For all you N scalers who have a helix incorporated on your layout, can you do me a favor and give me the outside dimensions of your entire helix assembly (hopefully using the smallest radius allowed).
I’m scheming a plan that will add an around-the-wall layout to our home office. It might be a little tricky, but I want to see if I can make a go of it.
Here’s what makes it tricky: the office has angled ceilings with two different heights. The southern ceiling (to the left as you walk in the room) is higher than the northern ceiling. The height of the track on the southern wall will be roughly 48 inches, while the height of the track on the northern wall will be only 24 inches.
Here’s how I envisioned it: Starting in the northwest corner and working counter-clockwise, the track would be at the same height on the west and south walls. As the train approached the southeast corner, it would go down a helix which would drop it to the level of the northern wall and then it would move along the east wall. It would continue from the east wall to the north wall at the same level. In the northwest corner, it would climb the helix back to the higher level.
I need to take up a little space as possible so if you use the minimum radius for your helix, that’s the ideal dimension I’m looking for.
You’re missing the factor of controlling grade. You can get pretty tight if you don’t mind a 6% grade. If you give you’re controlling grade, the rest can be calculated fairly easily.
I know, but I’m trying to avoid a dog bone if at all possible. The only way to do that is to drop it, then bring it back up. It’s an aweful space to try to cram a self railroad in to.
What he said… Just brainstorming here, to maintain clearances and allow space for the sub-road bed you are going to need to rise about 3 inches each loop. Since you need a 24 inch change in elevation you need 8 loops. Lets figure a 2% grade since I like easy numbers. That means each loop has to have 150 feet of track. If my math is right, and there is no good reason it should be, calculus class was almost 30 years ago, you need about a 48 inch radius. You could squash it into an oval with say a 10 inch radius half circles connected by a 43.5 inch straight run. Or you could make it steeper and change everything but the the math gets harder.
Or you could just attach the shelf to the sloped ceiling and block of the small, unusable part of the triangle with a back board. Just a thought.
A 20 inch radius with 2.7 inches between levels will give you a 2.3% corrected grade (figured for drag of curve). A 24 inch change in elevation would require 9 stories. You get a slim 2.7 inches between tiers by using 1/4 inch luan and 1/4 inch foam for roadbed with the tracks laid directly on it using silicone sealant. Then the levels are supported by long pieces of threaded stock with nuts screwed on at the proper heights to support strapping metal (or you could use sheet metal but it’s more of a pain to work with). Pieces of strapping metal also hold the vertical threaded stock pieces together side to side. The threaded stock pieces are placed every 12 inches or so around outside circumference of the helix.
You’ll end up with about 2 inches of vertical clearence from the railtops using Atlas code 83 (you actually want to use that track because of it’s bulletproof nature).
Thats how I did one years ago.
Again, just make sure your trackwork is bulletproof as it’s tough to get fingers in those tight places in the event of an emergency.
Erik, it isn’t as simple as picking the minimum radius for a helix. You want the train to be able to make it up the hill. How many cars do you plan to pull? 5 or 6 with a decent diesel could probably do 3%. If you want more cars, either add engines, or reduce grade. Remember, reducing grade makes the helix diameter larger.
The math is straight forward:
grade % = units rise / 100 units run
2 pi * r = run per turn
2" vertical clearence railhead to railhead is comfortable for N.
16" radius ~2%
12" radius ~3%
8" radius ~4%
With these numbers, you will need 12 turns to make the height you want.