Where rod engines fear to tread. Cass Shay #5 crests the hill at the Lower Switchback and will shortly take on the 6.3% uphill grade that you see on the right....in reverse....as she works her way toward Whittaker Station and beyond. Logging railroads commonly had to use switchbacks such as this one to find manageable grades up to the elevations where timber was being harvested. These switchbacks typically had fairly long tails, allowing lengthy, multi-car trains to clear the switch, and then reverse direction uphill. Needless to say, #5's Fireman has the injectors going full-tilt, making sure the crown sheet will be covered when all of the water in the boiler shifts forward.
At Cass, there are two of these switchbacks within a mile of each other, so when the trains reach Whittaker Station at MP 3.8, they were running forward once again. The grades you see on this mountain are far beyond anything that a normal rod engine could ever handle with a train. Four percent is commonly considered about the maximum for conventional engines. Geared engines such as this Shay however could handle more than twice that. With her weight evenly distributed across 3 trucks, and low-RPM power applied to each and every axle, the Shay is not very fast, but she is sure-footed. Indeed, the maximum grade on Cass Hill is a very steep 9% on the approach to Bald Knob.