• E Units Acceleration to High Speeds

  • Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.
Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.

Moderator: GOLDEN-ARM

  by Tommy Meehan
This came about during a steam vs. diesel discussion. A steam fan quoting some statements contained in one of the D. Carleton series of steam photo books.

Briefly, in the early 1950s New York Central had a small fleet of 4-8-4 passenger locomotives and would normally keep a couple under steam at Collinwood engine terminal in Cleveland in case one of the diesel-powered limiteds fell way behind schedule.

Apparently the book stated the Niagara could make up time faster than an E unit since the 4-8-4 could accelerate say a 16-car train to 100 mph in six or seven minutes. Two or three E units geared for 98 mph with the same size train would take twenty minutes to get to 100 mph.

The latter figure sounds kind of long to me. (In fact the commentary by the book author sounds like it might've been pulled out of thin air.)

But what was the rate of acceleration for E units? I know Milwaukee Road had Es that regularly hit the 100-mph rate. Would it take them twenty minutes if they were going all out?
  by D.Carleton
I’m sorry but I’m no where near the family library or archive so I’m going from memory. It sounds like you’re referring to our book Memories of New York Central Steam by Arnold Haas. To say Mr. Haas was a perfectionist would be an understatement. His notes and data were thoroughly scrutinized prior to typesetting. Any facts and performance data came from actual field observations, not rumor or hearsay. Obviously I wasn’t there but if Arnold says it took twenty minutes for a set of E-units to reach the century mark with a long train then it took twenty minutes. Of course Arnold was known to be rather preferential toward his “dirty beasts” but that’s another story.
  by Tommy Meehan
Thanks very much, Mr. Carleton, I've purchased and enjoyed many of your books.

Yes, I think it was the Hass book, Memories of New York Central Steam.

I wonder how he would know that, though, unless he was present during testing or regularly rode the head end where he could keep on eye on the speedometer. Who was he anyway, do you know his background?

One thing I can tell you, a number of former New York Central employees say it may be that he's right, but they never heard that story from colleagues. And some say it doesn't sound right, that the Es could get a train up to track speed fairly quickly, three of them had the same horsepower as a 4-8-4 Niagara but developed much more tractive force at the lower speed range.

Perhaps there was a lag between say about 65 and 100, where a Niagara would be just hitting its full power range and the diesel's tractive effort would be falling off.

Another point was whether Central would try and get delayed limiteds back on schedule by running them 100 mph from Cleveland to Buffalo or Toledo. Could be but former employees that you might think would know about that never seem to have heard that particular bit of Central lore.

But I learned never to say never a long time ago. :-)
  by Jtgshu
It takes a GP40 (well a single one) at times up to 10-15 minutes or longer to hit 100mph, and ive experienced that with just 3 or 4 commuter cars, but then sometimes other locos are more peppy than others and can do it quicker. From 80 to 100 takes a LOOOOONG time. Have to consider grades too - at those higher speeds, downhills REALLY help, and uphills REALLY hurt! hahaha
  by Tommy Meehan
Jtgshu wrote:...downhills REALLY help...
I've seen that, true. I once rode a Conrail late-afternoon Harlem Division commuter train with two FL9s and about five coaches. They were about 8 minutes late at White Plains and the train crew (who I was sitting with) were concerned because they had a very quick turnround at Grand Central. The conductor said the engineer was going to make up some of that time. We left White Plains and the head end kept pouring it on. There's a little southbound descending grade just out of White Plains and I swear that engineer used it like an acceleration ramp on an Interstate highway. Hartsdale station is at the foot of that grade and we were flying by the time we slammed through the platform area. I felt sorry for the people on the platform waiting for the local behind us. Never went through Hartsdale as fast and never expect to do it again.

Yes I have heard Amtrak engineers say once you get up there speedwise each additional mph can take some time.

jtgshu do the GP40Ps get up to 60-70 fairly quickly and then accelerate much more slowly over the next 20-30 mph?
  by Jtgshu
Indeed they do - they are VERY quick at slower speeds, when taking off, get up to like 15-20mph in no time, 20 to 40 takes some time, but isn't unreasonable, but you can see that its starting to slow down accelorating, as the ammeter backs off the faster you go. In Notch 8 at say 95mph, it might only be pulling 175-200amps, where as Notch 8 when starting off from a stop could load 12-13,000amps (well it could load more if there is a hill or whatever, and plunge down into the red, to 15k plus, but from a normal start for a commuter train, which is what im familar with) thats the drawback of DC motors, and the way they load, while AC motors will just keep giving you more and more power.

With say 1 GP40 geared for 102mph and 6 commuter cars (about 115,000 lbs each) it takes about .85 miles to get to 55mph ish, about 2.5 miles to get up to 80mph, but it can take 5-10 miles to hit 100mph.

Above like 70, its like 1MPH for every maybe 10-15 seconds, and from 90-100, that takes even longer, if it can even make it. Ive been on locos that haven't made 100mph with 3 cars, but then Ive dragged 8 Multilevels at 100MPH with a different, much more peppy Geep - each loco is different with how it performs, which also contributes alot to how fast shes gonna get from A to B!

so i think the slowness of the diesels compared to the steamers might be true!!! or at least possible and probable!
  by Allen Hazen
The New York Central did a careful comparative study of its "Niagara" 484 against EMD's E-7 over something like eleven months. The results were published as a pamphlet with a title like "A Practical Evaluation of Railroad Motive Power," with Paul Kiefer (the New York Central mechanical supremo known as the designer of the Hudsons and Niagaras) as at least nominal author: figures may come from there. (It's been a LONG time since I looked at a copy!)

A lot depends on whether you are talking about a 2-unit (4000 hp) or 3-unit (6000 hp) E-7 set. I don't remember specific figures about acceleration at high speeds, but in terms of train performance over a few hundred miles of "Water Level Route," I think the conclusion was that 3-units of E-7 could equal a Niagara, but that 2-units were more nearly the performance-equivalent of a Hudson... and that was enough, under normal conditions, for New York Central's timetables.

The general principle about diesels not being as good at accelerating at high speeds is true. A diesel-electric locomotive is close to being a constant-horsepower machine: once you are going fast enough to avoid wheel-slipping you get the same drawbar horsepower at all speeds: not QUITE a fixed proportion (about 82% for first- and second-generation diesels) of the engine horsepower, but pretty close. (If you don't, your locomotive's electrical system was badly designed!) Tractive EFFORT -- the force with which the locomotive pulls at the train -- is proportional to drawbar horsepower divided by speed, so at high speeds the diesel doesn't have much oomph for further acceleration. Steam locomotives are different: their horsepower increases (a bit less than linearly) with speed up to an optimum that was usually fairly high. I don't remember specifics, but I think a Niagara didn't reach peak horsepower until it was going over 60 mph. Bottom line: diesel locomotive will not be as good as steam in accelerating (say after a curve with a 60mph speed restriction) to maximum speed, but the steam locomotive will be MUCH worse at lower speeds. Leaving the station, a 2-unit E-7 will have a tractive effort of something like 100,000 pounds (adhesion limited: roughly a quarter of the weight on the eight motored axles) and so will get away faster than a Niagara whose peak tractive effort is closer to 60,000 pounds.
  by D.Carleton
I think everyone is drawing the same conclusions as Mr. Haas did. He never could understand how diesels could replace steam on passenger trains. Delays on passenger runs are inevitable. You cannot leave a station early, but you can leave late. Making up that time en route is difficult but even more difficult with diesels due to slower acceleration at higher speeds, i.e. accelerating out of curves, slow orders, etc.

As for Mr. Haas, I’ll let one of the other D.Carletons reply:
Arnold went to the same temple as the man who designed the Niagara. Their wives and children were friends. They had survived the Nazis. Arnold was younger and inherited all the pertinent data... Arnold had cab riding privileges on the New York Central. He rode New York to Buffalo at least two Sundays every month. He found that brand new E7s could accelerate a train from 0 to 80 as swiftly as a Niagara, and faster than a Hudson; and there it ended. The E units had the tractive effort but not the horsepower to continue accelerating. At eighty the Niagara was in the heart of its horsepower curve and could easily continue accelerating to 110.
As for my memories of Mr. Haas, he was the personification of dignity and grace; a gentleman’s gentleman. He always received us kindly and always imparted some facet of railroading wisdom to us.
  by Tommy Meehan
Allen Hazen wrote: A lot depends on whether you are talking about a 2-unit (4000 hp) or 3-unit (6000 hp) E-7 set.
Thanks very much. Very interesting reply.

One thing I can add -- this is from a former NYCRR design engineer familiar with the steam-to-diesel transition. The two-unit E consist was less costly to operate than a Niagara and adequate power for most passenger trains. A three-unit E unit consist was roughly equivalent to a Niagara (though more costly to operate) and could be made available when needed. (The 20th Century Limited almost always ran with an A-B-A locomotive.) In this former NYC engineering staff official's opinion, this alone doomed the Niagaras.

Mostly I thank Mr. D. Carleton for a fascinating peek behind the scenes.

I was especially interested to read that the late Arnold Hass was a very gracious man. The person paraphrasing him (on another list) made him sound just the reverse. To the extent that someone objected off-list that perhaps the reason Mr. Hass (and the poster) were so disgusted with New York Central management under Al Perlman was that they were anti-Semites. Since Mr. Hass was apparently Jewish -- as well as of gentlemanly disposition --I'm relieved to know this was not the case. (At least for Mr. Haas, that is.) :-)