I am currently working on the fourth section of my N scale layout, as the name probably implies there will be a grade on it, but this is my first time actually playing with grades in a serious depth. I know that slope (or im assuming grade, please correct me if im wrong) is rise over run. Using this formula i come up with a whole number…i dont know if this is right…Im looking for some guidance and possibly help. I realize this is very vague in terms of actual numbers but i guess i just want to start by making sure im using the right formula.
Easiest way is to measure the length in inches and measure the height you need, if in a 100 inches and you need a rise of 2" it is a 2% grade etc. Nowadays I just buy WS inclines and try to fit the grade I want, much easier than the old ways and you can stack or add foam to them to get any grade you want.
Grade is precisely as you say: rise over run. The verbose explanation is that the percent of a grade is the number of units traveled vertically divided by the number of units traveled on the horizontal plane.
Thus if you travel 100 inches horizontally, and have risen 2 inches, then your grade is 2/100=0.02=2%. Notes that the units of measure don’t actually matter. You could substitute miles or meters or yards - the equation would be the same.
Thus, if you travel 25 miles horizontally, and travel one mile vertically, then your grade is 1/25=0.04=4%
It’s also possible to come up with non-whole numbers as a grade. It just depends on how easily your run is divided by your rise.
You’re right. It’s rise divided by distance times 100. 2" rise in 100 inches is 2%. 2" rise in 50 inches is 4%. Inches, centimeters, whatever, it doesn’t matter so long as both rise and distance are measured in the same units.
However, Make sure you use the same unit of measure for the rise and run. 2"/3’ will give you a .666 grade or 66% whereas 2"/36" yields an accurate measurement of .055 or 5.5%. By the way, the grade doesn’t have to be a one or two digit number. In the above cases the numbers went to infinity and were rounded off.
When you get your rise over run answer on paper or on the calculator, just move the decimal two places to the right. That is the net effect of multiplying the answer by 100 to make it a percentage. Now, instead of it reading 2"/100" = 0.02, you will know to read it as if the decimal is to the right of the second digit after the decimal currently showing, which is simply 2…percent.
Depending on how much space you have you can vary the grade up your climb. Pic your maximum grade and if you have room lesson the grade or flatten it out completely in spots and start up again. I had a long six inch rise and was able to vary in a few spots and was delighted with how a varied climb looks. I just never went over 2%. Good luck.[:)]
While the N Scale CR&T is still in planning and layout room preparation – perhaps these thoughts may be helpful…
A 2-track Pennsy multi-level portion (with helix) will surround and interchange with the lower level-only CR&T (traction down in the valley), and; the PRR will be subject to grade requirements (not to exceed 2%) that are already addressed in this thread.
[1] Here’s one more way PRR grades are being considered:
A recent MR Fourm (Micro-Engineering Bridges) could work for the Pennsy’s “much milder” valley bridge-spanning needs (see spidge). For example, it is PRR-prototype for elevated (all dirt) mainlines & viaduct-style bridges. This scenery technique might reduce your grade requirements with careful planning.
[2] CR&T’s lower layout level does support tighter radius & steeper grades:
Interurban passenger service is Brill & PCC – single units without freight cars, and; short line Box Cabs will only have a handful of freight cars (if that many). A doodlebug (gas electric) only-service to the upper level community of Summit is planned, and; this all would follow prototype. What is there to haul?
So, another way to support no way around “a steeper grade” is to shorten the amount of freight cars in your consists.
You’ve heard a lot of people respond by now, and if you’ve paid attention you may have noticed the figure of 2% mentioned frequently. That’s because this is a good “target” grade for model railroading. In the real world, mainlines rarely go steeper than 2%, and where they do they affect operations significantly (requiring helpers, for instance). But since model railroaders tend to run shorter trains, it may be possible to use even 3% grades without much negative impact. Of course, the kind of railroad one is modeling makes a difference too; some of the Colorado narrow gauge lines got up into the 4% or more range, so 5% on a layout wouldn’t look out of place. There were logging lines that ran Shays or other geared engines up ramps as steep as 10%. And a cog railway, like the Pike’s Peak tram, might exceed 40%! As you are planning a layout, though, you’ll need to have in mind the maximum grade you want to employ. A simple way to calculate it, as you sketch with pencil on graph paper, is to figure it based on 8 feet of run. Why 8 feet? Because that’s 96 inches, close enough to 100 inches that you can figure your 2% grade will have climbed 2 inches after 8 feet of run. If Point A is 8 feet away from Point B, and there’s 3.25 inches of vertical separation between them, then you’re looking at about a 3.25% grade. Keep in mind this is approximate; since 96 is less than 100, the actual grade will be a little bit steeper than that. But it’s a good rule of thumb when you’re at the stage of counting off 12" boxes on your graph paper to position things. If you’re getting into detail, though, one thing to allow for is the transition between grades, called a vertical curve. To go from 0% to 3% abruptly can be a problem for some engines, so you need to ease into it. If you’re using plywood that bends upward continuously, it will flex into this vertical curve naturally. If using sheet foam in combination with Woodland Scenics’ risers, though, you’ll have an abrupt transition that you probably ought to do som
Remember back when your elementary school teachers was going over fractions in math and told the class to pay attention, that some day you would need to know that stuff.
Classic prototype Horseshoe Curve is an apx. 1.75% grade, and consistently requires helpers, which are turned around just west of the curve at the Gallitzin Tunnels Summit (see AR Tower pics) where they go downhill back to Altoona – links provided to North East Rails.
