Small personal hovercraft are fast becoming the expensive preferred toy of the younger set with enough money to enjoy themselves. A world class hover craft manufacturer will charge between 10000 and 15000 USD for such an air cushioned vehicle, depending on the options chosen. Such options may include a choice of engines, color (obviously) and additional features such as extra storage space, harnesses or short wave radio. Engine choice is an important point to consider before you buy a hovercraft.
Two stroke engines are common. These tend to be noisier and run at higher revolutions than their four stroke cousins and the fuel used is different. A two stroke hovercraft engine uses a lower octane mixture of gas (petrol) mixed with 2% oil. Basically, this means that the engine parts are lubricated by the oil mixed in with the fuel. A disadvantage of this is that the fuel needs to be mixed yourself, or either bought ready to use, which is expensive. The big advantage is that a two stroke engine is generally cheaper pound for pound, but is also noisier, particularly when used for lift and forward thrust applied to an ACV.
A four stroke motor has an oil reservoir, or sump, which is kept to a certain level and a pump moves it around the engine to ensure that all moving parts don't wear too much. Actually, the moving parts of an engine should never touch - a film of oil always separates their surfaces. A four stroke engine may be air or water cooled, depending on the size of the craft and it's intended use. Such uses can include leisure, rescue and survey operations both on dry land and over water.
The best hovercraft manufacturers design an engine compartment as part of the hull construction. This keeps the engine a little quieter and it's also safer in the event that it malfunctions, for example. A robust lid gives good access for maintenance and this can be locked securely until access is required. With clever hovercraft design, such a compartment could be sunk a little into the hull material without compromising it's impact strength, thereby optimizing space for passengers and equipment.
Smaller vehicles tend to use just one motor and ducting is used to redirect air flow downwards for upwards thrust, and to the rear for forward propulsion. It's obvious that a two motor machine will have more power for lift and thrust, and this may be necessary for machines designed for a heavy payload, or regularly lifting off water. However, such an arrangement will inevitably mean more noise and ear protection is recommended for all the family.
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