Helices

A helix is a device for moving a train between levels of a multi-level layout.  The train enters at one level, changes altitude gradually as it proceeds up or down a series of loops, and emerges at another level.

None of Linn Westcott's 101 Track Plans has a helix, but many modern track plans and club layouts do.  For an elegant example, see John Armstrong's Southern Pacific Lines Shasta Division, featured in Model Railroader, April 2005.

It takes some effort to draw a helix in TrackLayer, but it's worth it.  When a train enters the helix and climbs it in a series of slow loops, it comes to life and makes sense out of that bundle of looped wires on the track plan.

Drawing a Helix

Draw a helix by starting at the bottom, with the lower approach track and the lowest loop.  Proceed upwards, adding and connecting new loops right on top of the lower ones. 

To do this requires a special device, because normally if you put circles on top of each other, then when you try to add tangents, they won't snap to the right places.  The secret is to mark track as "untouchable."  Once a loop is in place, you can mark it so it will not be affected when you add the next loop.  As you draw each loop, you leave a little "handle" sticking out so you can connect it to the next loop.

In this example, we will construct a circular two-loop helix, with the lower approach from the northwest and the upper exit to the northeast.
 

1.  Draw a circle (Circle tool  ).
2.  Draw the lower approach track (Track tool  ).
3.  Draw a short straight segment at the top of the circle.  This completes a large curve, and serves as a handle to connect to the next loop.
4.  Mark the curve "untouchable."  Right-click on the curve so it highlights as shown, and choose Untouchable. This causes the curve to become unresponsive: it will not highlight, you cannot connect track to it, and most important, tangents you create on the next loop will not snap to it. Before you mark the curve untouchable, you might want to mark it Hidden.  See notes below.
5.  Draw a circle for the second loop (Circle tool  ).  Start at the center of the first circle, and drag until the circle is superimposed on the first one. This illustration shows the drag in process, not quite finished.
6.  This shows the second circle in place.
7.  Draw a short segment to connect the second loop to the first.  Begin by highlighting the circle as shown...
8.  ...and connect to the handle drawn in step 3. Don't worry about the kink in the track, you'll fix it shortly.  You now have the first leg of the second curve.
9.  Draw the other leg of the curve.  Begin on the circle at about the same place as in step 3...
10.  ...and drag to form a new handle, near (but not right on top of) the first.
11.  You now have one complete but kinked loop, and another almost-complete loop with handle.
12.  Fix the kink.  Use the Edit tool . Point to the junction so it highlights as shown, press and drag to move it into position.
13.  Release when the junction is on the circle.
14.  And so on.  Mark the second curve untouchable.
15.  Draw the next circle.
16.  Draw the segment to connect to the previous handle.
17.  Release when connected.
18.  Draw the upper approach track, tangent to the topmost circle.
19.  Fix the kink in the previous layer. Be careful when moving this junction that it does not land on top of the earlier one, i.e., do not release where you see a green highlight square.
20.  And you're done.
21.  Test the helix.  Add a loco on one of the approach tracks, give it some speed, and watch the show.  It should make two complete loops around before exiting.

Notes

• For best appearance, the train should hide as it goes around the lower loops, and appear when it gets to the top one.  You can arrange this by marking track as hidden, starting with the lowest loop and continuing until the top loop.  Mark each track as you add it, and be sure to apply the hidden mark before you mark a track untouchable, otherwise you won't be able to.

In the above example, tracks added in each of the following steps should be marked hidden before going on to the next step: 3, 4, 8, 10.

• If you mark a track untouchable by mistake, you can no longer select it so you can't unmark it.  Instead, choose All Retouchable from the track context menu.  All untouchable tracks become unmarked and touchable.