N-Scale Helix Minimum Radius

[WHartman]

I am in the process of planning a helix to link two levels that are separated by 16". I plan to run modern equipment that includes long trains of autoracks. What advice can anyone offer pertaining to minimum radius and minimum grade, and railhead-to-railhead vertical separation?

[Anonymous]

First, let me ask you a question then I'll do the research. What is the maximum radius you could have in the space you have for your helix. Remember the radius is to track center, so you have to add on at least an 1 or an 1 1/2 inches to the outside. So if the maximum radius you can have is 18 inches, then multiply that by 2 and you have 3 feet or 36 inches, then add on at least another three inches for construction etc. So you would need a space that could hold 39 inches round. And I haven't talked about seperation yet. So again, what is the maximum radius you could have?

[WHartman]

Thanks Rick,for the reply. I have an overall clear dimension of 3'-2 1/2". (38.5") which is the width of an area tucked under the stairs. I have plenty of vertical height available, approximately 60" at the furthest point away.

[Anonymous]

With that space, you will find it tight for a helix. It means your maximum radius will be 18 inches (36 diameter):

At 3 inches of seperation 2.5 % grade
at 3 1/2 inches of sep 2.9 %
at 4 inches of sep 3.4 %

[WHartman]

My initial calculations also indicated 18" radius at about 2%+ grade. I guess what I am wondering is, if that will give me trouble with a train of autoracks, let's say 25-30 cars long? I also was wondering if anyone has had luck with a shorter radius, say 16", and running long freight cars or passenger equipment?

I will be unable to answer email for a few days, so I'll check in again in a week.

[Anonymous]

The autoracks are what a lot of guys use to establish clearances for their rail road. Their thinking is that if an autorack clears, then just about everything will clear. I'm not sure of the seperation you want as I am in N scale. But stick with the widest radius in your small space as you can.

[Anonymous]

QUOTE: Originally posted by rsn48

With that space, you will find it tight for a helix. It means your maximum radius will be 18 inches (36 diameter):

At 3 inches of seperation 2.5 % grade
at 3 1/2 inches of sep 2.9 %
at 4 inches of sep 3.4 %

[Anonymous]

[From what you are saying it sounds as if 18 inch radius is pushing it a bit. I am just about to start construction of a helix. What is the optimum radius for 20-30 car consists?
Thanks]Originally posted by Simon Black

QUOTE: Originally posted by rsn48

With that space, you will find it tight for a helix. It means your maximum radius will be 18 inches (36 diameter):

At 3 inches of seperation 2.5 % grade
at 3 1/2 inches of sep 2.9 %
at 4 inches of sep 3.4 %

[Anonymous]

Simon and others,
Its kind of like playing pin the tail on the donkey blind folded without more information. The two critical measurements you need to tell us is the seperation from rail head to rail head you will have, then tell me what is the maximum radius you could physically have.

When most people start with helix's, it comes as a surprise as to how much room they take up. Most of my friends HO layout (I'm in N) use a 30 inch radius up, and a 28 inch radius down, or something close in that proximity. With a 30 inch radius, that means your helix will be over 5 feet across.