HO4-6-6-4 CSA-2 Challenger Locomotive UP #3823 (ATHG-1025)

An HO-scale Challenger CSA-2 locomotive in Union Pacific livery, UP #3823, this model recreates ALCO’s 4-6-6-4 Challenger with CSA-2-class detail. It captures prototype features such as an Elesco feedwater heater, a large sand dome, a covered vertical-bar pilot, satin paint, and an oil burner, all rendered with period-accurate detail. The articulated design with pivoting front and rear engines lets the locomotive negotiate HO-layout curves, while current pickup on all driver wheels supports steady pulling power for passenger and fast-freight work on modern layouts.

On the track, it offers realistic operation with illuminated number boards and headlights, a tender back-up light, and authentic sounds that synchronize with movement. The model includes a detailed boiler backhead with printed gauges and a range of individually applied details, plus an upgraded loco-to-tender connection for durability. The minimum recommended radius is 22 inches, with pivoting trucks enabling operation on curves as tight as 18 inches. For sound-equipped versions, a tender-mounted DCC decoder with SoundTraxx Tsunami2 provides realistic engine, whistle and bell sounds, two cube speakers for rich audio, and full DCC compatibility with CV-based adjustments and the option to lash up multiple units.