Train wheel in the context of "Track (rail transport)"

An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle is supported. In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. Sometimes, especially on bicycles, the latter type of axle is referred to as a spindle.

A wheelset is a pair of railroad vehicle wheels mounted rigidly on an axle. Wheelsets are often mounted in a bogie ("truck" in North America) – a pivoted frame assembly holding at least two wheelsets – at each end of the vehicle. Most modern freight cars and passenger cars have bogies each with two wheelsets, but three wheelsets (or more) are used in bogies of freight cars that carry heavy loads, and three-wheelset bogies are under some passenger cars. Four-wheeled goods wagons that were once near-universal in Europe and Great Britain and their colonies have only two wheelsets; in recent decades such vehicles have become less common as trainloads have become heavier.

A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength (as the flange of a steel beam such as an I-beam or a T-beam); for easy attachment/transfer of contact force with another object (as the flange on the end of a pipe, steam cylinder, etc., the circular or oval flange for securing truck and trailer tail lights, or on the lens mount of a camera); or for stabilizing and guiding the movements of a machine or its parts (as the inside flange of a rail car or tram wheel, which keep the wheels from running off the rails). Flanges are often attached using bolts in the pattern of a bolt circle.

Flanges play a pivotal role in piping systems by allowing easy access for maintenance, inspection, and modification. They provide a means to connect or disconnect pipes and equipment without the need for welding, which simplifies installation and reduces downtime during repairs or upgrades. Additionally, flanges facilitate the alignment of pipes, ensuring a proper fit and minimizing stress on the system.

Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer during both world wars. It produced battleships, U-boats, tanks, howitzers, guns, utilities, and hundreds of other commodities. The company also produced steel used to build railroads in the United States and to cap the Chrysler Building.

After the Nazis seized power in Germany, Krupp supported the regime and was one of many German businesses that profited from slave labor during World War II. Upon the war's end, the head of the company, Alfried Krupp, was tried and convicted as a war criminal for employing prisoners of war, foreign civilians and concentration camp inmates under inhumane conditions in support of the Nazi war effort. Despite being sentenced to imprisonment for twelve years, he served just three and was pardoned (but not acquitted) by John J. McCloy. As a result of this pardon, all of Krupp's holdings were restored.