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So, what is a Cog Railway;
and how does it work?

Many people have wondered what is a Cog Railway and how does it differ from a standard railroad. I will hopefully describe with text and pictures, the basics of the Cog system.

I think that most people are familiar with the operation of a "standard" railroad. That is to say there are two parallel rails spaced evenly onto which the locomotive and cars ride. The locomotive provides movement by getting traction on the steel rails. Movement relies entirely on the ability of the particular locomotive to move the trailing cars over the rails without spinning the wheels or losing traction. Standard locomotives are limited to the weight of the train over a specific piece of track. In other words, the heavier the train, the less of grade the locomotive can negotiate without losing traction. Averages grades, or steepness of the tracks, for standard trains on conventional tracks is just a few percent. It doesn't take much of a hill to stall a heavy train. Braking or stopping the train must also be considered. Stopping the train relies on the ability of the steel wheels to maintain traction on the rails. Steel on steel will slide!

It is quite obvious that a conventional type of railroad could never get a train and a car load of people up Mount Washington. The average grade is 25% with the steepest being 37.4%. That is to say the track at the steepest point rises at the rate of 37 feet for every 100 feet it goes forward. Depending on which car you are in, the people in the front are 14 feet higher than the people in the back! It takes a special type of railway indeed to accomplish the task of bringing people up to the summit of Mount Washington.

The Mount Washington Cog Railway is the first and oldest cog or rack railway in the world. Started in 1866, it was completed to the summit in 1869. The 2.8 miles of track are built entirely on wooden trestle. On top of this wooden trestle two light steel rails are laid in a method similar to standard railroad construction. The rails are raised to allow clearance for the spur gears which drive the locomotive. Located in the center of the steel rails is a cog rack. These three components make up the track work. This track is designed specifically for the unique cog engines of Mount Washington. The locomotives and cars are equipped with cogs that engage into the rack. The cog is driven by the steam pistons of the locomotive through a system of gears. This is a simplified explanation of the system.

A Cog engine is a unique piece of equipment. With its tilted boiler and towed tender, it is an operating piece of the past. The outward appearance of the locomotives and passenger coaches has changed little over the years. Most of the improvements are mechanical in nature and not readily visible. The majority of the changes have resulted in increased safety for all involved. On a mountain railroad operating at extreme grades, safety is always the first consideration. The 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. The coach is pushed up with the ratchet engaged.

It is interesting to note that at no time are the locomotive and passenger coach coupled to each other. The locomotive pushes the car up the track and remains in the same position for the trip down the mountain. The coach is braked separately and in fact does not even touch the locomotive on the way down!

Special thanks to Mr. Donald Bray for his review and comments. Mr. Bray is the author of They Said it Couldn't be Done and has long been associated with the Cog.

I encourage your comments and thoughts about this page! Did you understand it?? If not, please E-Mail Me.

 

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