 1812. Purpose to more closely follow the direction of the rails when travelling around a curve in the railroad. Bogies serve a number of purposes: • supporting the body of the rail vehicle • running stably on both straight and curved tracks • 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. Instability can occur when a combination of bogie design, springing, vehicle and bogie wheelbase, and track dynamics, causes the bogie to oscillate at high speed – a phenomenon known as "hunting". If unchecked, derailment can occur. Cars exhibiting hunting are removed immediately upon discovery of the defect. A tendency for more than one vehicle to hunt will result in investigations with a view to re-designing. Usually, two bogies are fitted to each carriage, wagon or locomotive, one at each end. Another configuration is often used in articulated vehicles, in which the bogies (often Jacobs bogies) are placed under the connection between the carriages or wagons. Most bogies have two axles, The journal boxes house plain bearings. Key components of a bogie include: Steam On a steam locomotive, the leading and trailing wheels may be mounted on bogies like Bissel trucks (also known as pony trucks). Articulated locomotives (e.g., Fairlie, Garratt or Mallet 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 to another track gauge. Transporter wagons apply the same concept at the level of a flatcar specialized to carry other cars as its load. Archbar bogies In archbar or diamond frame bogies, the side frames are fabricated rather than cast. File:Oigawa-Archbar-Truck.jpg|Japanese archbar bogie with axleboxes File:Diamond Frame bogie (elliptical).jpg|Diamond frame bogie, elliptical springs and American style journal boxes File:Diamond Frame bogie (coil).JPG|Diamond frame bogie, coil springs and journal boxes File:archbar ACL143.JPG |Archbar bogie with journal bearings in American-style journal boxes, as used on some steam locomotive tenders. Archbar bogies (trucks) were also used on freight cars. Tramway Modern 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 seldom 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 the articulations, a setup known 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 greater wear on both track and wheels and significantly reduces the speed at which a tram can round a curve. Historic In the past, many different types of bogies (trucks) have been used under tramcars (e.g., Brill, Peckham, maximum traction). A maximum traction truck has one driving axle with large wheels and one non-driving axle with smaller wheels. The bogie pivot is located off-centre, so more than half the weight rests on the driving axle. Hybrid systems of the pneumatic bogie system of an MP 89 carriage used on the Meteor metro, showing the two special wheelsets 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. == 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 pivoting as a whole. 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 wheelsets actively steer through curves, thereby 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:CP9112 SD90MAC.jpg|EMD HTCR radial steering trucks on an EMD SD9043MAC File:FSRR 01.jpg|GE radial steering trucks on a GE AC4400CW 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. == Articulated bogie ==

Siemens Desiro VT642 An articulated bogie (aka Jakob-type) is any one of several bogie designs that reduce weight, increase passenger comfort, and allow railway equipment to safely turn sharp corners, while reducing or eliminating the "screeching" normally associated with metal wheels rounding a bend in the rails. There are several such designs, and the term is also applied to train sets that incorporate articulation within the vehicle, rather than in the bogies themselves. If one considers a single bogie "up close", it resembles a small railcar with axles at either end. The same effect that causes the bogies to rub against the rails at a longer radius causes each of the pairs of wheels to rub on the rails and cause the screeching. Articulated bogies add a second pivot point between the two axles (wheelsets) to allow them to rotate to the correct angle even in these cases. == 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). == Tracked vehicles ==

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 a sprung suspension to smooth the ride over rough terrain. Bogie suspensions keep many 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. == Aircraft bogies ==