Western 4-2-2 "Bicycle" Locomotives in the USA

Class Addison Gilmore (Locobase 13519)

Data from Angus Sinclair, "Growth of the Locomotive" [one of a series later published as The Development of the Locomotive], Railway & Locomotive Engineering, Volume 17, No 4 (April 1904), p. 176-177 (Thanks to Chris Hohl for his 19 February 2024 email correcting the cylinder diameter.). See also Locobases 13517-13518 for a full discussion of two of Eddy's engines from the 1870s.

Wilson Eddy is a relatively unknown locomotive designer of the mid-19th century who deserves a full measure of fame for the many designs he crafted. His engines featured generous steaming spaces and a sizable grate and were considered so reliable they were known as "Eddy Clocks".

His first engine, shown here, was built in the Springfield shops of the Boston & Albany. As the specs suggest, the layout was atypical and consisted of a closely-spaced pair of axles in the leading truck with the cylinders riding above, one axle of very tall drivers with a spoke pattern like that of a daisy and driven by outside valve gear, and a large trailing axle behind the firebox. The cab had three pointed windows per side (sometimes called a cathedral cab).

The boiler was domeless and used the perforated steam pipe that would be a staple of Eddy's designs. It had the safety valve placed well forward. Although the grate may seem small in relation to the boiler, its area represented substantial growth.

The engine took two years to build. In its original form, it competed in and won a set of trials to demonstrate high-speed locomotive design of the time. Its trailing load was set by contest rules to comprise 6 freight cars each with a 5-ton load, 1 "long passenger car (and 21 passengers) -- the whole load weighing 85 tons. Over a course slightly under 9 miles long, the Addison Gilmore took 11 minutes 29 seconds to complete the run (about 47 mph). Its time beat the next fastest engine by almost a minute and a half.

Eddy soon replaced the trailing wheels with with another set of drivers. All 4 measured 72" in diameter each, which had a useful effect on tractive effort and led to a less slippery engine.

Sinclair passes a thoughtful and highly favorable judgement on Eddy's designs:

"Eddy Clocks, as his engines were popularly called, were held in high esteem, even affection, by enginemen, and never were beaten for efficiency and economy. A pecularity about all Eddy engines was their short steam ports, which were only 8 ins. long for cylinders 18 x28 ins."

Sinclair goes on to consider the wider range of Eddy's authority: "Decided difference of opinion now exists concerning the influence of Eddy's locomotives on the motive power of this continent. One thing is undeniable+ he made engines convenient to operate, easy to repair and so proportioned that maximum wear was secured before heavy repairs were necessary."

Sinclair also places him with Mason in having an unsuspectedly high degree of responsibility for the standardization of locomotive design in the United States between 1850 and 1860.