Percent of Grade?

Model Railroader General Discussion (Model Railroader)
1

How does one determing the percentage of a grade?

I know that a 3-4% grade is the maximum but how does one figure this out? I would like to keep my grades at a maximum of 2 to 2-1/2%.

Thanks!

Craig

2

Should you have an earlier addition of MR, the April 2001 copy (Back To Basics-Grades) should be helpful.

3

Hi Craig,

A 3 percent grade rises or falls three feet for every 100 feet of run. So, let’s say you want a 2 percent grade on your layout. It would rise or fall 1.67 inches for every 10 feet of linear run.

Here’s the math: Divide 2 inches by 120 inches to get 1.66666 inches.

Formula: Divide the height by the distance (use identical increments – feet, inches, etc.) to arrive at the gradient.

A grade that rises one foot in 12 feet is an 8.3 percent grade --way too steep except for a logging railroad. A grade that rises 1 inch in 50 inches is a 2 percent grade.

Hope this helps,

Paul Schmidt
Associate Editor
MODEL RAILROADER

4

Thanks, just what I needed!

5

You’re absolutely right! I divided when I should have multiplied.

Good catch and good formulas.

Paul

6

I think you got your math wrong. at 2% 120" (10ft) would give you 2.4" of rise or fall.

here’s how I do it.

If you know the run and you want to know the rise at a certain grade then run x gradient / 100

so for a 120" run @ 2% the rise is 120" x 0.02 = 2.4"

If you know the rise and you want to know the run at a certain grade then rise / gradient x 100

so for a 2.4" rise at 2% is 2.4 / 2 x 100
= 120"

finally if you want the gradient and you have the rise and run then rise / run / 100 = gradient

so for a 2.4" rise and a 120" run you get 2.4 / 120 /100 = 2%