Let's talk grades and radius!

Discussion in 'HO Scale Model Trains' started by XavierJ123, Dec 26, 2004.

  1. XavierJ123

    XavierJ123 Member

    Is there a chart anywhere that will compare the capabilities of steam engines? For example, what percentage grade can a 0-6-0 handle compared to a 2-8-8-2 and what is the minimum radius required. Do the manufacturers give this information in the box? And what about plastic versus metal cars? There was a metal HO box car in the hobby shop that weighted a ton. Why???? A fellow was selling some passenger cars on eBay because he didn't have the correct curve radius to accomodate them. It would be heart breaking to build a layout and then find out that your train can't make it from point A to point B, much less point C!:confused:
  2. kchronister

    kchronister Member

    I don't think such a chart would be feasible - at least as you put it. The capabilities of 0-6-0's or whatever vary tremendously from model to model and manufacturer to manufacturer. So you can't say "an 0-6-0 will pull X." The train magazines usually will give the drawbar pull in ounces when reviewing locos, which is probably the only way to judge accurately. But again, you'd basically need a chart showing every specific make/model/wheelbase of loco, not just generic.

    What you saw at your LHS was probably the recent offering from Model Power called "MetalTrain" - they have cars and locos all made of metal. Heavier cars tend to ride better, derail less, etc. BUT the metaltrain line has taken it to the extreme. Far heavier than the standard NMRA recommendation, and any responsible LHS owner will tell you that they're only meant to be pulled with the "metaltrain" locos specially designed to pull cars that heavy (and currently only available in a few models of diesel). I happen to know one of the guys at ModelPower (they're located nearby) and even he admits these are not meant for pulling long strings of cars, for much of any grade, etc. There are other all-metal cars available, most notably brass ones, but all will dramatically reduce the number of cars a loco can pull and up what sort of grade.

    Manufacturers WILL usually indicate a loco's minimum radius. Usually, not always. Always best to ask and use common sense. Radius is USUALLY determined by the length of fixed driving wheels - i.e. an X-4-X will generally go round much tighter curves than an X-10-X. Articulated locos often do better than you'd expect - getting a lot of driving wheels going while handling reasonable radius curves was one major point of the prototypes. There have been more than a few 4-8-8-4 "big boys" that will make 18" radius curves -- but they look pretty ridiculous doing it.

    Again, there's no "standard" out there. In my experience, running anything above an X-6-X on 18" radius is not going to work (or if it does, won't work well). X-8-X (no articulateds) is my limit on my layout with 22" radius curves. I have a branch section with VERY tight 15" radius curves, that will only do for the smallest engines (e.g. 4-4-0 "oldie" American style) or locos specifically designed for tight-radius work (e.g. two-truck heisler or shay).

    Hope that helps,

  3. wjstix

    wjstix Member

    Well...in the prototype, I don't think there would be much difference between an 0-6-0 and a 2-8-8-2 as far as how steep a grade they could go up. Neither could go up the very steep (10-11%) grades a geared engine like a Shay or Climax could. The 0-6-0 could go around a much sharper radius curve of course.

    As for how the grade would affect the pulling power, it would probably reduce the number of cars either locomotive could pull up the grade by a similar percentage.

    Let me put it this way - on Pg. 49 of John Armstrong's "Track Planning for Realistic Operation" (I have the old 1981 2nd edition, might be a different page on the version in hobby shops now) he has a chart called "Effect of grade on hauling capacity". It shows that a 2% grade would cut the length of a train an engine could pull by about 40%.

    So...an 0-6-0 that can move 10 cars on level track might only be able to push 4 cars up a 2% grade, and the 2-8-8-2 that could pull 100 cars (realistic for the real engine) might only be able to pull 40 cars up that same grade.

    As you allude to, experimentation is vital !! I found that say an Atlas GP-7 could pull about 25 ore cars on level track, but only 10 on the 2% grade going up to my ore dock - and couldn't quite make the 10 on a 3% grade. I would suggest getting some Woodland Scenic risers and experimenting to see how grade will affect your loco's, and a few pieces of Atlas snaptrack to test curves.
  4. XavierJ123

    XavierJ123 Member

    My Atlas RSD 4 Diesel

    My Atlas RSD 4 Diesel is pulling nine empty plastic cars on a flat surface. I had some real lumber on a flat car and it was pulling that as well but I decided it was a little too heavy and took the payload off. When Xmas is over I will experiment with grades as you suggested. So far, it seems the rule of thumb is 2%. Since no one can afford to buy every HO locomotive that is out there, it would be helpful if the railroaders would post their achievements briefly.
    For example::wave:
    XavierJ------Atlas RSD 4/5 Diesel pulls 9 cars flat.:confused:
    wjstix------ Atlas GP-7 pulls 25 flat/10 at 2%:D
    kchronister--Acme 4-8-2 pulls 289 flat/69 at 2%:thumb:
  5. spitfire

    spitfire Active Member

    That's why in a perfect world we would all test our engines and RS on the curves and grades we have planned - especially if they're steeper or tighter than we know they should be. My tightest radius is 22" so I should be ok, but I do plan to lay a small section of temporary test track with that radius just to be on the safe side.

    BTW, the NMRA has a radius chart, based on the type of rolling stock here.

  6. Russ Bellinis

    Russ Bellinis Active Member

    One thing to remember about brass is that the models are made to be prototypically accurate. Unfortunately, the prototype doesn't run radiuses nearly as tight as we modelers do. The result is that some brass models look neat, but operate as though a 30" radius is a tight radius!
  7. shaygetz

    shaygetz Active Member

    Rivarossi 4-8-8-2 Cab-forward with 1 1/2 ounces of added weight to the boiler pulls 25 NMRA weighted cars (nearly 8 pounds) up a 1.75% grade. While the locomotive is built to take 18" radius curves, I don't run it on any less than the club's 30" curves---and there is still considerable overhang even then.
  8. jwmurrayjr

    jwmurrayjr Member

    Very nice link Bob! :thumb:


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