Cowl unit

A cowl unit, in the context of rail transport, typically refers to a type of locomotive design where the body is fully enclosed, resembling a tunnel or cowl. This contrasts with older locomotive designs where much of the internal machinery was exposed.

The primary characteristic of a cowl unit is its full-width carbody construction, which extends the entire width of the locomotive and covers the majority of the internal components, including the engine, generators, and other equipment. This enclosed design offers several advantages, including:

• Improved aerodynamics: The smooth, streamlined shape of a cowl unit can reduce wind resistance, improving fuel efficiency and performance at higher speeds.
• Enhanced crew safety: The enclosed cab provides greater protection for the crew in the event of an accident. The structural integrity of the full-width carbody helps to shield the crew from impacts.
• Reduced noise: The enclosure helps to dampen the noise generated by the locomotive's machinery, both inside the cab and externally.
• Better weather protection: The enclosed design protects the internal components from the elements, reducing the risk of damage and improving reliability.
• Improved aesthetics: Many consider cowl units to be more aesthetically pleasing than older, more utilitarian locomotive designs.

Cowl units are commonly used in passenger service, where speed, comfort, and appearance are important considerations. They can also be found in freight service, where the benefits of improved aerodynamics and weather protection are valuable. While the term "cowl unit" is generally understood, it is not always consistently applied, and sometimes the terms "carbody locomotive" or simply "covered wagon" are used interchangeably, albeit "covered wagon" can refer to older, less aerodynamic designs as well. The specific features and benefits of a cowl unit can vary depending on the manufacturer and the intended application.