"Zig-zag" track systems

 

 

The two switchbacks on the Cass Scenic Railroad operate as mechanical "zig-zag" track systems designed to gain rapid elevation up the steep eastern face of Cheat Mountain without exceeding the climbing limits of geared steam locomotives.

Because the mountainside along Leatherbark Run is too sheer for standard sweeping curves or horseshoe loops, the railroad uses reversing tail tracks cut into the slopes.

The Mechanical Climbing Sequence

1.Approaching the First Switchback (Pulling Forward):

Departing the Cass depot, the Shay locomotive begins the climb facing forward up Leatherbark Run, pulling the passenger cars (or historically, empty log cars) up grades ranging from 4% to 7%.

2.Entering the Lower Tail Track (Switchback #1):The entire train must clear the switch points before stopping.

The train runs past a set of track switch points directly onto a dead-end spur called a tail track. The engineer pulls the full length of the train past the switch until the rear car clears the points, then brings the train to a complete stop.

3.Throwing the Switch & Reversing Direction:

A brakeman or switch tender aligns the ground-throw switch from the lower approach track to the upper climbing track. The engineer shifts the locomotive's valve gear into reverse.

Instead of pulling, the Shay now pushes the train up the next section of mountain. This upper leg climbs at a steeper pitch—frequently hitting 9% to 11% grade—zigzagging across the face of the mountain in the opposite direction.

4.Entering Switchback #2 and Final Ascent:Reversing once more restores the locomotive's pulling position.

At the second switchback, the train pushes past the second set of switch points into another dead-end tail track and stops.

The switch is thrown again to line up with the upper mainline toward Whittaker Station and Bald Knob. The engineer shifts back into forward gear, and the locomotive resumes pulling the train forward up the remaining mountain grade.

Why Geared Locomotives Make Switchbacks Work

• Equal Power in Forward and Reverse: Unlike traditional mainline rod locomotives (which are mechanically counterbalanced and designed primarily to pull forward at high speeds), Shay geared locomotives utilize an offset 3-cylinder vertical steam engine connected to a continuous driveshaft and geared wheel trucks. They deliver 100% of their tractive power and gear-reduction torque equally well in forward or reverse.
  
  
• All-Wheel Drive Traction: Every single wheel under the engine and tender is driven by bevel gears, turning every pound of engine weight into adhesion. This prevents wheelslip when starting a heavy train from a dead stop on an 11% incline inside the switchback.
  
  
• Safety Positioning: Operating the train in a push-pull cycle ensures the heavy locomotive remains positioned on the downhill side for critical portions of the steepest mountain shelf, providing maximum braking resistance and preventing runaway cars if a coupler should fail.