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Test Train Santa Fe made its rail- road available for EMD to test its new creations. This train, complete with the EMD test car (older B unit) and an ATSF caboose, was working through Arizona on the head end of a piggyback train. Test results were favorable, and EMD soon introduced the railroad market to its 645 line of motive power. — EMD photo, author’s collec- tion


434F The 434F idled with its sister on the C&O in Chi- cago on June 26, 1965. The unit did bear a strik- ing resemblance to the future SD45 even though it was considerably shorter. — J. David Ingles photo, Louis A. Marre collection


of passes of welding at the attach- ment. In 1972, EMD introduced a new “A” frame with a much larger footprint, the so-called “D-foot A- frame,” which proved very suc- cessful in service. In the 645F-se- ries engines developed in the late 1970s, EMD again changed the design of the attachment, provid- ing a formed key in the “A” frame that passed through a cutout in


74 RAILROAD MODEL CRAFTSMAN


the lower stress sheet and was welded on both sides of the com- ponent intersection.


EMD also encountered some problems with premature fail- ures of the clutch assembly in the gear train-assisted turbochargers used on the 645 engines. EMD engineers resolved these prob- lems through the development of improved clutch component de-


signs, including a double-angle ramp in the clutch camplate and the chrome plating of the clutch roller pockets. The clutch was further protected through the use of a spring drive gear that had several packs of coil springs between the engine gear train and the turbocharger drive gear. These springs cushioned the pow- er transmission in both the drive


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