3TNE84 3TNE88 3TNV88 Diesel Engine Crankshaft 729120-21700 For Excavator PC30 PC35

Specification

Description

Bearing Pressures and Stresses in Crankshaft

The bearing pressures are very important in the design of crankshafts. The maximum permissible bearing pressure depends upon the maximum gas pressure, journal velocity, amount, and method of lubrication and change of direction of bearing pressure.

The following two types of stresses are induced in the crankshaft.

1. Bending stress

2. Shear stress due to torsional moment on the shaft.

Function of crankshaft

Most crankshaft failures are caused by a progressive fracture due to repeated bending or reversed torsional stresses. Thus the crankshaft is under fatigue loading and, therefore, its design should be based upon endurance limit. Since the failure of a crankshaft is likely to cause serious engine destruction and neither all the forces nor all the stresses acting on the crankshaft can be determined accurately, therefore a high factor of safety from 3 to 4, based on the endurance limit, is used.

They are responsible for transforming the linear motion of the piston into the rotational motion. This specific part of the engine is made with the process of forging the alloy of iron ore called steel.

While visually inspecting the crankshaft, you can find the rod bearings are nearly offset or eccentric. Here the offset of the shaft transforms the reciprocating motion (up and down) of the piston in the rotating motion of the crankshaft.

Most often the shaft is drilled with minute holes which feed the engine with the oil necessary for smooth operations. Sometimes, this mechanical part consists of counterweights which help in balancing the system and the weight of the connecting rod. It also ensures to balance the force while rotation of the moving parts.

Every engine is designed specifically and so is the crankshaft. Its design varies with the size and number of cylinders in the engine. Featuring an example, in a four-stroke engine, the crankshaft will have four crank throws. These throws connect the four pistons and are efficiently connected to the flywheel of the engine.

While driving the engine or during the combustion cycle the crank throw works as a lever arm, which pushes and pulls the piston. This considerably creates a successive rotational motion in the engine.

The crankshaft helps the piston to complete its rotation and the throw will return the piston at the top of the cylinder. This product needs very sleek designing while production with respect to its weights and balancing. Such engineering is necessary to reduce the vibrations in the engine. Such, vibrations can be very harmful to the vehicle and can even lead to major accidents.