I'm trying to get a rough correspondence between MPH and prime mover notches - that is, at what approximate speed (mph) does a diesel locomotive notch up (8 times). I understand the notches are not specifically tied to speed (based on load being carried etc) but I'm trying to get a rough idea. Does anyone have any info on this they can share?
There is no way you could directly correlate the notch to speed. I've seen trains in run 8 doing 5 miles an hour up a grade. I've seen train in notch 3 and full dynamics holding 55mph on a downhill grade. There are too many variables to relate the two accurately on the modeling side.
Take the case of the F40PH - they nicknamed them "screamers" because to supply head-end power to the train, they had to run the prime mover wide open even at a standstill. With separate HEP sets, that need disappeared in later locos. Any engine pulling a train up a grade will be running at high output, regardless of speed, in order to generate the power needed to feed the traction motors under the load. So, as everyone else has said, there's really no fixed relation between throttle notches and speed.
Its also different from one locomotive to the next. Take GE U boat and she will wind up slower then a GP 38. Some times notch 5 is to slow and notch 6 is a bit to fast so you might be running notch 6 for a min or two then back to 5 for a bit and back up to 6 and so on.
