Hetch Hetchy Railroad, Shay Locomotive
Hetch Hetchy Railroad no. 6 is a standard gauge three truck Shay locomotive built for the Hetch Hetchy Railroad by Lima Locomotive Works in 1921. This static display is at El Portal in Yosemite National Park.
Shay locomotives had regular fire-tube boilers offset to the left to provide space for, and counterbalance the weight of, a two or three cylinder "motor," mounted vertically on the right with longitudinal drive shafts extending fore and aft from the crankshaft at wheel axle height. These shafts had universal joints and square sliding prismatic joints to accommodate the swiveling trucks. Each axle was driven by a separate bevel gear, with no side rods.
The strength of these engines is that all wheels, including, in some engines, those under the tender, are driven so that all the weight develops tractive effort. A high ratio of piston strokes to wheel revolutions allowed them to run at partial slip, where a conventional rod engine would spin its drive wheels and burn rails, losing all traction.
Shay locomotives were often known as sidewinders or stemwinders for their side-mounted drive shafts.
Hetch Hetchy Railroad, Shay Locomotive
Hetch Hetchy Railroad no. 6 is a standard gauge three truck Shay locomotive built for the Hetch Hetchy Railroad by Lima Locomotive Works in 1921. This static display is at El Portal in Yosemite National Park.
Shay locomotives had regular fire-tube boilers offset to the left to provide space for, and counterbalance the weight of, a two or three cylinder "motor," mounted vertically on the right with longitudinal drive shafts extending fore and aft from the crankshaft at wheel axle height. These shafts had universal joints and square sliding prismatic joints to accommodate the swiveling trucks. Each axle was driven by a separate bevel gear, with no side rods.
The strength of these engines is that all wheels, including, in some engines, those under the tender, are driven so that all the weight develops tractive effort. A high ratio of piston strokes to wheel revolutions allowed them to run at partial slip, where a conventional rod engine would spin its drive wheels and burn rails, losing all traction.
Shay locomotives were often known as sidewinders or stemwinders for their side-mounted drive shafts.