Next May, as many of you know, Big Boy #2014 will make it’s long awaited appearance by traveling under it’s own steam power from Cheyenne, Wyoming to Ogden, Utah. I am told by those more knowledgable than I that due to the size of the engine only certain tracks remain that can handle the load. Can anyone be more specific about these requirements? Thank you
Old Fat Robert
Look at the youtube webcam of Deshler OH’s diamond. The cars rock and roll and bounce. That’s one place you don’t want a million pounds of locomotive. It’s not a unique problem to Deshler’s diamond.
Any place slated for roadbed replacement. Old roadbed gets spongey.
I would imagine there are certain bridges where it would not be welcome.
I think the greatest limitations are turning facilities and curves. And the large overhang in curves can get problematic if tracks are too close together.
The Big Boy has axle loads of 67,500 lbs, nothing unusual on mainlines today, and it was designed to negotiate 20 degree curves. The axle loads alone are not critical for mainline bridges. The shock loads from the reciprocation action can be. But reducing speed can minimize/eliminate this problem
So there are much more routes the Big Boy can run on today than were when built. Problematic might be branch lines and shortlines with light rail and light bidges
I don’t see diamonds only as a temporary limitation. They get repaired on a regular basis.
Regards, Volker
20 degrees = 288’ = 40" HO
And that’s just one reason why I am fond of a 48" minimum radius.
Ed
Most of the restrictions were because of bridge loadings and turnout curvature.
In the last 40 years most of the lines that a Big Boy would operate on were upgraded to 286,000 lb or even 315,000 lb capacity and all the #10 crossover and center siding switches in the main track were removed.
Pretty much any main line curve is plenty wide enough for the Big Boy and with the advent of longer and higher cars side and vertical clearances have become bigger not narrower. The UP operates it’s 3985 all over the system so the Big Boy should be no problem whatsoever.
People get all in a tizzy because its a steam engine and the “biggest steam engine”. (Here’s a secret, its not. It wasn’t the fastest, longest, heaviest or most powerful steam engine.) But its a engine that was designed to be operated on a railroad. Its limitation is turning facilities and the places where the track is to weak or tight a radius are pretty much now confined to industrial lines and small yards where its not going to go anyway.
Back in the late 1980’s there was a movie called “Biloxi Blues” made that had a sequence using a 4-6-2 steam engine in the opening and closing credits. That engine was moved through N Little Rock on the MP dead it tow from the line to Memphis around the wye toward the line to Kansas City. The Superintendent was concerned about the engine making it around the wye because of the curvature and that the engine had “big drivers”. I pointed out to him that the MP operated 2-10-2’s and 4-8-4’s with bigger drivers on that same route and same track for decades with no problem, and that an SD60 had a longer rigid wheelbase than the 4-6-2. He was still worried. A couple years later the 844 came through nobody was concerned because it was “old hat” by then.
i had read that the Reading 4-8-4 was used on the Freedom Train in the northeast because the SP 4-8-4 couldn’t negotiate the trackage in the northeast.
At the risk of exposing my ignorance to the whole world, (why that would be a concern now is also questionable), what is the math on your calculations?
Old Fat Robert
Assuming you mean me, because I believe my post has the closest thing to a calculation:
Well, for a start, there was no math–I just looked it up on a handy chart:
Here’s a link to a more extensive version:
http://www.trainweb.org/freemoslo/Modules/Tips-and-Techniques/degrees_of_curve_to_radius.htm
I think the interesting part about the “degrees of curvature” is WHY?
Well, when you’re laying out a curve in the real world, it’s awfully hard to swing a radius bar that’s a thousand feet long (as opposed to one 30" long on a piece of plywood). So “the guys” developed a different way to lay out a curve. You set up your transit at a point on your already established curve. You set the telescope axis tangent with that curve at that point. Then you turn your telescope the appropriate number of degrees “into” the curve. You have your minion go out the standard distance and position his survey stick centered in your telescope. THAT POINT is on the curve you’re trying to build. Keep doing it, and you have a curve laid out in the real world without ever having to put your bad self at the center of the curve. Which may well be WAY UP on top of a very steep slope. Or across a river.
&
“Negotiate the trackage” is a relative thing. You have to realize that the limitation is the clearances with overhead wires/catenary and platforms. Its not that the track was weak or the curves too sharp.
Amtrak bought P32-8’s but couldn’t use them in the east because of the same clearance issues. The RDG had lots of tight clearances, electrified territory and high level passenger platforms, so its engines were designed to clear all that. The SP, not so much.
The Big Boy won’t be coming East (as far as I know) so comparing to clearences in the Northeast is probably immaterial.
I think it’s safe to assume UP has thought about where it cannot go like industrial siding’s
While both locos are 4-8-4’s, their size is rather different:
A Southern Pacific GS4 has 80" drivers and a driver wheelbase of 21’-6"
A Reading T-1 has 70" drivers and a driver wheelbase of 19’-3"
That 2’-3" difference means a lot in terms of how tight a curve at what speed.
The east is full of endless “medium sharp” curves, locos need to be more “nible”.
The west has more long straight-a-ways, locos need to be faster, but can slow down more for a few “medium” curves.
That is why the “most powerful” steam loco was an eastern loco with a 2-6-6-6 wheel arrangement.
Sheldon
Curvature has nothing to do with it. Curvature may mean an engine has to slow down, clearance issues (too tall or wide) keep it from operating altogether.
In some cases boiler swing comes into play that’s one reason Big Boy couldn’t be used in the East However. the 3985 was used on the Clinchfield since Clinchfield had similar 4-6-6-4s.
Well then we need someone with specific information to answer the question because:
The GS4, the T1 and the N&W J are all the same 10’-8" wide over all appliances.
The GS4 and the J are very close in total loco wheel base, the T1 is a little shorter.
The GS4 is the longest boiler/cab/pilot of the three, but not by much, so pilot corner projection on curves would be a little more.
The GS4 is the tallest of three at 16’-4", but the J is 16’-0", as are a number of other east coast locomotives. The T1 is under 15’.
So based on these numbers, and other known east coast locos, curves, or possibly pilot beam clearence on curves, seems to be the most likely limiting clearance factor.
And if that is the case, the controling dimension adding to that extended pilot beam swing is…driver wheelbase because of four axles with 80" drivers.
I do not even pretend to know all the clearence restrictions of all the east coast routes, but I know there are/where a few notable ones.
Fact is, most east coast roads avoided or later got away from long rigid wheel bases, and drivers over 70" tall. The PRR being the biggest exception, since they did not like articulated locos.
On the C&O, rather than buy more track pounding 2-10-4’s, they moved to the H8 and the 2-8-4.
The B&O could really only use its great 2-10-2’s on Sand Patch, they dumped several over trying them on the route through WV.
EVERYTHING on the B&O except the S classes had rigid wheelbases less than 20’.
It’s not that a GS4 can’t make those east coast curves, it simply has to slow down too much. And maybe pilot beam swing was the limiti
I am not seeing how a longer driver wheelbase would cause a significantly larger overhang on the front or rear of locomotives that are the same length.
Ed
seems that there a three things that matter:
looks like the railroads kept track of curvature requirements for each type of locomotive
Its also the clearance diagram. That is how wide is it at different heights on different curvatures. If its too wide, too low it will hit the lower braces on bridges and scrape passenger platforms. If its too wide too high it can corner passenger platform covers and truss bridge braces. Today its not as big a deal because many routes are now cleared for high cube and double stack cars. But in 1976, many of those routes, particularly in the east weren’t cleared for high wide shipments and had legacy tight clearances. Today, a big engine isn’t as big a deal, back in 1976, it was a real concern.
The wheelbase doesn’t really have as much to do with it much as how long the engine is compared to the wheel base.
That’s why AMTK couldn’t run C40-8’s (P32-8’s) on its eastern passenger trains. It didn’t have anything to do with curvature or axle loadings or wheelbase, but it was all about the pilot sheet/snowplows clearing station platforms and 3rd rails, and the horns, antennas and radiators getting too close to overhead catenary. About 5 or 6 years ago, BNSF wanted to reconfigure the steps on its new locomotives to make them easier to get on and off, the problem was it would foul a large number of passenger platforms, particularly in the east. Amtrak said no way.
To give you an idea, look at a Baldwin Centipede diesel. It has a really long rigid frame. Notice that the cab and the rear of the carbody narrow. That was to make it clear side restrictions on curves.
Another issue today can be the track condition of secondary trackage, especially things like wyes for turning. Maintenance is kept up on the main tracks and the more heavily used yard tracks, but it can be hard to get approval for time and materials for the rest. A big new locomotive appears, such as an SD90 or AC4400, and the spikes can not hold the rail against the extra lateral forces on a tight curve. The ties were good enough in the steam era, but now they are getting tired! Usually after a pattern of diesels stubbing their toes emerges, the track is brought back up to a higher standard. A big steam engine will probably also find the same type of weakness today.
What about this thing?
Number 5550 is under construction and will be in service around 2030, the T1s were known to easily surpass 120 mph and with that rigid frame, yikes! It would be an awesome sight for sure.
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