1% grade is 1" vertical rise in 100 inches. It’s really simple to figure out.
2.5% is 2.5" vertical rise in 100 inches, or roughly .300" vertical rise per foot.
Could anyone tell me the ratio of height in inches to running foot of rail to achieve a 2.5% grade??
Yes, it is 0.300" vertical rise per horizontal foot (12").
If by “running foot” it is the slope distance that is desired then using the Pythagorean theorem a^2 + b^2 = c^2
the slope distance for a 0.3" rise would be the square root of 12x12 + 0.3x.03 = 144.09 which is 12.0037 inches.
The rise for every 12" of slope distance it would be 12/12.0037x0.3 = 0.2999 inches
The difference is insiginificant for the distances on a model railroad.
What would be a simple rule of thumb for the added % for inclines on a curve (needed for a “nolex”)?
Most folks write that “nolix” as in “no helix” – “Nolix” was a John Armstrong play on words for a place name on one track plan that others have borrowed to describe any climbing tracks that aren’t hidden circular helixes.
As far as the equivalent grade in HO, John Allen suggested the formula 32/R, “R” being the radius. The result is added to the nominal grade for the effective grade.
So for a 2% nominal grade through a 24" radius curve, the calculation would be 32/24 = 1.33% plus the 2% grade for an equivalent grade of 3.33%
For a 2% nominal grade through a 36" radius curve, the calculation would be 32/36 = .89% plus the 2% grade for an equivalent grade of 2.89%
I’m doing some empirical testing of this formula now with modern rolling stock and it seems to be too low for tighter curves and the steepest nominal grades, but about right for curves over 30" and gentler nominal grades. The results aren’t ready to publish yet, but they do suggest John Allen’s 32/R is a good first estimation for HO.
Byron
LION cut wood risers. For his 4 track helix he used 2x6s. Each one was 1/4" longer than the previous one. The pitch of his helix was controlled by how far apart these were. What controlled this was getting the second level above the first level so that the trains could pass under it.LION put a builder’s shim on the top of the riser to give the entire helix a super elevation. Subsequent layers are just set on spacers which maintain the angle of the incline and the cant of the elevation.
LION neither knows or cares what percentage of a curve this is. It is what it has to be. The helix is 5’ in outside diameter. Tracks are laid against the outside and work their way in. The LION neither knows or cares what the radius is. It is what it has to be.
Bottom line: IT WORKS! IT WORKS!
ROAR
Thank you for the information Byron, while I won’t be running long consists, it’s something to keep in the back of my mind. I would consider leaving the 30R curves “on the flat” but need their length to gain the height I need. Already losing rise due to switches and the 1% lead in to the 2% incline.
One reads what one reads. In a way it is a helix just with a rather long straight section or two or three.
Alan