Helix

[cav]

What is the tightest radius you can do for an N scale helix?

 

[choops]

I did some maths.

2" of rise per turn.
2% grade needs 100" of length 100/3.14= 32"diameter
3% grade needs 67" of length 67/3.14= 21"diameter
4% grade needs 50" of length 50/3.14= 16"diameter

hope this helps
Steve

 

[cav]

Thanks, that helps

 

[Selector]

Try really hard for no more than 2.5-2.7%. Once you get nearer to 3% and above, you can figure on trains less than half the length they would be on the flats, and that's without a tight curve around which to drag all those flanges rubbing on the inside rail head.

IOW, go beyond a 20" curve if you can. Remember that you need clearance between the top of the lower rail head and the wheels atop the rails on the level above. Between those two points you must pass your highest rolling stock, including caboose chimneys or MOW wrecker cranes, maybe some double-stacks if you are in modern times, the road bed, and the tracks resting on the roadbed.

 

[cav]

Thats what I was thinking I only need two inches of height and I can get a little bit of that with a straight incline also. I need to get some peices cut and built and see I guess.