Beating Dr. Diesel - Diesel World

A 6 hp Hornsby Oil Engine

Diesel’s 1898 patent on the compression ignition engine is the well-charted beginning of the engine type we now call a diesel. Missed in all that historical hoopla… when the first production diesels entered the market, they weren’t the only engines running on fuel oil. The Hornsby-Akroyd vaporizing oil engine had been in production six years at that point and tens of thousands had been sold all over the world.


Dave Tomblson’s engine is a Hornsby 1912-style, Type L, and has a 3.9 x 5.5-inch bore and stroke. It was rated at 6 horsepower at a whopping 260 rpm. That calculates to about 121 lbs-ft of torque. Production began in 1912 and they were a third evolution of the original Hornsby-Akroyd design with a number of improvements and updates. They were built into 1934, from 1918 with a Ruston & Hornsby tag. This one is mounted on a cast iron base that doubles as a fuel tank. The rusty part is the vaporizing chamber and it has a cover with a removable cap. The intake valve is on this side of the engine and the shaft that comes from the crankshaft drives the open roller cam that operate both valves and the injection pump. The injection pump is the part that hangs down and you can see the priming lever.

Herbert Akroyd-Stuart (1864-1927) started work on his vaporizing oil engine in 1885 after accidentally setting a fire with paraffin (kerosene). Lamp-grade kerosene is not volatile, which is why it was used indoors as lamp oil, but when he spilled some into a pot of molten tin, it vaporized and was ignited by a nearby open flame. At the time, internal combustion engineers were trying to resolve fuel volatility issues, with gasoline being considered too dangerous for many applications. Fuel oil satisfied the safety aspects (which is why oil engines were often marketed as “safety engines”) but was difficult to ignite. Akroyd-Stuart’s accident had given him a simple idea for igniting fuel oil, kerosene and other less volatile petroleum products.

The Vaporizing Oil Engine Debuts

The idea of vaporizing fuel with heat took form in an 1886 prototype built in Akroyd-Stuart’s father’s Bletchley, England, iron works. Experimentation was ongoing until 1890, when a patent was filed. Rather than creating a company to produce engines, Akroyd-Stuart licensed the design to an existing manufacturer, Richard Hornsby & Sons, of Grantham, England. Hornsby was a well known manufacturer of steam engines but very quickly devoted all it’s effort into perfecting and marketing Akroyd-Stuart’s engine. Production of the Hornsby-Akroyd vaporizing oil engine began in June of 1891 and the first two sales came in the summer of 1892. Those first two engines weren’t retired until 1923, a testament to their design and utility.


The Hornsby-Akroyd vaporizing oil engine, was a four-stroke engine that ran reliably on petroleum products heavier than gasoline or the lightest, most volatile grades of kerosene. That was one of it’s most attractive selling points. An oil engine was safer less complex than steam, which often required special insurance and licenses and it could run on the wildly varied and largely uncategorized range of petroleum products available across the globe in those days, including crude oil. It ran most reliably on what became known as bunker oil because some of the less refined products (like most grades of crude oil) tended to leave heavy deposits that eventually had to be manually cleaned out of the combustion chambers.

Different Than Diesel

Akroyd-Stuart’s design featured a split combustion chamber with a passage between them. One chamber was right above the piston in the cylinder and benefitted from the liquid cooling system. The other was above the head in what was called a vaporizing chamber. It was uncooled and the goal was for it to retain as much heat as possible so when fuel was injected against the hot metal in the chamber, it instantly vaporized. If this reminds you of an indirect-injected diesel, your thinking is right on track.

Two things set Hornsby-Akroyd’s oil engine apart from the Dr. Diesels original compression ignition engine. First, it used fuel injection. It was a squirt of not-very-well-atomized fuel but the Hornsby-Akroyd was the first production solid fuel injection system on an internal combustion engine. Second, the oil engine had a very low compression ratio, about 3:1, which is obviously not enough to fire the fuel by heat of compression alone. That’s where the vaporizing chamber came in.


Here we can see the injector close up. It delivers fuel to the vaporizing chamber. The bronze flyweight-type governor in the background controlled engine speed via the long arm that runs to the injector. As governor rotational speed increased, the balls were swung outboard pushing the lever down. It controls speed by releasing fuel pressure, dribbling the bled-off fuel into the funnel and return it to the tank. Crude by today’s standards, but effective.

For starting, the vaporizing chamber was externally heated, usually by a kerosene blowtorch.  When the chamber was almost red hot, a few squirts of fuel into the hot chamber using the manual primer would vaporize. That heated and vaporized fuel was right at the edge of combustion already but in a largely air-free chamber. The engine would be rolled around manually via the flywheel and with the incoming rush of air, even with just a 3:1 compression ratio, the mixture ignited. Once the engine had run for a while, the vaporizing chamber retained enough heat that the external kerosene burner could be shut off. Combustion started in the vaporizer but finished in both chambers and there was plenty of turbulence to mix fuel vapor and air once the engine was running.

Strong on the Market At First

Combustion in the vaporizing oil engine was a slow process and it wasn’t the most efficient system. There were definite rpm limits and it delivered much less fuel economy than the diesel. The vaporizing oil engine had some advantages in the late 1800s and early 1900s, the biggest two being size and cost. At this point in time, the vaporizing oil engine could be downsized and made portable, while the diesel could not. Early diesels used compressed air to atomize and inject fuel, so they had a lot of ancillary equipment that gave them a pretty big footprint. Plus, they were quite expensive, partly due to Dr. Diesel’s costly licensing agreements. On top of that diesels were much more picky on fuel than oil engines, requiring a more refined variety of oil and the infrastructure wasn’t everywhere to supply it. Plus, lower grade fuel oil was about half the cost. All that would quickly change and the diesel would rise to dominate, but the oil engine still had a long time on the market.


Lots to see here, starting with the underside of the vaporizing chamber. The rusty stuff is made up by the chamber itself (the “hot bulb”) and the cover (sometimes called the “chimney”). Typically a kerosene blowtorch applied the heat and the cover directed it up and out the stack on top. The cap on top was used to control the temperature, which could reach as much as 1000 degrees on the outer surface of the chamber. When the engine was generating enough heat on it’s own, the torch would be turned off and the cap placed on the stack to hold heat in the chamber. The section of the combustion chamber directly above the piston was usually cooled by water. Notice the exhaust rocker arm and follow it right to the actual cam lobe.

Many early internal combustion benchmarks were set by oil engines. The first self propelled oil-fueled internal combustion tractor, built by Hornsby in 1896, was powered by an Akroyd-Stuart type oil engine. They also built the first oil-fueled internal combustion locomotive. A Hornsby oil tractor was converted to tracks in 1905 and became the first fully tracked vehicle. All of these benchmarks were set way before the diesel had been downsized enough to operate on a ground vehicle.

Famously, Hornsby-Akroyd-licensed oil engines, built in the U.S., powered a generator that illuminated the Statue of Liberty for the first time with electricity. The Taj Mahal was also illuminated by a Hornsby-Akroyd generator. A Hornsby-Akroyd-derived engine ran the generator that powered Guglielmo Marconi’s radio for the first transatlantic radio transmission in 1904, chosen because it didn’t have an ignition system to interfere with the radio. They were popular the world over to power lighthouse fog horns and lamps and they remained popular over the time it took to standardized petroleum fuel production so people could reliably get the right fuel for the right engine type.


The curved spokes on the flywheel is one giveaway visual for a Hornsby-Akroyd. Apparently, spinning it by hand or foot a little easier with curved spokes.

The Hornsby engineering team had dropped all their steam work to improve the oil engine and they developed many new models and made many improvements that continued through World War I. The First World War is when highly developed diesel engines became practical and the infrastructure improved to support them. The oil engine business slacked off enough that it became advisable for Hornsby to merge with another company and that company was Ruston & Proctor Ltd.

The Ruston Connection

Ruston was an accomplished engine maker in it’s own right and when the Akroyd-Stuart patent expired in 1904, they began building oil engines based on those principles and improved upon them. Hornsby merged with Ruston in 1918 and the new company became Ruston & Hornsby. Ruston was a bit more forward thinking than Hornsby had been and was more able to keep abreast of the internal combustion technology curve. It moved quickly into “true” diesels and on to set other benchmarks in engine manufacturing, including gas turbines, and a part of the company continues to this day as a subsidiary of Siemens. Ruston continued to build Hornsby-style engines into the 1930s because there were still remote parts of the British Empire where an oil engine was a good choice.

The American Connection

There was an American connection to the Hornsby-Akroyd engines and it furthered the development of internal combustion technology here. In 1893, John De La Vergne of New York purchased a license to build the Hornsby-Akroyd engine in the U.S. His firm, De La Vergne Refrigerating Company, was already long and well established in the world of refrigeration but needed to improve the way their refrigeration plants were powered. Before high voltage electricity was everywhere, steam plants were the mainstay of all sorts of powered machinery, including refrigeration. Steam posed all sorts of safety issues in urban environments and internal combustion provided a safe answer. De La Vergne chose the oil engine because of it’s “omnivorous” ability to burn a variety of fuels. When they sold a refrigeration plant, they needed to know it was going to work no matter where in the world it was set up.


This version of the Hornsby-Akroyd has a counterbalanced crankshaft, an unusual feature in the day. The engine is not pressure lubricated but has oil reservoirs with  drip feed at the strategic spots.


This engine was sold in December of 1927 to Coppage & Sons, Brecon, Powys, mid-Wales, in December of 1927.The history books show Coppage & Sons specialized in pumps so one might assume that’s how it was used. How it got to the USA is unknown and it’s had several owners since coming here. Current owner Dave Tumblson in an antique engine collector and has owned it about two years. He hasn’t had it running yet, but it’s on his short list.

De La Vergne started with a Hornsby-Akroyd type they called the Model HA, applying improvements and building it exclusively until 1910. Their engineering team then introduced new lines of engines starting with the FH which edged the oil engine towards being a prechamber style diesel by increasing the compression ratio and reducing the size of the vaporizing chamber. Gradually, De La Vergne became a well known as an engine builder and could be called one of the forgotten “missing links” in the evolution of the diesel. It became a part of the Baldwin Locomotive Works in 1931 as Baldwin attempted to use De La Vergne’s diesel expertise to switch from steam to diesel locomotive manufacture. This was largely unsuccessful and Baldwin’s decline took De La Vergne down with it. Baldwin merged with another failing locomotive works, Lima Hamilton, in 1951 and the diesel line became known as Baldwin-Lima-Hamilton but by this time, the engines weren’t highly regarded and well behind the times. BLH finally shut down in 1956, except for their crane line that lasted until 1980.

Place in History

Akroyd-Stuart’s vaporizing oil engine is often compared to Diesel’s compression ignition engine. They were really two different animals. You could say the diesel and the vaporizing oil engine were adjacent roads that eventually merged to combine a prechamber and solid fuel injection with compression ignition.