Harnessing Horsepower

From four legs to 16 cylinders, marine power has come a long way.
By Dudley Dawson ,

When marine engineers speak of harnessing horsepower, they are generally speaking of optimizing the components of a modern yacht’s drivetrain: designing a more efficient propeller, selecting a better gear ratio or turbocharging an engine to deliver more speed. There was a time, though, when harnessing horsepower literally involved both harnesses and horses. 

In a review of the history of marine propulsion and horsepower, two names commonly come to the fore. The first is James Watt, a Scottish mining engineer who measured the power of a horse to determine the value of “horsepower.” The second is Robert Fulton, inventor of the steamboat.

Well, don’t believe everything you read, because both of the previous two sentences are horse tales, utterly false in their central assertions.

The lifts at Scottish mines were actually powered by ponies rather than horses. It seems the question, “How many ponies under the hood?” is more historically accurate than, “What’s her horsepower?” Watt, whose name appears today as a power rating on everything from light bulbs to diesel engines, measured how far the mine ponies could lift a certain weight in a certain amount of time. In his travels to sell steam-powered equipment, he soon discovered that horses were more common than ponies in other places and other applications. Seeking to maximize his sales, he arbitrarily increased the power-equivalency number to account for the assumed amount of extra power of a horse over a pony. It turns out his assumption was significantly off, but this was before truth-in-advertising laws, so Watt’s inaccurate numbers remain the standard to this day.

Although Fulton has his place in steamboat history, the first related patent was actually granted to John Fitch. Delaware Indians captured and later released Fitch in the 18th-century American frontier, and the experience both haunted and inspired the inventor. The drawing accompanying his steamboat patent shows not paddlewheels, but rather a moving rail on each side of the vessel with multiple paddles attached, looking much like a mechanized version of a party of native Americans propelling a war canoe into battle.

Later versions of Fitch’s design substituted paddlewheels for the individual paddles on each side, but more germane to our topic is an earlier version that was not steam-powered, but rather propelled by a pair of living, breathing, hay-burning horses. The draft animals, on opposite sides facing in opposite directions, were harnessed in stalls where they trod on a full-beam wheel, mounted horizontally below the deck, a giant turntable of sorts. The turning wheel, through gears and cranks, propelled the vessel at whatever speed two horsepower would take it.

Fitch’s advance was not in the mechanicals, but in freeing them from the shore and taking them to sea. The concept and the mechanism were similar in configuration to those commonly used in shoreside industrial applications of the day. New England had waterwheels to power their mills, and Holland had windmills to power their drainage pumps, but many other areas had only animal power: horses, mules, oxen, elephants, even humans.

Fitch’s invention was a technological success, but a commercial failure. He couldn’t find investors or buyers in America, so he traveled to Europe, particularly France, hoping for more interest. It did not materialize, so he returned to the United States so depressed that he eventually took his own life. Fulton, on the other hand, became wealthy exploiting Fitch’s invention, transporting freight and passengers on several lucrative routes. Thus it is Fulton’s name we associate with the first steamboats, rather than Fitch’s, in a classic case of the victor rewriting the history.

Fitch was not the first to use animals for marine propulsion, nor was he the last. More direct systems were in use for hundreds of years along canals on both sides of the Atlantic. Horses, mules or oxen were hitched to tow lines, and the animals, walking on towpaths adjacent to the canals, drew heavily laden barges slowly but surely to their destinations. America’s first president, George Washington, was involved with surveying and constructing the Chesapeake & Ohio Canal, a 184-mile waterway around the rapids of the upper Potomac River. It served commercial transportation interests for nearly a hundred years and continues today as a national park where visitors can ride the barges and bike or hike the well-worn towpath.

Most instances of horse-powered vessels today are of the towboat variety, similar to those on the C&O Canal and targeted to the tourist trade. There are rumors of commercial craft powered by horses and other animals, still actively serving as ferries crossing narrow rivers in remote areas, but these have been difficult to document.

The 154-foot (46.9-meter) Usher’s pristine engine room features two red V-16 MTU diesels that transform the space into a virtual work of art.

What is known with surety, though, is that mechanical power generally, and marine propulsion in particular, would not have developed into what we have today if not for the pioneering work of Watt, Fitch and others. Once the steam engine was developed, and later internal combustion engines fueled by gasoline or diesel rather than hay, it was a relatively simple matter to unhitch the horse and pile on the horsepower. Watt surely did not foresee electrical grids linked to steam and nuclear powerplants rated in multiple megawatts, any more than Fitch envisioned marine engines rated in thousands of horsepower propelling yachts at speeds exceeding 40 knots.

Most assuredly, though, these pioneers played a key role in making modern yachting into the pleasurable and exciting sport we enjoy today.  

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