Construction Machinery Essentials: Types & Functions
Bulldozers: Types and Applications
Bulldozers are powerful earthmoving machines designed for pushing, digging, and ripping. They feature a robust blade at the front for various tasks.
Bulldozer Blade Types
- Straight Blade Dozer: Features a rigid blade perpendicular to the tractor. Very rigid and compact.
- Angledozer: Equipped with a slender, leaf-shaped blade that angles to the direction of travel, offering less rigidity than a straight blade.
- Tiltdozer: Features a blade with vertical tilt. Useful for digging on sloping land or concentrating all efforts on a specific spot by maximizing digging force.
Blade Characteristics
- Box-shaped Blade: Wider than the tractor and curved to turn material. Can be raised or lowered, pushing earth in shallow depths and over short distances (50-60m).
- Bulldozer Blade Profiles:
- Reduced length, greater height, accumulating more material. Often features an upper curve.
- Available in Semi-U or U-shaped configurations.
- Angledozer Blade Profiles: Increased upper curvature, more stylized.
Bulldozer Applications
Bulldozers are used for pushing, scratching, ripping, assisting scrapers, and helping to push wheel loaders.
Ripper Attachment
An accessory for tearing land, typically mounted at the rear. Available with 1, 2, or 3 shanks.
Loaders: Material Handling & Transport
Loaders are essential machines for loading and transporting materials over short distances, primarily utilizing hydraulic systems.
Loader Types
- Crawler Loaders: More stable on leveled, rocky, or muddy terrain. Speed up to 10 km/h, requiring special transport for longer distances.
- Pneumatic Loaders (Wheel Loaders): Feature 4-wheel drive and articulated chassis for improved stability and maneuverability.
Loader Components
Key components include an articulated arm, linkage, a bucket, and cutting edge teeth.
Loader Performance Parameters
- Tipping Load:
- Static (Stop and Horizontal): Maximum load the machine can handle while stationary.
- Dynamic (Movement at 6.5 km/h): Load must not exceed 50% of the static tipping load.
- Hydraulic Lift Capacity: Measured with the machine anchored and stabilized.
- Breakout Force: The lifting force at the edge of the bucket.
- Dump Height: The maximum height at which material can be discharged.
Loader Bucket Types
Buckets vary according to use and terrain. Mouth size is a factor: a greater width may reduce breakout force.
- General Purpose Buckets: Available in various widths with a straight profile. Designed for optimal capacity to store materials.
- Rock Buckets: Feature a straight or V-shaped profile, built for durability in demanding rock applications.
Hydraulic Excavators: Precision Digging
Hydraulic excavators are versatile machines designed for digging, lifting, and moving earth with precision.
Hydraulic Excavator Parts
- Chassis and Running Gear Components: The base and tracks/wheels for movement.
- Superstructure: The upper part connected to the chassis for translation via the turntable.
- Cab: Operator’s station.
- Diesel Engines: Power the machine.
- Hydraulics: Flow offset ensures maximum power is directed where needed, allowing simultaneous movements even when the engine works at low RPMs. Acting on valve levers sends pressurized oil to the corresponding cylinders to move the bucket, stick, excavator arm, and stabilizers.
- Turntable: Made up of ring gears: the lower, fixed to the chassis for translation, and the upper, or pinion, fixed to the superstructure.
Hydraulic Excavator Equipment
- Boom Types:
- One-Piece (Monoboom): Standard configuration.
- Two-Piece Boom: Offers greater maneuverability and is ideal for deep excavation.
- Arm Lengths: Standard, short, or long arms are available to suit different reach and digging depth requirements.
- Bucket Types: Equipped with teeth and blades. Available in normal, narrow, scarifying, trapezoidal, sand, and embankment configurations.
Backhoe Loaders: Versatility on Site
A backhoe loader is a self-propelled wheeled machine with a particular frame designed to mount both a front loader and a rear backhoe, allowing them to be used interchangeably.
Backhoe Loader Operation
- As an Excavator: The machine normally digs below ground level with bucket motion towards the machine, then raises, collects, transports, and discharges material while the machine remains stationary.
- As a Loader: It loads or excavates through displacement and movement of arms, then lifts, transports, and discharges material.
Backhoe Loader Types
- Rigid Frame, Traction on Both Axles and Steerable Axles: Offers robustness and stability, easy operation, and good torsional rigidity.
- Articulated Frame, Traction on Both Axles: Provides maximum maneuverability, making it ideal for small spaces.
- Rigid Frame, Traction and Steering on Both Axles (AWS: All Wheel Steer): Offers robustness and stability for both front and rear attachments. Good torsional rigidity. Provides the smallest turning radius among rigid chassis units with front steering.
Land Transportation Equipment
Specialized vehicles for moving materials across construction sites and other terrains.
- Articulated Dump Trucks (Autovolquetes): Capacities typically 1-3 tonnes, 0.5-1.8 m³ (front or side tipping).
- Work Trucks (Rigid Dump Trucks): Often with capacities around 15 tonnes.
- Heavy-Duty Dump Trucks (Rigid Haul Trucks): Larger capacities, typically 12-32 tonnes.
- Container Carriers: Vehicles designed for transporting shipping containers.
Compactors: Soil & Material Density
Compactors are self-propelled or towed machines on wheels, rollers, or masses, designed to increase material density through various methods.
Compaction Methods
Compaction is achieved through: static weight, impact, vibration, kneading (dynamic pressure), or a combination of these effects.
Compaction Systems
- Static Compaction: Achieved primarily by the machine’s weight.
- Dynamic Compaction: Achieves compaction through the machine’s weight combined with vibration.