Spiral Tunnels.

Anyone who has ever taken the Kicking Horse Pass through the Rockies (if you've driven the Trans-Canada, you've been through the Pass) will have seen the signs for the Spiral Tunnels. Most drivers pass right by, but many stop if only for the excuse to stretch their legs. Yet the Spiral Tunnels aare a fascinating part of Canadian history, and reveal the power of understanding simple machines.

Just west of the Continental Divide lies what was called "Big Hill" - a stretch where the railway needed to descend about 330m over a 16km straighway between the mountains. This may not seem like a very big deal, but it was the steepest part of the entire cross-Canada route. (According to the information signs at the lookout, the engine of a 5-car train would be a full 5m below the rear!) Trains travelling up the pass required twice as many engines to make it to the top. And even though safety switches were installed (the train equivalent of the truckers runaway lane) disasters were very common. The first train to ever use the completed line derailed, plunging into the river.

In order to save time, money and lives, an ingenius solution was devised; a new path would be created for the rail line by blasting into the mountains, no easy task in 1906. The track could loop around, extending the distance the train took to go from the summit to the valley floor (a spiral is the railway equivalent of a switchback). Two partial loops were excavated under Cathedral Mountain (called "Number One" and visible from the road up to Takakkaw Falls) and Mount Ogden ("Number Two" - the tunnel visible from the highway).

The highway running down the middle is the site of the original line.

The Spiral Tunnels are an example of a simple machine - in this case, the ramp or inclined plane. Using my awesome MS Paint skills, I will attempt to explain why an inclined plane creates a mechanical advantage.

In physics, work is not the same thing as effort, even though we tend to use the words interchangeably in every day life. (force is the closest approximation to effort) Work is the product of the amount of force needed to move an object over a certain distance and the distance moved. Whether you lift an object straight up, or slide it up a ramp, you do the same amount of work, since the height difference is the same in both cases.

The longer distance provided by the ramp means that it takes less effort to do the same amount of work (arrive at the same result). The engineers who designed the Spiral Tunnels needed to increase the distance travelled by the train to achieve this effect - they used a corkscrew pattern since they couldn't do it in a straight manner. (A screw is another simple machine... it is just a circular inclined plane).

By stretching out the distance, the trains experience a 22m elevation change for every kilometer of distance (a very safe rate compared to the extreme 45m of elevation per kilometer of Big Hill). In the case of the Tunnels, a sufficiently long train can actually pass over itself while it goes through the loop.



The engines are exiting the tunnel at the bottom, while the rear
of the train continues to enter up top.

Typically, when one stops at the Spiral Tunnels lookout, all one can see is some holes in the trees on the other side of the valley. When we stopped on the way back from Golden, we saw not one, not two, but three trains using the tunnels! It was very exciting (trust me)!