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| PULLEY EXAMINATION - QUESTION |
| V. Ryan © 2006-2017 |
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Pulley systems are used widely in industry and on
production lines. The power hacksaw shown below moves backwards and
forwards continuously, cutting metal. A basic drawing of this machine is
shown below.
The diagram has been divided into two sides - A and B
1. On side ‘A’ add a pulley system
that connects shaft 1 and 2 so that two different speeds can be
selected. USE NOTES AND SKETCHES
2. On side ‘B’ show how a single
pulley is held securely on to the shaft. USE NOTES AND SKETCHES |
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| POSSIBLE ANSWER |
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Two pulley wheels are added to shaft 2. They have
different diameters.
Changing to the large pulley slows down movement of the hacksaw.
Changing to the small pulley speeds up movement |
A cotter pin can be used. It is tapped through a
hole that runs through the pulley and the shaft, holding it firmly
together. |
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| 2b. Why are different speeds needed
for the power hacksaw needed? |
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| POSSIBLE ANSWER |
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| 2b. Why are different speeds needed
for the power hacksaw needed? |
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| Each type of metal has a particular speed at which it
can be cut efficiently. Choosing the wrong speed may damage the blade
and it may take longer to cut through the metal. |
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| 3. To make the power hacksaw safe to
use to ‘push to make’ (PTM) switches have been added. The incomplete
circuit below shows one of the switches in position. Complete the
circuit be adding the second switch. |
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| 3b. What is the colour of the ON
button of any machine? |
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| 3c. What is the colour of the OFF
button of any machine? |
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| 3b. What is the colour of the ON
button of any machine? |
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| POSSIBLE ANSWER |
| GREEN IS NORMALLY THE 'ON' BUTTON |
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| 3c. What is the colour of the OFF
button of any machine? |
| RED IS NORMALLY THE 'OFF' BUTTON |
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| 4. Why should the switches be placed
at least 500mm apart? |
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| POSSIBLE ANSWER |
| 4. Why should the switches be placed
at least 500mm apart? |
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| Placing the buttons 500mm apart means that both hands
of the operator must be used to turn the machine on. This means that the
operators hands cannot be near the saw blade. |
| 5. The drawing of
a new style of power hacksaw needs two types of switches - a foot switch
and a normal ON/OFF switch. Draw each switch in its best position on the
diagram and explain your reasoning with notes. |
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| POSSIBLE ANSWER |
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| POSITION OF FOOT SWITCH - EXPLANATION: |
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| POSITION OF NORMAL SWITCH - EXPLANATION: |
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| POSSIBLE ANSWERS |
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| POSITION OF FOOT SWITCH - EXPLANATION:
The operator
can stand at the front and watch the machine working. He/she can turn it
off using the foot switch without getting close to the moving blade. |
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| POSITION OF NORMAL SWITCH - EXPLANATION:
The operator
can stand at the side of the machine and switch it on, then move to a
more suitable position to watch it cut.
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