Hello;
Question. if you build a helix with the following specifications; an 18" radius-36: Diameter, Ramps 4" wide, and 3-1/2" between spirals. What grade does that work out to be?
Thanks
Ron
The formula for a circle (or one turn on the helix) is PI * diameter, 3.14 * 36 = 113 inches. Grade is height / length of one turn, 3.5 / 113 = .0309 or 3.1%.
Enjoy
Paul
Here’s a handy little helix calculator!
http://www.fortunecity.com/westwood/beautiful/819/HeliCal.htm
What grade? I give it a D Minus or and F. Unless you are running trolley cars, doodlebugs, Budds or HOn3 you might get away with an S-1 and 2 cars plus a caboose up that steep hill with such a tight radius. Better to find room for a nolix behind some scenery or else where. Grade should be kept to two percent and the largest, not the smallest, radius curves you have room for. I built my first helix over 30 years ago. It was an oval, not a circle with 30 inch radius curves at two percent rise… One turn around got me enough height to allow crossing over other tracks below. By stretching it out to an oval you can gain more elevation with a more practical grade. My rule: nolix first, helix when all else fails.
That’s interesting Rusty, I never heard of anyone using a nolix, but I can see the advantages if you have the room. I agree with you on the grade, anything over 2% in a helix is not practical. Joe Fugate had some good info on his DVD re helix and what he learned from his first helix.
Thanks all for the good information. The formula was especially helpful. I’m working in N scale but 3.1 % is way to high unless I turn it into a cog helix :)
. I recalculated the height and 3" wold allow clearance but return a 2.6 grade. Still high but better than 3.1. I’ll recheck my space and see if I can enlarge the radius.
BTW: What is a nolex ? (I’m new so forgive the ignorance).
Thanks
Ron
I believe that Rusty was saying, avoid a helix if at all possible, but if you must, adhere to the 2% rule. And what Rusty did was to build his helix as an oval, which gives him more climbing space per 360 degrees.
Technically, a nolix is a layout that IS a helix. Picture it this way,…you stand in the middle of the helix that goes around the walls of the room and has scenery on it. Yards and sidings are level, but the main is on a constant climb so that when the track gets back around the room to the starting point it’s high enough over the bottom track that it clears the backdrop of the level below it. Depending on the size of the room it can give you a grade of just “.” something or other instead of a much larger grade that a helix yields. Make sence, or are you thourghly confused now?
Wow! That is just a little to much room for me. I have a 25’ run that I could use to get down to the second level. But the grade for a 12’ - 18" drop would, I believe be way more than a helix.
Thanks
Ron
Switchman,
Given that your working in N scale, if you wish to keep a tight helix diameter, you could drop your clearance between levels from 3 1/2" to 2 5/32". I believe N-scale track with cork is no more than 1/4" thick and you can easily built the subroadbed in your helix from 1/4" plywood as it can be supported at very short intervals. (A better option is to cut 90 degree arcs from 1/8" plywood and then laminate those together, offsetting the joints to get 1/4" thick roadbed.) That leaves the NMRA minimum clearance of 1 21/32". The grade for a helix with an 18" radius and 2 5/32 rise per turn gives a grade of 1.9%.
You are correct about the 25 feet not being enough to get 1 to 1 1/2 feet of rise at a reasonable grade. That is a 4 to 6% grade. However, with the nolix, do not think you have to get the rise in just one section of track. I am designing a nolix style layout and I use every section of track that is not a town, yard, or siding to climb. Add up the length of track you have between yards, towns, and sidings and divide the desired nominal clearance by the previous sum to get your grade.
Eric
Eric,
That’s correct. If you had a rectangular room for example that was say 25’ x 10’, you’d essentially have 70’, minus any towns or yards, in which to gain the needed height.