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Curtiss OX-5 V8: A Deep Dive Into America's First Great Airplane Engine
Glenn Hammond Curtiss personified the eccentric billionaire aviator at a time when Elon Musk's grandparents were just toddlers. Everyone from Howard Hughes to Musk himself fit perfectly into the persona that Mr. Curtiss formulated decades earlier. It all began in large part thanks to one of Curtiss's first flagship airplane engines.

Curtiss OX-5 V8: A Deep Dive Into America's First Great Airplane Engine

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In many ways, the Curtiss OX-5 V8 was the finest creation Hammondsport, New York native Glenn Curtiss ever devised. In a time when the bulk of his profits still came from motorcycle engines, the OX-5 ensured Curtiss was ready to make that profound leap to the skies. In doing so, he paved the way for both the motorcycle and aeronautical industries of America. Let's take a closer look at the details.

For those who aren't familiar with the story of Glenn H Curtiss, we took the pleasure of visiting an entire museum dedicated to his honor earlier this year, and we highly recommend you check it out if you'd like to learn more. But the long and short of it goes something like this. Early in his engineering career, short on money and yet to be a global celebrity, Curtiss was forced to fashion his first motorcycle carburetor from an old soup can.

Of course, things wouldn't stay that primitive for long, as Curtiss's bread and butter soon began building some of the most advanced and powerful motorcycle engines of the turn of the 20th century. Simple single-cylinder designs evolved into novel V-Twin and three-cylinder engines that turned Curtiss bikes into some of the most desirable American motorcycles of the 1900s.

Curtiss's motorcycle engines formed a fertile cradle for what Curtiss had planned going forward. Little by little, cylinder by cylinder, Curtiss paired together his famous V-twin engines, added cylinders, and likely drove himself mad trying to make it all work in tandem. These were the early days of internal combustion, and key things like engine timing and adjusting fuel-to-air ratios were still in the early stages. But if there was anyone to work out the details, it was Glenn Curtiss.

By 1906, Curtiss had finally made it to eight cylinders. At this juncture, Curtiss realized his true calling in the engineering field wasn't motorcycles but rather airplanes. By 1908, an antifreeze-based coolant system was added to accommodate the hotter, enlarged cylinders. At this point, the Curtiss V8 lineage splits into the liquid-cooled V8 engine and the air-cooled Curtiss B-8 famous in the V8 motorcycle and the AEA June Bug. Curtiss abandoned the valve-in-block with flat cylinder head systems similar to that of the automotive flathead V8s early in testing, opting for overhead-valve cross-flow heads by 1909.

Curtiss made this change just in time for the U.S. Navy to take notice when they needed an engine for their new A-1 amphibious scout plane. A tweaked version of that engine was introduced in 1910 as the OX-5. Though it wasn't the most reliable engine in modern terms, no aviation engine was exactly reliable in the late 1900s and early 1910s. They all leaked oil, usually into the pilot's face, and any flight that didn't see an engine failure was considered a rousing success.

While not the most sophisticated or powerful engine, Curtiss was able to crank out these OX-5 V8s in the thousands. As many as 12,600 were built since its first test run in 1915. That resulted in them being cheap to buy. A luxury other aeronautical engines didn't have. Owing to its low cruising RPM, it was also decently fuel-efficient. Because horsepower calculation wasn't an exact science 110 years ago, historians estimate the OX-5 generated anywhere in the neighborhood of 90 horsepower in its most famous application, the Curtiss JN, lovingly called the Jenny.

By the time the OX-5 found its way into a Jenny airframe, the engine was already considered outdated and antiquated. But with the fearsome combination of a cheap, easy-to-produce airplane and an equally numerous engine, the fledgling U.S. Army Air Service suddenly had the perfect means to bolster their aircraft fleet. Mounted inside the Jenny, the OX-5 V8 served with the militaries of the U.S., United Kingdom, Canada, Brazil, China, Argentina, and Cuba, among others.

It was one of the most prolific combinations of an airplane and engine on this side of a Spitfire and a Merlin V12. Today, surviving OX-5s are on display in museums across the U.S. and Canada. One is mounted inside a numbers-matching 1917 Curtiss JN-4D Jenny currently under restoration in the very town where Glenn H. Curtiss built his very first engines. At the Glenn H Curtiss Museum in Hammondsport, New York. 

Check back soon for more from V8 Month right here on autoevolution.


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