HO Scale Rivarossi 4-8-8-4 Big Boy w/Oil Tender Sound & DCC Union Pacific #4014 HR2884S. This Hornby Rivarossi 4-8-8-4 Big Boy is a model of the largest steam locomotive in the U.S. It was operated by the Union Pacific in heavy freight service and could reach speeds over 70 miles per hour. With the huge American celebration of the 150th anniversary of the completion of the Transcontinental Railroad and the driving of the Golden Spike Big Boy No. 4014 has been restored to operation to help commemorate the event. This Rivarossi model from Hornby comes equipped with a five-pole motor and dual flywheels for smooth performance. It is equipped with a sound and DCC decoder. The 4-8-8-4 Big Boy features fine detailing, accurate decoration, many separately applied details and magnetic knuckle couplers.