I have not been watching this forum for a while. If this is an old topic, I sure did not see it. I know for certain that Alco made an RSD-4 and an RSD-5. They were two different locomotives.Yes? So why the **** do the model manufacturers continue to market an RSD-4/RSD-5 as one in the same?? Are these locos really identical? Or what? Thanks for any insight into this off the betean track (pun intended) topic.
According to “The Second Diesel Spotter’s Guide” the RSD4 and RSD5s were externally indistiguishable. The few differences there were were all internal.
Looks like if there were any external differnces it was placement of battery boxes, even then some differences between RRs.
Rick
The RSD4 and RSD5 were sold almost concurrently by Alco. The difference was ‘internal’:
- The RSD4 has the same main generator that the RS3 and FA1.
- The RSD5 has the large capacity main generator that was used in the PA2.
Most external differences(air filter grills) followed normal production changes on both models. RSD4 production started in 1951, and the first RSD5 demonstrator was built in 1952. Most railroads ordered the RSD5 after 8/52 and the last RSD4 was produced in 8/52. The higher capacity main generator option was due to EMD offering the SD7 in 2/52. The Alco RSC2/3 and RSD4 were offerings directed at light axle loading operations on branch lines. The RSD4 could be ballasted to ‘normal’ axle loading standards, but the RSD5’s higher capacity main generator was able to supply 6 weighted traction motors better. EMD offered the SD7 in 2 versions:
- A 50,000 lb axle loading ‘lightweight’ version(300,000 lb total engine weight).
- A ‘normal’ 60,000 lb axle loading version(365,000 lb total engine weight).
Both versions of the SD7 used the same main generator. The Atlas car body is of an early production RS3/RSD4/RSD5 - Many RSD5’s did have the latter car body filters or were upgraded by the users. I think the actual production change in the filters happened in 1953…
Jim Bernier