In the Whyte notation for classifying steam locomotives by wheel arrangement, a 4-6-6-4 is a railroad steam locomotive that has four leading wheels followed by two sets of six coupled driving wheels and four trailing wheels. 4-6-6-4's are commonly known as Challengers.

The Union Pacific Challengers are a type of simple articulated 4-6-6-4 steam locomotive built by American Locomotive Company (ALCO) from 1936 to 1944 and operated by the Union Pacific Railroad until the late 1950s.

Nov 4, 2024 · The 4-6-6-4 represented the zenith of steam locomotive innovation. It was equipped with state-of-the-art features including roller bearings on all axles—both engine and tender—a massive boiler, and a sizable firebox.

The Union Pacific Railroad took delivery of the very first locomotive with the 4-6-6-4 wheel arrangement in 1936 when it received 15 of them from the American Locomotive Company. These newly named "Challengers" were designated Class CSA-1.

Feb 1, 2023 · The 4-6-6-4 Challenger was the most successful articulated steam locomotive design. Union Pacific Challenger 3953 rounds a curve near Sherman, Wyo., highest point on the Overland Route at 8,013 feet, with an eastbound freight in 1951.

4-6-6-4 "Challenger" Locomotives in the USA In the 1930s, with freight traffic increasing, the Union Pacific Railroad had to use combinations of its 2-8-8-0 and 2-10-2 locomotives to get trains over the rugged grades of the Wahsatch Mountains.

Jun 13, 2006 · Hence, the new locomotive would be a 4-6-6-4. Union Pacific Challenger No. 3976 was one of six coal-burning 4-6-6-4s later converted to oil and assigned to passenger train service. In 1946, the engine received smoke deflectors and a …

These locomotives had (4) 23 x 32 cylinders, 69" drivers, a 250 psi boiler pressure, exerted 104,500 lbs of tractive effort and weighed 621,000 pounds. Numbers 900 and 901 were sold to the Great Northern Railroad shortly after they arrived in 1937.

Clinchfield Challenger 4-6-6-4 Locomotives The Clinchfield had a total of 18 Challengers, but in the time before they were purchased, CRR had owned and operated many articulated engines. These larger engines allowed the Clinchfield to move longer and …

Feb 20, 2020 · Union Pacific 4-6-6-4 Challenger type steam locomotive No. 3985 pulls an excursion in Iowa in 2002. •MANUFACTURERS: Alco, Baldwin. •NAME: Challenger. •QUANTITY: 252; Union Pacific had the most with 105. •BOILER PRESSURE: 255-280 psi. •KNOWN FOR: High speed freight and passenger service.