Allen Hazen wrote:I wonder what sort of engine governors were used on earlier GE locomotives with Cooper-Bessemer engines (70-tonners, export U-series)?
It’s an old thread, but I have only just seen this question buried within it. A partial answer:
The export Universals with C-B engines (U9, U12, U18 et seq), as announced in 1956, had Woodward PG governors with built-in load regulator rheostats. They had gear-driven auxiliary generators and exciters, using the customary triplex drive at the free end of the main generator, with the third leg mechanically driving the equipment blower. The overall control system was quite simple, and generally what one might expect from GE. The main generator was heavily decompounded with resultant steeply drooped curves that dropped on to the standstill line to provide carefully graduated starting tractive effort steps. The load regulator rheostat, in series with the exciter battery field, essentially trimmed the curves over their middle ranges to the respective constant power hyperbolae, but their basic positioning was determined by the fixed resistances, switched by throttle sequence relays, also in series with the battery field. Fine power control of the humping type was optional, and as far as I know it was used on the South African U18C1, which may have been a little “light-footed” as compared with the regular U18C. Potential wire dynamic brake control was obtained simply by feeding the exciter battery field directly from the DBX trainwire, which this provided battery field current as well as the reference voltage.
The 70-tonner had a Woodward UG8 governor with solenoid shutdown (energize-to-run). For non-MU units, the 7-notch throttle was mechanically operated. For MU units, the 7-notch throttle was electrically operated by the GE17MK3 electropneumatic throttle operator, external to the governor. All four cylinders of the latter were used in various combinations (although not in all possible combinations) to obtain the 7 steps. It had a belt-driven exciter-auxiliary generator unit, with split-pole exciter, and used inherent characteristic (Lemp 1924) load control. Thus it was much like the Alco-GE 539-engined switchers, except that the latter had 8 notches, and in MU form, used three units of the 17MK3 to obtain 8 steps according to the normal pattern for three-binary-unit, 8-step mechanisms. But there were variations. The Queensland Railways A1A+A1A version, as far as I know, had a 7-notch pneumatically operated throttle (essentially the same as used on the USG 54-ton model) with the UG8 governor. Possibly the earlier C+C versions (supplied to Bolivia, Brasil and Chile) had the same.
Pre-Universal GE export models fitted with C-B 12-cylinder engine were the shovel nose A1A-A1A cab units supplied to Argentina and Chile, and the C-C road switchers supplied to Queensland. The former had amplidyne control with GE 17MG3 governors. The latter had belt-driven exciter-auxiliary generator units and UG8 governors with 8-notch pneumatically operated throttles. As far as I know, they also had inherent characteristic load control. There were several GE export models with the Alco 12-244 engine; C-C shovel-nose cab units for the Congo, Uruguay, Argentina and Chile; C-2-C shovel-nose cab units for Indonesia, C-C cab units for New South Wales, C+B+C road switchers for Guatemala and Columbia, and C-C road switchers for Brasil. To the best of my knowledge, all of these had amplidyne control with GE 17MG3 or 17MG6 governors.
The White Pass & Yukon shovel-nose cab units with Alco 6-251 engines I am not sure about. They had a belt-driven exciter-auxiliary generator unit. So they might have been somewhat like the 70-tonner, with inherent characteristic load control. But then one could not outrule the use of Woodward PG governors with integral load-control rheostats. The latter, together with the belt-driven combination machine, was used in the Alco 6-251 powered DL531 export model of few years later. The WP&Y units had dynamic braking, and my guess here is that the exciter battery field was fed direct from the DBX trainwire as on the later export Universals.
It may be seen that GE had a long and ongoing relationship with Woodward, going back to the 1930s, when the UG8 was a new item. Quite why it made an excursion into its own 17MG series of governors is not recorded, but perhaps one may construct a reasonably plausible story. Its planning for the post-WWII Alco-GE road units included using its amplidyne system, and it may have wanted more precise engine speed and load control than was hitherto possible, whilst avoiding undue mechanical complexity. At the time the Woodward PG governor was apparently still in the future, and possibly GE may not have been aware of it. For the twin-539-engined Alco-GE road units, it had used UG8 governors with rod-shutdown and 8-speed electro-pneumatic throttle operators. Load control was basically by inherent characteristic using split-pole exciters, but speed-switch assisted. So something better was needed. EMD, for its 567 engine at least, had adopted Lemp 1914 load control but with the modification that load point was proportional to set engine speed for each notch, something not in the original Lemp patent. It did this by using the UG8 (or a similar) governor with an external 8-speed electro-pneumatic operator (perhaps based upon the GE unit) and with an external floating lever and load control pilot valve. EMD may have invented this means of speed-proportional load control, and it had a couple of pertinent patents. But on the other hand at about the same time, Sulzer had a patent for the same arrangement inside a governor along with an 8-speed control (and also an optional two-load setting for each speed). So who knows who did what first. The rationale for engine speed-proportional load control was that highly turbocharged engines, unlike their naturally aspirated forbears, did not have flattish torque curves, and needed lower torque settings at lower speeds. The same tended to be true for two-stroke engines, even those without turbocharging.
EMD was evidently happy with what it had in principle, but moved over to the Woodward PG governor starting with its F-3 model. As far as I know it was the first user of the PG. Essentially what the PG did was put the throttle operator, the floating lever, and the load control pilot valve inside the governor, otherwise mimicking exactly the behaviour of EMD's previous arrangement. The PG included a rather neat arrangement for the electro-hydraulic speed control mechanism, which enable the D solenoid to be used both for shutdown when used alone and as a subtractive speed setting element when combined with one or more of the A, B or C solenoids. Whilst I have not seen the exact layout for the earlier electro-pneumatic speed setter, it surely had a set of conjugating levers that allowed the A, B and C cylinders to be additive for speed setting, with the D cylinder subtractive, and when used alone, moving the fuel rod upwards enough to operate the rod stop mechanism. It certainly looks as if the PG was designed precisely to meet EMD’s requirements. Whether EMD claimed any intellectual property is unknown, but it did have a patent that looks pertinent (and which also referred to the addition of the overriding solenoid). If nothing else, it is possible that Woodward kept quiet about the PG until EMD announced the F-3. Or perhaps GE was committed to the 17MG before Woodward started work on the PG. The evidence here is circumstantial and incomplete, leaving one to draw inferences that will not necessarily be correct.
Be that as it may, GE developed its 17MG governor for use in association with its amplidyne control system as its path to improving upon what had gone before. It too had engine speed-related load points, but these were obtained by limiting fuel rod travel, with lower settings for the lower notches. As far as I know, this idea was first added to Lemp 1914 load control by Brown Boveri, although by different means. The GE approach though did not enforce a monotonic relationship between engine speed and load.
One may imagine the eventual ubiquity of the Woodward PG governor – used worldwide by locomotive builders – forced a rethink by GE, hence its selection for the Universal models. Possibly GE had something to do with the development of the integral load regulator rheostat. That was not part of the original; EMD, controlling main generator battery field directly and not via an exciter, required a larger external load regulator rheostat. On the other hand, the integral rheostat was well-suited to the light current requirement of an exciter battery field.
The persuasiveness of industry standardization may also be why GE chose the regular version of the Woodward PG for the U25B, even though it wanted 16-notch control. Conceivably the PG could have been modified to provide 16 speeds without great difficulty. For example, within a couple of years Regulateurs had a 4-solenoid 16-speed version of its 1100 series governor, as well as an 8-speed version. And by circa 1960, Westinghouse had a 4-concentric cylinder, 16-speed external electro-pneumatic throttle operator for railroad applications. Alternatively, two load points for each of 8 speeds would have been possible with a single additional solenoid following the Sulzer example. But either of these pathways would have resulted in a non-standard governor, so may have been outruled for that reason alone. So GE settled for 16 basic main generator curves, giving fine control of standstill tractive effort – which I think was its primary goal - but 8 supervening load curves, meaning that adjacent (half) notches were sharing the same curves over the respective constant power regions. Whether there was actual compromise in respect of the original goal is unknown, but it may be noted that for the UP 8500 hp GTELs, GE had used simple electronics to construct 20 constant power load curves, one for each notch, with the addition of supervening exhaust temperature load control. And I have heard that it was the GTEL precedent that prompted GE to seek more than 8 notches for what in those days was a relatively high power-per-axle diesel locomotive.
Cheers,
