Stuart Rae, traveling far from home in the American Pacific Northwest, through one of his always-interesting photographs, introduced me to the Heisler geared steam locomotive, with which I had not previously been familiar. Later, Stuart added some photos of the Shay geared locomotives. This all led to a series of discussions from me of the mechanisms of these machines.
By way of completing the circle, I will here briefly mention the third of the three most important types of geared steam locomotive, the Climax locomotive. (How appropriate!)
Here we see a lovely shot of a class B Climax locomotive of the later design of that class:
Photographer unknown: Class B two-truck Climax geared locomotive
From the Geared Steam Locomotive Works Web site
The later Type B Climax and the Type C Climax locomotive had two inclined steam cylinders. They drove a cross shaft which, through either skew or hypoid bevel gearing, drove a longitudinal drive shaft. This in turn, through other sets of skew or hypoid bevel gears, drove both axles of the two or three driven trucks (two in the class B, three in the class C).
Hypoid bevel gearing, the type found in many rear-wheel drive auto differentials and most truck differentials, and its simpler cousin, skew bevel gearing, allows the input shaft to be in a different plane than the output shaft. Thus, in this case, it allows the longitudinal drive shaft to be continuous across all the driven axle shafts (and in fact the engine shaft as well.)
Universal joints were provided in the drive shaft to allow for the articulation of the trucks.
On the class C version, a tender sat on the third driven truck.I believe that in that case the "box" behind the cab was the water tank, the tender being for fuel only.
The catalog of the Climax Manufacturing Company for the Climax geared locomotive (date yet unknown) includes this lovely passage:
The locomotive is equipped complete with all tools and fittings for its operation, including steam brake, steam syphon and suction hose for taking water, two injectors, sight feed lubricator, water gauge try cocks, steam gauge headlight, bell, whistle, pop valve, machinist hammer, pipe wrench, monkey wrench, chisel, punch, oil cans, clinker bar and poker. It is painted, varnished, lettered and numbered as desired.
Best regards,
Doug