The objective of this experiment is to make a comparison between the efficiency of

different bearing materials by determining the resistance of friction to rotation. The bearing

materials which are being used in this experiment are tufnol, cast iron and ball bearing. The

fundamental device comprises of single flywheel on a horizontal shaft which both closures

will be connected with the center section of testing bearings. A weight load is hang up on the

shaft of flywheel by using string The amount of weight load which required for each bearing

material to initiate rotation of flywheel at constant speed is entirely different. Besides that,

grease lubricant is also used to test the resistance of friction to rotation of the bearing

materials. Based on the data obtained, contrast between materials of bearing used are shown

clearly. Therefore, the tendency for rotation of the flywheel depends on the frictional

resistance of bearing materials.

INTRODUCTION

The word "bearing" incorporates the meaning of "to bear," in the sense of "to

support," and "to carry a burden." This refers to the fact that bearings support and carry the

burden of revolving axles. The application of bearings are beneficial to our daily life these

days especially for various industries that rely on machinery Plain bearings are composed of

just the bearing surface with no rolling elements and have a high load-carrying capacity while

rolling element bearings are built to handle both radial and thrust loads which are relatively

small. The jewel bearings are plain bearings with a metal spindle that turns in a jewel-lined

pivot hole which usually used in mechanical watches or clocks whereas fluid bearings are

used in high load, high speed or high precision applications. On the other hand, the magnetic

bearings carry the loads by relying on the magnetic fields while the flexure bearings are

similar as hinge, in which motion is supported by a load element that bend.

In this experiment, different type of bearing materials is being used to test whether how much

load is needed to make flywheel to rotate with constant speed under different condition is

determined. Furthermore, grease oil is also being introduced to investigate the efficiency of

bearing in minimizing the friction caused by the rotational motion of shaft.

Discussion

Based on the results obtained, it is shown that the most weight load needed initiate the

rotation of flywheel is tufnol without grease application whereas the least weight load

required is ball bearing. When pulling force is applied onto the flywheel, the horizontal shaft

start to rotate due to the kinetic energy generated by the pulling force and gravitational force

of weight load.

The configuration of the ball bearing separates the rotating shaft from the fixed

bearing frame with free rolling elements while different type of material surfaces are adopted

by the other types of bearing to reduce the sliding friction rotation of horizontal shaft. Thus,

the ball bearings encounters a much smaller friction comparing to the other bearings.

Furthermore, a small layer of lubricant has been added on to the surface of ball bearing to

eliminate power loss and starting strain. Besides, the use of ball bearings also help to save

cost as no adjustment, repair or attention is necessary other than periodical lubrication. As a

summary, the advantages of ball bearing enable it to become more popular than other types of

bearing as well as increment of its usage in various industrial fields.

The quantity of weight load needed for flywheel to rotate with constant speed is

affected by some factors. One of the utmost factors is the application of grease. Grease is a

solid to semi-fluid product of dispersion of a thickening agent in liquid lubricant. The

lubricating grease is formed by three main components which are oil, thickener and additives.

The function of grease is to remain in contact with and lubricate moving surfaces without

leaking out under the force of gravity, centrifugal action or being squeezed out under

pressure. Its major practical requirement is that it retains its properties under shear forces at

all temperatures it experiences during use. Therefore, it has been used widely on a lot of

machineries as it is less costly and has high consistency.

Error Analysis

By comparing the data in two tables above, it can be seen that the coefficient of

rotational friction of the theoretical data is higher than the experimental data. This is because

some errors have occurred when running the experiments. One of the error is that the force

applied to pull the flywheel is not constant as the amount of force required for each bearing

material to start the rotation is different. Besides that, the status of the apparatus is not closely

inspected before the experiment is carried out. Furthermore, the deviation of the experimental

data from the theoretical data can also be caused by the imbalance amount of greased applied

onto the bearings due to careless when applying it. Moreover, error in obtaining the result

exists when wrong measurements are made by the observer. Last but not least, excessive

friction and energy loss can be the causes with the coating of the bearing and flywheel.

Conclusion

By observing the tabulated data, the coefficient of rotational friction for the surface

of testing bearing is smaller when the weight quantity needed to make the flywheel to rotate

with constant speed is lower. Besides that, the amount of weight load required will be

minimized by the presence of grease application because of the formation of lubrication layer

that can help to decrease the coefficient of rotational friction. To prevent and minimize the

experimental errors , status of the experimental apparatus need to be inspected carefully in

order to ensure its functionality so that the accurate experimental results can be obtained.

Lastly, it is important to repeat the experiment procedures for several times to determine the

average value as this can help to reduce the deviation of experimental data from its respective

theoretical value.