I know the Alco RS locos were introdeced in the 40’s What about the RSD’s? Visually, they look like RS’s with 6 axles. Would they be out of place on a 50’s layout? Were they longer than the RS’s?
Most of the RSD and RSC units were sold at the same time as their B-B bretheren.
Short answer. No, they would not be out of place.
Dave H.
RSC’s had an unpowered middle axle on each truck–used to distribute weight on light rail. RSD’s had all six axles equipped with traction motors.
RSC2/3’s would fit in your era and would be most appropriate on a weedy, light rail farm branch that sees very little traffic outside of the harvest rush.
RSD4/5’s are a bit heavier but would still fit on a light rail branch (C&NW in South Dakota) or in mine run service.