Shay locomotive

, who can be fairly credited with the popularization of the concept of a "geared steam locomotive". Although the design of Ephraim Shay's early locomotives differed from later ones, there is a clear line of development that joins all Shays.

Development

Ephraim Shay (1839-1916), has been credited as a schoolteacher, physician, civil engineer, logger, merchant, railway owner, and inventor. He lived in Michigan, and became a logger in the 1860s.

While a logger he wanted to find a new way to get logs to the mill, besides floating them on a river. He then built his own tramway in 1875, on 26 in. track, and wooden ties. This was very efficient and enabled him to beat his competitors because he saved so much money with the tram.

Two years would pass before he would invent the Shay Locomotive. In about 1877 he developed the idea of having an engine sit on a flat car with a boiler, gears, and trucks that could pivot. The first Shay only had two cylinders and operated through a series of gears over the inside portion of the rear truck. It did not take long for this idea to become popular.

When Lima Locomotive Works of Lima, Ohio received the Shay idea it was not impressed, until John Carnes influenced the company to utilize the idea, resulting in the classic Shay design.

During its lifetime, Lima Locomotive Works manufactured nearly every Shay, including the last and largest Shay Western Maryland Shay #6, which is still in operation at Cass. Six Shay Patent locomotives, known as Henderson style Shays, were built by the Michigan Iron Works in Cadillac, Michigan, USA. Geared locomotives built by Willamette and other manufactures are often incorrectly referred to as Shays.

Overview

Shay locomotives had regular fire-tube boilers offset to the left to provide space for a two or three cylinder "motor," mounted vertically on the right with longitudinal drive shafts extending fore and aft from the crankshaft at wheel axle height. These shafts had universal joints and square sliding slip joints to accommodate motion of the swiveling trucks. Each axle was driven by a separate bevel gear, and used no side rods.

Driving all wheels, including those of the tender, together with small diameter wheels were the strength of these engines, their entire weight developing tractive effort. A high ratio of piston strokes to wheel revolutions allowed them to run at partial slip, where a conventional rod engine would spin its drive wheels and burn rails, losing all traction.

Shay locomotives were often known as "sidewinders" or "stemwinders" for their side-mounted drive shafts. Most were built for use in the United States, while many found their way to 30 additional countries, territories or provinces.

Problems

Although the Shay was the most common geared locomotive, it had a significant flaw that was not corrected. Because the drive shaft lies outside the trucks, instead of along the centerline, truck rotation when following track curvature causes substantial drive line length change, unlike the central drive shafts of Heisler locomotives and Climax locomotives. In modern drive shafts, this effect is accommodated by roller splines instead of bronze slip joints (shown between "Sonora's universal joints") that lose their ability to slide under high torque.

Wreck photographs show Shay locomotives, before or after uphill curves, where they failed to respond to change in track curvature, thereby running off the track "for no apparent reason." Some texts refer to these locomotives as "rail spreaders" and "flange hounds," both characteristics of trucks that do not steer freely under heavy load.

Other disadvantages include the noise of the gearing, and the rather low top speed.

Classes

2768 Shay locomotives were built by Lima in four classes, from 6 to 160 tons between 1878 and 1945.

* Class A: two cylinders, two trucks. Weights between 6 and 24 tons.
* Class B: three cylinders, two trucks. Weights between 10 and 80 tons.
* Class C: three cylinders, three trucks. Weights between 40 and 160 tons.
* Class D: three cylinders, four trucks. Weights of 100 and 150 tons. Note: Two 15 ton Shays were built with two cylinders and three trucks.

Twenty Class D shays were built. They were no more powerful than Class C, but had greater fuel and water capacity, resulting in improved adhesion. Four Shays were built left-handed, all special ordered for the Sr. Octaviano B. Cabrera Co., San Luis de la Paz, Mexico.

urvivors

Only 115 Shays survive today, some a combination of parts of two Shays. The oldest surviving Shay sn-122, built in 1884, is currently displayed in Redding CA, at Turtle Bay Exploration Park. The last Shay, sn-3354 built in 1945, still operates on the Cass Scenic Railroad State Park. One of the largest Shays built, this 150 ton Class C locomotive was in service only five years when it was retired and placed in the Baltimore & Ohio Museum. In 1981 it was removed from static display, in exchange for a smaller Shay and a Porter locomotive, and placed in service on the Cass Scenic Railroad. It has now served in tourist and enthusiast service for a longer period than it did for its original owners. It is still in near-new condition. The Camino-Placerville & Lake Tahoe #2, a three-truck Shay, is on display at the Travel Town Museum in Los Angeles' Travel Town Museum. The Roaring Camp and Big Trees Narrow Gauge Railroad operates the class B "Dixiana" and the class C "Sonora". The Colorado Railroad Museum holds two shays, #12 and #14 which operated on the Georgetown Loop Railroad for about 20 years.

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External links

* [http://www.ShayLocomotives.com Shay Locomotives.com]
* [http://www.gearedsteam.com/shay/shay.htm Geared Steam Locomotive Works' Shay pages]
* [http://www.cassrailroad.com Cass Scenic Railroad]
* [http://www.ephraimshay.com Ephraim Shay website]
* [http://www.spikesys.com/Trains/grd_loco.html/| W&H Main Yards]
* [http://www.sciencetech.technomuses.ca/english/collection/shay.cfm The Shay Locomotive] at the Canada Science and Technology Museum
* [http://eldoradowestern.blogspot.com/ El Dorado Western Railway blog] Shay construction number 1896 under restoration