today I would like to ask for your help to explain to me the true power of steam. Today’s modern AC locomotives produce tractive efforts equivalent to that of the large articulated steam locomotives. At the same time the horsepower is not that much different either, so the pulling power should be the same. It seems to me that it is not, just look at this youtube video:
I have no idea what the grade is but for any locomotive to move 7300 tons at 35 mph up even a slight grade takes, a lot of power. Also the Yellowstones at the DM&IR moved 15000 ton trains by themselves and according to the magazine “Classic Trains” the C&O had their T-1’s haul 13500 ton coal trains.
So my question is are steam locomotive HP and torque values too low when compared to diesel locomotives with respect to what they can haul down the track?
Thank you for your replies
Frank
PS: Sorry, the [url]put the address here[/url does not work]
A diesel can START more train than it can pull at speed. A steam locomotive can pull more train than it can start.
The reason can be found in the graph of developed horsepower. A steam locomotive really doesn’t have much power (as compared to tractive effort) at a standing start. The horsepower curve climbs until the cylinders are using exactly as much steam as the boiler can generate. Beyond that speed, horsepower drops off. There is only a very narrow speed band where a specific steamer develops its maximum horsepower.
In contrast, the diesel prime mover can turn out its full rated horsepower at any speed from a dead stop to just before the traction motors fly apart. The horsepower ‘curve’ is almost a flat line.
As somebody wrote more than half a century ago, the key wasn’t the 6200 HP that a UP 4000 could develop at 55MPH. It was the <5000 HP that it sustained dragging a load up Weber Canyon. A 6000 HP diesel (one, two, or three units…) developed then, and develops now, 6000 HP starting, 6000 HP grinding upgrade and 6000 HP flying across the flatlands. Since it also is FAR more fuel efficient, doesn’t need water in massive gulps and gets by on a lot fewer maintenance man-hours per operating hour…
There is no difference in the definition of power between steam, diesel-electric, or electric locomotives. All locomotives simply produce a pulling force. The amount of force produced at a given speed is power, commonly know as “horsepower”. This is a mathematical definition, and what type of equipment produced the force doesn’t matter.
In other words, 4000 HP at 35mph is the same regardless of whether a steam, diesel, or electric locomotive is producing the power.
The tonnage you quoted for the C&O T1 was going in the downhill direction. Same with the DM&IR Yellowstones. They pulled their maximum tonnage downhill from the ore mines to the docks at Lake Superior. In fact, the DM&IR locomotives faced their hardest work pulling the empty cars back to the mines.
The B&O 2-8-8-4 EM1s, which were more advanced locomotives than the DM&IR versions, were only rated at 1500 tons going upgrade at the Sandpatch and 17 Mile Grades. The point being there is a huge difference between a real mountain grade, and a downhill / level run.
The video you posted of the Challenger was discussed in detail in another thread. Basically, that run is downhill, and Archer Hill is a slight upgrade in the downhill run. It is short enough where a heavy train can carry a lot of momentum into the grade, and thus the energy imparted to the train by gravity will help move the train up the small grade (similar to a roller coaster at an amusement park).
Here is a video of what modern AC’s can do. 2 CSX AC4400s, 19,000 tons, running at 50 mph.
We should remember, too, that a steamer can’t put it’s best shot onto the rail surfaces as a diesel can. For most/all diesels, all the axles are driven and they all share the distribution of weight for the entire mass of the loco, sprung and unsprung.
A steamer only drives with somewhat fewer wheels unless it is a truckless multi-coupled switcher or maybe a geared engine. The weight supported by the trucks fore and aft is just that, and contributes much less to the adhesion and tractive effort that the fewer centered drivers can admit to the process.
So, I think it is faulty at the outset to say that diesels are producing the tractive effort of the large articulated steamers…as if they have only just caught up in 2010. Not so! They may not have quite the horsepower, but what they produce is much more efficiently applied to the tractive effort intended by their respective designers. Your Challenger might produce 103K pounds of tractive effort, give or take, while a modern AC4400-type must be closer to 140-160K…not sure of my figures, but I must be essentially correct. ?
As always, you have to decide what steam locomotive to compare to what diesel.
The C&O 2-10-4s supposedly pulled their 13,500 ton trains up sustained 0.2% upgrades, but we don’t have much idea how fast they were pulling those trains, or how reliably. A single ES44/SD70AC would pull the same tonnage on 0.2%, and we don’t know whether it would pull it faster or not.
We don’t know for sure whether a single ES44/SD70 could do as well as the 4-6+6-4 on Archer Hill (probably not)-- but if you compare with two units…
A single ES44 would pull more total tonnage up Archer, thanks to its much better adhesion and higher TE. I suspect the 3985 would make faster time with a train it could pull, due to a 600 - 700 HP advantage it would have over the ES at 35-40 mph. Or maybe not. The 3985 has a small capacity boiler compared to a N&W Class A or Yellowstone…
The typical coal hopper of the era of the Challengers, Big Boys, EM-1’s, etc. was fifty tons, which was an upgrade from the earlier forty tons. Today, you may be hard-pressed to find a coal hopper (or ore, or whatever) under 100-ton capacity, what with modern bathtub-bottom cars. So, in effect, the two AC6000CW’s seen in the CSX video above are hauling a train 2.5-3 times as long as your train of B&O 2-8-8-4 days, with double the capacity–i.e. at least five times the train with (something like) double the locos…
… or not. Knowing the line in question and where they could be going, it’s about a 50-50 shot whether that train is empty (heading west from Baltimore for a reload) or full (heading down to the Pope’s Creek Secondary and two power plants down there). Even on the relatively flat Pope’s Creek, you need at least 1 hp per ton, which is barely acceptable for low-speed drag service…
Either way, the answers are pretty much the same, and do hearken back to that train-you-can-start versus train-you-can-run cliche. AC power trumps that one further, with much more ability to accept massive short-time starting “overloads” unacceptable for DC motors. (Electric locomotives are the same way: The PRR GG1 was rated for 4620 hp running, but could handle up to 10,000 hp short-term overload to get a train moving.)
When I said “Archer Hill” I was referring to the eastward climb where the 3985 put on its show with the stack train. We don’t know enough about the 4-6+6-4’s power vs speed to know whether it could beat an ES44AC there-- for that matter, we don’t know enough about the ES44’s power vs speed. It would of course beat the 4-6+6-4 on any long climb, but the down-then-up Archer Hill momentum climb is tougher to figure.
Whoa there. The diesel engine defines the unit horsepower, not the technical short-term overload capacity of the traction motors. There is no “massive” overload capacity in a diesel-electric locomotive.
The DC version overheats below app. 11 mph; the AC traction motor does not. A 4,000 hp locomotive generates the same maximum hp in the AC version as the DC version.
There is no difference in the definition of power between steam, diesel-electric, or electric locomotives. All locomotives simply produce a pulling force. The amount of force produced at a given speed is power, commonly know as “horsepower”. This is a mathematical definition, and what type of equipment produced the force doesn’t matter.
In other words, 4000 HP at 35mph is the same regardless of whether a steam, diesel, or electric locomotive is producing the power.
The tonnage you quoted for the C&O T1 was going in the downhill direction. Same with the DM&IR Yellowstones. They pulled their maximum tonnage downhill from the ore mines to the docks at Lake Superior. In fact, the DM&IR locomotives faced their hardest work pulling the empty cars back to the mines.
The B&O 2-8-8-4 EM1s, which were more advanced locomotives than the DM&IR versions, were only rated at 1500 tons going upgrade at the Sandpatch and 17 Mile Grades. The point being there is a huge difference between a real mountain grade, and a downhill / level run.
The video you posted of the Challenger was discussed in detail in another thread. Basically, that run is downhill, and Archer Hill is a slight upgrade in the downhill run. It is short enough where a heavy train can carry a lot of momentum into the grade, and thus the energy imparted to the train by gravity will help move the train up the small grade (similar to a roller coaster at an amusement park).
Here is a video of what modern AC’s can do. 2 CSX AC4400s, 19,000 tons, running at 50 mph.
Six of CSXT’s high-tractive-effort 4400-hp GEs can move 130 coal loads (slightly above 17,500 tons) up 2.21% Cranberry Grade and, unless they encounter rail contamination, maintain speeds above eight miles per hour.
We should not forget that this happened 1990, now 20 years ago. I do not think 6000hp dieselz were common that era, so it was a bit more show that time…
17 Mile Grade hits 2.7%. The entire West End of the old B&O is one nasty piece of railroad through the Allegheny Mountains. It is the reason why GE developed the high tractive effort software available on AC locomotives.
The 2-8-8-4 EM1s would pull 1500 tons unassisted up 17 Mile. Heavier trains required multiple rear end helpers, either the 2-8-8-0 EL5 or the 2-10-2 S1a. The rear end helpers served two functions, (1) to provide extra total TE, and (2) prevent the EM1s from pulling the train apart. EM1s then use their high speed capacity on downhill and level sections to maintain line speed.
Thank you for your reply. I remember to have even seen a pair of EM1s functioning as rear end-helpers, that must been quite a show, but do not know it was Cranberry “Sand Patch” or another grade.
Far as us fans know, B&O was built to not exceed 116 ft altitude gain per mile-- i.e. an average of 2.2% for any one mile. So if there were, say, a half-mile of 2.7% then the half-mile just above it and the half-mile just below it were not supposed to exceed 1.7%. I’ve never examined the West End grades, but I’m guessing B&O succeeded in keeping the grade more constant than that.
That’s actual grade, tho-- if a 10-degree curve happens to be on a stretch of 2.3%, that’s ordinarily considered to be around 2.7% compensated for curvature. If you do include curve resistance, the steepest mile on Cranberry or 17 Mile is probably around 2.35%, maybe 2.4% average compensated.