How do the SP 4449 GS4 and the N&W J611 compare in performance?
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Like apples and oranges. They both served their respective railroads perfectly.
Bobby Ogage posted:How do the SP 4449 GS4 and the N&W J611 compare in performance?
Google is you friend.
Never would happen, but seeing 611 NB on the grade north of San Louis would be a very interesting sight!
Really as has been stated they are 2 different locomotives that were built for 2 different roads, that operated in very different terrain predominantly. They both performed and continue to perform admirably in their current assignments. Either way Lima and Roanoke sure knew what they were doing. I would recommend some googling and that way you can compare the numbers at least and see where they differ in that regard. 
Bobby Ogage posted:How do the SP 4449 GS4 and the N&W J611 compare in performance?
Seems like a potentially interesting subject for discussion. They were both dual-service 4-8-4 locomotives capable of handling trains at a good speed, also able to tackle significant grades. Both were allegedly capable of 110mph top speeds. Both classes were new in approximately the same time frame. They were both prestigious and successful locomotives for their respective railroads. Both classes have a preserved operational unit.
you might want to look at the specs on this chart:
Ace posted:Bobby Ogage posted:How do the SP 4449 GS4 and the N&W J611 compare in performance?
Seems like a potentially interesting subject for discussion. They were both dual-service 4-8-4 locomotives
The SP GS-4/GS-5 class locomotive would not have been considered "dual service", with those 80" diameter drive wheels, i.e. a "passenger service" locomotive. At least that was what the War Production Board ruled, when the SP wanted to purchase additional 4-8-4s. They were subsequently forced to purchase "dual service" GS-6 class locomotives with 75" drive wheels.
capable of handling trains at a good speed, also able to tackle significant grades. Both were allegedly capable of 110mph top speeds.
The N&W J Class was indeed capable of speeds well over 100 MPH, however the SP GS class locomotives were not. Even with those 80" diameter drive wheels, the GS-4/GS-5 class locomotives had running gear balanced for only 108 MPH, but with all axles on the GS-3/GS-4 class being plain bearings, and the SP not being known as a "high speed railroad", the GS class locomotives rarely exceeded 90 MPH for any great distances.
Both classes were new in approximately the same time frame. They were both prestigious and successful locomotives for their respective railroads. Both classes have a preserved operational unit.
"a preserved operational unit"? Neither the 4449 nor the 611 are "units" please!
What is surprising to me is how much horsepower the SP GS4 produced, with only 90.4 feet of grate area. Trains Magazine did a dynamometer test of 4449 many years ago and concluded that she was the equivalent of about 2 1/2 E8's (about 5300-5600 horsepower). The N&W 4-8-4 had 107.7 feet of grate and has been oft quoted as producing 5300 DBHP. Both locomotives had 300 psi boilers......and quite similar horsepower production.
Grate area in an oil fired loco is moot. The total heating surfaces of both engines are almost identical.
Heating surfaces: N&W J: 7448 sq ft SP GS4: 6973 sq ft
If the GS4 had 45.2 sq ft grate area, and burned oil, would it produce the same power?
Ace posted:.... They were both dual-service 4-8-4 locomotives capable of handling trains at a good speed,
You are correct that at the very bitter end of the steam era, the N&W Class J was pressed into limited freight service. The Class J was, however designed specifically for passenger service.
mark s posted:Heating surfaces: N&W J: 7448 sq ft SP GS4: 6973 sq ft
If the GS4 had 45.2 sq ft grate area, and burned oil, would it produce the same power?
"Power" as in "Tractive Effort?
Tractive effort is a function of driver diameter, piston size and boiler pressure, not grate area.
Power as in horsepower. TE is not an issue.
"Tractive effort is a function of driver diameter, piston size and boiler pressure, not grate area."
There is one component of the above equation that I really never understood.
Assume everything is the same except boiler pressure in my scenario:
Train A with 63 inch drivers, 24 x 30 pistons, and 200 psi boiler pressure and the engine spins the wheels starting 10 passenger cars.
Train B with everything the same except now with 300psi boiler pressure. This engine still spins the wheels trying to start the same string of passenger cars.
Why is locomotive B considered to have more tractive effort?
It seems to me the boiler pressure (200 psi or 1000psi) is irrelevant in transferring energy to the rail head.
What am I missing?
Thanks.
Charlie
Charlie posted:"Tractive effort is a function of driver diameter, piston size and boiler pressure, not grate area."
There is one component of the above equation that I really never understood.
Assume everything is the same except boiler pressure in my scenario:
Train A with 63 inch drivers, 24 x 30 pistons, 65 feet of grate area and 200 psi boiler pressure and the engine spins the wheels starting 10 passenger cars.
Train B with everything the same except now with 300psi boiler pressure. This engine still spins the wheels trying to start the same string of passenger cars.
Why is locomotive B considered to have more tractive effort?
It seems to me the boiler pressure (200 psi or 1000psi) is irrelevant in transferring energy to the rail head.
What am I missing?
Weight on drive wheels.
Thanks.
Charlie
Jack:
I assumed weight on the drive wheels, weight of train, condition of the track is all the same.
Charlie
Would think higher boiler pressure would produce more horsepower, hence more power to break the wheels free, to spin. More piston thrust.
As an addendum to Steve's observation, the Erie Triplex (2-8-8-8-2) had tremendous tractive effort, could start huge trains, but would run out of steam shortly after leaving the yard. Why? Inadequate steam production as a result of a small grate area. The boiler could not meet the steam requirements of the 6 cylinders, to do any consequential work.
Hot Water posted:The N&W J Class was indeed capable of speeds well over 100 MPH, however the SP GS class locomotives were not. Even with those 80" diameter drive wheels, the GS-4/GS-5 class locomotives had running gear balanced for only 108 MPH, but with all axles on the GS-3/GS-4 class being plain bearings, and the SP not being known as a "high speed railroad", the GS class locomotives rarely exceeded 90 MPH for any great distances.
So the GS-5s with their roller bearings weren't rated at any speeds higher than the 4s? I never knew that. I once had a long discussion with a retired SP steam hogger and he said he ran GS's but couldn't recall the specific handling between the different types within the class.
"Horsepower" is a moving target when talking about steam locomotives. Starting horsepower may be less than the horsepower generated at speed.
smd4 posted:"Horsepower" is a moving target when talking about steam locomotives. Starting horsepower may be less than the horsepower generated at speed.
Direct-drive steam locomotives generate horsepower that builds with speed, essentially.
One of the most fundamental limitations of steam locomotion is the inability to apply as much effort to start a train, compared to diesel or straight-electric power. Steam cylinders have to develop starting power from a standing stop because of the direct drive with no variable transmission effect.
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smd4 posted:"Horsepower" is a moving target when talking about steam locomotives. Starting horsepower may be less than the horsepower generated at speed.
Good point. Remember that, generally a steam locomotive is a constant torque, variable horse power machine. The diesel electric is just the opposite, i.e. constant horse power, variable torque.
Another point to consider with steam locomotives; it is not the pressure of the steam supply from the boiler that does the "work". It is the temperature of the steam, i.e. the heat of expansion that does the "work". A steam engine, is essentially a "heat machine" with the higher the temperature, the higher the horse power. Thus, a boiler with a max working pressure of 200 psi, and assuming superheated, the temperature of the steam will be no where near has high as the steam from a boiler with 300 psi superheated steam.
mark s posted:As an addendum to Steve's observation, the Erie Triplex (2-8-8-8-2) had tremendous tractive effort, could start huge trains, but would run out of steam shortly after leaving the yard. Why? Inadequate steam production as a result of a small grate area. The boiler could not meet the steam requirements of the 6 cylinders, to do any consequential work.
Another factor was that the exhaust from the rear low-pressure cylinders was not used to assist the firebox draft, because it was distant from the stack. The draft is essential to develop a more intense fire for sustained power.
The Triplex is a classic example of high tractive effort but inadequate horsepower.
UP, and I would think, ATSF, were "high speed" railroads in the time period of this thread. But what number was considered "high speed": 80 MPH, 90 MPH, 90 MPH....?
Dominic Mazoch posted:UP, and I would think, ATSF, were "high speed" railroads in the time period of this thread. But what number was considered "high speed": 80 MPH, 90 MPH, 90 MPH....?
Generally 90 to 100+ MPH was considered "high speed", such as railroads like CMStP&P, UP, NYC, AT&SF, and PRR.
All this discussion makes me yet again marvel at how steam locomotives were ever designed and built back in the day. All that engineering done with notepads and sliderules.
mark s posted:Heating surfaces: N&W J: 7448 sq ft SP GS4: 6973 sq ft
If the GS4 had 45.2 sq ft grate area, and burned oil, would it produce the same power?
In an oil burner, the oil doesn't burn on the grate like coal does. The term grate area in an oil burner merely applies to the square footage of the bottom of the firebox which also has adjustable dampers to regulate the incoming air into the firebox.
You're confusing drawbar HP with boiler HP. The two boilers have about the same heating surface area and therefore should in theory make about the same boiler HP. Whether or not the machinery under the boiler can change the boiler HP into TE and DBHP is up to the designer. In the OP's case, they are totally different applications requiring totally different machines. The N&W was an undulating kinda mountainous railroad, and the SP was flatter with more open area to support the use of taller drivers.
Both engines reportedly make in the neighborhood of 5300 DBHP. The J will have this HP at a lower speed merely because of the smaller drivers. Rich has commented several times about the difference between 765 and 261 on the New River Trains. The 74 inch drivers on 261 made it a little less powerful in the lower speeds encountered on the climb in the gorge compared to 765.
Hot Water posted:"a preserved operational unit"? Neither the 4449 nor the 611 are "units" please!
I thought about you recently when I was reading an article about the prototype PRR T1s 6110 and 6111 in "Train Shed Cyclopedia No. 56".
The "Train Shed Cyclopedia" series of softcover volumes contains reprints of articles from "Railway Mechanical Engineer".
Volume 56 covers Steam Locomotives of the '40s and '50s.
Anyway, appearing in this article was the following line: "The tractive effort of the locomotives is 65,000 lbs. plus 13,500 for the booster with which one of the two units is equipped."
I chuckled and thought to myself "Jack's not going to like this one bit." 
So, then, a J COULD have pulled the Daylight's load at track speed.
Dominic Mazoch posted:So, then, a J COULD have pulled the Daylight's load at track speed.
Based upon the PRR test of the N&W 610 J, my answer would be "absolutely". The wild card would be the J would be burning the quality Bituminous coal it was designed to burn. Otherwise, all bets are off.
Parts of the Daylight route are not exactly FLAT! Of course, the J would have one issue. SP by this time was using oil as a fuel!
I've been lucky enough to have ridden behind both. GS-4 under Freedom Train and 611 under the SRR Steam program.
In my mind I give the J a SLIGHT lead......only in my mind. The J really seemed like the ultimate precision machine. At the same time the J seemed more alive.....not sure what all that means 'who's best' wise!!
This reminds of the arguments on the show, "Big Bang Theory" where they're debating which superhero would win in a fight with another...
Something that hasn't been mentioned here so far, the J had not-so-tall 70" drivers considering its speed capability, but it was built with unusually good counterbalancing which made it as fast as other passenger locos with taller drivers. The GS-4 had 80" drivers. And yet both classes had the same 32" piston stroke, so the J had to run faster piston speeds. Wonder if they needed enhanced cylinder lubrication for that?
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Reason for the J's very large roller bearings???
AMCDave posted:Reason for the J's very large roller bearings???
Side rods equipped with roller bearings were always much larger at the housing for the roller bearing, as compared to plain bearings. Never have seem "small" roller bearings on steam locomotive side rods/main rods.
Dominic Mazoch posted:So, then, a J COULD have pulled the Daylight's load at track speed.
I guess you weren't paying attention back in May?
And, this is a steeper grade than the more famous "Blue Ridge".
Very interesting and informative discussion.......
Maybe this is possible. Both units, er, engines, SP 4449 and N&W 611 are still running. Hence, there are blueprints for them. How about programming computers so they would be virtual steamers. Then run both of them with the same train on different lines. Not the same as a steam off. But it is as close as one can get to today.
Another contest would be a UP 4000 VS a C&O 1600!
