Bulldozer modifications

Bulldozers have been further modified over time to evolve into new machines which are capable of working in ways that the original bulldozer can’t. One example is that loader tractors were created by removing the blade and substituting a large volume bucket and hydraulic arms which can raise and lower the bucket, thus making it useful for scooping up earth and loading it into trucks.

Other modifications to the original bulldozer include making it smaller to let it operate in small work areas where movement is limited, such as in mining. A very small bulldozer is sometimes called a calfdozer.

Nevertheless, the original earthmoving bulldozers are still irreplaceable as their tasks are concentrated in deforestation, earthmoving, ground levelling, and road carving. The heavy bulldozers are mainly employed to level the terrain to make it fit to construct on. The construction, however, is mainly done by small bulldozers and loader tractors.

Notes:

evolve – развивать

substitute – заменять

scoop – копать

calf – детёныш

Exercise 12. Translate the text with a dictionary in written form:

Text C

Continuous track

Continuous track, also called tank tread or caterpillar track, is a system of vehicle propulsion in which a continuous band of treads is driven by two or more wheels. This band is typically made of modular steel plates, or rubber reinforced with steel wires. The large surface area of the tracks distributes the weight of the vehicle better than steel or rubber tyres on an equivalent vehicle, enabling a continuous tracked vehicle to traverse soft ground with less likelihood of becoming stuck due to sinking. The prominent treads of the metal plates are both hard-wearing and damage resistant, especially in comparison to rubber tyres. The aggressive treads of the tracks provide good traction in soft surfaces but can damage paved surfaces. Special tracks that incorporate rubber pads can be installed for use on paved surfaces to prevent the damage that can be caused by all-metal tracks.

Modern tracks are built from modular chain links which together compose a closed chain. The links are jointed by a hinge, which allows the track to be flexible and wrap around a set of wheels to make an endless loop.

Agricultural and construction vehicles opt for a track with shoes that attach to the chain with bolts and do not form part of the chain's structure. This allows track shoes to break without compromising the ability of the vehicle to move and decreases productivity but increases the overall weight of the track and vehicle. Extra weight is an advantage when optimizing for traction and power over speed and mobility.

The vehicle's weight is transferred to the bottom length of track by a number of road wheels, or sets of wheels called bogies. Road wheels are typically mounted on some form of suspension to cushion the ride over rough ground.

Transfer of power to the track is accomplished by a drive wheel, or drive sprocket, driven by the motor and engaging with holes in the track links or with pegs on them to drive the track. A non-powered wheel, an idler, is placed at the opposite end of the track, primarily to tension the track, since loose track could be easily thrown (slipped) off the wheels. To prevent throwing, the inner surface of the track links usually has vertical guide horns engaging grooves, or gaps between the doubled road and idler or sprocket wheels.

Continuous tracks can be traced back as far as 1770 and today are commonly used on a variety of vehicles including bulldozers, excavators, tanks, and tractors, but can be found on any vehicle used in an application that can benefit from the added traction, low ground pressure and durability inherent in continuous track propulsion systems.

Notes:

opt for – выбирать

bogie – ходовая часть

Unit 8

Grammar:

Revision.

Exercise 1. Translate Text A with a dictionary and make its grammar analysis:

Text A