VI. Find the equivalents to the following word combinations.

1. Dig longitudinal cuts a) передвигаться слишком быстро

2. To shape slopes b) многоковшовый экскаватор

3. Longitudinal multi-bucket excavator продольного копания

4. Cross cutting multi-bucket excavator c) гусеничный, пневмоколесный

или рельсовый ход

5. Travel too fast d) профилировать откосы

6. Crawler, air-tired or rail track e) копать продольные выемки

f) многоковшовый экскаватор

поперечного копания

VII. Read and translate the following text.

MULTI-BUCKET EXCAVATORS

Multi-bucket excavators (Fig.7) are employed to dig longitudinal cuts (trenches, ditches) and to shape their slopes. It should be noted that some types of multi-bucket excavators can be used to excavate mineral resources or strip capping in baring operations. When digging soil with stony inclusions, the excavator will operate normally if the size of these inclusions does not exceed 0.25 of the bucket width.

a) Excavator mounted on a wheel tractor

b) Chain excavator with an inclined frame

Fig. 7. Multi-bucket excavators

Multi-bucket excavators can be classified by:

1. the design of the operating equipment: chain-type and wheel- or rotary-type;

2. the method of excavation: longitudinal cutting multi-bucket excavators and cross cutting multi-bucket excavators;

3. the type of drive: with internal combustion engine and mechanical power train, with mains-powered electric motors, with diesel-electric power plant;

4. the size: trench excavators are differentiated by the cutting depth, chain quarry excavators by the capacity of the buckets, and wheel excavators by the hourly output.

Chain excavators make trenches for cables, sewerage pipes, etc., to a depth of 6 meters and a width of 2 meters.

Wheel excavators are widely used to excavate trenches up to 2.5 meters deep and 2.6 meters wide for gas and oil lines.

Chain excavators may have an inclined or vertical bucket frame. The bucket frame is lifted and lowered by a winch and a system of cables and pulleys. When a chain excavator begins to operate, its inclined frame is lowered onto the ground and its buckets gradually bite into the soil.

It should be pointed out that if the excavator travels too fast or the bucket chain moves too slowly the buckets will be under-loaded or, in the opposite case, spill some of the material.

The vertical frame of the trencher is raised and lowered by a chain and a hoist. A small conveyer is mounted inside the bucket frame. The buckets are dumped forward in the direction of motion onto the conveyer. The bucket chain is driven by the engine through the reduction gear.

Wheel excavators are more wear-resistant than chain-type excavators. They also have a greater capacity, although they can dig trenches no deeper than 2.5 meters. Wheel excavators are generally mounted on air-tired 35 hp tractors or on crawler tractors with engines rated at 55 and 100 hp.