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Union Pacific FEF 844 Black (4-8-4)

and the UP FEF 837 (Greyhound)

The Union Pacific FEF 844 is recognized by train aficionados around the world as one of the most significant US steam locomotives still operational, next to the Challenger 3985.  Aster Hobby Co. Inc. is now designing a pilot model of  the FEF 844 which will equal or better in detail, performance and appeal with any earlier released Aster US prototype model. Aster Hobby USA LLC will again play a support roll in this development.  

The UP FEF 844 was built in black (as preserved today and pictured above) and in "Greyhound" livery # 837.

Happy to report that the UP FEF

have now been shipped to those who made reservations .

A few are available in inventory, we welcome your inquiry!



Aster UP FEF / UP FEF3 #844


a video preview


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UP FEF - Pete Comley's "Portland Rose"


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About the Prototype

The first 20 engines of this class numbered 800-819 were delivered to the Union Pacific from ALCO in 1938. These were to replace the then dominating 4-8-2 UP steam power with increased efficiency and higher operating speeds. A further 15 units numbered 820-834 followed a year later, equipped with larger cylinders , larger drivers and "centipede" tenders instead of the original 6 axle tenders.  

These locomotives were referred to simply as FEF's which stands for "four-eight -four" which is their wheel arrangement. The first batch of 20 engines became the FEF-1's, the second order FEF-2's and the final batch of ten engines  delivered in 1944 were FEF-3's , numbered 835 - 844.  

The FEF's were coal and oil fired depending on their division assignment. The war effort converted many oil fired engines to coal, then back to oil firing again after war's end. These locomotives were able to operate at 100 mile sustained speeds on designated sections of track. The newly designed tapered coupled rods with forked rod ends and separate sleeved bearings better absorbed the thrust and pull forces of the fast reciprocating mass of steel. The operational speed for this design was limited to 110 miles per hour.  

The FEF's were primarily entrusted with express trains carrying passengers, mail and perishable goods. In the mid 1950's Diesels started to appear more frequently on the head ends of such trains and the FEF's eventually retired from service, most of them going directly to the scrap yard. However, publicity conscious Union Pacific saved engine 844 and kept here serviceable until today for frequent performances with steam fans and other public relations service. Other UP FEF's escaping the cutting torch are # 814 in Council Bluffs and # 833 and #838 in undisclosed locations.






4-8-4 Northern type

dry weight  locomotive only

22 lbs. 


C-type with 7 fire tubes

Super heater

Opening fire door

Gauge glass

Pressure gauge

Blower valve

Gauge glass blow-down valve

By-pass valve

Water cap. (not yet specified)

Twin safety valves


Boiler blow-down valve


Alcohol / Methanol

Fuel cap. not yet determined

Removable fuel tank


Two cylinders

Piston dia. 15 mm

 2x Rulon rings each

Walschaerts valve gear

Drain cocks


D-slide valves

Twin exhaust pipes


Water feed

 Axle driven piston pump

Tender hand pump



Roscoe displacement type


Drive wheels

BoxPok  63mm

Fully equalized

Steel tires / brass centers

Other features

Working headlight

Working emerg. stop light (red)

Functional cab windows 


Centipede type 

Weight 9.2 lbs.

Water drain plug

7 axles with coil springs

Fuel tank removable

RC battery compartment

Water cap. 830 ccm

Fuel line shut off valve

Fuel cap. 600 ccm

Total Length of locomotive and tender over couplers  

43.5 inches






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