What are the horses doing in the fiscal horses of a vehicle?


Before the advent of the industrial revolution, the horse was not only used to pull omnibuses or plows. It will give way to the steam engine in all workshops and eventually, even in the countryside. Steam horse, tax horse, this is how the power of a vehicle is still calculated with reference to this noble animal.

The invention of a Scottish engineer: James Watt?

While in 1771, Joseph Cugnot, a military engineer with a brain teeming with ideas and innovation, created the first motor vehicle. Unfortunately, its cart designed to transport the cannons will never be used due to lack of funding. The Scottish engineer James Watt, on the other side of the Atlantic, in 1780, also proposed a steam engine intended for industrialists. In 1879, man’s greatest conquest was also used to tow motor vehicles, Parisian transport, raise water from wells and transport carts of coal to the bottom of the mines. In order to market it and above all convince manufacturers of the efficiency of his machine, he decides to compare it to the strength of the draft horse.

The birth of horse power

To give weight to his invention and prove its effectiveness, he chose to calculate the power necessary for the animal to turn a grain mill. In England, the metrics are not the same as in France, since we speak of pounds for weight and feet for distances. By adding the distance, James Watt wrote the equation which would give rise to horse-power or hp. The latter would later become the watt, a unit of measurement of power which is equivalent to the work of one joule per second.

Different metrics give rise to horsepower around the world

While most countries in the world, Europe and France use the metric system, it was necessary to convert the horse-power — now watt — to our metric system. In order to calculate the power developed by steam engines, then the power of our combustion engines and our electric motors, a definition is agreed. The horsepower will choose as a unit the force released by the animal to raise a mass of seventy-five kilograms over one meter in one second. We add to this clever calculation the value of the newton, or 9.81 m/s/s. In our metric system, the final equation to calculate the power of a motor will be: 1 s x 75 kg x 9.81 m/s/s.

The tax horse, an arbitrary assessment of the power of an engine for calculating tax

The tax horsepower determines the theoretical power of your vehicle’s engine and has nothing to do with the power expressed in DIN, which corresponds to the horsepower of your automobile, expressed in kilowatts.

The tax power is used to calculate the tax rate, the tax and the cost of your vehicle registration in France, Belgium, Germany, Italy and Great Britain. The fiscal horse or CV therefore no longer has anything to do with the mechanical power of the engine under your hood. This administrative value is intended to determine the tax applicable for vehicle registration. However, the CV tax of your car takes into account the actual power of its engine in kW, its type and its approval date to calculate the amount of the registration document.

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