The Bay Line RS1 may have been equipped with the old Alco standard of two connectors with 12 and 21 pins.
blue streak 1 Many years ago in Pannama City,Fl there was a bay line Alcoa in a park. Opened the MU connector and it had fewer than 27 points. Maybe 18?. Cab ride on Amtrak on NYP - PHL commuter train with 2 AEMs train performance terrible. Head unit 95x ? Maintenance went back at stop and cut second unit out. Ran much better. Much later read somewhere that early AEMs did not have notches but used something called "P" control.. Not compatible with later 8 notch AEMs. Also read "P" was later eliminated ? Anyone know more ?
Many years ago in Pannama City,Fl there was a bay line Alcoa in a park. Opened the MU connector and it had fewer than 27 points. Maybe 18?.
Cab ride on Amtrak on NYP - PHL commuter train with 2 AEMs train performance terrible. Head unit 95x ? Maintenance went back at stop and cut second unit out. Ran much better. Much later read somewhere that early AEMs did not have notches but used something called "P" control.. Not compatible with later 8 notch AEMs. Also read "P" was later eliminated ? Anyone know more ?
https://railroad.net/p-wire-question-t77859.html
.
I see Kalmbach is trying to quadruple my posts again. At least I caught it myself this time.
Former Car MaintainerSpeaking of ignitrons, weren't they used in Budd's shotwelding machine , along with precision timing charge networks, for controlling spot weld time while constructing the Burlington Zephyrs?
Both were described in this article (from 1937):
https://worldradiohistory.com/hd2/IDX-Site-Early-Radio/Archive-Radio-Engineering-IDX/IDX/37/Radio-Engineering-1937-04-OCR-Page-0012.pdf
The way this was written appears to indicate that the Budd Company was preferring to use the mechanical timer system for much of its heavier work later than the time the Zephyrs were built, but I don't know.
Closely associated with the practical development of Shotwelding was a system that could quickly assess weld quality. The original version of this to be patented was 2093932, which was filed in 1932 but not granted until 1937, not being improved in process; this shows only the mechanical timer. Heitman's improved version, 2138790 (filed 1935 and granted 1938) clearly references a "Thyratron timer" as an essential component.
Have to do more reading!
(The posts on October 21 and 22, 2008 really answered the original poster's question regarding 'why the eight-notch throttle', so I think you're right about letting what's left of the horse find surcease... )
Speaking of ignitrons, weren't they used in Budd's shotwelding machine , along with precision timing charge networks, for controlling spot weld time while constructing the Burlington Zephyrs? And back to throttle settings...guess enough has been said...
Former Car MaintainerWhich makes me think....if locomotives had to be built to MIL specs?
Which makes me think....if locomotives had to be built to MIL specs?
Not that I have anything but serious respect for Welte-Mignon, or the technology of fluidic amplification used by the Air Force in the '50s, or the Honeywell proportional control in the A-12. There's a lot to be said for full proportional control; we have it in most drive-by-wire automobiles, and as noted this 'could' be made multiple-unit compliant with a comparatively small amount of technology (strain gages trainlined with some kind of high-rate multiplexing). All you really have to do is equilibrate the strain-gage readings among the engines in the consist, with simple feedback control of the throttle positions when necessary to develop more power at rpm and of the load regulators...
Now, decatrons I'll grant you are as pointless as EBCDIC ... base 10 is sooooo much less useful than base 16.
I think one of the chief attractions of the air throttle (aside from getting around EMD patent coverage) is that most of the components would be familiar to existing shops. One of Westing's books, I believe, mentions the culture shock involved in putting injector-rebuild facilities for Baldwin engines in one of the PRR shops -- the idea of very clean, essentially controlled-atmosphere facilities being alien to their general practice. We might conclude that their working on EMD 567 unit injectors -- where a fingerprint on some of the components precludes assembly -- would be more difficult still...
The technology of the air throttle is a reminder of the pneumatic player piano/orchestrions or calculators built from decatron tubes....
Former Car Maintainerhttps://patents.google.com/patent/US2311285A/en?oq=Us2311285a This may more accurately show the throttle/load regulation scheme, and 1941 would better date it.
This may more accurately show the throttle/load regulation scheme, and 1941 would better date it.
It would be interesting to see how engineer Stamm would rig this for effective multiple-unit control, let alone compatibility with 8-notch AAR MU -- I think it might be difficult to do it effectively with contemporary technology. Thinking about the PCC accelerator, though, leads me to wonder if progressive position of the 'wiper arm' around the circle of progressive resistances in the accelerator could toggle different combinations of solenoids just as they do different contactor combinations in electric-car acceleration, to give proportional engine speed and hence HP range as governed (that could be sent through AAR-compatible MU wires and pins) with the Carbonstat then performing appropriate duty comparable to an EMD load regulator...
It would be interesting to see how engineer Stamm would rig this for effective multiple-unit control, let alone compatibility with 8-notch AAR MU -- I think it might be difficult to do it effectively with contemporary technology. Thinking about the PCC accelerator, though, leads me to wonder if steps in the progressive resistance could toggle different combinations of solenoids just as they do different contactor combinations in electric-car acceleration, to give proportional engine speed and hence HP range as governed, with the Carbonstat then performing appropriate duty comparable to an EMD load regulator...
Former Car MaintainerWhile not a direct reference to steam, diesel or electric locomotive controls, of interest is a 99 point (notch), PCC car controller operated by a foot pedal.
PCC4609_4cam_Accelerator
which shows the coordination as the limit relay is modulated with the foot pedal.
Note his comment that the dynamic braking resistances are the ones in this controller! That gives you the proportional braking action...
I had a piece of stereo equipment with a volume control rigged much this way: the 'premise' was that a wired potentiometer introduced undesireable inductance into the musical signal, so a printed circuit with about 99 individual contacts each with a calibrated resistor was provided, with a wiper on the volume control knob. I thought this was nifty, but I never saw it used again.
Perhaps a "better" method was the "Opto-Isolator Module" I commented on in years past, in the Collins Radio mixdown board provided with our original stereo-FM broadcast transmitter at WPRB. This provided essentially stepless volume control in each pot, without any distortion. These were beautiful spun and brushed-finish modules, with proud enameled etched markings, that plugged into an octal socket. When one of these went out, we actually arranged to have a replacement overnight couriered to Newark Airport (the fastest service available then!) before the chief engineer and I figured it could be no harm to open the thing up and see the complex wonder inside.
What was inside was a flashlight bulb -- a threaded bulb with soldered connections, to add to the kludge -- shining on a photo-Darlington. Turn the pot up, the light got brighter, the Darlington response shifted ... audio volume control without capacitive or inductive changes!
(I went to the local hardware store, bought a comparable flashlight bulb, soldered it in, and bingo! back on the air. I was told there was no comment at Collins Radio when someone called back to cancel the courier order and said 'we fixed it'... )
Meanwhile -- note that Chicago PCC cars had 135 discrete steps in their controllers!
It would be interesting to see if there were any way to synchronize the motors driving these controllers to get "MU" effect. I keep thinking of big selsyns; you could rig something on the shaft that would allow motor coordination 'close enough' to get the effect, and that by default handles most of what would be needed for the transition contactor stepping...
Since I cannot get the oocities link to render correctly on any browser I have (or to paste correctly into the forum software) here is what it says (as I recall, this was written by Will Davis):
It is fairly well known in railfan circles that many Baldwin and Baldwin-Lima-Hamilton diesel locomotives were built with air operated throttles, and as such could only operate with similarly equipped units. The actual story is more complicated than that; there were two different air throttles available over the years, and there actually was one electric throttle as well. Let's take a look at these and examine some of the differences.
Here is an illustration from Baldwin manual DS-107, which is the Operator's Manual for 660-1000-1500 HP Switchers, Revised 12-1-48. (Yes, road switcher type locomotives which were not fitted with multiple unit controls were referred to in some early manuals as "switchers.")
https://www.oocities.org/wbd641/blwD1old.jpg">https://www.oocities.org/wbd641/blwD1old.jpg
This control stand contains the simplest and earliest air throttle, which was known as the D-1 Controlair. The throttle handle is No. 24 on the drawing; the slot for insertion of the reverser is just below it. Pulling the throttle back towards the engineer results in the air throttle mechanism increasing air pressure in the "throttle pipe," which acts upon the governor on the engine to increase engine speed. In some units, there is also an air operated Carbonstat Load Regulator which serves to control generator loading which is also connected to the throttle pipe. In all units which use this D-1 throttle, also connected to the throttle pipe is something called a "K-3 Throttle Switch." When the throttle is all the way forward, air pressure in the throttle pipe is zero. When it is pulled back, air pressure starts to rise; when it reaches 8 psi, the K-3 throttle switch closes. The throttle lever itself may, or may not, have a notch that you can feel it enter after it is pulled back a short angle from the idle position. This is called the "first notch" position --- but remember that through most of the motion of the throttle on any of these air throttles, movement is smooth with no 'notches' in the EMD solenoid-controlled sense. You can finely adjust power wherever you want it, which was advertised as a big advantage compared to 8-notch electric throttles.
In that "first notch" position, air pressure in the throttle pipe for a D-1 should be between 14 and 16 psi. Obviously, before this pressure is reached, the K-3 switch has closed, and power is being delivered to the traction motors. The engine is still at idle speed in this first 'notch' position. Above this, as the throttle is opened, pressure rises until the throttle is wide open, at which pressure will be between 50 and 55 pounds.
Some locomotives have yet another device connected to the throttle pipe, called a Field Control Switch, used to alter traction motor fields for soft starting. Many don't. [Note: this is the thing that Matt Imbrogno was referring to... I cannot tell if this used the same Carbonstat mentioned above or a second one, but it would involve the same 'tasimeter' technology]
href="https://www.oocities.org/wbd641/blwD1new.jpg">https://www.oocities.org/wbd641/blwD1new.jpg
Here is a slightly different cab arrangement, still including the D-1 Controlair control stand and throttle. This is from Baldwin-Lima-Hamilton manual AS-101-A, Operator's Manual for Standard 1600-HP All-Service Diesel-Electric Locomotives with D-1 Controller and 6-SL Brake Equipment, Plus Modifications such as Multiple Unit Control, Dynamic Braking, CE-100 Control Stand, 24-RL Brake Equipment, Dual Control Stands, etc. (Yes, that's the full title of the manual from the title page!!) The use of the D-1 control stand does NOT rule out having multiple unit controls. You can use this control stand with MU. However, this control arrangement cannot be used with any of the other optional throttles.
The D-1 was the standard throttle, and the others (which are below) were optional, based upon specified equipment or customer order. The D-1 Controlair is the old, original setup. Inclusion of equipment designed later than the D-1 ended up requiring a new master controller, which could perform more functions. This new air throttle controller was known as the CE-100.
href="https://www.oocities.org/wbd641/BLHce100AS.jpg">https://www.oocities.org/wbd641/BLHce100AS.jpg
From the same AS-101-A manual is this shot. This is the 'improved' CE-100 control stand, for units with multiple unit control and dynamic braking. Note that the controller itself is quite large, and is cylindrical. The throttle operator shaft comes straight out the top, with the bent throttle handle attached to a turret. The reverser is mounted in the controller below the throttle lever, on the front. It has either three notches, if the unit does not have dynamic brakes, or five notches if the unit does have dynamics. There may or may not be a latch on the lever which has to be released to allow it to move, but it also cannot be moved unless the throttle is all the way forward in "idle."
On the CE-100, right at the forward end of the throttle movement, there are two notches. All the way forward is idle, and right next to it is the "first notch position". On this throttle, this is actually an electric switch contained inside the throttle. It causes the main power contactors to close, which applies power to the traction motors. Pressure in the throttle pipe will be 8 to 10 pounds in this position. With the CE-100, air pressure in the throttle pipe at wide open throttle is 60 to 65 pounds. There may or may not be three notches spaced out at the wide open end -- according to some manuals, these provide "running positions". The throttle lever is also used for dynamic brake control. The CE-100 was, of course, used much more often on streamlined road locomotives.
Let's take a look at pictures from two rare manuals.
href="https://www.oocities.org/wbd641/blwDR441600CE100.jpg">https://www.oocities.org/wbd641/blwDR441600CE100.jpg
This picture is from the New York Central Railroad Company "Instructions for Operation of Diesel Electric Road Locomotives - All Classes", which was produced by the railroad in 1949. It shows the control setup for the "babyface" Baldwin road locomotives owned by the NYC (Models DR-4-4-1500 and DR-6-4-1500.) NYC owned exactly four sets of these units. All four sets were three-unit, A-B-A sets rated 4500 horsepower. Two of the sets contained B-B freight locomotives with dynamic braking. The other two contained A1A-A1A passenger locomotives with steam generators. [As delivered these latter were the Gerties...]
The shot here is generally applicable to both types, but is specific to the freight units, as the passenger units had a different gauge panel on the dash in front of the engineer:
href="https://www.oocities.org/wbd641/blwDR641500panel.jpg">https://www.oocities.org/wbd641/blwDR641500panel.jpg
Other controls were basically the same between freight and passenger types.
This is a picture from an early manual for what are popularly known as "Shark" or "Sharknose" units. It is for neither model DR-4-4-1500 nor model RF-16. Some explanation is necessary (you've already noted the CE-100 controller, I'm sure).
Baldwin changed over from the old, "babyface" body to the new, angular "shark" body in early 1949, and units of model DR-4-4-1500 with this new body were built until June 1950. Between June and November 1950 no units of this kind were built. When production began again, the units were not yet model RF-16 as is commonly assumed. They were model DR-4-4-1600. This shot is from the manual for these locomotives; here is further explanation from the standpoint of operator's manuals:
In May, 1950, Baldwin Locomotive Works issued manual number DF-105, which covered the last group of units delivered to the Pennsylvania Railroad. These units had some slight external differences as compared to previous "shark" units, but small external details are meaningless as regards model designation by the manufacturer. Internally, these units began to change over to equipment which would be necessary when the anticipated uprating of the units took place at some point. Changes began to be made to the auxiliary generator/exciter, for example. These units are frequently totally mislabeled in railfan circles as "RF-15" units, which model never existed as far as Baldwin was concerned. They were still model DR-4-4-1500.
When production was about to restart, which was the result of an order by the Baltimore & Ohio for 1600 HP road freight locomotives, Baldwin issued manual number DF-106. This manual was issued in October 1950. Manual DF-106 consists of the majority of the content of DF-105, plus the addition of green revision and update pages in the front of the manual itself indicating that the manual was originally published in May 1950 as DF-105 and that alterations in design and/or customer order had required modifications to the manual with revision as DF-106. The model of the locomotive is clearly given as DR-4-4-1600/1, which means that the normal railfan-published sequencing of model numbers at this time by Baldwin is completely incorrect.
Following the merger with Lima-Hamilton, which occurred in November, 1950, the official model designations were simplified and changed, and at that time, model RF-16 replaced model DR-4-4-1600 as the mainline road freight unit.
href="https://www.oocities.org/wbd641/weXM781controller.jpg">https://www.oocities.org/wbd641/weXM781controller.jpg
Now that we are all through that, here is the last kind of controller which was optional in Baldwin and Baldwin-Lima-Hamilton locomotives. It is difficult to find an actual Baldwin manual which shows this controller, so I've used my Lima-Hamilton manual 1200STD, for 1200 HP Diesel-Electric Switching Locomotives.
This is the Westinghouse XM-781 controller. It is an eight-notch electric throttle. It was available with or without MU and with or without dynamic brake. In MU applications, an extra selector lever like that in other brands was added; it would be sticking out of the top of the controller, behind the throttle lever.
No. 7 in this illustration is the reverser lever.
This setup could be built with a number of MU cable and pin combinations to allow Baldwin (or B-L-H, or for that matter Lima-Hamilton or Fairbanks-Morse) units to operate in multiple with EMD or ALCO-GE locomotives with electric throttles. As you might assume, there's just no way to operate an electric throttle with an air throttle.
There you have it; all of the variants of Westinghouse throttles used in Baldwin and Baldwin-Lima-Hamilton diesel-electric units postwar. Hopefully, this will clear up a lot of confusion aboutthis kind of equipment in the railfan world!
While not a direct reference to steam, diesel or electric locomotive controls, of interest is a 99 point (notch), PCC car controller operated by a foot pedal. The foot pedal equated to a near linear accelerator/throttle for the electric motors in a street car. To my knowledge it was never adapted to a MU configuration.
https://www.youtube.com/watch?v=pgSWuTxQh6s
https://patents.google.com/patent/US2311285A/en?oq=Us2311285a
I will have to wait to reply until I get to a computer; either crApple or $@&#% Kalmbach keeps resetting pages and 'saving me from myself' by trying to access the cached oocities content -- which is there; I tricked iOS Safari into displaying it exactly once, from the second time the link was posted, but never again.
That was enough to confirm that all three things, the 'Carbonstat', the carbon-pile device in the Gerties article, and Imbrogno's soft starting all refer to the same thing: load control, where the Westinghouse system does with pressure on the equivalent of a telephone carbon-button transmitter what an EMD load regulator does with rotation.
That is not a function of drive to the Woodward governors, nor of how they need to be actuated, nor their homeostatic action in holding commanded rpm.
More later.
https://www.oocities.org/wbd641/BLWcontrols.html
This link is an archive of a geocities link mentioned earlier in this forum.
it outlines the Baldwin D1 Controlair, the CE-100 control and the XM-781 controller.
The pneumatic diagram in the Gravel Gerties article, does not detail the pneumatic to electrical interface described by Imbrogno. The Westinghouse patent drawing link helps the imagination to see the possible electrical interface.
in any event it can be easily summised that the air throttle was not compatible with the adopted standard for MU. The notch system was a carryover from the trolley days, worked for its intended purpose, was familiar to operators, and did the job.
A small consideration for the air throttle system might have been improved fuel efficiency, certainly not ease of maintenance...
SD70DudeI can't speak for anything else, but mechanically injected EMD engines have a throttle handle: the layshaft.
https://www.supremecourt.gov/opinions/URLs_Cited/OT2011/10-879/10-879.PDF
The CKD Praha 'Baldwin' engine page at oocities doesn't open for me whatever I do; presumably it contains a similar manual.
The governor is a Woodward type, and it acts on a layshaft with similar function to the rack on an EMD, so the two can be said to be the 'reverse of throttled' (more fuel fed as the shaft is moved) although the actual injector mechanisms are different.
It will probably be amusing to you all, but I read the Gravel Gerties article with great interest a few years ago... but did not scroll all the way to the bottom when reading and never saw the arrangement diagram for the MU throttle. The pneumatic actuator shown would act on the Woodward governor, and if I recall correctly later specifications for the 608A read almost identically to the earlier ones with only the substitution of 'electrical' for 'hydraulic' control input -- someone like Matt Imbrogno will likely have firsthand experience with the 'AAR MU compatible' version of one of these.
The patent cited was for a cockamamie scheme using either compressor bleed or turbo/supercharger static boost pressure to regulate, among other things, the carbon-pile load regulator mentioned in the Gerties article directly (note the reference to gas-turbine control, a 'hot topic' for Westinghouse in the late '40s leading up to the Blue Goose B-B-B-B locomotive) if I'm reading it correctly. The system used in the production Baldwin diesel-electrics does not involve this (although theoretically it 'could'); to my knowledge the control air is taken from main-reservoir pressure and externally regulated, with the speed reference to the Woodward governor provided by Morse chain.
I do suspect, though it is like pulling teeth to check on a phone, that there will be patents in the 'patents cited by' list in the '023 patent that cover aspects of the system that is used on production locomotives. The date might be considerably earlier than the '40s, though.
Someone with a larger screen might look through the available information on the Essl locomotive, which had a 'modular' design with individual 408-engined gensets each connected to and driving only one axle. Presumably these were commonly controlled within a few rpm or the racket would be intolerable; likewise very fast response to one wheel slipping traction would be needed. Doing this with control air, without overshoot, eould seem to me to require careful detail design...
Overmod Had to dig for it, but found it: Some explanation of the Baldwin air throttle: http://baldwindiesels.railfan.net/throttle/index.html
Had to dig for it, but found it: Some explanation of the Baldwin air throttle:
http://baldwindiesels.railfan.net/throttle/index.html
https://nycshs.files.wordpress.com/2014/12/gravelgerties.pdf
not sure if this applies https://patents.google.com/patent/US2546023
I can't speak for anything else, but mechanically injected EMD engines have a throttle handle: the layshaft.
Of course it's on the engine instead of being in the cab.
Greetings from Alberta
-an Articulate Malcontent
Overmod Diesel-electrics don't have throttles at all
Diesel-electrics don't have throttles at all
https://en.wikipedia.org/wiki/Diesel_locomotive#Throttle_operation
i digress to the semantics of throttle, notches, steps, and their analogies...
Overmod ... Where the 'magic' happens with actual speed control is in the load regulator, and indeed if you were to want a 'foot-feed' for diesel-electrics using 8-notch binary that is the part of the system that would do most of the 'accelerator-like' response...
...
Where the 'magic' happens with actual speed control is in the load regulator, and indeed if you were to want a 'foot-feed' for diesel-electrics using 8-notch binary that is the part of the system that would do most of the 'accelerator-like' response...
EMD Engineering found several uses for the SDP40F trade-ins that happened in the late 70's - the first as I recall, was the 134 (EMD project numbers were given to these, the 169 and 218 were a couple of others) that was converted to a turbo 12-645 to do development work on the control systems for the huge off-highway trucks that EMD was supplying components for such as Unit-Rig. The loco was modified to have accelerator and brake pedals to duplicate the truck arrangement and was driven around the property with those, although it never left EMD. I have no idea what throttle speed schedule was used or any other details.
This loco was later used as the test bed for the first computer control system at EMD in advance of the 60-series, the first used an Atari 800 to prove the concept.
Dave
Perfect answer to all three uncertainties raised elsewhere; thanks!
SD70Dude rdamon Didn't the Alaska RR SD70-MACs do something like that with one of the traction motors? Yes. They use one of the traction inverters to supply HEP. When operating in HEP mode only three or four traction motors are powered. I'm not sure which is correct, there is conflicting information floating around online, but I suspect Dave Goding will know the correct answer.
rdamon Didn't the Alaska RR SD70-MACs do something like that with one of the traction motors?
Didn't the Alaska RR SD70-MACs do something like that with one of the traction motors?
Yes. They use one of the traction inverters to supply HEP.
When operating in HEP mode only three or four traction motors are powered. I'm not sure which is correct, there is conflicting information floating around online, but I suspect Dave Goding will know the correct answer.
Being SD70MAC's, they had a single inverter for each truck, with one inverter forward of the engine and one behind it. When the CSX bought an order of SD70MAC's around 2004, they wanted EMD to make space available for them to add a small keep-warm engine, don't recall the maker. All the prior SD70MAC's had a battery box on each side of the carbody at the very rear under the cooling system. I was tasked with coming up with an arrangement to make the space for the small engine and its accompanying parts (a skid about 6' long, 2' wide, and 4' tall). The simple solution was to stack the batteries on one side which opened up enough space.
Shortly after that, the Alaska RR asked what we could do to offer HEP at a reasonable price for their new SD70MAC's, the easiest solution was to put a transformer and switchgear in the new open space behind the #2 truck inverter cabinet. We had worked with Siemens for inverter HEP on the DE30AC's so we had a transformer design that fit the space and left room above it for the switchgear.
So here's the long answer to the question of how many motors were powered when in HEP mode - only the 3 in the front truck were powered, the rear truck was disconnected and the full inverter power was available for HEP. The DE30AC transformer was sized for 1,000kW (it powered all the loco fans and blowers and had 800 kw available for external power) so those SD70MAC's could have had that much HEP capacity but I don't know if they limited it in operation. The 70MAC inverters could provide 60% of the full engine power to either truck so they weren't limited to half the full traction power but a bit more.
Jay Boggess was the lead electrical engineer on the Alaska HEP project and eventually worked for a time for the Alaska RR.
Diesel-electrics don't have throttles at all, and that is important to understand in the notch system. The actual 'engine governor' in a Woodward is precisely analogous to the throttle in a steam engine in regulating the amount of 'potential power' that gets into the engine. Here it is important to note that the Woodward control governs nearly steplessly, by moving the rack that adjusts the unit injectors. It would be easy to implement a continuous power control like a car or truck accelerator, and in fact on the EMD's little cousin the Jimmy that's just what you have.
Dilworth et al. made a conscious decision to use speed rather than 'power' steps in the engine control -- I believe this is covered in the SAE paper on the development of the 567. The point is this: in EMD locomotives the MU-capable 'command' is done via calibrated 'notches', the 'Run' settings corresponding to defined engine speeds, and the engine fuel burn is (nearly steplessly) adjusted to hold that speed regardless of load.
Where the 'magic' happens with actual speed control is in the load regulator, and indeed if you were to want a 'foot-feed' for diesel-electrics using 8-notch binary that is the part of the system that would do most of the 'accelerator-like' response... but it would do it a funny way, by loading the generator down until an internal 'map' indicated a quantized change in engine constant rpm -- then the engine goes to the new speed via the rack control solenoids while the field drops to match the new engine output. Note that the engine never lugs or bogs down: its fuel feed is adjusted automatically up to the point it's getting maximal injection (and producing max MEP) at a given crank speed -- at which point it jumps to a higher speed that can burn more fuel per hour and hence produce more horsepower.
You could build a car this way, and in fact some were: there are clear advantages to running an internal-combustion engine at constant speed for emissions.
Meanwhile the gear ratio of the final drive remains unchanged, this being a conscious decision. Westinghouse and GE both developed 'traction motors with gear transmissions' and patented them... but you will note that no successful road locomotives use them. That mechanical transmissions work nicely in lighter vehicles is easily demonstrated in the many countries that successfully use various types of mechanical-drive railcar, and there are ways to build gear transmissions for the required power per axle if modern road locomotives. But these are expensive, need to be maintained, introduce additional points of failure, etc. And it might be observed here that one vaunted advantage of 'electric cars' (as with steam cars, btw) is that "no expensive and complex transmission is needed"
The role of more efficiently using the available engine power, which is what the transmission does for engines with restricted powerband, is instead done electrically, either by manipulating series/parallel as in transition or doing field weakening of the motors in the time-honored EMD methods (which themselves have changed over the years). Note that this is not acting in the same thing the load-regulation control is -- it is control of motor characteristics that allow a trade off between speed and available torque... which is exactly what a geared transmission actually allows.
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