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The Cultivator

Thoughts from the editor.

Learning by Accident and the Monovalve Diesel Engine

I learn a lot by accident, although I think serendipity is a better word, the learning often the result of a chain of events sparked by a simple question or observation.

This issue’s Patent Page, an examination of a unique single valve – or monovalve – 4-stroke diesel engine, underscores this thought. Prior to last issue, I was unaware of the American Diesel Engine Co. and the 2- and 4-cylinder monovalve diesel engines it produced in the 1930s, but then reader Brian Barber wrote in to ask about a monovalve diesel engine he vaguely remembered. A little research turned up an article by Warwick Bryce in the October/November 1994 issue of GEM  about the American Diesel Engine Co. and the monovalve diesel designed by Charles A. Winslow, which led to some leads to more information on the engine, which led to a further examination of the design for this issue.

Winslow’s monovalve engines were an interesting bid to grab a share of the growing diesel engine market by offering a unique product that, it was claimed, possessed distinct advantages over any other engine available, a superior product guaranteed to render superior service. That’s hardly an unfamiliar claim, and judging by what little we know it might have been true, yet the monovalve failed to find market footing.

There could have been many reasons for that. While it did seem to offer some advantages – chief among them low fuel consumption – the design also had inherent limitations, including flexibility in engine speed. With a single valve and a huge opening duration, an engine like this would perform best in industrial applications, where steady speeds are desired, but would likely perform poorly in automotive applications, where engine speed flexibility is key.

Yet the monovalve 4-stroke diesel concept was, for at least a time, a high-profile, developing technology. In the late 1920s and early 1930s, both Packard Motor Car Co. and Guiberson Diesel Engine Co. manufactured a 9-cylinder radial monovalve diesel engine. Packard’s engine, the DR-980, was intended as a competitor to the popular 9-cylinder radial Wright J-5 Whirlwind, the engine that powered Charles Lindberg across the Atlantic in 1927. The Packard engine proved to be very efficient in tests, but was ultimately a non-starter owing to poor development and running issues including extreme vibration. Packard had high hopes for the engine, anticipating production of 6,000 units a year. Ultimately, it’s believed fewer than 100 DR-980 engines were built.

Guiberson, which developed its monovalve diesel around the same time as Packard, turned to a standard intake and exhaust valve layout and continued production of diesel radial aircraft and tank engines through World War II.

Ultimately, other designs prospered and the monovalve concept faded away, revived briefly in 2011 as the subject of a Southern Illinois University engineering thesis.

Richard Backus