A Boxpok is a steam locomotive

Steam locomotive

A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

 wheel

Wheel

A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

 that gains its strength through being made of a number of box sections rather than having traditional solid spoke

Spoke

A spoke is one of some number of rods radiating from the center of a wheel , connecting the hub with the round traction surface....

s (the name is a variation on "box-spoke"). Being hollow, they allow better counterbalancing than conventional drivers, which is important for fast locomotives. The Boxpok wheel was patented by General Steel Castings

General Steel Castings

The General Steel Castings Corporation was a steel casting corporation in the United States established in 1928by the Baldwin Locomotive Works, American Locomotive Company, and American Steel Foundries....

 Corporation of Granite City

Granite City, Illinois

Granite City is a city in Madison County, Illinois, United States, part of the Greater St. Louis metropolitan area. At the 2010 census, the population was 29,849, making it the third largest city in the Metro-East and Southern Illinois, behind Alton and Belleville...

, Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

.

Bulleid Firth Brown (BFB) wheels designed by Oliver Bulleid

Oliver Bulleid

Oliver Vaughan Snell Bulleid was a British railway and mechanical engineer best known as the Chief Mechanical Engineer of the Southern Railway between 1937 and the 1948 nationalisation, developing many well-known locomotives.- Early life and Great Northern Railway :He was born in Invercargill,...

 and Firth Brown were a later variation through a separate patent where a lighter wheel was obtained by using a strengthened rim.

One of its major advantages over a spoked wheel is the more uniform support provided to the tyre.