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The Geared Locomotive or What Wood You Shay To?

Written by Kevin H. Evans

Geared locomotives were developed to handle rough track industrial applications. Most notable were logging short lines and mining short lines. The traditional steam locomotive has cylinders parallel to the ground with the effort of those cylinders transferred to the drive wheels via reciprocating side rods. A geared locomotive transfers the power to the wheels by a shaft connected to the wheels through a gear meshed to another gear on the wheel or axle of the locomotive. Said wheels are usually about the same size as the wheels found on the load carrying cars. Some of these locomotives used power transferred to the center of the axle sets, but the most common type had all the power train (engine, shafts. and gears) mounted on the side of the locomotive.

This type, the "Shay" (named after it's inventor, a logger of the same name from Minnesota), had the great advantage that all the working parts were easily accessible and mounted where the Engineer could see them. Additionally the short wheel base of the driven wheel sets (or trucks as they are called) allowed the locomotive to use extremely rough track. In fact the small wheels gave the geared locomotive a lot of adhesion and allowed the movement of large loads for relatively low horsepowers. It was commonly said that you could "Draw two lines on the ground and a 'Shay' would follow them." This made it a supremely good locomotive for industrial use. Temporary track, tight turns, and difficult grades were handled with ease. The greatest failing of the geared locomotive was its slow speed. Because of the gearing a Shay sounds like it is going a hundred miles an hour when it is really making about fifteen miles per hour.

The geared locomotive would also be attractive to the residents of Grantville because a large well run tourist railroad, the "Cass Valley Scenic RR," is only three hours drive from the pre-ROF location of Grantville. This operation, formerly a logging road, has what is probably the best collection of geared locomotives in existence. Railroad fans, large machinery enthusiasts, machinery restorationists, and industrial historians would be frequent visitors and would be well aware of the advantages of the geared locomotives in use there.

Building a geared locomotive first would be very attractive because: first, all the "works" are where you can get at them. Second, you can get a lot of work for a lower horsepower prime mover. Third, the locomotive can handle really rough track. Fourth, many of the structural components can be made from wood. Lastly the suspension and equalization of the locomotive is much simpler.

So how they would build it? Well, first it would not look like a product of the 1920s industrial age. It would be coal fired, wood framed, and steam driven. The locomotive would look a lot like a flat car with an engine hanging over the side. Set a boiler on the flat car, wrap the boiler with a saddle type water tank, and add a cab with a fuel bunker on the back.. Lights, bells and whistles would be nice, but secondary to getting the mover on the track..

The first thing to build would be the actual engine. In view of the need for a strong locomotive as quickly as possible, converting a big block "V-eight" engine to steam would have to do. This conversion has problems as the block would have small cylinders compared to a purpose-built engine. It would only have power on the down stroke of those cylinders and need extensive refitting to run on steam. Luckily, by using an engine block from a big ICE (internal combustion engine) you would have a reciprocating cylinder/piston set without having to do all the design work and machining from scratch.

Converting an engine block to steam can be done in a number of ways, but the easiest is to make it into what is commonly called a bash valve engine. A bash valve engine, also known to the model aircraft crowd as a CO2 engine, uses a rod mounted to the top of each piston to lift a ball off of its seat when the piston reaches "Top dead center". This allows steam to enter the cylinder and pushes the piston down. When the piston reaches "Bottom Dead Center" it reveals an exhaust opening that allows the steam to escape. The steam is collected and used to power the draft of the boiler or alternatively condensed to add to the power of the engine and extend the amount of time between water stops.

In order to fit the new valving, the block must be stripped. The valve heads, timing belt, front pulley, and water pumps ...