# Helix/Spiral radii in N Scale?

Discussion in 'N / Z Scale Model Trains' started by Meiriongwril, Mar 1, 2006.

1. ### MeiriongwrilMember

Joined:
Mar 1, 2006
Messages:
208
0
I'd like to include helices in my new N layout. I have a run of 2 foot by 11 foot down one wall, linked by a shelf to a 36" long by 30" wide run on the opposite wall. The 2 foot wide run could be widened by maybe 6" or so at its far end to accommodate a helix.

I'd like to have a helix at either end of the 'U' down to staging below (baseboards at 48" high currently). However, I'm unsure of the minimum radius I could get away with (i.e. to fit in the board widths). I'm using Atlas code 55, and they have curves down to 10". What can get round curves this tight? I've got a diesel only fleet (SP and Cotton Belt) of various sizes, but freight only rolling stock with nothing much longer than 65' gondolas.

Also - does anyone know of a helix builder - I'm no woodworker!!
2. ### pgandwActive Member

Joined:
Jul 9, 2005
Messages:
1,113
0
I don't think what you have in mind is going to work, regardless of whether your equipment can go around the curves you have in mind. Biggest obstacle in N is keeping sufficient vertical clearance to get your hand in to rerail a car or loco while keeping the grade reasonable. How much vertical clearance do you need? You pretty much have to allow 1/2 inch for your roadbed and track, plus 2 inches just for vertical clearance. This leaves nothing for your fingers, but we'll take it as a starting point. For a 2.5% grade, you need 100 inches of run every 360 degrees of helix. On a circular helix that translates to 100 divided by 2*pi = 16 inch radius. Your helix would need to be 36 inches across to allow a little room for a derailed train to stay on the helix instead of heading for the floor. N scale locomotive performance really takes a hit on grades over 3% unless there are traction tires. Also, N scale is much more subject to string lining where the cars derail inward as they are being pulled up a curving grade. All in all, I'd say the 16 inch radius example is about the absolute minimum for a successful helix in N.

N scalers who have built helixes can correct me if I'm wrong, but I'm pretty sure of the above.

yours in climbing curves

Joined:
Aug 10, 2003
Messages:
101