NRE 3GS21B Genset

These are N scale 3D printable files for the National Railway Equipment (NRE) 3GS21B Genset locomotive in Union Pacific Railroad markings — one of the most innovative and environmentally significant locomotive designs of the 21st century. Designed to fit on an Atlas B23-7 frame. Includes UP decals.

The Genset locomotive concept was developed in the 2000s as a direct response to increasingly stringent EPA Tier emissions regulations targeting diesel locomotive exhaust in urban and industrial areas. Traditional switcher and local freight locomotives run a single large prime mover continuously, even when only a fraction of its power is needed — resulting in high fuel consumption and emissions during the low-power switching and idling operations that dominate yard and industrial work. The Genset solution was elegantly simple: instead of one large engine, use multiple smaller, cleaner diesel generator sets that can be started and stopped individually as power demand changes, dramatically reducing fuel consumption and emissions during light-duty operations.

The NRE 3GS21B — the "3" denoting three generator sets and "21B" referring to the 2,100 horsepower total output — was built by National Railway Equipment Company of Mount Vernon, Illinois, one of the leading independent locomotive manufacturers and rebuilders in North America. The three individual generator sets can operate independently, with the locomotive's control system automatically bringing additional sets online as tractive effort demands increase and shutting them down when power requirements drop — a form of locomotive load management that was revolutionary for its time.

Union Pacific was one of the largest operators of Genset locomotives in North America, deploying them extensively in its California yards and industrial switching operations where South Coast Air Quality Management District (SCAQMD) and other regional air quality regulations made low-emission switching power a practical necessity. The UP's 3GS21B units worked the dense industrial switching territory of Los Angeles, the Inland Empire, and the San Francisco Bay Area, quietly revolutionizing yard operations one generator set at a time.

After purchase, your digital files will be available for immediate direct download from your order confirmation. These files are for Personal Use Only — if you are interested in a commercial license, please contact us.

Please allow a few weeks for 3D printing and shipping. Decals are shipped separately — please allow some additional time for decal printing and shipping after ordering.