how much nominal power does each notch correspond to?
are they proportional to max power
1 0.0 %
2 14.3 %
3 28.6 %
4 42.9 %
5 57.1 %
6 71.4 %
7 85.7 %
8 100.0 %
or perhaps something where the difference for each notch is a little more than the previous one and the 2nd notch is small enough to move the loco without any cars
1 0.0 %
2 5.4 %
3 15.3 %
4 28.1 %
5 43.2 %
6 60.4 %
7 79.4 %
8 100.0 %
Notch 1 isnât zero power-- Idle is.
In the 1970s, Run 5 was around 50% power.
how about?
1 70.0 3 %
2 150.0 7 %
3 335.0 17 %
4 595.0 30 %
5 875.0 45 %
6 1200.0 61 %
7 1565.0 80 %
8 1940.0 100 %
I am staying out of the discussion on this side (it matches a more involved topic in the MR forum) because I donât have quick access to the sort of EMD technical material available through RyPN or some of the online technical resources on Woodward governors and the evolution of MU systems. I have seen âhardâ discussions of governed speed and main-generator excitation for locomotives with 567s and 645s and have seen a number of very detailed discussions of Alco and GE practice from the Amplidyne days forward, but I donât want to discuss them without references at hand.
W J White, How Diesel-Electric Locomotives Operate: The Last 25 Years, Including ACs (Second Professional Edition), p 3-10.
Fuel Consumption of B36-7
Notch Gross HP
1 125
2 370
3 770
4 1245
5 1875
6 2465
7 3190
8 3845
The power appears to step up in 600 HP increments in the higher notches, smaller increments in the lower notches, with notch 1 being below the smallest increment. This helps give finer control at the lower power settings used in low-speed âcreeping.â
This GE unit is rated at 3600 HP, which is at the input to the traction alternator after powering auxiliaries. The power at the wheel rims is 20% less given an 80% efficient drive for DC traction motors; the peak gross power of 3845 is presumable at the crank shaft of the diesel engine.
The notches on the GE unit appear to be more even than on an EMD unit. Although this source lists only fuel consumption and not HP with throttle notch, turbocharged EMDs have a big jump in fuel consumption between notch 5 and notch 6. This is the result of the turbocharger switching from direct drive to power the scavenging of the 2-stroke diesel unique to the EMD to a true turbocharger mode where the exhaust gas is able to power the turbine portion of the turbocharger.
The turbo âcutting inâ has a big boost in fuel usage but an even bigger boost in horsepower as the engine operates more efficiently in turbo mode.
It was interesting that some unnamed railroads in pursuing fuel and cost economy ask their crews to not exceed notch 5 or 6. Running in notch 6 rather than notch 5 offers substantial fuel savings with EMD units, assuming, of course, that the trailing load is sized so
the curve of paulâs fuel data is comparable to the values i posted last
it think the answer to my question is that each notch step provides a higher change in power than from the previous step (mildly exponential).
wonder how the NS practice that limited the MAX HP allowed was less than published HP on some of their units ? Did that change the schedule or not ? Is that still a practice in todayâs PSR operation? /
NS notoriously ordered a bunch of GEs intentionally derated to âsave fuel and wearâ. It would not make sense to rate those to take a train with any higher resistance than appropriate for their nominal performance profile (which would be interesting to compare with one producing âstockâ horsepower level in the running notches).
Of course you then have notch restriction exercises on top of such derating, probably with the intended result more of slower peak speed rather than increasing the risk of stalling or doubling --which is more likely from derating than voluntary throttle use.
Rather famously, although I donât have firsthand knowledge, NS turned up many of the D9-40s to higher horsepower. I would surmise that the result â full availability, but operating notch restriction â gave them the real-world fuel management they found best.
Why 8 levels? Why not, say, 10?
Do/did all diesels have 8 settings? EMD, GE, Alco, etc.
Are these 8 levels available in a switch engine, say an SE type?
It is actually binary, the result of combinations of four relays on the engine governor. Read up on the Woodward governor for more on how the MU system is designed.
In order to use electric MU a locomotive had to share the relay control structure and some proportional power at each combination of relay action. [EDIT: note carefully what M636C says about avoiding engine critical or resonance speeds, or at least transitioning through them, up or down, quickly]
There were other approaches to engine control, Baldwin for example using stepless air control; there were some late examples where Baldwins were explicitly built with electric MU capability. Alco had very different control over how the electrical generation was done and regulated, but kept notches for Diesel engine control â again, for compatibility.
GE at one point developed a âhalf notchâ system, where there were eight compatibility notches but also some âin betweenâ positions (of course available only to other 15-notch controllers) for finer control.
Any GM engine with a Woodward governor could have the 8-notch control as it saved considerable complexity and opportunities for failure. (Just what is an SE switcher, though?)
Thanks, OM.
I mistyped; should be SW.
One reason for eight notches was the need to avoid engine speeds where torsional vibration in the crankshaft would become a problem.
This is shown in a diagram in Eugene Ketteringâs ASME paper on the development of the 567 engine, which I think is available on the Utah Rails website.
This seems to be more of a problem on the EMD two stroke engine than on the four stroke engines used by GE and Alco.
The firing order was changed on the 8-567C (becoming the 8-567CR) and on the 12-710G3A (becoming the 12N-710G3B) to avoid these problems.
Peter
I have the fuel usage for each notch setting for a number of locomotives from just about all of the manufacturers and models.
Caldreamer
I of course would like to see these listed âin one placeâ to take them down for reference. Others may differ in their interest. Perhaps you could list them in something like a word-processing file to be sent by e-mail in response to a PM or other request if it is a problem to get it in posts here.
As a perhaps relevant point in this discussion: the principles of âdoubleheadingâ apply to MUed consists just as they do for individual control. So it is not technically necessary for all locomotives to produce equivalent horsepower at the same notch, or turn at the same rpm, or even have the same rate of electrical loading or transition when power is changed OTHER than to preclude âhuntingâ under conditions like particular ranges of balancing speed under particular conditions.
We have remarked from time to time that mixed consists can âbumpâ each other when faster-loading power is coupled in with slower-loading, this being independent of actual horsepower rating when settled in at a commanded notch. With loose buffers on given locomotives this might be noticeable in the cab, and I suspect at least some of the engineers here will be familiar with it.
Until dunno-when, GEs had 16-notch throttles â the engine speed increased at alternate notches, with just an excitation increase in the in-between notches.
In the 1970s, GE (trying to save fuel) tried running with three (?) engine speeds instead of eight â the engine was at 1050 RPM in notches 6, 7 and 8, or some such thing. And everyone remembers UPâs rebuilt SD24 with its constant-speed engine â donât recall how long that lasted.
Fifteen-notch, Tim⌠itâs the math of intermediate spaces between eight steps with the first representing idle.
I have to wonder at the sense of this, 1050 already representing substantial âoverclockingâ of the prime mover for competitive horsepower-rating numbers and a known reliability reducer in practice. Not saying they didnât, just that it would be goofy.
Perhaps the less said the better; it makes only slightly more marginal sense to run HEP that way. And this purely on economical grounds, leaving the noise and other issues for crews out of it. Those who are familiar with the effects of extreme âthermodynamic optimizationâ attempts on big recip steam will be smiling inside as they read the story of that UP projectâŚ
Overmod:
I have them in an Excel spreadsheet. If you emiil me off list I will attach the file and send it to you.
Caldreamer
Fascinating story to me, I liked the line about the dipstick being the only thing that didnât give a problem. It puts into focus the difficulty in designing a new engine or any other complex system perfect out of the box.
Dave