The Behemoth Helix

On the day after Thanksgiving, 2005, I finally started construction of the giant four-track, six-tier helix that connects the two levels of the railroad. While still in progress as of this writing (December 2005), progress is good. My good friend Walt has helped tremendously - this is a job that would be almost impossible for just one person, I think. My wife Denise also lent a helping hand as construction has progressed.

For other topics, click on the text links below.

The Roadbed Factory

Super-elevating the curves

Finding the layout's "Zero," or starting, elevation

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05_11_25_1000_Nuts_500_Washers.JPG (283601 bytes)Here you see most of the hardware required to build this baby - over 1000 (that's one thousand) 5/16th nuts and nearly three hundred each of flat washers and fender (extra-large outside diameter) washers. They're laying on my helix template, which will be the bottom tier in the finished helix. Not shown are the 36 5/16" threaded rods that will suspend the helix from the ceiling. Each tier of the helix will require two sheets of 1/2" plywood - the largest radius is 42 inches. With six tiers, that's twelve sheet of plywood. Add to that two 3/4" sheets of plywood for the main framework and you've got most of what it took to build this helix.

05_11_25_Walt_Marking_the_Suspension_Frame.JPG (282035 bytes)Here Walt is marking out the curves for one end of the elongated helix on the main suspension framework. The basic approach for construction is to suspend the subroadbed from a framework attached to the basement ceiling. The threaded rods I mentioned above are the suspension members. Different levels for the helix will be adjusted to proper height using nuts threaded onto the rods. The rods are suspended from a main framework that looks just like one of the tiers of the helix, except it's made from 3/4 inch plywood rather than the tiers' 1/2 inch plywood.

This will get clearer as you look at the photos below.

05_11_25_Drilling_the_Stack_1.JPG (285478 bytes)Here Walt is drilling the locations for the suspension roads in all tiers of the helix at once. All rod locations were marked on the template, and then all the pieces are stacked, aligned and drilled. This way we know the rod holes will all line up in the assembled helix. The lighter-colored thicker piece of plywood just below the template is the main framework.

I didn't put a picture of us cutting the helix sections from sheets of plywood - that would have been pretty boring!

05_11_27_Supports_4.JPG (276314 bytes)After we drilled all the rod holes, we assembled the main suspension frame and installed it near the ceiling. We temporarily supported it while adjusting it's final location to the track plan, then began constructing the simple mounts you see here.

The mounts are constructed of scraps of 1/2" plywood, with a few having 2X3 legs. The legs are just screwed to joists, and a horizontal bar is attached to those under the framework, neatly supporting the frame while allowing for a little bit of adjustment in the helix position.

05_11_27_Supports_5.JPG (278502 bytes)Another view of some supports. Their construction is quick and dirty, but sturdy and flexible enough to allow for varying reaches across joists - whatever span is required.

When the rest of the helix framework is assembled and I'm certain everything aligns properly, I'll trim the excess off all the support legs and joist ends.

05_11_28_Main_Suspension_Framework_Completedd.JPG (274579 bytes)Here is the main suspension framework completely installed and ready to support the helix itself.
05_11_30_Rod_Installation_in_Semicircle_Complete___Installing_tiers.JPG (287139 bytes)The suspension rods, all 16 of them, are installed on the nearest semi-circle, and the top level of the helix is installed. The second level is mounted onto the bottom of the rods but not yet raised. All tiers except the lowest will be run clear up to the top of the suspension rods to allow tracklaying on the lowest level. As tracklaying progresses, additional sections of the helix will be lowered into position and tied to completed sections to allow tracklaying to proceed around the helix from bottom to top. That means all four tracks will be laid at the same time on each level, even though some of those track won't be used for several years. They will be tested thoroughly, however!
Assembly details.JPG (75572 bytes)This photo shows the details of the suspension assemblies. Briefly: The rods protrude upwards through the 3/4" main suspension framework, where a nut carries the weight of the helix below. Between the nut and the plywood is two fender washers, to help distribute the rod load into the plywood. A second nut is added, acting as a jamb nut against the first to prevent the nut from slowly turning on the rod (which would allow the entire helix to go out of alignment). A standard washer, then two more nuts, are used to "clamp up" the rod in the plywood framework, effectively locking the rod into the plywood. This is repeated for each level of the helix, except that the fender washer is on the bottom and the standard washer is on top, and only one fender washer is used instead of two. The fender washers go on the bottom on the track tiers because the plywood load is going into the rod below the plywood, rather than into the top of the plywood as happens on the main suspension framework.
05_12_12_Two_tiers_at_Top.JPG (282939 bytes)Two tiers are now run up to the top of the rods in this view from near Laurel. This is the point construction is at as of December 20th, 2005. As the helix progresses, more detail will be added here.
All the helix tiers have been installed in this shot from mid-January. You can see three stacked at the top of the helix, with the lower two in place and cork roadbed being installed on the top-most positioned tier.
The two tiers that in place. The roadbed on the upper tier is pinned in place for the glue to dry. The two tracks that curve to the right towards the back are the Wyoming Mainline tracks, while the one that goes straight off to the left is the Frannie Cutoff that will connect to the NP Mainline at Laurel. Since the second deck is some years from construction, I'm installing a temporary connection that will tie the Frannie Cutoff into the track that leads to Glenrock on the lower level. That way the NP Mainline will connect with the remainder of the layout, making it available for early operations (which I suspect will commence after most of the Wyoming Mainline on the lower level is laid). It will make for a strange station sequence, but not too bad because the NP Mainline will simply represent the CB&Q east of Glenrock. It will assume its primary role as the NP Mainline (while still serving as the CB&Q east of Orin) in the future.
There is now one completed tier of tracks on the helix, save for final wiring. There are only three track here because the Cody Branch, the fourth helix track, leaves the helix in the back on the next tier up. For this one tier I've used about 30 pieces of flextrack.
We're looking at the test train from the back corner of the layout, standing right next to where Cody will be located. The train is to test both the track and the pulling power of the loco. I'm pleased to report that the trackwork is good so far, and the loco pulls a respectable train up the grade. Photo is early February 2006.
Just in case the trackwork is slightly less than perfect in one or two spots, I'm adding rerailers in each track on each straight section in the helix. Better safe than sorry. The loco is a new Spectrum.
So how did we run all those nuts up and down those rods without going crazy? With the help of a rubber sanding disk holder and an electric drill! Without the sand paper on the disk, the rubber was able to grip the edge of the nut enough to turn the nut, running it quickly up or down the rod as required. Otherwise I'd still be threading those nuts into place!
On each tier, the roadbed for all tracks is laid, then sanded smooth. After that track is laid and I moved on to the next tier.
At the end of the second tier climbing upwards, the Cody end of the Cody branch enter the helix on it's climb to Powell on the top deck.
Track for the lead into the helix from Cody has been laid. Even though the threaded rods are about 16 inches apart on the outside edge of the helix, I still had to be very careful positioning the Cody lead-in to avoid having trains side-swiping the rod to the right of the lead-in in the future.
Power is delivered to the helix tracks on each side of ech tier via sub-feeders tied in to the track feeders themselves via terminal strips. The strips are each eight connector to allow for two feeders to each of the four tracks. Feeders are telephone wire (22-gauge, I think) soldered to the track.
Sub-feeders, which are 18-gauge thermostat wire, get their power in turn from the main bus, a 12-gauge stranded wire. All sub-feeders are fed down underneath the lowest tier of the helix, where they tie to the buses via two six-position terminal strips (I used two six-position strips instead of one twelve-position because the twelve-position strips are about four times more expensive than the six-position ones)
Looking up at the bottom of the helix we see a scene like this. The fender washers carry the load of each tier through the nuts and into the threaded rod, which then carries it up to the 3/4-inch thick suspension frame at the ceiling. If any area needs the grade tweaked a bit to even it out, I can simply loosen the nuts and screw them up or down a bit.
The completed helix, seen from the door to the train room on 22 November 2006. Testing is complete, and trains run smoothly up the entire length of the helix.


Construction Methods