Here is an animation of a CSA-1/CSA-2 Union Pacific Challenger. These two classes of 4-6-6-4 Challengers are known as the "Original Challengers" or "Light Challengers". The CSA-1's and 2's were powerful however they struggled to climb the Sherman Hill grade with a heavy train which could bring a train down to 20-30 MPH. The CSA-1's and 2's were eventually outclassed by CSA-3 and CSA-4 Challengers and 4-8-8-4 "Big Boy's". None of the CSA-1's or 2's survived the scrapper's torch. The only "Challengers" that survive today are CSA-3 #3985 which is currently undergoing restoration (It had been used in excursion service from 1985 to 2010), and CSA-3 #3977 which is on display at Cody Park, Nebraska. It is displayed in the UP's Greyhound livery (Which was distinctive to the Union Pacific's FEF 4-8-4's) and smoke deflectors (Which CSA-3 Challengers some were equipped with).
Thanks to @Porche911GTSR for his original vector drawing
