1897 Mietz and Weiss Oil Engine
In the late 1800s and early 1900s, Rudolph Diesel had a worldwide stranglehold on patents related to his four-stroke compression ignition cycle. Engineers found they could get partway there without being sued for a patent violation and that’s how the oil engine came to be.
We talked about Herbert Stuart-Akroyd and his invention of the four-stroke vaporizing oil engine in England (see it at www.dieselworldmag.com/diesel-engines/vintage-diesels/beating-dr-diesel) and how that engine offered a lower cost engine that could operate on a variety of heavy fuel oils. An enterprising German emigrant named Carl W. Weiss did something similar in the USA, with a few clever tweaks.
Mietz and Weiss
Carl Wilhelm Weiss (1858-1940) was born in Prussia and attended engineering school in Holland. He travelled to the U.S. in 1876 to see the 1876 Centennial Exposition in Philadelphia, Pennsylvania, and decide to stay. Finding employment as an engineer, he patented a number of items outside the engine realm, including a pneumatic typewriter and engineered things elated to cash registers and adding machines, but internal combustion engines had captivated his interest. He had the knack and by1893 had developed a vaporizing oil engine. Lacking funds for a full startup, he began looking for investors.
Weiss soon teamed up with August Mietz (1834-1917) of New York City. Mietz was also a Prussian with an engineering background. He had emigrated to the U.S. in 1859 and by the time he and Weiss started working together, he had a large and well-established foundry/machine shop on Mott Street in Lower Manhattan, New York. It was the perfect place to put Weiss’ designs into production and it was done quickly. As far as we can tell, the Mietz & Weiss (M&W) engines were the first American designed oil engine to go on sale here. Weiss continued perfecting the designs and ran the technical side of M&W for many years. The partnership of Mietz & Weiss produced oil engines in a variety of styles and outputs, as well as gasoline engines and, reportedly, alcohol fueled engines.
Oil and Water- Hit and Miss
The Mietz & Weiss oil engines were two-stroke, hit and miss, crankcase scavenged, vaporizing oil engines. They were the first American hot bulb engine and utilized the vaporizing principle first used by Akroyd-Stuart. Well, that doesn’t tell you a lot, does it, but looking at the nearby illustration and reading the caption will tell you more.
Oil engines are not “diesels” but they are on the diesel family tree. In concept, they are most like the prechamber style, indirect injected (IDI) diesels of the recent past but with very low compression ratios (3:1 to 5:1). In fact, the oil engine developed into the IDI diesel. Oil engines use heat of compression for ignition and they are (generally) fuel injected, but they need a heat source in the combustion chamber to vaporize the oil into a more volatile mixture. This is where the hot bulb comes in. The hot bulb is externally heated with a torch initially but after the engine heats up, it stays hot enough to sustain vaporization. The bulb is not cooled at all by the engine cooling system, so it can retain heat for vaporization. As the oil engine evolved into the diesel, compression ratios got higher and the vaporizing chamber got smaller.
The M&W oil engines were unique in using water injection to slow combustion and reduce knock. The first M&W oil engines used a manually adjusted water injection system. Later ones had a “toilet tank” style system with a float valve to automatically adjust water feed. The water jacket around the cylinder was used to heat water into low pressure steam, about as much as comes of a teapot, that was pushed into the intake tract at slightly more than atmospheric camber. The engine needed a supply of water, either from a pressure-regulated city water system or a gravity tank. Running at light loads, the engines do not need the water injection and typically modern hobbyists do not use it. Under load, it’s pretty important.
The M&W oil engine was unusual in another way; it was a hit and miss. Many large flywheel gasoline engines of the day were hit and miss, but the M&W is the only oil engine we can find with that feature. Basically, hit and miss is a way of governing engine speed. If the engine has a carburetor with a throttle plate, a governor can control speed with it. Gasoline hit and miss engines speed are speed controlled by cutting off the spark. The heavy flywheel keeps the engine rolling until speed drops to the governed point and then cuts in the spark. A hit and miss oil engine works the same way except that the fuel injection is cut off. With either style, with a light load and depending on where the governor is set, a hit and miss might fire once or twice in every five revolutions. Under a heavy load, it will usually fire every revolution.
This Old Engine
The engine featured here has been dated at 1897. It’s serial number 579 and is one of the earliest surviving and running M&W oil engines. It can been seen in the Founder’s Building at the Coolspring Power Museum, in Coolspring, Pennsylvania. It’s a 6 horsepower model with a 7 x 8 inch bore and stroke. It was used on a Farm in Claysville, Pennsylvania, and has been at the museum since 1970. During events there, it is often found hitting and missing for days on end.
The M&W Legacy
Mietz & Weiss was a going concern in the 1890s and early 1900s. Their oil engines were at the forefront of the technology for that time and had a great reputation for reliability. Besides single-cylinder horizontal oil engines from 1-1/2 to 35 horsepower, they built gasoline engines from 1/2 to 18 horsepower. Their horizontal twin cylinders produced up to 70 horsepower. M&W were also known for vertical engines, particularly their vertical marine oil engines from one to four-cylinders and 2 to 80 horsepower.
It’s known that some time before 1908, Mietz semi-retired and left the day-to-day operation of the company to his son-in-law, Emil Rueff. Sources conflict but Meitz died in either 1915 or 1917. Carl Weiss, who is sometimes called the “Dean of Oil Engineers,” left the company in 1917 and started his own engine manufacturing outfit called Weiss Engine Company in 1918. It didn’t go very far and some sources state he ran afoul of patents owned by August Mietz Company and had to settle a lawsuit. Wiess finished his career running the Carl W. Weiss Engineering Company, which was in operation as late as 1939, though little is known about what was done there.
With both Weiss and Mietz gone, the company slowed down and some time between 1920 and 1922, it shut down and Charter Gas engine Company acquired the rights to some M&W designs and began manufacturing them in Illinois. Charter went out of around 1930 and still had M&W oil engines in the catalog right to the end. Interestingly, the ornate Mietz Factory, still called the Mietz building, exists on Mott Street in Manhattan, long since repurposed into offices. It gained another claim to fame by serving as a backdrop in the mafia movie, The Godfather.
Coolspring Power Museum