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8/7/2019 labbbbbbbb mechaniccccc

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1. Title of the presentation

Report of Bearing (LAB 05)

2. Theoretical Fundamental

Broadly speaking, there are two main types of bearings: 1.) the plain bearing which producessliding friction between the cylindrical surfaces of the shaft and the bearing and, 2.) the balland roller bearing which produce rolling friction between the hard steel balls (or rollers) andthe surface in contact.

All bearings absorb power due to friction. Therefore, lubrication plays an important role inreducing the power losse s (particularly for plain bearings). Nevertheless, lubrication by oil isnot always convenient.

The objective of this experiment is to compare the resistance of bearing to turn, due tofriction. Four cantilevered bearing (of different type of materials) are used in this experiment.

3. Experiment set-up

Apparatus

ApparatusQuantity

/SpecificationFigure

Mounting panel 1 NIL

Bearing assembly 1

Knurled nuts 2

Weight hooks 2

Weights 1 set NIL

Cord approximately 550 mmlong

1

Figure 1: Experiment Setup


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4. Experiment Procedure

4.1 Preparation

1. The mounting panel were secured in the vertical position.

2. The bearing assembly were secured to the mounting panel as shown in Figure 1.

4.2 Test 1 (Wood and steel)

1. Cord are taken and made one completed turn around the left pulley.

2. The end of the cord was hung downwards. A weight hook was attached to each end andeach weight hook was added to 1N.

3. The additional weight overcomes the friction in the bearing by added weight to one of theweight hooks and the weight on the other end of the cord was raised slo wly(to helpovercome the effect of static friction by tapping the panel slightly. )

3. Required to turn the shaft in the bearings, Weight (W) were recorded. The pulley weresupported by the weight, weight hooks (0.4N) are included.

4. Weights of 2N, 4N and 5N on both weight hooks are repeated.

4.3 Test 2 (Brass and steel)

1. Steps as in Test 1 are repeated using the next bearing at the right hand side (the cordaround the pulley not turn completely instead, simply hung the cord over the pulley).

4.4 Test 3 (Self-lubricating bronze and steel)

1. Steps as Test 2 repeated using the next bearing at the right hand side.

4.5 Test 4 (Ball bearing)

1. Steps as in Test 2 repeated using the next bearing at the right hand side.


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5. Results

Table 1: Weight of loads, Wand the force needed to move them, F.

Weight, W(N)Force to move the Weight, F(N)

Test 1 Test 2 Test 3 Test 4

1 N 12 2 2 1

2 N 13 3 3 2

4 N 16 4 4 4

5 N 20 6 6 5

Comparison of the slope of each test:

1. Test 1 (Wood and steel) got the highest gradient compare to the whole test.2. Test 4 (Ball bearing) got the lowest gradient compare to the other test.3. Test 2 (Brass and steel) and test 3(self -lubricating bronze and steel) have the same

gradient.


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6. Summary

Discussions

1. What are the comparative frictional characteristics of each bearing?

Wood and steel bearing posses highest frictional characteristics compare to others.

2. What is the fundamental difference between plain bearing and ball bearing?

Plain Bearing Ball Bearing

Use surfaces in rubbing contact oftenwith a lubricant such as oil or graphite

Uses balls to maintain the separationbetween the moving parts ofthe bearing .

3. How can friction be reduced on plain bearings?

Can be reduced by virtue of its shape, by its material, or by introducing and containing afluid between surfaces or by separating the surfaces with an electromagnetic field.

4. Self-lubricating bearings are frequently used on electric motors. Can you explain whythey are more preferred than bearings that require lubrication?

The bearings has excellent compressive strength, wearability and is shock resistant.

Conclusions

Wood and steel bearing is hard to make the pulley turn which the cord have one completedturn and required a high weight to make the turn compare to the other .

The cord around the pulley that not makes one completed turn for example Brass and Steel

bearing and Self-lubricating bronze bearing and steel is easy to turn it and there required aaverage weight to make the turn.

Ball bearing is the easiest and posses the minimum weight to make the pulley turn.

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