In other words: the propeller-pitch can be controlled by adjusting the blades. The blades can even be put in such a position that the sailing direction can be altered from ahead to astern.
The advantage of the C.P.P. is that the number of revolutions per minute (RPM) will remain constant, in spite of an increase or reduction of sailing-speed.
The engine will have a longer life, because it does not suffer from extensive wear that is normally caused by a constantly changing RPM.
The Shaft
The shaft consists of the propeller shaft, the intermediate shaft and the crankshaft. They are connected to each other by means of flanges.
The end of the propeller shaft is conical (tapered) to make it easier to mount the propeller. The intermediate shaft is a distance piece between the crank shaft and the propeller shaft. Bearing-blocks and thrust blocks support the shaft. Thrust blocks take up the propulsion forces of the screw and convey them to the hull of the ship.
ESSENTIAL PARTS OF A DIESEL ENGINE
The diesel engine is composed of the following parts:
Bedplate (engine frame) and crankcase.
These two parts make a supporting structure to hold the cylinders, crankshaft and main bearings. The crankcase serves as oil sump for the forced lubrication system.
Cylinders are made of cast iron. They are fixed to the frame by means of long through-bolts. The cylinders are provided with large removable inspection doors through which the cooling water spaces may be inspected and cleaned.
Cylinder covers (heads) close the top end of the cylinders.
Cylinder liners.
Piston and piston rings: The piston is made of steel, cast iron or special alloy which is highly resistant to heat stresses.
According to size, the piston is provided with piston rings to produce compression and scraper rings to prevent lubricating oil from penetrating into the combustion chamber.
Connecting rods. The connecting rod is made of steel.
The connecting rod connects the piston to the crank on the crankshaft. It transmits force in either direction from the piston to the crank on the crankshaft
The crankshaft is made of forged steel. It has bored ducts conveying the forced lubrication oil to all bearings.
Valves serve to admit the air and to discharge the exhaust gases.
The camshaft is of steel and is driven from the crankshaft through gear wheels.
The bearings are roller and ball bearings. The cams are of case hardened steel. The camshaft drives the fuel pumps, one for each cylinder.
The flywheel is a heavy wheel fastened to the crankshaft. Its purpose is to keep the engine running smoothly from the time of one power stroke to the next power stroke.
In double acting engines a crosshead and a piston rod are included.