When you talk about grades like most use 2% grade how much distance do I need for this incline? I dont have that chart handy
There is no specific distance…
An increase in height of a 1/2" over 25" of distance is a 2% grade.
An increase in height of 1" over 50" of distance is a 2% grade.
An increase in height of 2" over 100" of distance is a 2% grade.
An increase in height of 4" over 200" of distance is a 2% grade.
Got it?
The number that pertains to a grade, regardless of scale, is the percentage of elevation change in the distance you have to complete the elevation change. That means you have two variables, and they are expressed as a percentage because the elevation change is divided by the horizontal distance travelled.
As given in the examples previously, expressing them as a fraction, such as 2/100 yields the decimal equivalent of 0.02 when you divide the numerator (height) by the denominator (distance taken to achieve the height). Moving the decimal over two places makes the expression readable as a simple percentage…in this case 2%.
If you want to know what the grade will be when you make your trains climbe 4" in only 85 inches of horizontal travel, you divide 4 by 85 to get 0.471 (rounded), which we can read as 4.7%…very steep!
Just be sure to use the same units of distance in the numerator and in the denominator. Using feet in one instance and not the other will give you some head scratching results.
One last biggie: you can’t have a sudden onset of your grade and then get back to level at the top suddenly. At the top, your cars will uncouple and race to the bottom ,and your engine will probably stall and spin at the abrupt change at the bottom. So, you need a curve into the grade, something gradual so that things don’t get stuck. You need a similar one on the other end. That’s two chunks of your available space eaten up with a vertical curves. What’s left, and how steep will hit have to be to get you up to the height you have in mind? Isn’t looking very promising, suddenly.
-Crandell