Recipocating Engines Oral

They are classified according to cylinder arrangement with respect to the crankshaft (in-line, V-type, radial, and opposed), or according to method of cooling (liquid cooled or air cooled).

Compression rings, oil control rings, and scraper rings.

They are used to control the thickness of the oil film on the cylinder walls.

Excessive oil consumption

A master and articulating rod assembly

Plain bearings, which are generally used for crankshaft cam ring, camshaft, connecting rods, and accessory drive shaft bearings. Roller bearings, which are used primarily as crankshaft main bearings but have other applications, as well. Ball bearings, which are used for supercharger impeller shaft bearings, rocker arm bearings in some engines, and as propeller thrust bearings.

Valve blow-by is indicated by a hissing or whistle when pulling the propeller through, prior to starting the engine. A cylinder compression check should be made to identify the faulty cylinder.

A valve spring will resonate (or surge) at certain engine speeds. When the spring resonates, it loses its ability to keep the valve closed and the valve begins to float. By using two springs (different sizes, one inside the other) this problem is eliminated. The springs will resonate at separate engine speeds so the valve is always held closed by at least one spring.

Valve overlap permits better volumetric efficiency and lowers the cylinder operating temperatures.

They should be cleaned thoroughly and then visually inspected for evidence of overheating, cracks, broken ends, and for compression strength.

Some intake and exhaust valve stems are hollow and partially filled with metallic sodium.

Sodium is used because it is an excellent heat conductor. The sodium melts at about 208° F. and the movement of the valves circulates the liquid sodium which enables it to carry the heat from the valve head to the stem, where it is dissipated through the value guide to the cylinder head and cooling fins.

Striking an object or engine seizure due to internal damage

The propeller drive shaft must be checked for misalignment and the propeller checked for track.

Dampers are used to overcome forces that cause deflection of the crankshaft and torsional vibration. These forces are generated by the power impulses of the pistons. Crankshaft vibrations are reduced by placing floating dampers (weights) in the counterweight assembly, particularly in a single throw-type crankshaft.

Remove the propeller from the shaft and attach a dial indicator gauge to the front of the crankcase. Adjust the position of the gauge needle so that it is touching the shaft. Turn the engine through with the starter and note any changes in the gauge reading.

Normal combustion is when the fuel-air mixture burns at a uniform rate across the combustion chamber. The temperature and pressure within the cylinder rises at a normal rate as the mixture burns. All fuels have critical limits of temperature and compression, and beyond this limit, they will ignite spontaneously and burn with explosive violence. This instantaneous explosive burning of the last portion of the charge is called the detonation.

The valves must be depressed (unloaded) in order to remove the pressure from the side positions on the cam and thus permit the cam to slide away from the valves to be adjusted. This prevents the cam from introducing errors in the valve clearance settings.

From the cylinder compression check you can determine if the valves, piston rings, and pistons are adequately sealing the combustion chamber.

A cold cylinder check can be made with a cold cylinder indicator, sometimes called a "magic wand," to locate any cylinder that has a temperature lower than the normal operating temperature of the other cylinders.

A cylinder bore can be checked with a dial indicator, a telescopic gauge and outside micrometer, or an inside micrometer.