1
1: Commercial helix kits available in several scales
can save the time and effort of calculating grades and
radii, and can eliminate the need for specialized tools.
photo.
QUESTIONS AND ANSWERS
Plan a helix
Q.
What is the smallest practical radius for a helix in N scale?
My layout plans include one, but I only have room for a small
radius. I am beginning to think a long ramp with a return loop
and a staging yard may be better. I will run mostly freight, usually
with two locos, and a maximum of 12 to 15 cars. Most of my cars
are 4" and my locos are mostly SD40-size six-axle types.
– Paul
A.
Prof Klyzlr scribbled a dazzling array of numbers and formulas
on the back of an old shopping bag and came up with the follow-
ing answers:
Radius – 15 ¼” curve radius. This is based on 130mm loco
length x 3 = 390mm curve radius. We may be able to go tighter,
but this would be a good radius to aim for so everything stays
coupled and runs reasonably. 2 times pi times the radius
(2x3.14x15.25) equals about a 96” trip around the circle.
Vertical space – A Life-Like SW1200 is just under 1-1/2" tall,
from the roadbed to the top of the cab, including the track the
loco is sitting on. Allow more for excess-height cars and dou-
ble-stacks! Allow 1” for roadbed, possibly ½” or ¾” plywood or
another material. Allow 2" between the top of the equipment
and the bottom of the next turn of the helix for finger room to
rerail cars. Total: 4 ½” to 5” from one rail up to the next.
Questions, Answers & Tips - 1
MRH-Mar 2014
