V-Twin Power. Here's a close-up of Meadow River Heisler #6 as she negotiates the sweeping horseshoe curve near MP 92.1 on the old C&O Greenbrier Division, between Durbin and Cass, WV. She's a 90-ton, 3-Truck model, built in 1929 by the Heisler Locomotive Works in Erie, PA. One of approximately 625 locomotives of this design, built between 1891 and 1941, she's also one of perhaps just 8-10 that can still operate.
This view provides a great study of the key features that made the Heisler design relatively popular with logging operations all around the US. The boiler is conventional and is centered on a simple frame consisting of two steel I-beams, running the length of the locomotive. She has two cylinders, arranged in a V-Twin configuration, on either side of the boiler, just forward of the steam dome. Her dry (steam) pipes are clearly visible, running from the steam dome to the cylinder heads. A piston inside each cylinder is connected to a drive shaft underneath the centerline of the locomotive, and running along its entire length. The drive shaft is geared to one wheel set in each of the 3 trucks, and the other wheel set in each truck is powered by a short connecting rod. Although the machinery on this design is not as accessible or as easy to maintain as on the more popular Shay design, it is better protected and more efficient. Heislers also tended to have higher speeds on level track than Shays, giving them increased utility for their operators. Fuel for the Heisler design, which can be coal, oil or wood, is carried in a bunker behind the cab. On 2-Truck models, this bunker also carries water. On the 3-Truck models, such as #6 pictured here, the water is carried in a separate tank behind the fuel bunker, which rides on the 3rd powered truck. The tank articulates, allowing the locomotive to negotiate the tight curves which often existed on remote logging lines.