I understand notching is not directly associated with speed, but could someone please give me a ballpark on what scale miles per hour might typically be associated with notches 1-8?
I'm seem to remember seeing a SoundTraxx chart along these lines.
Depends...
On a lot of things.
More importantly than what notch you're in is what mode of transition your in. Transition used to be a manual control and after the later F3s and E7s, I think, it became an automatic operation. It involves switching the traction motor primary wiring from series, to series—parallel, to parallel as speed increased and load decreased. Voltage would rise in the main generator and cause "flashover". Transition helped reduce that.
Consider it in a similar fashion to a geared transmission.
Therefore you could be hauling a 100 car coal drag up a 1.5% grade in notch 8 and barely be making 20 miles an hour, or you could be in run 2 on the flatlands with a passenger train doing 79.
I'll have to look in some of the operating manuals I have around here for the recommended speeds for making the transition. If I recall you had to return the throttle to idle while making the change, you couldn't switch under load. Too much arcing at the main relays.
Newer AC locomotives do not require the transition and recent DC locomotives utilize the main generator for regulating the current to the traction motors through electronic controls.
Regards, Ed
Modern DC locomotives still make transition. It's been automatic (on most engines) since the later F series EMD engines. You don't have to close the throttle on ones that work automatically. (I recall RI SW1200 switch engines didn't automatically make backward transition when speed was dropping. For those if one was on line in a consist, the engineer did have to momentarily close the throttle.)
On UP SD70m models it happens around 25 mph. I've noticed NS DC engines make it at a slightly different speed, 27mph as I recall. You feel it because the engines momentarily drop their load. Nothing like having a tonnage train on a stiff grade and feel that lunge. It sometimes leads to breaking a knuckle.
Modern DC engines no longer have the short time ratings to avoid overheating the traction motors. The electronic controls will derate the engine automatically to avoid damaging the motors. Older ones still have the short time ratings on the ammeter.
Jeff
Well, there's 8 'notches, so if your decoder is set for 128 speed steps, and you're using a straight line speed curve, you're going up one 'notch' every 16 speed steps (128 divided by 8). If you then determine how fast your engine is going on the highest speed step, and divide that speed by 16, it will tell you how many scale MPH per notches you have. For example, if the engine's top speed is 60 scale MPHs, it will go up one notch every 3.75 scale MPH (60 divided by 16).
You can do it the other way around too...divide the top speed (60) by the speed steps (128) to get .46875 scale MPH per speed step. Multiply that by 8 notches, and you still get 3.75.
The problem is, most decoders are set up that it goes up one 'notch' every so many speed steps. As someone pointed out, they're kinda set up to sound like a sewing machine (or moto-tool); the faster the model goes, the higher pitched the engine sound is. That's not at all how a real diesel locomotive runs.
The engineer might put the real loco in Run 6 or higher when starting the train, then notch down to say 3 or 4 once the train is up to speed. We're just starting to see sound decoders that do that automatically - rev up when starting, or when going upgrade, then notch down when up to speed or drifting downhill.
There really isn't speeds associated with notches, notches are more aligned with load. You could be in run 8 doing 20 mph up hill or in run 3 doing 70 mph on the flats.
"Notches" are equivalent to pressing on the gas pedal of your car. When you want to accelerate, you press on the pedal (increase the notch) then you go faster. When you reach your cruising speed you back off on the gas pedal (reduce the notch) to maintain speed.
Dave H. Painted side goes up. My website : wnbranch.com
That's true, but I think the OP is talking about model sound decoders...at least, that's what I took it as, since he mentions Soundtraxx. Most sound decoders are set up to move the sound up a notch (usually by raising the pitch of the motor rumble a step) as the modeller increases the speed of the engine. Not really what a real engine sounds like, but at this point that's what most of them do. If you take the maximum speed that your model engine goes, and divide it 16, that will tell you how many scale MPHs the speed has to increase for it go up another 'notch' in sound.