07-22-2009, 10:51 AM
Josh,
Minimum thickness for a module using 2" foam is about 4", including roadbed and track. The 2" foam is actually strong enough to be supported only every 24" or so. So a 2x4 module, built from nominal 1x3 (good pine, or ripped from 3/4" ply) with a cross bar in the middle is your basic building block.
Now if you want 14" between the surface of the bottom module, and bottom of the upper deck, you'll actually need to climb 18".
I also think that it would be better to have 2 1/4" between the tracks on a curve like that (see <!-- m --><a class="postlink" href="http://www.nmra.org/standards/sandrp/s-8.html">http://www.nmra.org/standards/sandrp/s-8.html</a><!-- m -->). SO you will have to go to 24 1/4" radius on the outside, or reduce the inner to 21 3/4".
Anyway, some calculations for your consideration:
Circumference = pi x diameter OR pi x 2 x radius
3.14 x 2 x 24 = 150" or 12.5 feet per complete turn for the 24" radius AND
3.14 x 2 x 22 = 138" or 11.5 feet per complete turn for the 22" radius
So that's 24 feet of track for each turn the radius makes.
Now you need to go up 3" with every turn (<!-- m --><a class="postlink" href="http://www.nmra.org/standards/sandrp/s-7.html">http://www.nmra.org/standards/sandrp/s-7.html</a><!-- m -->), but that's from the railhead. So call it 4" if you make your helix subroadbed out of something like 3/4" ply.
Grade% = rise / run x 100%
4"/150" x 100 = 2.6%
Don't forget that the inside will be effectively steeper, since there is less run.
4"/138" x 100 = 2.9%
Can you live with that grade? Since it is on a curve as well, the length of the trains will be quite restricted. The only way to reduce the grade is to increase the radius, since the 4" clearance is pretty much non-negotiable.
So going up 18" using a 4" climb with every turn requires 4.5 turns.
4.5 x 24 feet per turn = 108 feet of helix track.
Something to think about...! I hope it is helpful. I am going to put some other comments in your layout design thread too.
Andrew
Minimum thickness for a module using 2" foam is about 4", including roadbed and track. The 2" foam is actually strong enough to be supported only every 24" or so. So a 2x4 module, built from nominal 1x3 (good pine, or ripped from 3/4" ply) with a cross bar in the middle is your basic building block.
Now if you want 14" between the surface of the bottom module, and bottom of the upper deck, you'll actually need to climb 18".
I also think that it would be better to have 2 1/4" between the tracks on a curve like that (see <!-- m --><a class="postlink" href="http://www.nmra.org/standards/sandrp/s-8.html">http://www.nmra.org/standards/sandrp/s-8.html</a><!-- m -->). SO you will have to go to 24 1/4" radius on the outside, or reduce the inner to 21 3/4".
Anyway, some calculations for your consideration:
Circumference = pi x diameter OR pi x 2 x radius
3.14 x 2 x 24 = 150" or 12.5 feet per complete turn for the 24" radius AND
3.14 x 2 x 22 = 138" or 11.5 feet per complete turn for the 22" radius
So that's 24 feet of track for each turn the radius makes.
Now you need to go up 3" with every turn (<!-- m --><a class="postlink" href="http://www.nmra.org/standards/sandrp/s-7.html">http://www.nmra.org/standards/sandrp/s-7.html</a><!-- m -->), but that's from the railhead. So call it 4" if you make your helix subroadbed out of something like 3/4" ply.
Grade% = rise / run x 100%
4"/150" x 100 = 2.6%
Don't forget that the inside will be effectively steeper, since there is less run.
4"/138" x 100 = 2.9%
Can you live with that grade? Since it is on a curve as well, the length of the trains will be quite restricted. The only way to reduce the grade is to increase the radius, since the 4" clearance is pretty much non-negotiable.
So going up 18" using a 4" climb with every turn requires 4.5 turns.
4.5 x 24 feet per turn = 108 feet of helix track.
Something to think about...! I hope it is helpful. I am going to put some other comments in your layout design thread too.
Andrew