Grade question

I have a simple question for all you experts. What is the formula for measuring a grade percentage? I realize it works with the amount of rise per foot etc... but in simple terms if you have 12 feet to rise 4 inches what grade would that be. I trust you will all have very informative answers.

Thanks
Bryan

 

You take the amount of rise (4) divided by the length of the run (144) and you get the percent grade (2.8%)

Daryl

 

Thanks I knew I would get the info I needed! You guys are great.

Bryan

 

Or you can choose the maximum grade you wish your trains to handle, say 2.8%. Then you use this formula 12 X 2.8% = 0.336" x12 ft =4.03" rise over the twelve ft.

However, remember that you're working at 1/160th here. So a mile of N scale track works out to 33 ft. A twelve ft. run is only a little over 1/3 of an N scale mile, .36 of a mile to be exact or 1900.8 ft.

A 4" rise in N scale works out to be about 53ft. A 53 ft. rise in about a third of mile or 1900.8 ft.? That's a pretty step grade when you look at it that way. Still think it's only a 2.8% grade?

Surprise....2.8% of 1900.8 ft. works out to be exactly 53.2 ft.

So the first reply you got is right on and a lot simpler than doing the way engineers do.

 

Now I know why I am a designer not an engineer. Math is like a foreign language to me sometimes. Next question, in your opinions what is the max grades you all would have on a layout (for a mainline)?

Bryan

 

Today I think most major road mainlines max out at 1 - 1.5 % For models, I think 2%-3% is the max unless you're modeling a logging raiload of some sort.

Daryl

 

I'm contemplating the same question Bryan and I wish I had the cad equipment I used at work in engineering, so that I could design my layout in 3d.

I think maximum gradiants will depend on how long of a run you are going to be able to get and how high you want to climb. But I think 3% grades are getting kind of steep and on short runs look a little hokey.

I'm going to use spirals to get my elevation. I have one built now and it has a 33"dia and goes four times around and I gain 12" in elevation.

To figure out the grade of this spiral you have to use pye,r,squared. A 33" radius gives you a run of 103" each time around for a total of 412" or 34 ft. in a 33" dia area. Kind of amazing. I believe it worked out to about a 3% grade. So if I cut the rise down to 6" in the same radius, I end up with a very comfortable 1.5% grade. The nice part of a spiral, is the grade is hidden.

I tested a Kato Mikado, an Atlas GP9 and a Kato F3A unit on the completed spiral and each individual engine had no trouble pulling 15 MT box cars up to the top.

Of course I'll need a pretty big mountain in the corner of my layout to hide that spiral.

 

Ok ,so whats the percentage of grade for a 4" rise in 16 ft?

 

16 feet is 192 inches, so 4 divided by 192 is a 2.1% grade.

This is how I incorporate grades on my layouts. I try to make everything as level as I can. This way I end up with some small grades here and there. The grades are noticable, yet do not need extra power or cause other grade related problems.

Daryl

 

Thanks Dayrl,I couldn't get the calculator on this puter to recognize what I was doing.So I figured to ask some one who actually knew what I need to know.

 

Catt, I find it easier to remember that:

1/8 th of an inch rise per ft....=a 1.04 % grade.
3/16 th of an inch rise per ft. =a 1.56 % grade.
1/4 of an inch rise per ft........=a 2.08 % grade.
5/16 th of an inch rise per ft..=a 2.60% grade. 3/8th of an inch.....................=a 3.12 % grade.

This way you can work your grades out over shorter distances by the foot instead of 16 ft. That allows you to keep the steeper part of your climb on the straight track and the curves to the lower % rise. That makes for less pull on the couplers.