Following its purchase of ten EMD FT locomotives in 1945, the Reading took delivery of 6 A/B sets of EMD F3 locomotives in November, 1948. These units were classed DF-2 (for Diesel-Freight-2nd purchase) and were numbered 260 A/B through 265 A/B. The Reading's units were considered "Phase IV" units, as they were among the last to be constructed by EMD. Changes on these Phase 4 models were Farr-Air stainless steel grills replacing the "chicken wire" screening along the top of the carbody, horizontal louvers replacing screened vents and no extended vertical shrouds on the roof fans. In addition, the F3s had fewer porthole windows along the sides than the earlier FTs. Each A/B set had 3000 horsepower.
As part of its ongoing dieselization efforts, the Reading operated the F3's in 4-unit sets for a total of 6000 horsepower. These locomotives were initially assigned to exclusive service on the Shamokin Division in order to eliminate the need for helper service on the Catawissa Branch. The delivery of the F3s, along with the concurrent arrival of the Alco FA-1s, caused a "ripple effect" that cascaded throughout the system. The Reading's FT locomotives were now assigned to Main Line service, which bumped the T-1s to New Jersey runs that had previously been handled by the Reading's big M-1 2-8-2 Mikado steam locomotives. Along with this replacement, some N-1s, remaining I-10s, and I-9s were downgraded, and 30 I-8 consolidations were retired.
During their initial time in service, the Reading experienced frequent pull-aparts when the F3s operated as four-unit sets. After revision of assigned tonnage ratings failed to solve the problem, the Reading began operating the F3s (and the Alco FAs) as three-unit sets with lower tonnage ratings. This apparently solved the problem, and the remaining F3s were sent to the Reading Division where they operated as two-unit sets.
The Reading saw fit to further improve the F3 locomotives after just 3 months of service. In March 1949, the F3's were modified with wash stands, retrackers, lube oil cans and pans, knuckle racks and emergency knuckles, diaphragm collapsing lugs, marker lights and larger sand boxes. The Reading's F3's did not operate with other types of motive power until 1956. From then to the end of first generation diesel power, F3's were mated with most other types of first-generation road power depending on tonnage needs. As was done with the FT units, the F3's were traded to EMD in 1963 toward the purchase of the new GP35's.
MODELING NOTES: Since the Reading's F3s were "Phase IV" units that very closely resemble F7 locomotives, modeling an F3 is a fairly straightforward proposition. However, there is one notable spotting difference - the location of the dynamic brake fan on the top of the locomotive behind the cab. The F3's had a blower, which was recessed below the roof under some gridwork, while the F7 units actually had a raised fan in this location, giving the F7's 5 fans, instead of the F3's 4 fans. Other than this difference, most other body details are identical to the F7s. Working from a good prototype photo will give you information as to additional details such as grab irons, etc. Refer to the above text for infomration as to how these units were used on the Reading, bearing in mind that they were off the property by 1963. There could have been a very short window where the F3s could have been seen with the GP30s, but that's about the only "mix" of first and second-generation power that would have been visible.