Union Pacific ® 4-6-6-4 Challenger Steam Locomotive

By Hans Riddervold

Making the Challenger in Z scale is finally completing the 1996 dreams of former Small Scale Works where I was a shareholder. I am extremely excited about our upcoming release and AZL and AJIN are working hard with the engineering details at the moment.

UP selected ALCO as the producer for their big Challengers and acquired a total of 105 which were delivered in 5 batches from 1936 to 1944. The AZL release will not include the two first batches since these locomotives were quite different from the later 3 batches. The 3 last batches were delivered from 1941 on and used the following road numbers:

courtesy Union Pacific

3950 – 3969 (1941) / 3975 – 3999 (1943) / 3930 – 3949 (1944)

The locomotives made for D&RGW used road numbers 3800 – 3805. After WWII these Challengers were sold to Clinchfield which renumbered the locomotives to 670 – 675 and also converted the Challengers to single stacks.

AZL will basically produce three different versions of the UP Challengers and the one D&RGW version. There is much written about whether the Challengers were coal or oil fired and the answer is both. When delivered, all Challengers were coal burners, but a coal strike in 1952 had Union Pacific convert some to oil burners. It is rumored that the conversion job only took one day! The bulk of the AZL UP Challengers will represent coal burners in black livery. UP also repainted some Challengers in a two tone grey and mounted smoke reflectors (ears) and this version will also be made. The last version will be today’s only operational Challenger, road number 3985. This locomotive has been converted to an oil burner and will show these changes on the tender. Speaking of the tender, UP standardized the tender for their last big steam locomotives, thus the Big Boy (4-8-8-4) and the FEF (4-8-4) all used the same “Centipede” tender as the Challenger.

Where did the UP Challengers operate? Unlike the Big Boy’s which only operated out of Cheyenne (WY), the Challengers were used on UP’s main routes in the West. UP used the Challengers for freight as well as passenger service.

AZL hope to show some Challenger metal at the NTS in July, but we might be a little ahead of ourselves. In the meantime check out the two remaining UP Challengers. 3985 is scheduled for several runs this year and 3977 is on static display in North Platte, Nebraska.

Yours Sincerely,
Hans Riddervold

Rail Miniatures