DW,
appreciated but I think you are describing medium-speed Truck type diesels not the locomotive type.
...... Diesel's run wide open and engine speed is determined solely by the amount of fuel being injected.
GM's 567+645, GE's 7-FDL and ALCo 251 operate on the principle with the Power Controller(handle position) contactors energizing the 4 Solenoid valves in the Woodward Governor(an electro-hydraulic apparatus) thus controlling and actuating the Injectors; for specific RPM settings obtained by Controller notch settings.
The Injector won't open any further than the Notch setting allows unless manually over-ridden with the layshaft lever or in the case of the GE 7-FDL, one can manually pull out an individual(or 2) cylinder injector itself(like the Alco, the GE has the junk outside unlike the GM, which is enclosed).
An Overspeed trip lever is set to a specific RPM to shut down the prime mover if tripped, which was 1050 rpm(315 idle-900notch8) on the 645E(GM) and 1130rpm(444idle-1055notch8) 7-FDL(GE).
Rated(Max) engine operating speed for the MLW DL535E (listed elsewhere) at 1100rpm but not the overspeed trip rpm's.
Since the description and operation is complex, if you wish, you can read about the
Woodward Governor operation. This next link describes the Gov.(including hunting) and ALCo Injector (pg 37) [
www.rr-fallenflags.org]
Disclaimer: Not the manual for the DL535E I6-251 nor the model of Woodward fitted to such. The latest Engine models now have no Governor, being taken up by microprocessors.
Note the Injector settings are described, there in that description one can determine the complexity of the ALCo fuel pump control linkage(pg35) and gather, that with wear and misalignment, just how the ALCo gets its sound(basically complex junk design, GM 645E being the pinnacle).
From what I gather the earliest GE U-25B was the only Diesel Electric to depart from the usual
8 notch Controller adopted during the 1940's, that model GE had a 16 notch set-up. I didn't include the 10-notch English Electric controllers on the earliest NZR mainline Diesel loco's, outside this discussion.
But all that's in the realm of the Diesel Fitter with Trade Certificate, not in the Enginedrivers Certificate(other than a basic ability to describe the workings of the Diesel engine itself, and the Governor, Injector and Load Regulator).
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