Walthers Proto
PROTO 2000 Diesel EMD SD7 Powered w/Sound & DCC
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Great Northern #561 (Big Sky Blue)
Walthers Part # 920-40731
HO scale, $249.98, sold out at Walthers
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EMD SD7 is Model of First Special Duty Series Locomotive
* Prototype-Specific Detailing
* Magnetic Knuckle Couplers
* All Wheel Drive & Electrical Pick-Up
* Dual Machined Brass Flywheels
* Constant & Directional Headlights
* RP-25 Wheels
* Heavy Diecast Chassis
* Five-Pole Skew-Wound Motor
* Factory-Installed Sound & DCC
Sound can be operated with standard DC power pack or DCC controllers. Sound
features include: Diesel Engine, Horn, Bell, Squealing Brakes, Doppler
Effect, Air Let Off (in neutral), Headlight, and Trailer which mutes
whistle and bell for double heading.
Originally intended for use on branch lines, EMD introduced its Special
Duty series in 1952 with the SD7. This loco also introduced the three-axle
Flexi-Coil truck with its powered center axle. This was a major departure
from earlier three-axle designs where an unpowered center axle was used to
spread the engine's weight over more wheels, reducing the strain on the
lighter rail and lower capacity bridges found on branches. EMD's design not
only spread the weight but the extra traction motors provided a bit more
power to get trains started. The SD's longer trucks required a longer
frame, and buyers could also specify a heavier frame for engines working
transfers and other low speed service. Somewhat underpowered with only 1500
horsepower (same as a four-axle GP7), only 188 SD7s were built from
February of 1952 through November of 1953; the more powerful SD9 was
introduced the following January.
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