In another thread, a couple of us have started a hunt of sorts to see how locomotives compare in different categories such as weight, tractive effort, length, and others. Unfortunately, we sort of hijacked a screenshot thread, so I took the liberty of starting this one. With that being said, feel free to add your locomotives of choice and their respective performance specifications.
North American Locomotive Tractive Effort Discussion
- Thread starter GN1996
- Start date
Some locomotives I previously posted about include GN's R-1's and R-2's as well as the Big Boy and C&O's allegheny.
Tractive Effort
R-1 --------- 142,165 lbs.
R-2 --------- 162,475 lbs.
Allegheny - 110,211 lbs.
Big Boy ---- 135,375 lbs.
Wheel Configuration
R-1 --------- 2-8-8-2
R-2 --------- 2-8-8-2
Allegheny - 2-6-6-6
Big Boy ---- 4-8-8-4
Tractive Effort
R-1 --------- 142,165 lbs.
R-2 --------- 162,475 lbs.
Allegheny - 110,211 lbs.
Big Boy ---- 135,375 lbs.
Wheel Configuration
R-1 --------- 2-8-8-2
R-2 --------- 2-8-8-2
Allegheny - 2-6-6-6
Big Boy ---- 4-8-8-4
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Actually, they were 2-6-6-6.
Want to compare tractive effort, weight and other things check out this great website. If there's something steam that I'm looking for, I tend to go there first.
http://www.steamlocomotive.com/
jacksonbarno
Alco Spoken Here
I don't know much about tractive effort, but maybe because the GN R series had one less trailing and pilot axle, then more weight rested on the driving wheels, therefore giving it more tractive effort. It would sacrifice a larger firebox, but the tractive effort from the added weight on the driving wheels would give it more pulling power. The opposite was true on the PRR S1. Because more weight rested on the pilot and trailing trucks, it had less tractive effort. The PRR solved the problem in their Q2 design, which had a large amount of tractive effort.
Tractive Effort
Q2 ------- 71,900 lbs
Wheel Arrangement
Q2 ----------- 4-4-6-4
Tractive Effort
Q2 ------- 71,900 lbs
Wheel Arrangement
Q2 ----------- 4-4-6-4
Virginian Railway Class X-A, 2-8-8-8-4, 166,300 (compound), 199,560 (simple)
Virginian Railway, Class AE, 2-10-10-2, 147,200 (compound), 176,600 (simple)
You can figure the tractive force or drawbar pull of any two-cylinder steam locomotive using the formula C²xSxP/D.
C² = diameter of cylinders (inches), squared
S = piston stroke (inches)
P = 85% of boiler pressure (psi)
D = diameter of driving wheels (inches)
There's also a formula for compound locomotives, see below:
Virginian Railway, Class AE, 2-10-10-2, 147,200 (compound), 176,600 (simple)
You can figure the tractive force or drawbar pull of any two-cylinder steam locomotive using the formula C²xSxP/D.
C² = diameter of cylinders (inches), squared
S = piston stroke (inches)
P = 85% of boiler pressure (psi)
D = diameter of driving wheels (inches)
There's also a formula for compound locomotives, see below:
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jjanmarine3
Active member
My all time favourite the South African Railways Beyer-Peacock Garrat, I watched it often pulling heavy stuff up steep grades, pulling out couplers or breaking knuckles on a few occasions.
3'6 gauge
4-8-2 2-8-4
Tractive effort 78650 LBS or 349.9 KN
Weight 218 tons
I hope it will be created for trainz some day soon.
3'6 gauge
4-8-2 2-8-4
Tractive effort 78650 LBS or 349.9 KN
Weight 218 tons
I hope it will be created for trainz some day soon.
jadebullet
might be back?
The R1 and R2 engines are a little odd for this sort of Tractive Effort comparison though, since unlike the Allegheny and the Big Boy, the GN engines were equipped with boosters on their trailing trucks. Thus, their tractive effort at lower speeds would be significantly higher than at higher speeds when the booster had to be cut out. That being said, the GN engines were damn fine engines.
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Tractive effort measure what a locomotive can move at slow speed. If you look at the formula I posted, the smaller the drivers' diameter, the larger the tractive effort will be, if all other factors are equal.
The locomotives with short drivers may have had high tractive effort ratings but they were extremely slow. During the drag freight era, when 15 MPH was "fast enough", this wasn't a problem. But by the '30s things had begun to change. The Big Boy, Allegheny, and N&W Class A locomotives, with their higher drivers, were built for moving long trains at higher speeds, in the 50 MPH+ range.
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jacksonbarno
Alco Spoken Here
^ One example of this on the PRR is the fact that the Q1 had passenger-sized drivers, 77 inch to be exact.
Looking only at the tractive effort rating reveals only one aspect of a given locomotive. The figure quoted is usually the loco's starting tractive effort rather than its continuous tractive effort (at X MPH).
The USRA Light 2-8-2 and the USRA 0-8-0 has tractive effort rating that were very similar. But the Mike could make much better time hauling a 50 car train than the switcher could.
It also helps to avoid comparing apples with oranges. The PRR Class Q1, Q2, S1, and T1 locomotives were actually non-articulated (rigid frame) locomotives, so comparing them with articulated locomotives isn't all that meaningful a comparison.
SteamLocomotive.com has an excellent page, What was the largest steam locomotive?, comparing various steam locomotives in terms of tractive effort, horsepower, length, and weight.
jacksonbarno
Alco Spoken Here
I was aware that they wee not articulated, but would this effect tractive effort?
I didn't say it would. But why compare an apple to an orange?
jacksonbarno
Alco Spoken Here
True, but it should be noted that the Q2 had more drawbar horsepower than the Allegheny. It is comparing apples to oranges in a sense, but one could also say that they are more similar than different. Just a thought.
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Any comparison of steam locomotives requires an understanding of the job they were designed to perform. It's no accident that the hefty high tractive locomotives tended to be built by roads that had high volumes of heavy, low value loads, such as coal, where speed, as opposed to maintaining a steady stream of the commodity to the users, was unimportant. On the other hand, roads like the UP had Challengers and Big Boys, which could start heavy loads, but also generate horsepower to move them at speed. The Big Boys were spectacularly huge, but there were several locomotives of the superpower era that produced much higher tractive effort. As the speed increased, so did the horsepower, and the tractive effort exerted by the locomotive would decrease as well. An Allegheny would have been a complete failure on the Espee, but a Cab Forward with a mere 125,000 lbs tractive effort would never do as well as the Allegheny on the C&O hauling coal.
Bernie
Bernie
jadebullet
might be back?
Actually, the Allegheny was designed for 45mph running, but was mainly used for drag freight, wasting its potential. On the SP it probably would have done adequately.
Well, you could lump them all together since they were all locomotives propelled by steam.
But I find it fascinating to examine each separately, not just their particular specs, but also their design and how they were utilized. To really consider any locomotive one has to look beyond specs. To me it's interesting that some of the locomotives that scored the highest in terms of tractive effort, horsepower, etc. were locomotives that were outlived by locomotives with lesser specs (the Jawn Henry, C&O M1, the Triplexes, come to mind.)
The Q2s are another example of a high-spec'ed loco that was outlived by the older J1s, even though the Q2s had higher horsepower ratings. If I remember correctly, the 7,987 HP @ 57.4 MPH rating for the Q2 was from tests performed by the PRR at their static testing facility, and I believe the 6,552 HP @ 85.5 MPH rating for the PRR J1s came from the same plant. In other words, the data was probably very realistic (which is probably not the case for many of the specs oft' quoted.)
The Q2's HP advantage seems impressive but the operational and maintenance costs were about 50% higher (if I remember correctly) for the Q2s vs the J1s, so the J1s won out. The Q2 were scrapped in the early '50s while the J1s survived until 100% dieselization occurred. The Q2s were also outlived by the C&O/VGN 2-6-6-6 locos and the N&W Class A 2-6-6-4 locos, despite the fact that those locos had slightly lower horsepower ratings.
One aspect of the Q2 design was suppose to solve the "hammer blow" problems PRR was having with its J1s. Specifically, both used 10 drive wheels, but the Q2 used 4 cylinders vs. the 2 used on the J1s. Doing so meant that lighter rods, axles, counterbalances, etc. could be used on the Q2, since the powerful trusts from the cylinders could be divided among two sets of drivers. This idea apparently worked very well (the Q2 could achiever higher speeds without "hammer blow" problems) but in the meantime, PRR managed to solve the J1 problem by replacing the J1s' counterbalances with re-designed counterbalances. As it turned out, the C&O had done this very thing years earlier on their T1 Class (the locos the PRR J2 were based on) but the PRR was apparently unaware of it when the J1s were being ordered, thus the PRR J1s were built to the original specs (before the re-counterbalancing was done.)
In theory, the Q2s were capable of hauling freight at higher speeds than J1s, but in reality the PRR had few stretches of track that permitted operation >50MPH, so the Q2s advantage could never fully be realized. With higher operating and maintenance costs, using the Q2s offered no real monetary advantage over the J1s.
Like the C&O/VGN 2-6-6-6s and the N&W 2-6-6-4s, the Q2s were horribly underutilized. All should have been running 60 MPH+ freight consists, but they were only able to do so briefly on short sections. The Challengers and Big Boys fared much better in this regard...
It's a shame the 100% dieselization occurred so early. It would have been interesting if steam had lasted through the 1970s for example, with diesels performing the grunt work and the best from the last generation of steam being able to stretch their legs handling high-speed freight runs.