HO4-6-6-4 CSA-1 Challenger Locomotive UP #3907 (ATHG-1024)

An HO-scale Challenger CSA-1 four-axle articulated locomotive representing Union Pacific’s 1936 Challenger class, UP 3907. Built by ALCO, these engines combined power with speed for fast freights and even passenger service, and this model captures that commanding presence with satin paint and authentic detailing. It’s designed to serve as a historically informed centerpiece for a mid‑century UP‑era layout.

Beyond its authentic appearance, the model is engineered for engaging operation: illuminated number boards and headlights, a tender light, and current pickup from all driving wheels for reliable pulling power. The front and rear engines pivot to negotiate 18-inch radius curves, with a 22-inch minimum radius recommended for smooth running. For sound enthusiasts, a tender-mounted DCC decoder with SoundTraxx Tsunami2 delivers synchronized chuff, whistle, bell, and more through dual cube speakers, and it runs in both DC and DCC modes with full NMRA compatibility in DCC. CV adjustments support MU lashups and fine-tuning, and an upgraded loco‑to‑tender harness enhances durability and serviceability.