Theoretical size limit to rolling stock?

Discussion in 'The Real Thing- North America' started by nachoman, Jun 14, 2008.

  1. nachoman

    nachoman Guest

    A thought that crosses my mind from time to time is how much larger railroad rolling stock is than even 25 years ago. Consider the size of an SD40-2 versus the latest offerings from EMD or GE. But rail cars have also gotten larger and higher. Go back another genreation and an SD40-2 is much larger than an SD-9, and most railcars were shorter even shorter still. If one has the opportunity to see a newer GE or EMD next to a non-articulated steam engine, the newer diesel is larger (if you exclude the tender)

    So, the trend is for larger and bigger capacity. Will things continue to get larger, or will they somehow reach a maximum? I assume one limitiation to size would be the rail gauge, and another being the clearance of many overpasses and tunnels. Will we eventually see 100 foot long boxcars and hoppers, with 8 axles per car? sign1

  2. jbaakko

    jbaakko Active Member

    SD40-2: 68' 10"
    Dash 9: 73' 2"
    Difference: 5' 8"

    Not very much if you ask me. Larger capacities are inevitable, but one of the major limitations currently will be track.

    GE AMD103 Genesis (P32/P40/P42) 70', half the distance between an SD40-2 & a Dash 9, height 14' 8"... Now compare to ATSF #3751, she's 94' 10.5" long, and 16' tall! That does NOT include the tender.

    Attached Files:

  3. logicman

    logicman Greybeard

    The theoretical limit to length arises when the coupling mechanism
    tends to pull the front of a wagon across the track, rather than along
    the track on curves.

    Before that, a point arises when a train going around a mountain trail
    has to carry explosives to clear the rock wall for the massive central

    Even before that, considering how close railfanners stand to the track,
    there's a small matter of inside curve overhang and the compensation culture.

  4. nachoman

    nachoman Guest

    granted, 3751 is larger than the genesis unit and the dash-9, but I guess i was thinking more of the standard 2-8-2.

    And you are right, 5'8" is not that much longer, but the SD40 had longer "porches" on each end, was a little less tall, and a lot less massive in appearance. Freight cars have gone from 40ft in th late stam era to 60 feet of more.

  5. TinGoat

    TinGoat Ignorant know it all

    Loading Gauge

    Hi Kevin,

    Take a look at WIKIPEDIA: Loading Gauge.

    Or google Loading Gauge for more information...

    There are limits to what will fit under bridges and through tunnels.

    In the West Toronto Junction, Canadian Pacific had the city remove the Old Weston Road Bridge over the railway tracks when they started to operate Piggy-back and double stack equipment.

    For free-lancing rolling stock you can follow this:

    The Golden rule for a loading gauge:

    WIDTH 3.25 times track gauge

    HEIGHT 5.25 times track gauge

    This should give you equipment that looks proportional and operates reliably.

    As for length of equipment, you have to consider overhang and coupler swing.

    For coupler swing, model trains adapted by mounting the couplers on the trucks/bogies instead of on the bodies of the rolling stock in order to negotiate the tight radius curves on toy trains.

    On Traction and Trolley Equipment that have to negotiate prototypical tight curves, they use radial couplers that swing wider than regular body mounted couplers.

    So called "Talgo" couplers that are mounted on the truck/bogie have a bad rap because they can cause problems when being pushed instead of pulled through curves and turnouts for switching.
  6. chooch.42

    chooch.42 Member

    Hi, Kevin ! Just some observations...Newer power looks more massive for several reasons: the "Wide-cab is more imposing, larger (volume),placed higher and far forward,and full width to the nose; though the diesel is actually no larger, the auxiliary power/cooling/accessory/control/fuel systems require more space (look at an an SD-80MAC or a SD-90-43 - the hood is lowest over the prime mover); and trucks/suspension create a (visually) higher sill/walkway line. Why don't you include the tender in "size"? It's the steamer's FUEL tank even though its not on the same frame - perhaps a Garrett steamer could be a more direct comparison. Physical size isn't the only limit to equipment - these locos weigh in excess of 200 TONS, produce 4000 to 6000 HP and transfer the dynamic force of moving 5000 tons or more of train EACH to the track and roadbed ! Stuff may get BIGGER still, but it'll cost in infrastructure (BIG $$$$$) - think of the bridges, tunnels, curves, etc. changed to allow Double-Stack traffic, so limits will be slow to expand this way. Am I answering part of your question,or am I down the wrong track ? Tryin' ta Help...Bob C.announce1
  7. brakie

    brakie Active Member

    I always thought the SW1500 look big till I seen the MP15.Still nothing as come close of looking like brute force like the H24-66.What I am saying there is room for more but,within limitations due to curve radius-remember the Big Boy's limitations.Then there is locomotive and freight car weight versus the track's weight limit.Even today there is some track where certain large locomotives and large freight cars can not operate on due to the track weight versus the weight of the locomotive and loaded freight car.I have heard rail strain under the weight of a GP38.
  8. jbaakko

    jbaakko Active Member

    Wait, now I'm confused, it does, or does not? I said 94' you said 108'?
  9. Russ Bellinis

    Russ Bellinis Active Member

    A few years ago the S.P. cut out the bottom of all of the tunnels in Tehachapie in order to lower the rails so that double stacks could be hauled over Tehachapie. Equipment may get longer. Excess weight can be mollified to some extent by adding extra axles to cars and locomotives to spread out the weight more, but the cost of increasing height clearance on bridges, and tunnels probably will put a limit on increasing height.
  10. nkp174

    nkp174 Active Member

    IMO, I think bridge ratings are the greatest limitation...with tunnels a very close 2nd.

    Bridge ratings are based off of the Cooper bridge rating system. Having worked with it some...I can tell you that today, many a bridges aren't what they were 60 years ago. The reason? The Cooper ratings on many steam engines were higher than they are on current freight cars/diesels (although that gap is closing). If you get much beyond the load of steam engines, you'll need to replace a sizable percentage of our bridges...which is very expensive.
  11. Russ Bellinis

    Russ Bellinis Active Member

    Good point, I had forgotten about the problem of excess weight on bridges and the cost of rebuilding them to take more weight.

    Their also isn't really much need to increase the size of individual pieces of rolling stock. They have increased the size of locomotives a bit, but the new EMD's and GE power is only a little bit longer than an sd40-2. As someone mentioned earlier, the wide "comfort cabs" the locomotives look a lot bigger; but when you see the new models next to an sd40-2 it really isn't a lot bigger. They may get more powerful, but they are finding ways to make more power out of smaller packages so the locomotive stays the same size. With diesels if you need more power, just mu the equipment. With freight cars, if you need something larger than a 91 footer, articulate. We've already seen that done with some of the "super sized" Canadian grain hoppers and intermodal platforms.
  12. Triplex

    Triplex Active Member

    The largest non-articulated freight car I've ever heard of was an 8-axle tank car about 96' long. A DDA40X was a little longer than that.

Share This Page