Wordless Wednesday

DRGW3155 Leads the Ski Train west out of Tunnel 1 in March 1997 - Photo by James Belmont.

Cameron Turner

Wordless Wednesday

A trio of Citirail engines is leading an Eastbound over the Moffat. Not only are these engines unusual, but the 2 DPUs exiting Tunnel 1 (upper right) are a CSX and BNSF unit. Photo by John Shine. February 17, 2017.

Cameron Turner

The Turning Point – Part 6: Coal Creek Canyon Revised

The major purpose of the climb from Rocky Siding, through the Big 10 curves, continuing through Clay siding and into Coal Creek Canyon is to transition from the first deck to the second deck of the layout. The question becomes as to whether there is sufficient elevation gain to make this feasible. Concern about the tight vertical clearances and the resulting physical viewability/operability of that section of the layout is at question. Improving the configuration is the necessary goal of this revision to the layout. The original Coal Creek Canyon section of the layout looked like this.

Original Coal Creek Canyon Track Plan.

In the original track plan, there was about 6" between the siding level and the bottom of the upper deck. By the time we get into the turnback loop in Coal Creek Canyon, the bottom of the upper deck is at about 15.5", and the Rocky Flats Branch would be at about 10", providing a gap of 5.5". This is workable, but tight. The space to the mainline is a little better, resulting in a gap of about 11", which is much better.

Revised Track Plan for Coal Creek Canyon.

The revised plan does a little better, but not much. The separation between Rocky Siding and the lower deck is still about 6". but rapidly increases. The Rocky Flats Branch would now be 6" below the bottom of the upper deck with Coal Creek Canyon above. However, the main line is now nearly 13" below the bottom of the benchwork by the time the mainline reaches Tunnel 1. The big difference in the plans is that the grade climbs more from C&S Junction, all the way to Rocky. The grades through the LDEs max out at about 2.2%, and the mainline tends to lie towards the front of the benchwork in the tightest areas. By the Coal Creek Canyon turnback curve, the main line has more than 8" of clearance to the bottom of the upper deck.

I would still like to do better, but as it was before, this is acceptable. With the other improvements to the flow of the layout, the new configuration is definitively better than the original configuration. Other than a slight elevation change, the layout continues through Tunnel 1 as previously designed. The next change comes with Plain siding, which has now been relocated to head towards the bottom of the room. So, we will continue examining the line as we head towards Plain.

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Cameron Turner

Wordless Wednesday

DRGW 3098 leads a train west to Tunnel 1 in December 1990. Photo by JohnShine.

Cameron Turner

Wordless Wednesday

December 1993, DRGW 5396 leading a train west towards Tunnel 1. Photo by John Shine.

Cameron Turner

Wordless Wednesday

UP7085 leads a train west through Coal Creek Canyon towards Tunnel #1. Photo by John Crisanti.

Cameron Turner

Into the Tunnels: Tunnel 1

The Moffat is known for the tunnel district. Between Denver and the Moffat Tunnel, a distance of 50 miles by rail, there are 28 tunnels. These are clustered in a span of 17.3 miles, starting with Tunnel 1 (MP 23.2) and ending with Tunnel 30 (MP 40.5). (Note that Tunnel 9 and Tunnel 28 no longer exist.) This series of tunnels and the regions through which they take the Rio Grande is one of the major reasons for my interest in the line.

Caboose 01460 rolls by while a gaggle of SD45s pulls the train into Tunnel 1 on the far side of Coal Creek Canyon. Photograph by Chuck Conway.

The tunnels at the ends of the district are orphans. They are different from the rest of their siblings. Tunnel 1 allows the main line to withdraw from its first encounter with the front range and retreat to climb along the Flatirons that make up this barrier. Indeed, there are 2 miles between Tunnel 1 and Tunnel 2. Furthermore, one could also argue that it is a full 3.5 miles before the railroad once again tries to thrust its way into the mountains like it does in Coal Creek Canyon. Tunnel 1 is a prologue to what is coming, and Tunnel 30 is a reminder of what the railroad has gone through to get there.

Tunnel 1 is 299 feet long, or 22 inches in N-scale. Indeed, it could be modeled in full scale at that size. However, as I worked on developing track plans to model the tunnel district, I found that while some tunnels could be modeled at scale (Tunnel 29 is only 78 feet long), others would be challenging (Tunnel 17 is 1730 feet long). Early on, I adopted a goal to model the tunnels using a formula so that the shortest tunnels would be full scale, while the longest tunnels would be shortened to something more reasonable. Using this formula, I established the following goals for modeling each tunnel, as shown below.

Table of the actual versus target design lengths for the layout tunnels.

I am pleased to note that the median (0.84) and average (0.83) compression ratios are very similar. Furthermore, the target tunnel lengths all maintain the rank ordering of tunnels in terms of their length. Several tunnels (4, 7, 22 and 29) have little or no compression, while the longest tunnels (10, 17, and 23) all are much more palatable in terms of length. For instance, tunnel 10 would be 117.9” long at full scale, but its target design length is now 75.46”. At a little more than 6 feet long, that is still a long tunnel, but many trains will still be long enough to be visible while in the tunnel. If modeled to full scale, that would not be the case. Yet, a six foot tunnel still garners the feel of an immense tunnel.

Tunnel 1 is the first tunnel to transverse a sand and pebble conglomerate that forms the backbone of the flatirons. The flatirons are up thrust sedimentary slabs that form a picturesque backdrop to Boulder, Colorado. The railroad east and west portals are both concrete with sprayed concrete and gunite added in between to maintain the stability of the tunnel. The exterior of the rocky outcrop through which the tunnel passes is dotted with ponderosa pine trees. Based on the target length for Tunnel 1, the model should be approximately 20 inches in length, about 89% of the full-scale tunnel length but still substantial. 

Plan for the Tunnel 1 area.

Just to the railroad west of Tunnel 1 is a grassy area where the mainline curves around as it prepares to swing around to the north and enter a flat spot known as Plainview. I positioned Tunnel 1 to allow for this curve while achieving the target design length of 20" which works out to be about 267 scale feet. This is very close to the target length. This last stretch of main line also brings to an end the steepest climb on the railroad. Just as on the real thing, the main line grade moderates at Plainview as the line enters Plain Siding, but more on the design of Plainview in another post.

Cameron Turner