Roller chains

A roller chain or a bush roller chain is the type of chain most commonly used for transmission of mechanical power. It is simple, reliable, and efficient, but requires more attention to maintenance than may be desired by potential owners; therefore there has been a tendency towards the use of other modes of power transmission, such as a timing belt. Though Hans Renold invented a roller chain in 1880, sketches by Leonardo da Vinci in the 16th century show a chain with a roller bearing.

The roller chain design reduces friction compared to simpler designs, resulting in higher efficiency and less wear. The original power transmission chain varieties lacked rollers and bushings, with both the inner and outer plates held by pins which directly contacted the sprocket teeth; however this configuration exhibited extremely rapid wear of both the sprocket teeth, and the plates where they are pivoted on the pins. This problem was partially solved by the development of bushed chains, with the pins holding the outer plates passing through bushings or sleeves connecting the inner plates, thus distributing the wear over a greater area; however the teeth of the sprockets still wore more rapidly than is desirable from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of the chain and providing rolling contact with the teeth of the sprockets provided excellent resistance to wear of both sprockets and the chain as well as very low friction, provided that the chain is sufficiently lubricated.

Notes:

maintenance – эксплуатация, уход, текущий ремонт

sprocket – цепное или зубчатое колесо

sleeve – муфта, втулка

Unit 5

Grammar:

Participle;

Absolute Participle Construction.

Exercise 1. Work out the following sounds

[x] track, latter, travel, flat, caterpillar

[eI] crane, rail, main, make, stationary

[e] many, heavy, self, metal, them, overhead

Exercise 2. Match the transcription to the words given below and define their meanings:

1. ['steISqnqrI]	1. extremely	1. шина
2. ['krLlq(r)]	2. gantry	2. портальный кран
3. [kqn'strAkS(q)n]	3. site	3. удельный
4. [Ik'strkJmlI]	4. tyre	4. строительный участок
5. [rI'mRkqb(q)l]	5. crawler	5. крайне
6. [spI'sIfIk]	6. stationary	6. гусеница
7. ['gxntrI]	7. construction	7. башня
8. ['taVq(r)]	8. remarkable	8. строительство
9. [taIq(r)]	9. specific	9. неподвижный
10. [saIt]	10. tower	10. отличающийся

Text A

Running gear

Cranes, power shovels and many other machines used in construction have to move during operation or when travelling to the site of work. Movement is the principal kind of functional operations of trucks, crawler and wheel tractors, self- propelled and towed equipment.

Machine running gear can be classified into rail and trackless, the latter being further subdivided into crawler- mounted and walking.

Machines that travel on rails are: railway jib cranes, self- dumping flat cars (dumpcars), tower building cranes, overhead and gantry cranes, monorail telphers, etc.

Crawler traction is remarkable for its small specific pressure on the ground. It is used mainly in the absence of roads, when high speeds of travel are not important. Crawler tracks are used in tractors, power shovels and different types of road- making machinery.

Wheel traction is most universally used when passability is of secondary importance. This type of running gear may be designed with rigid metal wheels or air tyres. Rigid wheels are employed for stationary machines, where wheels are needed only to move them over short distances.

Tyre-mounted wheels are the main type of trackless running gear.

Walking gear ensures a still lower specific pressure on the ground than caterpillar traction and can sustain besides very heavy vertical loads. It operates, however, at an extremely low speed. It finds application only in large power shovels.

Exercise 3. Answer the following questions:

1. What equipment has to move during operation?

2. What kinds can the machine running gear be classified into?

3. What machines travelling on rails do you know?

4. Where are crawler tracks used?

5. When is wheel traction most universally used?

6. What wheels may this type of traction be designed with?

7. What does walking gear ensure?

Exercise 4. Translate the following words into Russian:

Running gear, site, crawler, tow, equipment, rail, trackless, walking gear, jib crane, self-dumping, dumpcar, tower crane, overhead crane, gantry crane, monorail telpher, traction, tyre, caterpillar, stationary, employ, power shovel, sustain, rigid, be remarkable for, than, over, besides, however.

Exercise 5. Translate from Russian into English:

Гусеница или гусеничный ход, ходовая часть, шина, строительный участок, тяга, буксировать, выдерживать, монорельсовый тельфер, жесткий, оборудование, портальный кран, рельс, мостовой кран, отличаться, безрельсовый, башенный кран, шагающее ходовое оборудование, опрокидывающаяся вагонетка или думпкар, кран-укосина, самоопрокидывающийся, неподвижный, использовать, экскаватор.

Exercise 6. Match the following words (A) with their definitions (B):

«A»

1. site

2. tow

3. dumpcar

4. tyre

5. dump

6. crane

7. equipment

8. specific

9. stationary

10. rigid

«B»

1. fixed, determined

2. a vehicle with a large movable container, used for carrying and emptying heavy loads

3. not easy to bend

4. to pull along by a rope or chain

5. standing still, not moving

6. a band of rubber, solid or filled with air that fits round the outside edge of a wheel

7. a set of things needed for a particular activity

8. a machine with a long movable arm, used for lifting and moving heavy objects

9. to drop or unload any material

10. a piece of ground for building on

Exercise 7. Form Participle 1 and Participle 2 and translate them according to the following patterns:

do:

P1 – doing – делающий, делая;

P2 – done – сделанный.

use:

P1 – using – использующий, используя;

P2 – used – использованный, используемый.

Attach, achieve, break, build, deliver, design, dig, drive, excavate, improve, know, mount, read, say, transmit, take, write.

Exercise 8. Define the functions of Participles and translate the following sentences:

1. People have used machines since early times.

2. They are installing the most modern equipment at their plant.

3. Gears transmit motion between a shaft and a component having linear motion.

4. Gears of different sizes are often used in pairs for a mechanical advantage, allowing the torque of the driving gear to produce a larger torque in the driven gear at lower speed or a smaller torque at higher speed.

5. When used in sets pulleys reduce the amount of force needed to lift a load.

6. If specially designed belts and pulleys transmit power between two points.

7. The demands for a belt drive transmission system are large and this has led to many variations.

8. The V-belt tends to wedge into the groove as the load increases, improving transmission and making the V-belt an effective solution.

9. Large cranes are being produced at our plant now.

Exercise 9. Translate the following sentences, paying attention to Absolute Participle Construction:

1. Loads being of different types, builders use various handling equipment for their transportation.

2. The piston goes forward, the wheel making half a turn.

3. The structure being very high, the builders used giant cranes.

4. The crane was used at the construction site, its lifting capacity being up to 50 tons.

5. The crane having been dismantled, the workers transported it to another place of work.

6. Steam was heated, its pressure becoming higher.

Exercise 10. Translate the following sentences paying attention to ed- forms:

1. The builders lifted concrete blocks by means of hoisting equipment.

2. The blocks lifted by hoisting equipment weighed up to 400 lb.

3. The blocks were lifted by means of hoisting equipment.

4. When lifted by the crane the blocks were carefully positioned.

5. They have already lifted the blocks.

6. A machine can be lifted with various attachments.

7. The framework mounted on a turntable supports the lifting mechanism.

8. A transfer box with high/low range produced a total 10 speeds in either direction.

9. If heated the mixture explodes.

10. The engineers had finished testing the device by the end of the week.

Exercise 11. Analyze the sentences underlined in Text A. Find Participles and define their function. Find the sentence with the Absolute Participle Construction and translate it properly.

Exercise 12. Translate the text without a dictionary:

Text B