Farm Power & Machinery

Air cooling system

• In this type of cooling system, air is used as a medium for removing heat from engine to atmosphere. Air cooled engines are those engines, in which heat is conducted from the working components of the engine to the atmosphere directly. In such engines, cylinders are generally not grouped in a block. Air cooling is usually employed for light vehicles.
• Radial ribs or fins (Plate 5.1) are used to increase the external surface area of the cylinder. The length of these fins will be the greatest where the cylinder is the hottest, particularly near the cylinder head and will progressively reduce towards the crank case. Air-cooled engines are mounted on motorcycle frame. They are usually exposed to the surrounding atmosphere. They relay on natural air stream. Air circulates around the cylinders, head and crank case during forward movement of the vehicle.
  
  Plate : 5.1 A view of fins provided on the cylinder
• In some engines, the cylinder of an air cooled engine has fins to increase the area of contact with air for speedy cooling. The cylinder is normally enclosed in a sheet metal casing called Cowling. The flywheel has blades projecting from its face, so that it acts like a fan drawing air through a hole in the cowling and directing it around the cylinder fins. For maintenance of air cooling system, passage of air is kept clean. This is done by removing the cowling and cleaning out the dirt etc, by a stiff brush or compressed air. When separate fan is provided, the belt tension is to be checked and adjusted if necessary.

Advantages of air cooled engine
• It is simpler in design and construction.
• Water jackets, radiators, water pump, thermostat, pipes, hoses etc. are eliminated.
• It is more compact.
• Air-cooled engines operate well in both hot and cold climates.
• Air-cooled engines, rapidly reach their working temperature from cold.
• Air cooling is natural cooling and it is free from corrosive products.
• This system is more reliable and less maintenance is required.
• Air-cooled engines can operate at higher working temperatures than equivalent liquid cooled.
• Air cooled engines have no coolant leakage (or) problems.
• It is comparatively lighter in weight.

Disadvantages of air cooled engine
There is uneven cooling of the engine parts.
Each cylinder has to be cast individually. Fin design and casting is difficult.
Used only in small engines provided in brush cutter and weeder engines, portable engines, lawn mower engines, etc.,