• Fairbanks-Morse Control Systems

  • Discussion of Fairbanks-Morse locomotive products. Official web site can be found here: www.fairbanksmorse.com.
Discussion of Fairbanks-Morse locomotive products. Official web site can be found here: www.fairbanksmorse.com.

Moderator: pablo

  by Pneudyne
Transferred from the EMD “Field loop Dynamic Brake Control: thread, https://www.railroad.net/emd-field-loop ... 52156.html, specifically from this posting: https://www.railroad.net/post1617096.html#p1617096.
Typewriters wrote: Wed Mar 01, 2023 10:25 am
Off topic for an EMD thread here but F-M also adapted GE control equipment to use an air throttle. That's actually pretty straight forward except in the case of amplidyne excitation they had to add an air operated step controller to set current (excitation) limits progressively as the throttle pipe pressure increased since they couldn't get that signal another way.
That is one that I had not previously known about!

GE itself did use air throttles here and there, examples being the Queensland Railways 1150 and 1170 classes, and the US Gypsum (USG) 54-ton model. But these were with the simple split-pole excitation system. Also, notched throttles (7 or 8 notches) were used, which did allow for some electrical switching at notch changes, and I think this was done for the USG model.

I guess that with the change from Westinghouse to GE electrical equipment, F-M wanted to retain air throttles on those models that had previously used them. And at say the 1600 hp and above level, the split-pole system was probably seen as inadequate, hence the need to adapt the GE Amplidyne system.

Nonetheless, the “translation” from air pressure to electrical control signals does seem to have been viewed as being a more difficult proposition than the other way around, and perhaps something to be avoided if possible. For example, in the British Rail case, it developed an electric-to-air conversion technique, but it addressed the air-to-electric requirement by sidestepping it, and equipping locomotives with dual-function master controllers that could deliver both air and electric signals.

Another case of avoidance was with the early Locotrol system. Rather than “translate” from air pressure to electrical signals, braking control was done electrically by push buttons on the Locotrol control panel, and then translated into the air pressure domain.

Thus, necessity meant that F-M made quite a bold step in using air pressure to electrical translation.

That said, I understand that the original Westinghouse proposal (not implemented) for acceleration control on the PCC streetcar was to use an air manifold with multiple diaphragm operated switches, set to close at progressively higher air pressures, with manifold air pressure progressively increasing under the control of the acceleration relay. So the air-to-electric idea was not new. And techniques were developed in the 1960s when the need arose for blended dynamic braking.

Returning to the F-M case, it did appear to have used a variety of control systems, a partial list being:

Its own air throttle system with Westinghouse equipment on some of the earlier H-series models.

GE Amplidyne with potential wire dynamic braking control on the “Erie-built” models.

Wemco with field loop dynamic braking control on the “Consolidation” line and early TrainMasters.

GE Amplidyne and then Static with its own Universal dynamic brake control on later TrainMasters.

GE Amplidyne with its own air throttle and interface on some later H-series models.

I am not sure if dynamic braking was ever used with any of the F-M air throttle variations.

  by Typewriters
Air throttle: I believe there were no Fairbanks-Morse locomotives built with air throttle and dynamic brake. I do know that over time there were two different pressure ranges employed.

Universal Dynamic Brake: I've just acquired an operators manual for NYNH&H 1600-1614, which were model H16-44 and whose contract information sheet carries approval dates of 3/26/56 and 3/27/56. In the information boxes at the top of this sheet you find a line labeled "MU DATA" and on this one we find "ALCO DL701 EMD GP9 MTR & BRK" (motoring and braking) and sure enough in the list of "electrical specialties" below that we find Universal Dynamic Brake. So far, I can guarantee that the last batch of B&O H16-44 units, these H16-44 units, and Reading 806-807 had the universal dynamic brake; there must have been more but I have no information to tell me which had and didn't have it.
  by Pneudyne
F-M Manual #1204B of 1951 February, covering the H16 and H20 models (1), gave two pressure ranges for the pneumatic throttle, as shown in this page:

F-M H-Series 195102 Sec 132A p.17.png

One may then ask, why two ranges, and did one precede the other.

The H16 and H20 were shown as having the pneumatic-hydraulic version of the Woodward PG governor, thus with internal speed control.

Previously, though, F-M had used the Wabco external diaphragm-type pneumatic governor actuator, as shown in this diagram from McGowan (2):

McGowan p.272,273.png

There is some evidence that this kind of actuator was typically operated with a 60 lbf/in² full throttle pressure. The same or a very similar unit was offered by Westinghouse UK, and used for example by Rolls Royce on DMU powerplants. The 60 lbf/in² number was mentioned in Doherty:

Doherty p.219,220.png

Baldwin also used the same actuator a 60 lbf/in² maximum nominal pressure, but that is something for the Baldwin forum.

Possibly then F-M started with the 60 lbf/in² Wabco number, then when it started using the Woodward PG governor, found that it would work well or perhaps better with a 30 lbf/in² maximum, and chose to standardize on thus number. Although why 30lbf/in² would be better is a matter for speculation. But it still needed to offer the 60 lbf/in² maximum for customers who required backward compatibility with earlier F-M units.

Manual #1204B shows the H16 and H20 as having had what might be called “conventional load control, with the pilot valve internal to the PG governor, this controlling external rotary rheostats. (Unusual though was that these were operated by governor oil, whereas the norm for external rheostats was to use engine oil.) Anyway, with the standard PG governor arrangement, load increased monotonically with engine speed (although there were variations on this for some builders).

How load control was done for the earlier F-M units with Wabco actuators is unknown, other than that it was probably external to the governor. There one finds some variations, e.g. EMD with an external floating lever and pilot valve used with the Woodward (old) SI governor, and Baldwin with a maximum-only load control switch with the Woodward UG8 governor.

(1) F-M Manual #1204B is available at: https://www.rr-fallenflags.org/manual/fm-index.html

(2) George F. McGowan; Diesel-Electric Locomotive Handbook – Electrical Equipment; Simmons-Boardman, 1951.

(3) J.M. Doherty; Diesel Locomotive Practice; Odhams, 1962.

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  by Pneudyne
I should also mention that F-M Manual #1204B had scant mention of dynamic braking. It was referred to only in connection with the selector lever function with the Wemco electric throttle control, and not at all in connection with pneumatic throttle control:

F-M H-Series 195102 Sec 101A p.09.png

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