Dual fuel (kerosine or gasoline) spark ignition tractor

Mr. David Arnold sent me a very interesting mail that he wrote after reading the Otto vs Diesel article. It was nice to read about old-days engine solutions. I especially liked the part about water injection.

12 October 2011

Dear Mr. Gorupec,

I enjoyed reading your Charming Engineering articles. I have some knowledge that might add a small amount to the story of how diesel and gasoline engines were used.

In the late 1960s a friend's family had a dual fuel spark ignition John Deere tractor. I recall an impression that the paint looked 20-30 years old, so the machine might have been made in the 1930s-1940s. Somehow, part of the operation manual for the engine was available to a curious youngster. I do not remember whether the manual was a printed pamphlet, or a large label on the tractor and protected from weather.

The designers expected the slow evaporation of kerosene fuel mist and the preignition and possible detonation of low octane kerosene fuel to cause problems.

When kerosene would be the working fuel, the engine was started and warmed from an auxiliary gasoline fuel supply, and then switched to the kerosene fuel. The in-line two-cylinder engine may have had a working speed of about 500 rpm. (They had a very large flywheel and were nicknamed Johnny Poppers.) The fuel mixture had much time to burn, far from the walls of the large cylinders.

To avoid preignition, a water mist was mixed with the kerosene fuel mist. The water came from reserve coolant of the engine liquid cooling system. The engine had a gravity circulated liquid cooling system with several gallons of water coolant (maybe five gallons). I suspect that the cooling system could function with boiling water that condensed in the radiator, so maybe a declining coolant level was not a problem.

Coolant consumption probably was conveniently manageable. Common farm tractor engines from that era were not large--maybe 10-15 horsepower--and field workers often returned to the home for a midday meal and for refueling. Routine farm chores would not take long, and would generally not stray far from the homestead.

I recall reading that some World War 2 aircraft engines used water and alcohol mist ingestion to avoid preignition and detonation during high power. If that was the earliest use of water injection, then the tractor might have been made sometime after the mid 1940s. Injecting water into a running engine is daring, but not hard to do, so maybe the method was used earlier. On the other hand, the ancient Romans could have used movable type and semaphore telegraphy if they had thought of them. Everything began somewhere, and sometimes at a late date.

I do not know how the fuel system produced proper fuel mixtures for the two types of fuel. A separate carburetter throat, fuel bowl, and metering jet for each fuel, and valves that could immediately enable or disable the metering jet of either carburetter would give rapid fuel switchover. If some sputtering could be tolerated while a single fuel bowl held mixed fuel, then simply switching duel fuel supplies and fuel metering jets of a single carburetter might work well enough.

I do not know whether many people used kerosene for motor fuel. When that tractor was made and first used, people and fuel suppliers here had been long accustomed to using much kerosene for lamp fuel and for heating. Electrical co-operative organizations in this area installed home electric power distribution in the 1930-1940s, and people here used kerosene (and coal and firewood) for home heat until the 1960s. Except during World War 2, gasoline was readily available for motor fuel, but I do not know whether the prices of gasoline and kerosene farm fuel differed much.

Yours truly,
David Arnold
Milan, Missouri USA

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