Question about 4% grade

Discussion in 'N / Z Scale Model Trains' started by jasbourre, Dec 14, 2004.

  1. jasbourre

    jasbourre Member

    I'm trying to figure this out 4% grade, does this mean it takes 100 inch of track to climb 4 inch, or 25 inches to climb 1 inch. Is this right???

  2. SteamerFan

    SteamerFan Member

    both are right.

    1" over 100" is a 1% grade
  3. dwight77

    dwight77 Member

    Is there a rule of thumb on what percent incline can or is recommended for use???? I guess it can be more difficult to go up if curves are involved.???
  4. 77railer

    77railer Member

    It depends on your traction. For mainline diesel or steam, use no more than a 1 percent grade, and for branch lines keep it below 3 percent (the lower the better) - 3 percent will be a struggle for steam. Electric trains can handle steeper climbs and some systems have 6 percent grades.
    The steepest grade east of the Mississippi River in the U.S. is Saluda Grade in western North Carolina - 6 percent. That is steep. Offhand I'd say you should be ok if you stick to grades under 2%.

    Courtesy of Gary's Trainz Pages
  5. 60103

    60103 Pooh Bah

    Model railroaders tend to use steeper grades than prototype, just as they use sharper curves. Since we have shorter trains, we get away with it.
    The logging fans use extremely steep grades.
    You might want to test a typical train. Put track along an 8 foot straight plank (2x4 or such). Raise one end an inch and see how the train likes it. Raise it another inch and test again. Each inch is about 1%. You'll want a very high quality plank for this -- no dips or twists.
  6. Fred_M

    Fred_M Guest

    The accepted max has been 2% max. grade for as long as I can remember. Loggers/miners/narrow gaugers will run 6 or 7% because their locos are geared different and the loads are smaller. But get a mainline consist of 3 powered units and 50 cars on a 2% grade and watch it slow down or stop altogether. Forget 3% or 4% unless you are willing to live with 3 power units pulling 15 or so cars. David has the best suggestion, try it and see for yourself before you mess up your layout. Same with tight curves, S curves, and snap switch turnouts. Don't kid yourself by saying "yeah, I know, but I can live with 15 inch radius curves on a 6% grade witha a snapswitch at the top into an S curve. " :D Fred
  7. SteamerFan

    SteamerFan Member

    Hmm..sounds like someones speaking from expirience. :p
  8. davido

    davido Member

    i can pull an eleven car train with my cheap arnold sw1500 cow up a 3% grade. do not yet own enough rolling stock to make it spin.

    my kato e8/9 makes the same pull at slooooooow speed. crank it up and it's like there is no incline.


  9. SD90

    SD90 Active Member

    I have between 2.08% and 2.4% grade on my Laggan Sub layout,(the same grade as the real Laggan Sub.) and that grade is about 120 feet long. I run 40-50 car trains with 3-4 locomotives on them, and the tightest curve is 24" raius. 2 Kato SD90's will pull a 40 car unit grain train with no problem, I actually have 1 in the front and 1 in the middle. If I use SD40-2's, I'll need 3 for the same train.
  10. igoldberg

    igoldberg New Member

    My steepest grade is 6 feet of 2.77% on the foothills sub.. My longest grade is 36'9" of 1.91% grade.on the mountain sub.
  11. Bikerdad

    Bikerdad Member


    There are, essentially, two rules of thumb. The first one, articulated by 77Railer, is essentially what the prototypes aim to achieve. The second is "use whatever grade you want, as long as it meets your needs." If you need to boost a train 2" in 4', then do it. You'll need more locos to pull it, and some locos may not make it at all, but if your trackplan and space requirements demand a 4% grade, go for it. Real railroads generally deal with a different set of physical and economic limitations than model railroads. Generally, laying track through tunnels and winding up canyons costs real railroads a lot more than laying it across flat plains. For us, not much more. Operating trains up steep grades costs real railroads a lot more, not so with us. Conversely, buying right of way X as opposed to Y doesn't cost a railroad much more, whereas for us to expand the amount of space we have available (thus reducing the gradient needed) can be prohibitively expensive, and that's just the economic cost.

    So, while there are certain limitations imposed by physics (don't expect your loco to go up a 30% grade), those are the only one's set in stone. Fortunately, it doesn't cost us any money to determine the grade limitations of any given loco, unlike the prototypes, so you can experiment. All other aspects of the "rules of thumb" are flexible.
  12. rcwatkins

    rcwatkins Member

    Don't try it. I would feel that 2-2.5% is good enough for mainline. But if you're willing to tell us the fun you had w/4%, go for it.
  13. 60103

    60103 Pooh Bah

    Canadian Pacific had a really fierce grade in the Rockies, which was called the Big Hill. I think it was over 4%. Besides having to triple-head trains going up the hill, there was a major problem with runaways going down the hill.
    The hill was replaced by the famous Spiral Tunnels, and the grade is now used by the Trans Canada Highway (where all the units are over-engined).
  14. webmaster

    webmaster Member

    Guys, I know this is an old thread, but rather than start a new one, I did a forum search for gradient & this was the newest LOL.

    This is the first time I've ever worked with gradients, and I've been doing a lot of head scratching. So for my own peace of mind I just wanted to know if I am right in my calculations here?

    1" rise in 100" = 1%
    1" rise in 50" = 2%
    1" rise in 25" = 3%
    1" rise in 12.5" is 4%
    1" in 6.25" is 5%

    Is that right or have I made a total pigs ear of it? :D

    Edit: Or is there a simple formula such as Height divided by Length = ??%
  15. ezdays

    ezdays Out AZ way

    You were doing fine until you reached 25", which should be 4% with a 1" rise. 1" in 12.5" is 8%. You have the forumla correct. Divide the rise by the run and you get the incline or grade in percent.
  16. cidchase

    cidchase Active Member

    Ya, a nice pig's ear :D :D

    (never really heard that before, web, thanx fer the lesson!!)
  17. GeorgeHO

    GeorgeHO Member

    On the aforementioned 6% grade, the railroad (N&W I think) was required by the state to have empty hoppers spaced throughout the train of loaded hoppers for additional braking power while descending the mountain. If you want to (or need to) model a similar steep grade, then you also could intersperse empties with the loads for the descent, and also use helper locos for the ascent. If the real (prototype) railroads did it, you can too. The extra operations involved with the setup could prove enjoyable.
    For your math problems, first figure out the rise in 100", 1"=1%, 2"=2%, 6"=6%, THEN extrapolate it to the total length you are considering. Are you considering the grades for overpasses and underpasses, or just for mountain scenery? It makes a huge difference wether you just want it or really need it to have enough headroom for the train passing below.
  18. webmaster

    webmaster Member

    Yes George it's for my On30 switchback layout, so it will be underpass in to overpass.

    Thanks for clearing that up ezdays. :thumb:

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