Tractor vaporising oil (TVO) is a fuel for
petrol-paraffin engine
A petrol-paraffin engine, TVO engine (United Kingdom) or gasoline-kerosene engine (North America) is an old-fashioned type of dual-fuel internal combustion engine with spark-ignition, designed to start on petrol (gasoline) and then to switch to ...
s. It is seldom made or used today. In the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
and
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, after the
Second World War
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, it was commonly used for
tractor
A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most common ...
s until
diesel engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...
s became commonplace, especially from the 1960s onward. In
Australian English
Australian English (AusE, AusEng, AuE, AuEng, en-AU) is the set of varieties of the English language native to Australia. It is the country's common language and ''de facto'' national language; while Australia has no official language, Engli ...
it was known as power kerosene.
History
TVO existed for at least fifteen years before it became widely used. A 1920 publication mentions it as a product of
British Petroleum.
But it was not until the late 1930s that it first became widely used. The
post war
In Western usage, the phrase post-war era (or postwar era) usually refers to the time since the end of World War II. More broadly, a post-war period (or postwar period) is the interval immediately following the end of a war. A post-war period c ...
Ferguson TE20
The Ferguson TE20 is an agricultural tractor designed by Harry Ferguson. By far his most successful design, it was manufactured from 1946 until 1956, and was commonly known as the ''Little Grey Fergie''. It marked a major advance in tractor d ...
tractor, a carefully researched and near-ideal tractor for use on British farms, was designed around a
petrol
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
(gasoline) engine, the
Standard inline-four. Although there was a campaign for the reintroduction of agricultural Road Duty (tax)-free petrol, which had been curtailed during the war, this was not forthcoming.
Perkins Engines
Perkins Engines Company Limited, a subsidiary of Caterpillar Inc since 1998, is primarily a diesel engine manufacturer for several markets including agricultural, construction, material handling, power generation, and industrial. It was establis ...
supplied some conversions into diesel engines which could use untaxed
red diesel
Fuel dyes are dyes added to fuels, as in some countries it is required by law to dye a low-tax fuel to deter its use in applications intended for higher-taxed ones. Untaxed fuels are referred to as "dyed", while taxed ones are called "clear" or "w ...
.
On the early
Fordson
Fordson was a brand name of tractors and trucks. It was used on a range of mass-produced general-purpose tractors manufactured by Henry Ford & Son Inc from 1917 to 1920, by Ford Motor Company (U.S.) and Ford Motor Company Ltd (U.K.) from 1920 to ...
model N, the tap which changed over from petrol to TVO was marked G for gasoline and K for kerosene, reflecting that these tractors had their design origin in the USA. In the UK tractor vaporising oil was usually called TVO.
Octane rating
As a substitute for petrol, TVO was developed. Paraffin (kerosene) was commonly used as a domestic heating fuel and was untaxed. Paraffin has a low
octane rating
An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonating ...
and would damage an engine built for petrol. The manufacture of paraffin involves the removal of
aromatic hydrocarbon
Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...
s from what is now sold as
heating oil
Heating oil is any petroleum product or other oil used for heating; a fuel oil. Most commonly, it refers to low viscosity grades of fuel oil used for furnaces or boilers use for home heating and in other buildings. Home heating oil is often a ...
. These aromatics have an octane rating, so adding some of that otherwise waste product material back in a controlled manner into paraffin gave TVO. The resulting octane rating of TVO was somewhere between 55 and 70.
* pbv = parts by volume
The words paraffin and kerosene are often used interchangeably but the tables suggest that this is incorrect because they have different
octane rating
An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonating ...
s. However, kerosene and
heating oil
Heating oil is any petroleum product or other oil used for heating; a fuel oil. Most commonly, it refers to low viscosity grades of fuel oil used for furnaces or boilers use for home heating and in other buildings. Home heating oil is often a ...
have similar octane ratings. Paraffin, kerosene and petrol (
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
) are all rather loosely defined. For example, gasoline may have an octane rating between 88 and 102.
Engine modifications
Compression ratio
Because TVO has a lower
octane rating
An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonating ...
than petrol, the engine needs a lower
compression ratio
The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values.
A fundamental specification for such engines, it is measured two ways: the stati ...
. On the TVO version of the Ferguson TE20 tractor, the
cylinder head
In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber.
In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...
was re-designed to reduce the compression ratio to 4.5:1. This reduced the power output, so the
cylinder bore
In a piston engine, the bore (or cylinder bore) is the diameter of each cylinder.
Engine displacement is calculated based on bore, stroke length and the number of cylinders:
displacement =
The stroke ratio, determined by dividing the bore by ...
was increased to 85 mm to restore the power.
The
petrol version had a compression ratio of 5.77:1 and a cylinder bore of 80 mm on early versions..
Vaporiser
In practice TVO had most of the properties of paraffin, including the need for heating to encourage vapourisation. As a result, the
exhaust
Exhaust, exhaustive, or exhaustion may refer to:
Law
*Exhaustion of intellectual property rights, limits to intellectual property rights in patent and copyright law
**Exhaustion doctrine, in patent law
** Exhaustion doctrine under U.S. law, in p ...
and
inlet manifold
In automotive engineering, an inlet manifold or intake manifold (in American English) is the part of an engine that supplies the fuel/air mixture to the cylinders. The word '' manifold'' comes from the Old English word ''manigfeald'' (from th ...
s were adapted so that more heat from the former warmed the latter. Such a setup was called a
vaporiser. To get the tractor to start from cold, a small second fuel tank was added that contained petrol. The tractor was started on the expensive petrol, then – once the engine was warm – the fuel supply switched over to TVO or paraffin. So long as the engine was working hard, as when
plough
A plough or plow ( US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms are drawn by tractors. A plough may have a wooden, iron or ...
ing or pulling a load, the TVO would burn well. Under light conditions, such as travelling unloaded on the highway, the engine was better on petrol.
Radiator blind
Some tractor designs included a
radiator
Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics.
A radiator is always a ...
"blind" that would restrict the flow of air over the radiator which led to the engine running hotter, which could help with starting. If the radiator blind was left shut, though, there was a risk of engine damage, especially in warm weather.
Terminology
The phrase
petrol-paraffin engine
A petrol-paraffin engine, TVO engine (United Kingdom) or gasoline-kerosene engine (North America) is an old-fashioned type of dual-fuel internal combustion engine with spark-ignition, designed to start on petrol (gasoline) and then to switch to ...
is often used to describe an engine that uses TVO. This can be interpreted either as
:*the use of the two fuels, starting on petrol then switching to the paraffin-based TVO
:*the use of a mixture of petrol and paraffin as a substitute for the proper TVO
Supply
TVO was withdrawn from sale by UK suppliers in 1974. An approximation to the correct specification can be made from
petrol
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
and
heating oil
Heating oil is any petroleum product or other oil used for heating; a fuel oil. Most commonly, it refers to low viscosity grades of fuel oil used for furnaces or boilers use for home heating and in other buildings. Home heating oil is often a ...
(burning oil). In the UK there is an exception that permits the use of rebated kerosene and fuel oils in vintage vehicles.
North American distillate fuel
In North America a similar product, called
distillate
Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heat ...
, was produced. Of lower quality than TVO, its octane rating varied between 33 and 45. Manufacture of tractors using distillate ended by 1956, when gasoline and diesel-engined tractors had captured the North American farming equipment market.
Notes and references
{{Reflist
Petroleum products
Tractors
Fuels
Internal combustion piston engines