N Scale info on clearance

[Anonymous]

Planning is everything! I'm planning the new layout in N-Scale having been in HO previously, but some time ago!

Three questions (yeah only three for now!)
How much clearance does one need from roadbed to bottom of overpass? What is a reasonable radius for most cars (90 scale feet as longest?)?
What is the reasonable diameter for a helix (under main roadbed)?

Thanks for anyones help!

Mike

[Anonymous]

My rule of thumb (just my own observations and experience) is for vertical clearances 2" minimum. 3/4 inch = 10 feet in N Scale, so 2 inches real is about 25 scale feet, which is about prototype minimum.

As for curve radii, if I were to start over, I would not go less than 12 inches in a tight industrial area, and 18 inches for long equipment (such as passenger cars) on the main line. Therefore for your helix, I would recomend a 3 foot (36 inch) diameter.

Hope this helps.

[Anonymous]

Thanks for the help...I was really lost on scale sizing.

Mike

[pcarrell]

Hi Mike,

Good to see you've come over from the dark side! Welcome to Normal scale!

The technical answer to question 1 is something like 1 5/8" from railheads to overhead obstruction, but I just go with 2" and call it done.

90' cars will operate on 15" curves, but they won't look very good doing it. 20" or more would look a lot better.

A helix is the same in any scale. The diameter is determined by the desired grade and the amount of seperation from railhead to railhead. For example; if you want 3.8" from railhead to railhead (this includes subroadbed, roadbed, and track thickness) and you want a 2% grade you'll need a radius of 30.6" to accomplish it. A 2.9% grade is the result if you cut the radius down to 21.3". This is all according to the Atlas RTS track planning software I have. It's a free download and it includes all the code 55 stuff and a helix calculator. You can download it at; http://www.atlasrr.com/righttrack.htm

EDIT: Darn, beat me to it!

[Anonymous]

I've got the software downloaded to my home computer, but nowhere does it tell you minimums for clearance or what should work good and bad!

I've fixed some things on my layout...and added 2 helixes to make some train runs longer...but now i need to check space and possibilities! Software is only as good as the operator!

Thanks Philip for the advice...I still like the guy with the box on his head!

Mike

[fwright]

To amplify what Phillip said in regards to a circular helix with tracks on top of each other, there are 3 driving dimensions - knowing 2 automatically sets the third.

- the radius
- the grade
- the vertical clearance between layers

On vertical clearance, you need to have enough for the rolling stock - 2" in N - plus thickness of support structure, roadbed, and track plus the space above the rolling stock for you to reach in and rerail something that came off the track. Put some N track in various size boxes with the opening facing you and try putting a tall car on the track. Measure the minimum height above the box bottom that you can achieve this without pushing against the top of the box. Support structure of 1/4" plywood seems to be about the thinnest practical support I have seen in helix construction. Double that for the splice plates - you now have 1/2" - and add your roadbed thickness - typically 1/8". So without any additional hand space we are at at least 2.75" of vertical clearance.

Grades of more than 3% severely impact train length, especially in N scale. So using 2.75% as an example, we need a run of 100" to achieve that grade with that amount of rise. Dividing 100 by 2*pi (6.28), we get a radius of 16". To build it we need a 36" diameter space.

Remember, we did not allow any room for reaching in. Allowing reach-in clearance either increases the grade or radius, or both.

Hope this helps
Fred W

[pcarrell]

[#ditto] What he said!

Fred, you put it so much better then I ever could!

And Mike, I think the guy with the box is classic too. I laugh at that thing every time I see it.[:p]