Drives, Hydraulics & Specialized Operations
Hydrostatic drive, articulated steering, hydraulic cavitation, positive air shutoff, gradeability, and bucket shock loading.
- Explain hydrostatic drive systems and their advantages
- Describe articulated steering and frame pivot systems
- Identify causes of hydraulic cavitation and its effects
- Explain positive air shutoff, gradeability, and bucket shock loading prevention
Leçon 1
Drive Systems & Hydrostatic Transmission
What is Hydrostatic Drive?
A hydrostatic drive is a hydraulic pump and motor drive system allowing variable speed and reverse without a conventional transmission. The engine drives a variable displacement hydraulic pump, which sends pressurized oil to hydraulic motors at the wheels or tracks. By changing the pump's displacement, the operator controls speed and direction smoothly and infinitely.
Hydrostatic Drive
Variable speed - infinite speed range
Smooth reversal - no gear shifting
Dynamic braking - pump provides braking
Common on: skid steers, compact loaders, dozers
Powershift Transmission
Fixed gear ratios - discrete speeds
Clutch shifting - under load
Higher efficiency at travel speeds
Common on: wheel loaders, haul trucks
Advantages of Hydrostatic Drive
Hydrostatic drives provide precise speed control, the ability to change direction without stopping, and inherent dynamic braking. When the operator releases the drive control, the pump stops sending oil and the motors resist movement, slowing the machine. This is especially useful on slopes and in tight working conditions.
Primary Cause of Rollovers
The primary cause of equipment rollovers includes operating on slopes improperly, speeding, and turns with raised loads. All drive system types are subject to rollover - the key prevention factors are proper speed, low center of gravity, and respect for slope limitations.
Hydrostatic Drive Benefit
Hydrostatic drives provide dynamic braking when the drive control is released. The pump stops flow and the motor resists movement, providing built-in deceleration.
A hydrostatic drive uses a hydraulic pump and motor for infinitely variable speed and smooth reversal. It provides dynamic braking when the drive control is released.