The Heisler was one of the three best-known American geared steam-locomotive types used on logging, mining, quarry, and industrial railroads.
Engineer Charles L. Heisler developed the design after working in mechanical engineering rather than beginning as a railroad operator.
The Heisler used two steam cylinders arranged in a V shape beneath or near the boiler.
Those cylinders turned a longitudinal crankshaft located along the locomotive centerline.
Bevel gearing transmitted power to the inner axle of each truck, while external side rods connected the inner and outer wheelsets.
That arrangement differed from the Shay, whose exposed shafting and gears ran along one side of the locomotive.
It also differed from the Climax, which used its own transverse-crank and centered driveshaft geometry.
Heisler locomotives gained a reputation for strong power relative to weight and protected gearing suited to industrial service.
Production never matched the total number of Shays, and far fewer Heislers survive today.
For TransitSatellite, visual identification should rely on the V-cylinder arrangement, centered shaft, and characteristic truck drive. Generic “logging locomotive” imagery would erase the mechanical differences that make the type historically important.