I have the Spectrum 2-6-6-2 and was wondering how the 2-6-6-4 and the challenger compare?
Are the 2-6-6-4 and the 4-6-6-4 challenger the same size?
Model train size.
Thanks [:)]
Lee
I don’t have the exact numbers, but a 2-6-6-4 and 4-6-6-4 would be pretty close to the same size. They both had fairly large drivers so they could run at mainline speed. The USRA 2-6-6-2 is smaller…actually the boiler isn’t much longer than a USRA 2-10-2 I believe. The 2-6-6-2 had much smaller drivers and had a max speed of around 20 MPH - or at least it could only go that fast before it started damaging the track. (Because of the small drivers, it was difficult to counter-balance the weight of the siderods, so above 20 MPH they would “pound” the track pretty hard from what I’ve read. A Challenger with something like 70" drivers could go much much faster.)
Hello Lee,
“Stix” is correct that both the N&W class A 2-6-6-4 and the UP class 4-6-6-4 Challenger are about the same size. The UP engine is about 27 tons heavier, and both are larger than the USRA 2-6-6-2. But all Challengers and all 2-6-6-4s weren’t equivalent.
The D&RGW and WM had Baldwin Challengers that were different from the UP’s Alco-built engines, and the NP’s Alco Challengers weren’t the same as the UP’s.
Likewise, the Seaboard Air Line and the Pittsburgh & West Virginia both had 2-6-6-4s that were smaller and lighter than the N&W’s. The current edition of Classic Trains magazine, Summer 2011, has a good article about the P&WV engines that compares all three designs that used the 2-6-6-4 wheel arrangement.
So long,
Andy
The typical Challenger is about 2" longer than the USRA 2-6-6-2. That’s without tender. And in HO. Tenders also “tend” to be longer, by an inch, maybe inch and a half.
Ed
Lee, as others have explained Challengers and the N&W Class A, are big modern steam locos, much bigger than the USRA 2-6-6-2. Also the UP Challenger and Class A are “simple” locos, meaning they use high presure steam on all cylinders, the 2-6-6-2 is a compound, using the steam first in the rear cylinders than in the front cylinders.
The 2-6-6-2 wasa medium sized road engine, very popular on the winding curves and steep grades of the C&O.
Stix is correct in that the 2-6-6-2’s are “drag freight” locos, but they could and did go a lot faster than 20 mph. Loco driveline balancing relates to more than just driver size, it also relates to number of axles, which increases connecting rod weight, which requires more counter weight on each wheel.
So a 2-6-2 with 56" drivers would be easier to balance than a 2-10-2 with 56" drivers. Keeping that in mind, the 2-6-6-2 is like two seperate 3 axle locos when it comes to balancing.
Actually, a USRA or similar 2-6-6-2 as used on the C&O (the Bachmann model you have) could and would have easily reached 40 mph or more with no problem and no track damage. The limiting factor would have been boiler capacity to maintain speeds over 40 mph for any amount of time.
Speeds in the 30-35 mph range with 2000 tons in tow would have been typical in day to day operations. Think of the 2-6-6-2 as a 4-8-2 or 2-10-2 that is better suited for grades and curves, but is about the same as them power wise.
A Challenger on the other hand is a modern high speed, high power dual purpose loco - the articulated step up from a big 4-8-4. The N&W Class A (2-6-6-4) and the C&O H8 (2-6-6-6) are similar in that regard - large drivers, very powerful and very fast. The H8 in fact actually makes more boiler HP than a Big Boy.
People not familar with Appalachian mountain railroading often miss and important point compaired to Rocky Mountain railroading. In the east, the distances are shorter, but there is no “prairie” on
To follow up this balance topic a little, one of the worst locos in that regard was the USRA Light 2-10-2. Its small drivers and long heavy side rods made it hard on its own frame and the track at speeds much over 20 mph. In the end, they where considered only useful as “transfer locos” - in other words over grown switchers.
Sheldon
How would that compare to a 0-10-2? Could the 2-6-6-2 be converted to a 2-6-6-4? How about a -6-4? I know I know I’m making up my own concoctions again.
Well, the few 0-10-2’s that existed where just that as well - giant switchers.
As for making a 2-6-6-4 out of a 2-6-6-2, that would not be practical. The reason for the 4 wheel trailing truck is to support a larger firebox - the firebox of the 2-6-6-2 simply does not justify a 4 wheel truck.
Railroads did change the wheel arrangements of locos from time to time. One good example was when the B&O converted 2-8-0’s into 0-8-0’s.
By removing the lead truck, this put more weight on the drivers making them better as switchers but limited speed.
Different railroads have/had different wieghts of rail and grades of roadbed, so they have different requirements for loco axle loading. Some locos had more lead/trailing wheels just to keep alxe loading within limits. Eample - the classic NKP Berkshire has lower axle loading than several of the largest Mikados built.
And some of those large Mikes where actually more powerful than the Berkshire. To simulate my own heavy Mikes I have converted Bachmann Berkshires to Mikes.
For whatever reason the Seaboard 2-6-6-4s were incredibly racy and fast looking, particularly in the original builder’s photos. Those 69" drivers look bigger than that in the pictures. The photo here does not quite do it justice – they cluttered it up in later years. Originally it was a very smooth and clean looking boiler.
Dave Nelson
So how was it that the B&O routinely used their 2-8-8-4 EM1 on 80 mph express mail trains through the mountains in PA and WVa? The EM1 was only 18 inches shorter than the Big Boy (engine vs. engine --the Big Boy’s tender was a few feet longer than the EM1’s tender).
The EM1 produced so much power at speed that the B&O was able to eliminate the pair of 4-8-2 Mountain class locomotives that was needed to handle the express mail trains. Seems to me that the similar Big Boy would fit right in to this type of service in the East.
It has nothing to do with overall length, it has every thing to do with the rigid wheelbase of each set of drivers. In that regard a Big Boy and the EM-1 are not very similar.
The Big Boy with its larger drivers (68") has a rigid wheelbase of 18’ - 9" compared to the EM-1 which had smaller drivers (64") and only had a rigid wheel base on each set of drivers of 16’ - 6".
Relative to drive size alone, comparing a BIg Boy to an EM-1 is like comparing a the average Mountain class to the average Mikado class.
This made the EM-1 more nimble and not as hard on trackage with lots of curves.
Yes the EM-1’s where well balanced and fast enough for 80 mph. But that would have been about their top speed. Remember they are only hitting those speeds on the long straights, not as they are winding through the mountains.
At 80 mph a Big Boy is just starting to “stretch its legs”, but would have had to slow down in the curves more than the EM-1.
A curve on which the
A few more thoughts that should be noted:
The nature of the way an articulated loco is hinged, makes the effect of its rigid wheelbase a little different than a non articulated loco like for example a Mountain class loco. The front Engine does put a side load on the rear engine as the loco goes through a curve.
Without the front set of drivers hinged out in front of it, a loco like a B&O T-3 does pretty well on curves even with its rigid wheelbase of 18’ - 3". But even at that, the EM-1 had the advantage in the application you mentioned because it could likely keep better speed over the whole route compared to a pair of Mountians or a BIg Boy.
And, if you study the development of 4-8-2’s on the B&O you will see they went backwards in driver size and wheel base from 76" drivers and 19’+ wheel bases on the early ones, to 70" drivers and 18’ - 3" wheelbases for the T-3, the only Mountains they had in quantity. I don’t know about the T-3 in particular, but many Mountain class locos also had lateral motion devices on the front driver, allowing them more side to side motion in curves.
In general many east coast lines experimented with longer wheel base locos in the twenties and early thirties but then moved back to shorter wheel bases for their last steam purchases. The C&O bought their 2-8-4’s AFTER buying 2-10-4’s, the Virginian’s last steam where 2-8-4’s and 2-6-6-6’s. The B&O EM-1’s came in 1944, way after the S1a, last built in 1926.
In the twnties it was the quest for tonnage - by the forties they wanted speed and power - on the trackage they had in place. The only way to get speed on thecurves in place was to make the locos more nimble while still making them bigger and super powered.
Sheldon
Sorry, as a Mechanical Engineer who has worked for 3 decades in this industry, I got to disagree with those statements.
First, The EM1 and Big Boy were indeed very similar engines with the exception of the Big Boy having a 4 wheel leading truck while the EM1 used a lateral cushioned 2 wheel truck for stability. While the Boy Boy operated at a higher pressure (The B&O specified a lower pressure on the EM1 to ensure a very high starting adhesion), the EM1 had a larger direct heating surface than the Big Boy, and its large Type E Superheaters raised the operating steam temperature to nearly 800 F. Based on its larger direct heating surface and higher steam temperature, I’d actually give the EM1 the horsepower advantage at higher speeds over the Big Boy.
Second, when you look at the curvature of the B&O main lines, the difference in wheel base is not important. You are only talking about 24" between the two. Speed restrictions on curves would be very similar for both engines.
Third, 80 mph was not “only stretching” the Big Boys legs. It wasn’t good for much more based on its machinery speeds. Both the Big Boy and EM1 were good for 80 mph “every day” running, but pushing either one of these big engines to 85-90 mph on a routine bas
[quote user=“GP40-2”]
ATLANTIC CENTRAL:
…The Big Boy with its larger drivers (68") has a rigid wheelbase of 18’ - 9" compared to the EM-1 which had smaller drivers (64") and only had a rigid wheel base on each set of drivers of 16’ - 6".
…Yes the EM-1’s where well balanced and fast enough for 80 mph. But that would have been about their top speed. Remember they are only hitting those speeds on the long straights, not as they are winding through the mountains.
At 80 mph a Big Boy is just starting to “stretch its legs”, but would have had to slow down in the curves more than the EM-1.
Sheldon
Sorry, as a Mechanical Engineer who has worked for 3 decades in this industry, I got to disagree with those statements.
First, The EM1 and Big Boy were indeed very similar engines with the exception of the Big Boy having a 4 wheel leading truck while the EM1 used a lateral cushioned 2 wheel truck for stability. While the Boy Boy operated at a higher pressure (The B&O specified a lower pressure on the EM1 to ensure a very high starting adhesion), the EM1 had a larger direct heating surface than the Big Boy, and its large Type E Superheaters raised the operating steam temperature to nearly 800 F. Based on its larger direct heating surface and higher steam temperature, I’d actually give the EM1 the horsepower advantage at higher speeds over the Big Boy.
Second, when you look at the curvature of the B&O main lines, the difference in wheel base is not important. You are only talking about 24" between the two. Speed restrictions on curves would be very similar for both engines.
Third, 80 mph was not “only stretching” the Big Boys legs. It wasn’t good for much more based on its machinery speeds
I did not say it never mattered. I said it didn’t matter on the B&O’s high speed main lines where the EM1 ran at top speed. On the Pittsburgh Line, the B&O even ran the 2-10-2 S1a at over 70 mph. If the track can take a 10 coupled loco running 70 mph+, it would be no problem for the articulated Big Boy to do the same.
Why would they bother wasting their money? For heavy fast freight, the S1a did the job in its territory just as well as any 4-8-4 could, if not better. Then there was the EM1, which would blow any 4-8-4 ever made into the weeds on a fast freight assignment.
When a SuperPower 4-8-4 actually did run on the B&O main lines, there was no issues at all. The C&O 614 had no trouble running at passenger speeds (79mph) on these lines. Neither did the 2101. I was on many of them in an official capacity, so I would know. In the steam era, the B&O P7, and T Class worked just fine in passenger service. The rigid wheelbase of a 4-8-4 was not the reason why the B&O didn’t buy any. They simply didn’t need them.
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The war production board did not force the 2-10-4 down the throats of the Pennsylvania railroad. The requirement was for an existing design to be used. The Pennsy tested a C&O 2-10-4 and an N&W 2-6-6-4 and chose the non articulated design. Some railroads did not like articulated locomotives.
In some railroad books available there are excellent discussions regarding the merits of each design and their short-comings. One that compares the big boy to the H-8 reveals how a much larger and deeper firebox could be used on the H-8 since it did not have to be placed above the drive wheels like the big boy.
In the case of the C&O the next evolution of the 2-10-4 was the 2-6-6-6, or what was originally thought of as a 2-12-6. Both the 2-6-6-6 and the 2-10-4 were used on heavy passenger trains. The 2-10-4s were not continued in passenger service as the side rods were so wide that they hammered through the passenger platforms due to lack of clearance.
One thing that does not seem to be addressed very often is the versatility of some of the designs used by the C&O. They were used in the flat lands of Ohio as well as the mountains in Kentucky, West Virginia and Virginia. The superpower designs were both fast and capable of drag work when needed.
When looking at the superpower designs 2-8-4, 2-10-4 and 2-6-6-6 they were the basis for or used by other roads and were quite numerous. More than twice as many 2-6-6-6s were built as big boys. The 2-10-4s were over 150 strong 125 for the Pennsy and 30 for the C&O if memory is accurate.
You are right. They didn’t force the 2-10-4, but they did force an existing design. The PRR wasn’t too happy with the Class A performance on mountain grades. The front drivers tended to slip a lot on hard pulls, which is why the N&W paired them with the Class Y in the mountains. The C&O 2-10-4s had better adhesion on mountain grades, but were a lot harder on the track at speed than the Class A. Given a choice, the PRR would have used neither design.
The H8 firebox was bigger than the Big Boys, but not by much. 762 sq.ft. for the H8 vs 704 sq.ft for the Big Boy. The H8 and EM1 had almost identical firebox sizes. 762 sq.ft. for the H8 vs. 758 sq.ft. for the EM1.
As far as the Op’s question. What is the reason for wanting to know the length of the model? Are you considering one on the layout? If that’s the case you could also consider the Y6B 2-8-8-2. It’s articulated and will work on most layouts.
Yes, the original question was related to how well something larger than my 2-6-6-2 would operate on my layout. i have a couple curves that are tight as 20", The rest are a little larger. I enjoyed the discussions.
Thanks to all that answered.
Lee