11.1 FIGURE 11.1 below shows a hydraulic lift. The lift needs to raise a maximum load of 4 500 kg at the ram with a diameter of 120 mm. The diameter of the plunger is 32 mm. Answer the questions that follow. Calculate the following: 11.1.1 The fluid pressure in the hydraulic system in MPa 11.1.2 The force to be applied on the plunger (5) 11.2 State ONE function of a hydraulic non-return valve. 11.3 Give TWO reasons why a spring-loaded double-action control valve is used in a water line. 11.4 Name the TWO different types of pressure gauges. 11.5 A pulley with a diameter of 375 mm is mounted on a shaft of a concrete mixer. The concrete mixer is driven by a pulley, with a diameter of 85 mm, on a motor which rotates at a speed of 1 320 r/min. The tensile force of the belt in the tight side is 275 N and the slack side is 120 N. HINT: The belt thickness may be ignored. Calculate the following: 11.5.1 The rotational frequency in r/s of the pulley on the concrete mixer 11.5.2 The power that can be transmitted in watt 11.6 FIGURE 11.6 below shows a gear drive system. Driver gear A meshes with driver gear B with 20 teeth on a counters shaft. The driver gear, C, with 45 teeth on a second counters shaft. On the second counters shaft is another gear, E, with 50 teeth that meshes with the gear D, which has TA = 20 teeth. If the input shaft is 320 r/min and the rotational frequency of the output shaft is 720 r/min. Answer the questions that follow. Calculate the following: 11.6.1 The number of teeth on the driver gear TA. 11.6.2 The gear ratio of the system.

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11.1 FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

Question 11

11.1 FIGURE 11.1 below shows a hydraulic lift. The lift needs to raise a maximum load of 4 500 kg at the ram with a diameter of 120 mm. The diameter of the plunger i... show full transcript

Worked Solution & Example Answer:11.1 FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

Step 1

The fluid pressure in the hydraulic system in MPa

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Answer

To calculate the fluid pressure in the hydraulic system, we use the formula:

$P = \frac{F}{A}$

Where:

$F = 4500 \text{ kg} \times 10 \text{ m/s}^2 = 45000 \text{ N}$
The area $A$ of the ram can be calculated using:

$A = \frac{\pi d^2}{4}$

Substituting the diameter of the ram, $d = 120 \text{ mm} = 0.12 \text{ m}$ :

$A = \frac{\pi (0.12)^2}{4} = 0.01131 \text{ m}^2$

Now, substituting this value into the pressure formula:

$P = \frac{45000}{0.01131} \approx 3978.5 \text{ N/m}^2 = 3.98 \text{ MPa}$

Step 2

The force to be applied on the plunger

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Answer

To find the force to be applied on the plunger, we can use the same principle but for the plunger area:

$A_{plunger} = \frac{\pi (0.032)^2}{4}$

Calculating this:

$A_{plunger} = \frac{\pi (0.032)^2}{4} \approx 0.000804 \text{ m}^2$

Now we can calculate:

$F = P \times A_{plunger} \approx 3.98 \times 10^6 \, \text{N/m}^2 \times 0.000804 \, \text{m}^2 \approx 3184 \text{ N}$

Step 3

State ONE function of a hydraulic non-return valve.

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Answer

A hydraulic non-return valve is used to provide one-directional oil flow and prevent the fluid from flowing back.

Step 4

Give TWO reasons why a spring-loaded double-action control valve is used in a water line.

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Answer

To protect water supplies from back flow.
To prevent water contamination in case one valve gets jammed.

Step 5

Name the TWO different types of pressure gauges.

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Answer

Bourdon tube gauge.
Schrader gauge.

Step 6

The rotational frequency in r/s of the pulley on the concrete mixer

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Answer

To find the rotational frequency, we can use:

$N = \frac{N_{motor} \times D_{motor}}{D_{pulley}}$

Given:

$N_{motor} = 1320 \text{ r/min}$
$D_{motor} = 0.085 \text{ m}$
$D_{pulley} = 0.375 \text{ m}$

Substituting, we first convert $N_{motor}$ to r/s:

$N = \frac{1320}{60} \approx 22 \text{ r/s}$

So,

$N = \frac{22 \times 0.085}{0.375} \approx 4.99 \text{ r/s}$

Step 7

The power that can be transmitted in watt

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Answer

The power transmitted can be calculated using:

$P = \frac{(T_{tight} - T_{slack}) \times \pi D \times N}{60}$

Where:

$T_{tight} = 275 \text{ N}$
$T_{slack} = 120 \text{ N}$
$D = 0.085 \text{ m}$
$N = 22 \text{ r/s}$

Calculating gives:

$P = \frac{(275-120) \times \pi \times 0.085 \times 1320}{60} \approx 911.59 \text{ W}$

Step 8

The number of teeth on the driver gear TA

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Answer

To find the number of teeth on driver gear A ( $T_A$ ), we can set up the equation:

$N_{input} = \frac{T_A \times T_E}{T_B \times T_F}$

Given:

$N_A = 320 \text{ r/min}$
$N_F = 720 \text{ r/min}$
$T_B = 20, T_E = 50, T_F = 20, T_C = 45$

We solve for $T_A$ :

$T_A = \frac{720 \times 20 \times 25}{320 \times 45} = 10$

Step 9

The gear ratio of the system

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Answer

Gear ratio can be calculated as:

$\text{Gear ratio} = \frac{\text{Product of the number of teeth on driven gears}}{\text{Product of the number of teeth on driving gears}}$

In our case: $\text{Gear ratio} = \frac{20 \times 25 \times 50}{10 \times 45 \times 20} = 0.44$

11.1 FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

Worked Solution & Example Answer:11.1 FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

The fluid pressure in the hydraulic system in MPa

The force to be applied on the plunger

State ONE function of a hydraulic non-return valve.

Give TWO reasons why a spring-loaded double-action control valve is used in a water line.

Name the TWO different types of pressure gauges.

The rotational frequency in r/s of the pulley on the concrete mixer

The power that can be transmitted in watt

The number of teeth on the driver gear TA

The gear ratio of the system

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