Union Pacific developed five types of challengers: the light CSA - 1 and CSA - 2 classes and the heavy for 664 - 3, 46644, and 46645 classes. The railroad stop powerful locomotive that can handle Mountain grades at high speeds. Previous articulated locomotive have been limited to slow speeds by their design. Technical breakthroughs allowed the u p challengers to operate with 280 lbf/in of boiler pressure, something usually reserved for passenger locomotives like the fef series.Speeds in excess of 60 miles per hour, while unheard-of on other railroads using articulated steam locomotives, became commonplace on the UP. This Rivarossi model reproduces the prototype 1597 clinchfield number 670 manufactured in 1995. Although this model is brand new and has never seen a track it will need tuned up and oiled to properly operate. The item "NIB Rivarossi 1597 Clinchfield 4-6-6-4 Challenger Steam Locomotive #670 HO Scale" is in sale since Saturday, August 1, 2020. This item is in the category "Toys & Hobbies\Model Railroads & Trains\HO Scale\Locomotives". The seller is "diamondlinkz" and is located in Lacey, Washington. This item can be shipped worldwide.