Guys,
Is there a simple formula for grades?I’ve been reading the posts and I just don’t seem to grasp it.What i’m asking for is something elementry.Something like 2%=1/2" of rise for X amount of linear inches.3%= 4%= You get the idea.Once I finalize my plan I’ll post it.
My plan is a modified dog bone with two reversing loops so the main line is about a 160 feet in length.My walls are framed and I’ll be getting the wallboard in a couple of weeks.I’ll start the electric today.
Thanks,Vince
A simple way to calculate the length of run needed (in inches) to rise 1 inch of grade would be:
Run = 100 / x%
So 100 / 2% = 50 inches of run to rise 1 inch at 2% grade (33.33 inches for 3%, etc.)
Don
But, that is if you go directly from level to grade and then to level again with no transition.
In order for your trains to work properly, mainly for reasons of coupling and traction, you must allow the entire train to ease vertically into the grade, and then to ease back out of it to level once again…up or down, it doesn’t matter the direction of travel. So, if you calculate that you’ll need x inches of horizontal distance to get Y inches in rise/fall, and don’t factor in about 12-18" of transition as an absolute minimum, you will be in trouble. Add the transitions, meaning there are two of them, and that leaves much less distance now for your average planned grade.
You must therefore keep in mind that your grades will probably be somewhere in the order of 20% longer than you think they’ll have to be when you place transitions on either end of them, depending on their lengths or steepness.
A 1% grade raises the track 1 inch every 100 inches
A 2% grade raises the track 1 inch every 50 inches
A 4% grade raises the track 1 inch every 25 inches.
Or…
A 1% grade raises the track 1 inch every 100 inches
A 2% grade raises the track 2 inches every 100 inches
A 3% grade raises the track 3 inches every 100 inches…etc.etc.
I am afraid that the idea of grade percentage simply confounds some folks who don’t have a good background in arithmetic. While it is nice to point out that a rise of 1" in 100" is the same as one percent, or 1%, they don’t realize that 1% is the same as the decimal 0.01. Since they can’t understand how it is derived, and since few of us can plan a layout with neat and exactly 100" runs, they don’t understand how to calculate the grade for the actual lengths of runs that they face.
So, how to calculate a grade - you must divide the total elevation, at the highest difference in elevation, by the length of run from the start of the grade to directly below the highest point…called the “run”. Rise divided by the run…every time…no matter what grade, what scale, or where on Earth you want to calculate the grade. You have a start point, and you want to end up higher, over “here” (pick a spot on your layout). Measure the change in height, or in elevation, whatever term you’d use. Use a single scale, whether inches, cm, feet, big toe, but keep it the same throughout…for both the rise and the run measurements. This is important!
Next, starting your measurement at the same spot, run the tape in as straight a line as possible to the point which is directly below the highest point you’d like to reach with your grade. This will ideally be a much longer distance than your height gain.
You now have two numbers. The smallest is your height gain. The longest is the distance you have to get up there. To calculate the grade, in a percentage, divide the rise by the run. Use a calculator if necessary. Let’s take an example: you measured a rise of 5", and your run came to 127" (lucky dog to have that much room!). Enter the digits…input 5, hit the divide si
You said “Something like 2%=1/2” of rise for X amount of linear inches."
Well, take 1/2" and divide it by .02. You get 25". So you need 25" of run to rise 1/2" with a 2% grade.
Going the other way. Lets say you have 25" of run and want to go up at 2%. Multiply 25 by .02 and you get the 1/2".
It’s either a multiply or a divide. If you don’t know which, try both multiply and divide and use the answer that makes sense (the other one will be WAY off).
Why .02? Because .02 is the decimal for 2%.
If you know the rise and run and want the percent. Divide rise by run and you get the decimal. Then convert to percent. Like 2" rise in 50" is 2/50 = .04 = 4%.