C&O 614 was indeed originally designed and specified for 74-inch drivers, but built with 72-inch drivers. The discrepancy stems from the original Lima-Hamilton design sheets and early clearance card drafts that listed 74″, which was later corrected once the engines were actually constructed. Every J-3a Greenbrier (Nos. 610–614) was built with 72-inch drivers. The 74″ figure persisted for years because the early documents and publicity materials were never formally revised by the C&O Mechanical Department.

Why It Was Done

The change to 72-inch drivers was a practical design decision made during the final production phase at Lima-Hamilton in 1948:

1. Size and weight considerations. To accommodate 74” drivers, everything below the boiler would have to have been made longer, larger, and heavier. The weight of the J3a in the design phase was already exceeding the specified weights
2. Better low-speed tractive effort: Dropping two inches in driver diameter slightly reduced top speed but increased the locomotive’s starting and hill-climbing power — valuable for the C&O’s heavy, hilly mainline operations through the Alleghenies.
3. Operational consistency: By the late 1940s, the C&O wanted their late-era passenger power (like the J3a) to be capable of dual service if needed — occasionally handling mail trains or even freight. The 72″ size gave them more flexibility without noticeably sacrificing passenger performance.
4. Ease of maintenance and tire interchange:

Using 72-inch driver tires (on 64” wheel centers) allowed closer commonality with other modern C&O engines, simplifying tire replacement and machining at the Huntington and Clifton Forge shops.

Primary & Archival Sources

1    Lima Locomotive Works Specification Sheets (1948)

– The official Lima-Hamilton “Locomotive Specification Card” for the C&O Class J3a (builder’s order no. 1173, locomotives 610–614) lists driver diameter: 72 inches.

– Copies of these sheets exist in the C&O Historical Society Archives in Clifton Forge, VA, and have been published in various C&OHS materials.

    2    Chesapeake & Ohio Railway Mechanical Department Records

– C&O’s Mechanical Department Clearance Diagrams (issued post-delivery) corrected the earlier 74″ figure. Early draft clearances used the design intent (74″), but the final “as-built” documents confirm 72″.

– These can also be referenced in the C&OHS publication Locomotive Diagrams of the Chesapeake & Ohio Railway (reprint editions).

Secondary & Published References

    3    C&O Historical Society publications and research papers:

    ◦    “C&O’s Greenbriers” by Eugene L. Huddleston, C&OHS Magazine, Vol. 12, No. 3 (1980s).

    ◦    “C&O Power” by Philip Shuster & Eugene Huddleston (TLC Publishing, 1989), pp. 182–184 — which explicitly notes that all J3a locomotives were built with 72-inch drivers, despite earlier documentation indicating 74″.

    4    Preserved engine measurement and restoration verification:

    ◦    Direct measurements of C&O 614’s driver centers and tires (by Ross Rowland’s SLCA restoration team in 1980 and again during the current Strasburg restoration) confirm the actual diameter is 72 inches.

    ◦    Strasburg Rail Road Mechanical Services has likewise verified this through current restoration work, including tire removal and measurement.

Summary

• Designed/spec’d: 74-inch drivers (on early Lima design drawings).
• Built & delivered: 72-inch drivers (as verified by Lima production records, C&O’s own mechanical data, and physical measurement).
• All J3a (610–614) shared the exact specification.
• Change rationale: operational flexibility, tractive effort, and commonality with shop tooling.