Has anyone done or seen a helix that runs around the outside of a mountain as it climbs? Is it even possible, with loops getting smaller as you go up?
Just trying to think of a way to prettify a helix and make it interesting.
as it spirals inward, would the change in elevation decrease in order to maintain a reasonable grade?
1 Like
Yes, but with there are caveats that the video shows.
Interior view of the helix.
I have also seen, in a model railroad magazine, I can’t remember which one, where the modeller did a cut away section which depicted the interior of a tunnel. Looked good to me.
Cheers, the Bear. 
4 Likes
A fine looking boat on that flatcar. How long is the mainline on that layout?
There was a guy on this forum I believe that built a Polar Express layout including that mountain scene. There may be a YouTube of it. I think it was N scale, it was spectacular.
2 Likes
I imagine it would have to decrease in elevation, now that you mention it. The calculations on that’ll require aspirin…
1 Like
If the mountainside helix won’t work, the cutaway tunnel sounds like a good alternative…
2 Likes
will those inner tracks near the top be behind the lower track?
1 Like
If you mean smaller radius, that’s what I was picturing. With a span bridge running from top of helix Mtn to level two.
1 Like
Gidday Brian, the number of aspirins required depends on several factors…
.
How much space do you have for a helix?
Where will it be situated in your “train” room?
What is your preferred minimum radius?
What is your preferred grade?
What elevation do you what to achieve?
Double or single tracked?
What scale?
Your construction skills?
Cheers, the Curious Bear.
1 Like
here’s one possibility
- 2" horizontal separation between tracks
- maintains 2% effective grade accounting for grade due to curvature of 32/rad (HO)
- requires ~39" initial radius to rise 16"
thickness = 1.5
# x z y rad gr
38.408 0.080 6.772 39.000 1.18
36.596 0.160 13.320 38.944 1.18
33.679 0.240 19.444 38.889 1.18
29.748 0.320 24.962 38.833 1.18
24.926 0.399 29.706 38.778 1.17
19.361 0.478 33.534 38.722 1.17
13.225 0.558 36.335 38.667 1.17
6.705 0.636 38.025 38.611 1.17
0.000 0.715 38.556 38.556 1.17
-6.685 0.794 37.915 38.500 1.17
-13.149 0.872 36.126 38.444 1.17
-19.194 0.950 33.246 38.389 1.17
-24.640 1.028 29.365 38.333 1.17
-29.322 1.106 24.604 38.278 1.16
-33.101 1.183 19.111 38.222 1.16
-35.865 1.261 13.054 38.167 1.16
-37.532 1.338 6.618 38.111 1.16
-38.056 1.415 0.000 38.056 1.16
-37.423 1.491 -6.599 38.000 1.16
-35.656 1.568 -12.978 37.944 1.16
-32.813 1.644 -18.944 37.889 1.16
-28.982 1.721 -24.319 37.833 1.15
-24.283 1.797 -28.939 37.778 1.15
-18.861 1.872 -32.668 37.722 1.15
-12.883 1.948 -35.395 37.667 1.15
-6.531 2.023 -37.040 37.611 1.15
-0.000 2.099 -37.556 37.556 1.15
6.512 2.174 -36.930 37.500 1.15
12.807 2.248 -35.186 37.444 1.15
18.694 2.323 -32.380 37.389 1.14
23.997 2.397 -28.599 37.333 1.14
28.556 2.472 -23.962 37.278 1.14
32.235 2.546 -18.611 37.222 1.14
34.925 2.620 -12.712 37.167 1.14
36.547 2.693 -6.444 37.111 1.14
37.056 2.767 -0.000 37.056 1.14
36.438 2.840 6.425 37.000 1.14
34.716 2.913 12.636 36.944 1.13
31.947 2.986 18.444 36.889 1.13
28.216 3.059 23.676 36.833 1.13
23.640 3.131 28.173 36.778 1.13
18.361 3.203 31.802 36.722 1.13
12.541 3.275 34.455 36.667 1.13
6.357 3.347 36.055 36.611 1.13
0.000 3.419 36.556 36.556 1.12
-6.338 3.491 35.945 36.500 1.12
-12.465 3.562 34.247 36.444 1.12
-18.194 3.633 31.514 36.389 1.12
-23.355 3.704 27.833 36.333 1.12
-27.790 3.775 23.319 36.278 1.12
-31.369 3.845 18.111 36.222 1.12
-33.986 3.916 12.370 36.167 1.12
-35.563 3.986 6.271 36.111 1.11
-36.056 4.056 0.000 36.056 1.11
-35.453 4.126 -6.251 36.000 1.11
-33.777 4.195 -12.294 35.944 1.11
-31.081 4.265 -17.944 35.889 1.11
-27.450 4.334 -23.033 35.833 1.11
-22.998 4.403 -27.407 35.778 1.11
-17.861 4.472 -30.936 35.722 1.10
-12.199 4.540 -33.516 35.667 1.10
-6.184 4.609 -35.070 35.611 1.10
-0.000 4.677 -35.556 35.556 1.10
6.165 4.745 -34.961 35.500 1.10
12.123 4.813 -33.307 35.444 1.10
17.694 4.880 -30.648 35.389 1.10
22.712 4.948 -27.067 35.333 1.09
27.024 5.015 -22.676 35.278 1.09
30.503 5.082 -17.611 35.222 1.09
33.046 5.149 -12.028 35.167 1.09
34.578 5.216 -6.097 35.111 1.09
35.056 5.282 -0.000 35.056 1.09
34.468 5.349 6.078 35.000 1.09
32.837 5.415 11.952 34.944 1.08
30.215 5.481 17.444 34.889 1.08
26.684 5.546 22.390 34.833 1.08
22.355 5.612 26.641 34.778 1.08
17.361 5.677 30.070 34.722 1.08
11.857 5.742 32.576 34.667 1.08
6.010 5.807 34.085 34.611 1.08
0.000 5.872 34.556 34.556 1.07
-5.991 5.936 33.976 34.500 1.07
-11.781 6.001 32.367 34.444 1.07
-17.194 6.065 29.782 34.389 1.07
-22.069 6.129 26.301 34.333 1.07
-26.258 6.193 22.033 34.278 1.07
-29.637 6.256 17.111 34.222 1.06
-32.106 6.320 11.686 34.167 1.06
-33.593 6.383 5.923 34.111 1.06
-34.056 6.446 0.000 34.056 1.06
-33.483 6.509 -5.904 34.000 1.06
-31.897 6.571 -11.610 33.944 1.06
-29.349 6.634 -16.944 33.889 1.06
-25.918 6.696 -21.748 33.833 1.05
-21.712 6.758 -25.875 33.778 1.05
-16.861 6.820 -29.204 33.722 1.05
-11.515 6.881 -31.636 33.667 1.05
-5.837 6.943 -33.100 33.611 1.05
-0.000 7.004 -33.556 33.556 1.05
5.817 7.065 -32.991 33.500 1.04
11.439 7.126 -31.427 33.444 1.04
16.694 7.187 -28.916 33.389 1.04
21.426 7.247 -25.535 33.333 1.04
25.492 7.308 -21.391 33.278 1.04
28.771 7.368 -16.611 33.222 1.04
31.166 7.428 -11.344 33.167 1.04
32.608 7.487 -5.750 33.111 1.03
33.056 7.547 -0.000 33.056 1.03
32.499 7.606 5.730 33.000 1.03
30.958 7.665 11.268 32.944 1.03
28.483 7.724 16.444 32.889 1.03
25.152 7.783 21.105 32.833 1.03
21.069 7.841 25.109 32.778 1.02
16.361 7.900 28.338 32.722 1.02
11.173 7.958 30.697 32.667 1.02
5.663 8.016 32.116 32.611 1.02
0.000 8.074 32.556 32.556 1.02
-5.644 8.131 32.006 32.500 1.02
-11.097 8.189 30.488 32.444 1.01
-16.194 8.246 28.050 32.389 1.01
-20.783 8.303 24.769 32.333 1.01
-24.726 8.360 20.748 32.278 1.01
-27.905 8.416 16.111 32.222 1.01
-30.227 8.473 11.002 32.167 1.01
-31.623 8.529 5.576 32.111 1.00
-32.056 8.585 0.000 32.056 1.00
-31.514 8.641 -5.557 32.000 1.00
-30.018 8.696 -10.926 31.944 1.00
-27.617 8.752 -15.944 31.889 1.00
-24.386 8.807 -20.462 31.833 0.99
-20.426 8.862 -24.343 31.778 0.99
-15.861 8.917 -27.472 31.722 0.99
-10.831 8.972 -29.757 31.667 0.99
-5.489 9.026 -31.131 31.611 0.99
-0.000 9.080 -31.556 31.556 0.99
5.470 9.134 -31.021 31.500 0.98
10.755 9.188 -29.548 31.444 0.98
15.694 9.242 -27.184 31.389 0.98
20.141 9.296 -24.003 31.333 0.98
23.960 9.349 -20.105 31.278 0.98
27.039 9.402 -15.611 31.222 0.98
29.287 9.455 -10.660 31.167 0.97
30.638 9.508 -5.402 31.111 0.97
31.056 9.560 -0.000 31.056 0.97
30.529 9.612 5.383 31.000 0.97
29.078 9.665 10.584 30.944 0.97
26.751 9.717 15.444 30.889 0.96
23.620 9.768 19.819 30.833 0.96
19.784 9.820 23.577 30.778 0.96
15.361 9.871 26.606 30.722 0.96
10.489 9.922 28.817 30.667 0.96
5.316 9.973 30.146 30.611 0.95
0.000 10.024 30.556 30.556 0.95
-5.296 10.075 30.037 30.500 0.95
-10.413 10.125 28.608 30.444 0.95
-15.194 10.175 26.318 30.389 0.95
-19.498 10.225 23.237 30.333 0.95
-23.194 10.275 19.462 30.278 0.94
-26.173 10.325 15.111 30.222 0.94
-28.347 10.374 10.318 30.167 0.94
-29.654 10.424 5.229 30.111 0.94
-30.056 10.473 0.000 30.056 0.94
-29.544 10.522 -5.209 30.000 0.93
-28.139 10.570 -10.242 29.944 0.93
-25.885 10.619 -14.944 29.889 0.93
-22.854 10.667 -19.176 29.833 0.93
-19.141 10.715 -22.811 29.778 0.93
-14.861 10.763 -25.740 29.722 0.92
-10.147 10.811 -27.878 29.667 0.92
-5.142 10.858 -29.161 29.611 0.92
-0.000 10.905 -29.556 29.556 0.92
5.123 10.953 -29.052 29.500 0.92
10.071 10.999 -27.669 29.444 0.91
14.694 11.046 -25.452 29.389 0.91
18.855 11.093 -22.471 29.333 0.91
22.428 11.139 -18.819 29.278 0.91
25.307 11.185 -14.611 29.222 0.90
27.408 11.231 -9.976 29.167 0.90
28.669 11.277 -5.055 29.111 0.90
29.056 11.322 -0.000 29.056 0.90
28.559 11.368 5.036 29.000 0.90
27.199 11.413 9.900 28.944 0.89
25.019 11.458 14.444 28.889 0.89
22.088 11.503 18.534 28.833 0.89
18.498 11.547 22.045 28.778 0.89
14.361 11.592 24.874 28.722 0.89
9.805 11.636 26.938 28.667 0.88
4.968 11.680 28.176 28.611 0.88
0.000 11.724 28.556 28.556 0.88
-4.949 11.767 28.067 28.500 0.88
-9.729 11.811 26.729 28.444 0.87
-14.194 11.854 24.585 28.389 0.87
-18.212 11.897 21.705 28.333 0.87
-21.662 11.940 18.177 28.278 0.87
-24.441 11.983 14.111 28.222 0.87
-26.468 12.025 9.634 28.167 0.86
-27.684 12.067 4.881 28.111 0.86
-28.056 12.109 -0.000 28.056 0.86
-27.575 12.151 -4.862 28.000 0.86
-26.259 12.193 -9.558 27.944 0.85
-24.152 12.234 -13.944 27.889 0.85
-21.322 12.276 -17.891 27.833 0.85
-17.855 12.317 -21.279 27.778 0.85
-13.861 12.358 -24.008 27.722 0.85
-9.463 12.398 -25.998 27.667 0.84
-4.795 12.439 -27.192 27.611 0.84
0.000 12.479 -27.556 27.556 0.84
4.775 12.519 -27.082 27.500 0.84
9.387 12.559 -25.789 27.444 0.83
13.694 12.599 -23.719 27.389 0.83
17.570 12.639 -20.939 27.333 0.83
20.896 12.678 -17.534 27.278 0.83
23.575 12.717 -13.611 27.222 0.82
25.528 12.756 -9.292 27.167 0.82
26.699 12.795 -4.708 27.111 0.82
27.056 12.834 0.000 27.056 0.82
26.590 12.872 4.689 27.000 0.81
25.319 12.910 9.216 26.944 0.81
23.286 12.948 13.444 26.889 0.81
20.556 12.986 17.248 26.833 0.81
17.212 13.024 20.513 26.778 0.80
13.361 13.061 23.142 26.722 0.80
9.121 13.098 25.058 26.667 0.80
4.621 13.135 26.207 26.611 0.80
-0.000 13.172 26.556 26.556 0.79
-4.602 13.209 26.097 26.500 0.79
-9.045 13.245 24.850 26.444 0.79
-13.194 13.281 22.853 26.389 0.79
-16.927 13.318 20.173 26.333 0.78
-20.130 13.353 16.891 26.278 0.78
-22.709 13.389 13.111 26.222 0.78
-24.589 13.425 8.950 26.167 0.78
-25.714 13.460 4.534 26.111 0.77
-26.056 13.495 -0.000 26.056 0.77
-25.605 13.530 -4.515 26.000 0.77
-24.380 13.565 -8.874 25.944 0.77
-22.420 13.599 -12.944 25.889 0.76
-19.789 13.633 -16.605 25.833 0.76
-16.570 13.668 -19.747 25.778 0.76
-12.861 13.701 -22.276 25.722 0.76
-8.779 13.735 -24.119 25.667 0.75
-4.447 13.769 -25.222 25.611 0.75
0.000 13.802 -25.556 25.556 0.75
4.428 13.835 -25.113 25.500 0.75
8.703 13.868 -23.910 25.444 0.74
12.694 13.901 -21.987 25.389 0.74
16.284 13.934 -19.406 25.333 0.74
19.364 13.966 -16.248 25.278 0.73
21.843 13.998 -12.611 25.222 0.73
23.649 14.030 -8.608 25.167 0.73
24.730 14.062 -4.360 25.111 0.73
25.056 14.094 0.000 25.056 0.72
24.620 14.125 4.341 25.000 0.72
23.440 14.156 8.532 24.944 0.72
21.554 14.187 12.444 24.889 0.71
19.023 14.218 15.963 24.833 0.71
15.927 14.249 18.981 24.778 0.71
12.361 14.279 21.410 24.722 0.71
8.436 14.309 23.179 24.667 0.70
4.274 14.339 24.237 24.611 0.70
-0.000 14.369 24.556 24.556 0.70
-4.254 14.399 24.128 24.500 0.69
-8.360 14.428 22.970 24.444 0.69
-12.194 14.458 21.121 24.389 0.69
-15.641 14.487 18.640 24.333 0.68
-18.598 14.516 15.605 24.278 0.68
-20.977 14.544 12.111 24.222 0.68
-22.709 14.573 8.265 24.167 0.68
-23.745 14.601 4.187 24.111 0.67
-24.056 14.629 -0.000 24.056 0.67
-23.635 14.657 -4.168 24.000 0.67
-22.500 14.685 -8.189 23.944 0.66
-20.688 14.712 -11.944 23.889 0.66
-18.257 14.740 -15.320 23.833 0.66
-15.284 14.767 -18.215 23.778 0.65
-11.861 14.794 -20.544 23.722 0.65
-8.094 14.821 -22.239 23.667 0.65
-4.100 14.847 -23.252 23.611 0.64
0.000 14.874 -23.556 23.556 0.64
4.081 14.900 -23.143 23.500 0.64
8.018 14.926 -22.031 23.444 0.64
11.694 14.952 -20.255 23.389 0.63
14.998 14.977 -17.874 23.333 0.63
17.832 15.003 -14.963 23.278 0.63
20.111 15.028 -11.611 23.222 0.62
21.770 15.053 -7.923 23.167 0.62
22.760 15.078 -4.013 23.111 0.62
23.056 15.102 0.000 23.056 0.61
22.651 15.127 3.994 23.000 0.61
21.561 15.151 7.847 22.944 0.61
19.822 15.175 11.444 22.889 0.60
17.491 15.199 14.677 22.833 0.60
14.641 15.223 17.449 22.778 0.60
11.361 15.246 19.678 22.722 0.59
7.752 15.269 21.300 22.667 0.59
3.926 15.292 22.268 22.611 0.58
-0.000 15.315 22.556 22.556 0.58
-3.907 15.338 22.158 22.500 0.58
-7.676 15.360 21.091 22.444 0.57
-11.194 15.383 19.389 22.389 0.57
-14.356 15.405 17.108 22.333 0.57
-17.066 15.427 14.320 22.278 0.56
-19.245 15.448 11.111 22.222 0.56
-20.830 15.470 7.581 22.167 0.56
-21.775 15.491 3.840 22.111 0.55
-22.056 15.512 -0.000 22.056 0.55
-21.666 15.533 -3.820 22.000 0.55
-20.621 15.554 -7.505 21.944 0.54
-18.956 15.575 -10.944 21.889 0.54
-16.725 15.595 -14.034 21.833 0.53
-13.998 15.615 -16.683 21.778 0.53
-10.861 15.635 -18.812 21.722 0.53
-7.410 15.655 -20.360 21.667 0.52
-3.753 15.675 -21.283 21.611 0.52
0.000 15.694 -21.556 21.556 0.52
3.733 15.713 -21.173 21.500 0.51
7.334 15.732 -20.151 21.444 0.51
10.694 15.751 -18.523 21.389 0.50
13.713 15.770 -16.342 21.333 0.50
16.300 15.788 -13.677 21.278 0.50
18.379 15.806 -10.611 21.222 0.49
19.890 15.824 -7.239 21.167 0.49
20.790 15.842 -3.666 21.111 0.48
21.056 15.860 0.000 21.056 0.48
20.681 15.877 3.647 21.000 0.48
19.681 15.895 7.163 20.944 0.47
18.090 15.912 10.444 20.889 0.47
15.959 15.928 13.391 20.833 0.46
13.356 15.945 15.917 20.778 0.46
10.361 15.962 17.946 20.722 0.46
7.068 15.978 19.420 20.667 0.45
3.579 15.994 20.298 20.611 0.45
-0.000 16.010 20.556 20.556 0.44
5 Likes
i don’t think that will work because there won’t be enough clearance between it and the next lower helix track
choose your grade
# rad tot-gr ht circ gr eff-gr N-scale
17 3.64 2.79 106.8 2.61 1.03
18 3.43 2.79 113.1 2.46 0.97
19 3.25 2.79 119.4 2.33 0.92
20 3.09 2.79 125.7 2.22 0.88
21 2.94 2.79 131.9 2.11 0.83
22 2.81 2.79 138.2 2.01 0.80
23 2.69 2.79 144.5 1.93 0.76
24 2.58 2.79 150.8 1.85 0.73
25 2.47 2.79 157.1 1.77 0.70
26 2.38 2.79 163.4 1.70 0.67
27 2.29 2.79 169.6 1.64 0.65
28 2.21 2.79 175.9 1.58 0.62
29 2.13 2.79 182.2 1.53 0.60
30 2.06 2.79 188.5 1.48 0.58
# rad tot-gr ht circ gr eff-gr HO-scale
24 3.80 3.71 150.8 2.46 1.33
25 3.65 3.71 157.1 2.37 1.28
26 3.50 3.71 163.4 2.27 1.23
27 3.38 3.71 169.6 2.19 1.19
28 3.25 3.71 175.9 2.11 1.14
29 3.14 3.71 182.2 2.04 1.10
30 3.04 3.71 188.5 1.97 1.07
31 2.94 3.71 194.8 1.91 1.03
32 2.85 3.71 201.1 1.85 1.00
33 2.76 3.71 207.3 1.79 0.97
34 2.68 3.71 213.6 1.74 0.94
35 2.60 3.71 219.9 1.69 0.91
36 2.53 3.71 226.2 1.64 0.89
37 2.46 3.71 232.5 1.60 0.86
38 2.40 3.71 238.8 1.56 0.84
39 2.34 3.71 245.0 1.52 0.82
40 2.28 3.71 251.3 1.48 0.80
41 2.22 3.71 257.6 1.44 0.78
42 2.17 3.71 263.9 1.41 0.76
43 2.12 3.71 270.2 1.38 0.74
44 2.07 3.71 276.5 1.34 0.73
45 2.03 3.71 282.7 1.31 0.71
46 1.98 3.71 289.0 1.29 0.70
2 Likes
I’m working in N scale, btw.
1 Like
still applies
1 Like
How much space do you have for a helix?
I was thinking 5-6’ square
Where will it be situated in your “train” room?
It would be in the empty garage, at on end of a wall wraparound (possibly two helix’, one at each end)
What is your preferred minimum radius?
I’m doing N scale. My preferred radius is the one that doesn’t cause derailments.
Though seriously, whatever I can get away with and still run long cars or even a Big Boy. Not so much worried about the aesthetics of it as long as they run.
What is your preferred grade?
2% max.
What elevation do you what to achieve?
Undefined as yet (still in the planning stages). I still can’t decide on distance between decks 1 and 2. I’m guessing between 18-24”?
Double or single tracked?
I really want double track, but doubt it’s feasible with decreasing radii including room for cliffs.
What scale?
N scale.
Your construction skills?
Moderate. I can almost always accomplish what I set out to do. Eventually.
1 Like
Understood, just wanted to make sure you’re calculating using the correct scale.
1 Like
the radius dictates the grade.
1 Like
The proportions will be the same; there may even be a bit less clearance in N because the physical distance down from the railheads to the bottom of the bridge structure may be greater in proportion.
It should be possible to adjust the helix turns so that the rise can be lessened at the last turn or two, with proper vertical-curve transitions, to clear the lowest effective interference with the bridge. Gregc’s program should facilitate the analysis.
1 Like
lessened? don’t you mean increased?
those last (top) turns are when the radius is the smallest and when it would require a significant grade to achieve the clearance above the previous turn, if not more that one turn
i think you’re better off with a conventional, constant radius helix, which i believe might be 25" for an effective grade of 2.47 (see above)
1 Like
What I mean is decreasing the track gradient given a fixed overall helix height, probably in more than one of the turns below the ‘bridge’ – it would then be slightly increased again for the last turn of the helix leading onto the bridge.
You’re correct in thinking there is a minimum vertical space available because the ‘compensation’ for curve and grade is determined by the tightening radius as you go up the ‘wedding cake’. What I’d propose is offsetting the last turn at the back of the top turn into an oval, even going out and back through a wall, to get the lower ruling grade on that section.
1 Like