Technique




	I first started building Chicago Tunnels in the mid-1980’s. I rent my shop from a cabinet maker, and as a consequence, I tended to use woodworking techniques in the early models. I have since moved on to model making foam which is distributed by Woodland Scenics. Regardless of the materials used, the general technique is the same. Straight Tunnels: Most of the Chicago Tunnel Company tunnels are straight single track tunnels. Most of the single track tunnels have a horseshoe shape.



				The typical tunnel is about 6 feet wide and 7’ 6” high. The effective tunnel height is somewhat lower because of the overhead electrical supply wire. The Company’s locomotives operated with 250 volts DC which came from this wire. So, in practice, the tunnel height is around 6’. At the bottom of the tunnel is the 2’ gauged track.



	Here, a tunnel segment under construction.

I took the drawings from “Forty Feet Below” and, after much fiddling on a photocopier, came up with a paper pattern the size of the tunnels that I wanted. I then transferred this drawing onto a hard piece of plastic, creating a pattern which I could use repeatedly.

But, the problem of viewing the underground railroad remained a problem. So, I created a second tunnel wall pattern, where one wall of the tunnel is opened to allow for viewing from the side.:


	By opening up one side of the tunnel, I created a way to view the inside of a tunnel segment as a cutaway. Also, tunnels could be “blind”, with only one open end; in this case, a small piece of mirrored plastric at the far end gives the appearance of a longer tunnel. Here, the second effort at creating a tunnel layout:




	A later effort, before track and tunnels were installed:


	This layout frame above has both end view tunnels and a long side view tunnel. The raised area in the middle of the photo represents one of several large rooms that were located around the system. These were dispatching areas, necessary since most of the tunnel walls made for a confined space:


	Those who worked for the Tunnel Company had to be small because of the limited confines of the system. Later tunnel construction appears to have been modified to correct this problem.


	Here, some foam tunnel segments and an end view:








	In the above end view, the track and tunnel floor have not yet been installed. Once in place, the foam tunnel segments will match up to the opening of the module side.

The above drawing shows two single track tunnels connecting to a larger tunnel. Typically, this would occur at some track switches, such as when a track diverged and then went down under the Chicago River.

Curves:

The issue of curved tunnels was the next to be addressed. There were a few purely curved tunnels, with the balance of the curved tunnels being part of track switches and junctions.

The curved segments of the tunnels are sections of straight tunnels that have been cut into pie shaped wedges:

Once the individual tunnel segments are cut into wedges, they are joined to form a curve. It seems logical that the wedges should be cut to an angle of about 22.5°, requiring four to make up one 90° curve. In the smaller scales, I chose to make a second tunnel template for the curved tunnel segments, making the tunnel width larger than for straight tracks, to allow for overhang of the locomotives and curves while operating on the curved sections.




	Curved tunnel pattern (above); it’s so much easier now with computers.

Turnouts:

It is the track switch (or turnout) that makes railroading interesting and useful. Here, a right hand turnout, probably leading into a building. For modeling purposes, the turnout segment of tunnel is a combination of straight and curved segments.


	Here, an earlier tunnel made with plywood segments:







	Crossings:



		Crossings are just two straight tunnel segments cut at an angle to each other. Again, straight tunnel segments are the basis, with each straight tunnel cut to allow alignment with other segment segments:

Further Details:

The tunnels were equipped with electric lighting at certain locations; apparently these lights used the overhead trolley wire for the source of electricity, with a second wire connected to the rails for ground-return.


	Pumps were located throughout the railroad to draw out any water that might have entered the tunnel system. They were built into small alcoves adjacent to the tracks.

The system primarily used telephones for train dispatching and operations. There were some signals located in certain locations, such as the one at the right. Many of the line’s crossings were protected by green reflectors located in the tunnel walls; the headlight of an approaching train would illuminate the reflector in the direction of the second train. Other signals protected train movements on the tunnel segments that went under the Chicago River.


	Other signs reminded Tunnel Company employees to operate their trains in a safe manner.


	Below: A Chicago Tunnel Company locomotive and cars in a department store basement. Note the overhead trolley wire with protecting guard.




	Page last updated 10/08/2006


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