Cog Railway (builder & owner) - Mt. Washington, New Hampshire
company currently has 7 steam powered "cog" geared locomotives in operation. These very unique steam locomotives in
conjunction with special track-work were very specifically designed to transport
passengers to the summit of Mt. Washington on a railroad with grades as steep as 37.4%.
Quoting Paul Forbes of The Mount Washington Cog Railway site,
the locomotives work as follows:
locomotives are coal fired and operate at approximately 150 pounds per square inch. The
steam is directed to two pairs of driving cylinders that are connected to the drive axle
which turns a pinion gear. The brake drum is also located on this shaft. The pinion gear
turns an axle shaft on which is keyed the spur gear, cog gear, and ratchet gear. The ratio
of the pinion gear to the spur gear is 5 1/3 to 1. The pawl is engaged on the trip up and
prevents any backward movement should the locomotive suffer a failure of some part. The
clinking metallic sound that is heard on the trip up is the pawl bouncing on the ratchet
gear, a reassuring sound! The coaches also have a pawl and ratchet. There are two axles on
the coaches onto which a cog gear, ratchet gear and a brake drum are keyed. The wheels on
the locomotives provide support and guide it on the rails. The wheels simply turn on an
axle and are not driven. All driving is accomplished by the cog gear meshing with the
rack. The locomotive proceeds up the mountain tooth by tooth."
In the past, the railway operated several other steam driven cog geared
locomotives. They are pictured on Paul's site mentioned below and above. The
site's extensive detail of this unique railway and locomotives is beyond the scope of what
can practically be accomplished here-in. Please visit his site for more
information on these.
Forbes of The Mount Washington Cog
Railway site - photos from same.