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  • Alco PA Top Speed for certain railroads?

  • Discussion of products from the American Locomotive Company. A web site with current Alco 251 information can be found here: Fairbanks-Morse/Alco 251.
Discussion of products from the American Locomotive Company. A web site with current Alco 251 information can be found here: Fairbanks-Morse/Alco 251.

Moderator: Alcoman

 #1551052  by jamosb
 
I know it could reach technically 117 MPH with certain gearing out of the factory. What I am asking is what Roads used to gear them to reach top speed and what that was?

Specifically, I read in a Santa Fe book that after the regulations in the early 1950's based on a 1946 crash, that without advanced signaling on the trains/tracks Passenger Trains were restricted to not upwards of 79 MPH.
But, Santa Fe on their tracks were given permission to run to 90 (I'm guessing class 5 tracks?) and they geared their PA's to 90 MPH.

Reason I really am interested in this I have a LAB consist for my HO DCC system of PA/PB/PA (Yes they used L for Lead) and have them now set at 90 sMPH.

Any insights on this and other Roads using PA's? I have a NYC PA that I have set to 80 sMPH top speed as I figured they were probably limited to not exceed 79 MPH.

Thanks for any help!

Jamos
 #1551158  by Allen Hazen
 
Maximum speed permitted by the gear ratio and maximum speed permitted by the railroad's rules aren't necessarily the same: I think it was common practice to get diesel locomotives with a gear ratio allowing a significantly higher speed than was anticipated in service. (Apparently it is not good practice -- subjects the gears to more wear than desirable -- to operate at the theoretical maximum speed very much. U30B and later 4-axle GE U-series locomotives were typically given gear ratios allowing 75mph (??? maybe more), but very few railroads would regularly have run freight trains at such speeds.)

With that caveat... George Elwood's great "Fallen Flags" rail image website has locomotive diagrams for the New York Central and the Pennsylvania (and a few other railroads): at least the New York Central's diagram includes the gear ratio.

The New Haven had its Dl-109 locomotives geared for 80mph (lowest gearing available for that model, which they bought as dual-service units). I think, but am not quite sure, that they continued that with their PA fleet.
 #1551163  by TrainDetainer
 
Max speed is not really about gear wear. It's about maximum rotational speed of the TMs. They are very dense and engineered to operate (up to) close to the point where the mass will fly apart. Turning a TM into a mess of spaghetti means locked axles and resultant destruction/derailment. Specifications for gearing above the RR published max speed is generally a safety margin issue. Higher gearing reduces starting TE, so it's only used for passenger and true hot-shot freight like Santa Fe's high speed intermodal.
 #1551166  by jamosb
 
Well I know for a fact that Santa Fe geared their PA's to only reach 90 MPH in the early 50's due to their tracks and trains meeting ICC guidelines. I believe they were originally geared for around 100 before that.
the famous ruling was this : Trains without "an automatic cab signal, automatic train stop or automatic train control system "may not exceed 79 mph." The order was issued in 1947 (effective 31 Dec 1951) by the Interstate Commerce Commission following a severe 1946 crash in Naperville, Illinois involving two Chicago, Burlington & Quincy Railroad trains.

So I am talking mid 1950's what PA's in what roads were geared to run at ?
I think some roads just left them geared for 100 mph and they just followed the track restrictions but I am guessing most didn't trust their engineers to follow this and geared them down. Also fuel savings would come into play to slow them down.
I think I have ATSF PA's covered correctly.
 #1551250  by jamosb
 
Ok just got Alco Locomotives from Brian Solomon:

Top speed 58:25 gearing rated for 117 MPH giving 24,000 continuous tractive force at 26 MPH, not sure if any were delivered with this gearing.

Most PA's had 62:23 gearing rated for 100 MPH giving 27,000 continuous tractive force at 23 MPH delivered.

After 1947 rulings:

Santa Fe and a few others (D&H for example) who had basic ATS geared 62:21 rated for 90 MPH giving 30,500 continuous tractive force at 20 MPH.

Most other railroads without basic ATS set the PA's to 64:19 gearing rated for 80 MPH giving 35,000 continuous tractive force at 17 MPH.

Still guessing SP, NYC, and PRR geared for 80 MPH after 1947.
 #1551306  by Allen Hazen
 
Background information: The "Fallen Flags" website (a great resource for railroad history!) also has some Alco manuals, including one that lists the various AVAILABLE gear ratios and speeds they were good for: I don't know if all the options were actually chosen by customers. Either this forum or the "Railroad.net" GE forum has a long string titled "PA-1 traction motors": lengthy discussion (me and also people better informed than I am) of the history of this aspect of the PA. ... Note that the PA was available with either 40" or 42" wheels, and with either 752 or, at least early on, 746 traction motors. (The 752 was introduced about the time the PA was released, and was a higher capacity motor than its predecessor, the 726, which had been used on at least the New Haven's Dl-109 units. The 746 was a more expensive, but available a bit earlier, motor that was standard on the Fairbanks-Morse "Erie built.")

A couple more data points:
--- The Pennsylvania Railroad bought its PA/PB locomotives geared for a 100mph top speed. They later decided to standardize on EMD E-units for passenger trains and reassigned (at least the cab units) of their PA fleet to freight service, and in 1954 regard the A units for 80 mph top speed. (Source: Stauffer's "Pennsy Power II".). I believe the Union Pacific also regard their PA units when reassigning them to freight duties, but that most railroads didn't bother. (Source: I don't remember; perhaps an article on the PA in "Trains" decades ago.)
--- The Southern Pacific's PA had the 90mph top speed gearing (62:21). (Source: an ancient SP roster in "Extra 2200 South," from the 1970s.)

(Train Detainer: Yes, the maximum speeds listed for various gear ratios are for preventing catastrophic "birds-nesting" of the traction motors. I did some arithmetic a few years ago, and the maximum speeds for different gear ratios are, in fact, correspond very closely to the same rotational speed of the traction motor: around 2200 rpm i.i.r.c. Someone, in a discussion on this or the GE forum a few years back said that the reasons for buying locomotives geared for a higher maximum speed than they would ever be run in service included gear wear issues. Being an amateur -- a railman -- I don't know the details.)
 #1551307  by Allen Hazen
 
Data point: The Nickel Plate had a 70mph mainline speed limit. Their "Bluebird" PA-1 units had the 62:21, 90mph, gearing. (Source: Rehor's "The Nickel Plate Story," p. 272.)
 #1551351  by RSD15
 
As for NYC all the PA1 and 2s came with 100mph gearing , EMD E8s 98 mph, even a group of FM Erie Built 103 mph later reduced to 97.
Apparently NYC felt the need for speed as their last freight units came with high speed gearing . Alco C430 and GE U30b both came geared for 75 mph and GP 40s for 77. There was also an odd group of GP35s geared for 85 mph.
 #1551361  by jamosb
 
Allen Hazen wrote: Fri Aug 28, 2020 10:57 pm Background information: The "Fallen Flags" website (a great resource for railroad history!) also has some Alco manuals, including one that lists the various AVAILABLE gear ratios and speeds they were good for: I don't know if all the options were actually chosen by customers. Either this forum or the "Railroad.net" GE forum has a long string titled "PA-1 traction motors": lengthy discussion (me and also people better informed than I am) of the history of this aspect of the PA. ... Note that the PA was available with either 40" or 42" wheels, and with either 752 or, at least early on, 746 traction motors. (The 752 was introduced about the time the PA was released, and was a higher capacity motor than its predecessor, the 726, which had been used on at least the New Haven's Dl-109 units. The 746 was a more expensive, but available a bit earlier, motor that was standard on the Fairbanks-Morse "Erie built.")

A couple more data points:
--- The Pennsylvania Railroad bought its PA/PB locomotives geared for a 100mph top speed. They later decided to standardize on EMD E-units for passenger trains and reassigned (at least the cab units) of their PA fleet to freight service, and in 1954 regard the A units for 80 mph top speed. (Source: Stauffer's "Pennsy Power II".). I believe the Union Pacific also regard their PA units when reassigning them to freight duties, but that most railroads didn't bother. (Source: I don't remember; perhaps an article on the PA in "Trains" decades ago.)
--- The Southern Pacific's PA had the 90mph top speed gearing (62:21). (Source: an ancient SP roster in "Extra 2200 South," from the 1970s.)

(Train Detainer: Yes, the maximum speeds listed for various gear ratios are for preventing catastrophic "birds-nesting" of the traction motors. I did some arithmetic a few years ago, and the maximum speeds for different gear ratios are, in fact, correspond very closely to the same rotational speed of the traction motor: around 2200 rpm i.i.r.c. Someone, in a discussion on this or the GE forum a few years back said that the reasons for buying locomotives geared for a higher maximum speed than they would ever be run in service included gear wear issues. Being an amateur -- a railman -- I don't know the details.)
Great info thanks! Pretty much matches mine about ATSF. I figured SP's were geared to 90 MPH also they were using ATS units also.
 #1551363  by jamosb
 
RSD15 wrote: Sat Aug 29, 2020 6:05 pm As for NYC all the PA1 and 2s came with 100mph gearing , EMD E8s 98 mph, even a group of FM Erie Built 103 mph later reduced to 97.
Apparently NYC felt the need for speed as their last freight units came with high speed gearing . Alco C430 and GE U30b both came geared for 75 mph and GP 40s for 77. There was also an odd group of GP35s geared for 85 mph.
I figured most were delivered with 100 MPH gearing even ATSF. But the fact that you say NYC GP35's were geared for 85 MPH has my assumptions thinking they geared their PA locos to 90 after 1951 as obviously they must of had ATS.

Do you know when track classification came into play what year? Class 5 was allowed up to 90, Class 4 (Most Mainlines) were restricted to 80 MPH. I also read that now that Amtrack is doing away with their ATS systems they will be slowed to 80 MPH in the near future.
 #1551417  by Allen Hazen
 
Re: "Apparently NYC felt the need for speed as their last freight units came with high speed gearing . Alco C430 and GE U30b both came geared for 75 mph and GP 40s for 77. There was also an odd group of GP35s geared for 85 mph."
----I don't think this was just a New York Central thing. The higher speed gearing was standard for U30B (and U33B and U36B), and Alco used GE electrical equipment and so would have followed GE practices in traction motor application. Very few railroads ran freight trains at 70+ mph. (I think the "Super C," the Santa Fe's super-express TOFC/COFC Chicago-Los Angeles train of the 1970s, may have run up to the 79mph speed limit in places: after Amtrak took over the Super Chief, ATSF used high-speed former passenger units, such as the FP45, on this train.)
I assume the reason for choosing the high-speed gear ratio as a standard for the U30B had to do with a desire on the part of GE to have a margin between expected operating speeds and nominal top speed. The drawback, of course, is that it would have raised the minimum continuous speed (the speed at which full power can be used for an unlimited time without overheating the traction motors), but high horsepower units like the U30B would have been operated at less than maximum power anyway at lower speeds, so I guess GE and its customers didn't think this was important.
---
As for New York Central's GP40... Some years back there was a retired GE person who regularly posted to (an ancestor of) this Forum. He recounted that one time a bunch of GP40 stalled with a freight on the West Albany Hill, and the train had to be rescued by a set of ... U25B units. When this was reported, there was great glee in Erie.
 #1551432  by jamosb
 
Allen Hazen wrote: Sun Aug 30, 2020 10:48 pm Re: "Apparently NYC felt the need for speed as their last freight units came with high speed gearing . Alco C430 and GE U30b both came geared for 75 mph and GP 40s for 77. There was also an odd group of GP35s geared for 85 mph."
----I don't think this was just a New York Central thing. The higher speed gearing was standard for U30B (and U33B and U36B), and Alco used GE electrical equipment and so would have followed GE practices in traction motor application. Very few railroads ran freight trains at 70+ mph. (I think the "Super C," the Santa Fe's super-express TOFC/COFC Chicago-Los Angeles train of the 1970s, may have run up to the 79mph speed limit in places: after Amtrak took over the Super Chief, ATSF used high-speed former passenger units, such as the FP45, on this train.)
I assume the reason for choosing the high-speed gear ratio as a standard for the U30B had to do with a desire on the part of GE to have a margin between expected operating speeds and nominal top speed. The drawback, of course, is that it would have raised the minimum continuous speed (the speed at which full power can be used for an unlimited time without overheating the traction motors), but high horsepower units like the U30B would have been operated at less than maximum power anyway at lower speeds, so I guess GE and its customers didn't think this was important.
---
As for New York Central's GP40... Some years back there was a retired GE person who regularly posted to (an ancestor of) this Forum. He recounted that one time a bunch of GP40 stalled with a freight on the West Albany Hill, and the train had to be rescued by a set of ... U25B units. When this was reported, there was great glee in Erie.
Still, giving them gearing so high would hurt their tractive power, so why do it when regulations restrict your speed anyways? Strange but that is NYC.
 #1551512  by Allen Hazen
 
Re: "Strange but that is NYC." --- Thing is, I don't think it WAS New York Central: GE used the same gearing on U30B for other railroads. So I think it was a GE thing: they must have thought the most sellable high-horsepower B-B unit (and the most maintenance free during the warrantee period!) was one geared for a top speed it would never reach in normal operation.
As for hurting the tractive power... I think the effect of changing the gear ratio on the short-time tractive power -- the amount of pull the locomotive could exert, at a given speed, for a period of minutes -- was minimal. What it affected was the CONTINUOUS rating: the amount of pull it could go on exerting for a long time without damaging its motors, and the speed at which it could do this. I think that GE's figuring was that a U30B would never be asked to use full power at low speeds for more than a short time (e.g. in starting a heavy train), and that any usefulness it lost in not having a lower continuous speed and higher continuous t.e. was outweighed by the advantages of the high speed gearing. (Advantages, I think, stemming from the maintenance costs of regularly operating at the maximum rated speed.)
 #1551518  by jamosb
 
And I always thought those U-boats were loved. Guess this is why EMD took over in the industry at that time. Alco with their maintenance issues with the 244 engine (mainly just bad reputation because the engines were fixed in the 50's), and later GE (after the split) doing poor design. Although today, GE rules and EMD is just hanging on, and of course Alco is history.