The pressure load is the amount of measured force directed at and from a reversing mechanism. For example, since the mechanism of a gear rotates on a shaft, it is both the load released from the gear in the direction it strikes as well as against the shaft it turns on, either forwards or backwards. In a typical mechanical installation, the bearing will not only provide a surface for equipment to sit on, it will also provide a surface for pressing against and thus dampening pressure load. A typical shaft that houses rotating components will usually have a measured amount of tolerance machined in to provide a certain amount of pressure load clearance.
Within a conventional car engine, a rotary unit consisting of a crankshaft, pistons and piston rods acts in a rotating manner. The crankshaft is mounted in the engine block and rides inside the main bearings. The bearings not only provide a smooth surface for the crankshaft to spin, but they also provide a surface to absorb and cushion pressure loads. As the pistons drive the crankshaft around its axis, it also attempts to be driven toward the rear of the engine block. A special main bearing, known as axial bearing, contains sides which contact an area machined on the crankshaft to cushion pressure load.
The distance pre-set into the jaw bearing is achieved by prying or knocking the crankshaft in both front and rear directions before pulling down to the main bearing cover. When the cap is tightened properly, a sensor blade is pushed between that side of the pressure bearing and the crankshaft and the amount of clearance is measured. If the amount of clearance is sufficient to protect against pressure load damage, the cap can be tightened to torque to its final specifications. Failure to set the pressure load bearing will damage the engine and possibly damage transmission. It is important to use only a dead blow, brass or lead hammer when tapping the crankshaft back and forth to prevent crankshaft damage.
When investigating the causes of premature pressure load bearing failure, there are a few places to start. The initial thrust setting should be verified to ensure proper stock pre-load was completed. The main bearings should be checked to confirm that everyone is torqued properly and the main caps are in the correct position on the main halls. The crankshaft should be examined and checked to make sure it is straight; a bent crankshaft can affect the pressure load in any engine.
- In a car engine, a rotary unit consisting of a crankshaft, pistons and piston rods acts in a rotating manner.