The Geared Locomotive or What Wood You Shay To?

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 would all be removed. New valve heads would be fabricated to hold the ball valves and return the lubrication galleries of the block. The block must have an exhaust port cut into each cylinder and have the port fitted with a steam recovery device. Also each piston must be fitted with a push rod for opening the ball valve as needed. Provision must be made so that the engine always rotates the same direction and the existing transmission can be used for forward and reverse. Note that only the forward and reverse gears are needed so second and third gears can be removed if needed or practical.

As for numbers, I am going to fiat the cylinder diameter as 5 inches (I haven’t torn down a big block for a long time). Therefore each cylinder will have an area of about 19.6 inches or about 157 square inches total. This, multiplied by the working pressure of the boiler, would give the foot pounds produced by the engine, or about 23,562 foot pounds at 150 psi. This translates into roughly forty-two “steam” horsepower delivered to the transmission.

The use of an automotive transmission would have an effect on the power delivered to the shaft and gearing. While low gears would deliver a lot of power, it would also serve to further limit the top speed of the locomotive. It may be more desirable to keep the forward/reverse gearing to a one to one ratio.

The power would be transferred to the wheels via a shaft and bevel gear set. This gear set serves to rotate the motion of the shaft by 90 degrees, and is accomplished by having a pinion gear meshed to a ring gear around the face of the wheel. Each wheel would be driven, and the shafts are usually square tubes with telescoping joints to allow motion to the trucks.

The trucks can be made with wooden frames and wheels. The construction would need to be fairly massive, and steel strap reinforcement will be desirable. The wooden wheels would need to be fitted with steel tires and the ring gears could be bolted directly to the wheels. Each truck would also have the shaft and pinion gear mounted to one side. The frames of the trucks would hold the journal boxes, (the bearings that the axles ride on) and would be sprung to a transverse bolster by leaf or coil springs. Also the wheels must be rigidly connected to the axles so as to transfer power to both sides of the truck.

The frame of the locomotive would be made from heavy timber, probably bigger than eight by twelve inch beams fastened by bolts and plates. Cross stringers would be added as needed and it all would be further strengthened by fish plates and tie rods.

The boiler would be offset to the side to allow the mount of the engine at the center edge of one side of the frame. Wrapped around the boiler would be a “Saddle Tank” to provide working water to the boiler and weight to the locomotive for better adhesion to the track. A cab containing a fuel bunker would be mounted to the rear of the boiler and contain the operating controls. The Fireman would be responsible for maintaining enough steam, (adding coal and water to the mix and preventing the boiler from exploding). The Engineer would be responsible for the operation of the locomotive and the safe transportation of the cargo.

Mandatory controls would be: water feed, sight glass, tri-cock water level test ports, safety pop valves, pressure gages, forward reverse lever, throttle control and safety warning devices. Stuff nice to have would be better whistles and bells, lights, cab heat, windows, cutoff control to the steam entering the cylinders, brake controls for the cars, brakes for the locomotive, and an air compressor to feed them.

Construction time would depend on how many workers the builder can throw at the project, materials, and the availability of the machine tooling for the fabrication of the finicky bits.

In conclusion, a twenty ton, forty Hp, geared locomotive could probably move ten to fifteen loaded cars over rough track on the level. This capacity will be sorely needed in many industrial applications, especially in places where a lot of materiel must be moved around, like a steel mill or construction of railways. A geared locomotive would get the town a lot of “bang for its buck” and could be upgraded as better materials become available.