Spare Power. Simmering on the passing track just below Marshfield Station, we find the day's spare power. Built in 1874 by the Manchester Locomotive Works, MWRC #6 "Kancamagus" is the oldest active steam engine on the property. Originally constructed with a vertical boiler, like many of The Cog's early engines, she was rebuilt to the present configuration in 1878. Her status as the "spare" on this particular day back in 2008 enabled me to obtain a rare photo of the engine without any accompanying coach.
As you can see, the nose on this engine is rather naked. She has no number plate, because no one would ever see it in normal operations. Also missing is any sort of front coupler. The little bumper seen on the pilot beam merely butts against a pad on the back of the coach and there is never any hard physical connection between the two.
Although these cog locomotives are often referred to as an 0-2-2-0, there is actually no Whyte System nomenclature for this type of engine. Quite simply, they have no drivers. The two pairs of cylinders you see drive independent shafts on the front and back of the chassis, both of which are geared to separate cog wheels that mesh with the center cog rail. The gearing on the forward shaft can be seen hanging immediately behind the right front wheel. The four wheels on the locomotive are free-floating and merely support the chassis. No power is applied to them.
You will note the inverted-Y-shaped dry-pipe, which carries the high-pressure steam from the steam dome to the cylinders. Along the base of the boiler, the exhaust pipe runs both forward to the smoke-box and aft, to the side-stack exhaust. This engine has no valve gear, so the Engineer must adjust the amount of back pressure that exhaust steam exerts on the piston, using side-stack valves. Side-stack steam is exhausted through the mast in front of the cab.
The little tender behind the engine holds a ton of soft coal and 700 gallons of water. With these supplies, she can make the ascent to the summit of Mt. Washington with just one water stop.
At one time, there were as many as eight of these engines at the Cog Railway. In 2012, there are perhaps four left that could still be fired, although there are seldom more than one or two hot. Fortunately, little #6 is one of the survivors. Although #9 is the primary duty engine these days, the 6 still gets to make the run up the rock pile once in a while, when # 9 is in for maintenance.