[citation needed] The PRR decided in 1948 to place diesel locomotives on all express passenger trains, leaving unanswered questions as to whether the T1's flaws were solvable, especially taking into account that the two prototypes did not have the problems inherent to the production units.

An article appearing in a 2008 issue of the Pennsylvania Railroad Technical and Historical Society Magazine showed that inadequate training for engineers transitioning to the T1 may have led to excessive throttle applications, resulting in driver slippage.

[10] However, there was a drawback of the metallurgy used; the poppet valve could not withstand the stress of sustained high-speed operation (meaning over 100 mph (160 km/h) on production T1s).

The S1 was built unnecessarily large for her exhibition at the 1939 New York World's Fair until October 1940; therefore, its turning radius prohibited it from operating over most of the PRR network.

The 6-4-4-6 design reduced driving set traction to the point that it was especially prone to wheel slip[citation needed]; thus only one Class S1 was built.

[11] Both prototypes had numerous teething problems and were prone to wheelslip if not handled carefully by the engineer, but favorable test reports resulted in a production order for 50 T1s, split between the PRR's own Altoona Works and Baldwin.

In late 1942 Islington Railway Workshops's chief engineer Frank Hugh Harrison saw the T1 in an american magazine whilst designing the 520 class.

Both engines held 100 mph with upwards of 13 cars, while their tenders allowed travel over the entire 713 miles route with only one stop for coal in Millbrook, Ohio.

[18] The 'Sharknose' monicker applied to the later production engines and subsequent Baldwin diesel units wasn't widely used, though a December 1942 article of the Times Leader refers to the T1's as Land Dreadnaughts.

The aggressive angles of the smokebox prow and accompanying portholes on the lower sides give the impression of an ocean vessel.

Problems were encountered with poor steaming, placement of sanders, spring equalization, and insufficient lateral motion leading to repeated low-speed derailments on some switches approaching Pittsburgh from the west.

In interviews with historian William L. Withuhn in the 1970s, Franklin engineers Julius Kirchhof and Ray Delano both claimed a Franklin technician charged with determining the cause of frequent poppet valve failures on the T1s saw them operated at speeds of up to 100-110 mph to make up time with short trains of six or seven cars, determining the speed by timing when the train passed mileposts.

The one other locomotive with Franklin Type A (also allocated to the Ft. Wayne Division) wasn't powerful enough to challenge the speed threshold of its poppet valves, let alone exceed it.

Late 1944 saw a Norfolk & Western J class trialed on the Ft. Wayne Division, at the suggestion of Vice President Symes due to dissatisfaction with the T1's performance.

Numerous benefits were displayed over the duplexes, with the J having better acceleration, better steaming on poor coal, and ride quality only outmatched by the S1.

One run with 610 saw a set of valve gear seize up at 110 mph just east of Ft. Wayne, though this was primarily from improper lubrication.

An inspector recorded of 6110 manage a 21 car train at 100 mph on the Middle Division (Harrisburg to Altoona) in adverse weather and still making up time.

This same inspector examined 6110 days later slipping violently to a standstill, resulting from a sharp throttle application.

Lessons learned from the prototypes lead to numerous design changes, included revised spring equalization and flatter prows to the smokebox casing.

They were immediately assigned to the "Fleet of Modernism," hauling trains of new lightweight equipment, as well as standard and refurbished heavyweight cars.

Not only were the production T1's placed into the same Harrisburg to Chicago service on a more frequent basis, they were also assigned trains to St. Louis and occasionally Detroit.

Several divisions worth of crews had insufficient experience with handling the T1's before the first production engines entered service, while others had practically none at all.

In addition to the Chicago Railroad Fair, T1's made display appearances in Sunbury, Reading, and Atlantic City.

Promotional print material, as well as the film Clear Track Ahead shows the T1's being the new face of the railroad, alongside the GG1 electrics and recently acquired diesels.

Tonnage was adjusted due to the T1's lower tractive effort, though its higher drivers hindered its climbing ability.

On one side was the development of a steam turbine locomotive, eventually designated as Class V1 resembling the later Chesepeake & Ohio M-1, albeit with a 4-8-0+4-8-0 wheel arrangement.

Subsequent orders to EMD, as well as for equivalent ALCo and Baldwin products, made the brand new T1's redundant for their intended roles.

By 1950, T1's were no longer running through services to Chicago, St. Louis, or Cincinnati, though some remained as standby or protection power in the event of a diesel set failing.

[24] The first piece of the locomotive, the keystone-shaped number plate, was cast in April 2014, followed by the first minor component, a driving spring link pin, in October 2014.

Major components completed as of March 2019[update] include two Boxpok drivers, the prow, cab, third-course boiler and fire door.