INTRODUCTION
The belt drive system is a process where the belt drives the pulleys. The purpose is to transmit
power and motion between shafts. The belt drive system consists of two or more pulleys connected
with belts. The pulleys are mounted on shafts that are supported by bearings. There are three
common types of belt drive system which is the flat belt, V-belt and synchronous belt also called
timing belt.
In this experiment, a further study on open belt drive system is conducted. The mechanism of open
belt drive works in a way that the driven pulley rotate in the same way as the driving pulley. During
drives, the tightened side is always on the lower side of the two pulleys while the slack side on the
upper part. In this case, the driving pulley (d=12.7 cm) and driven pulley (6.35 cm) is used. The
data of the experiment is tabulated in Table 1.
PROCEDURE
1. The handle of the 12.7 cm pulley is removed
2. The pulleys and belt is connected onto the mounting board with the 6.35 cm pulley on the
right side and 12.7 cm pulley on the left side together with 2 hexagonal studs.
3. Step 2 is completed by tightening them with knobs and washer.
4. The center distance between pulleys is measured.
5. The angle of contact of both pulleys is measured.
6. The handle is fixed back and tightened.
7. The indicators of both pulleys is set to 0.
8. The 12.7 cm pulley is rotated half a revolution clockwise, then the angle of rotation of 6.35
cm pulley is measured and its corresponding revolution is calculated.
9. Step 7 and 8 is repeated by rotating the 12.7 cm pulley for 1, 1 , 2, 2 , 3, 3 and 4
revolutions.
10. Step 7 to 9 is repeated in the opposite direction.
Center distance between pulleys : 0.15 m
Angle of contact for 12.7 cm pulley : 210 degree
Angle of contact for 6.35 cm pulley : 180 degree
Table 1 Experimental data
No. of Angle, Direction of Indicated No. of Complete Angle, 2 Difference,
Revolution of 1 rotation Angle, Revolution of (degree) (degree)
12.7 cm (degree) (degree) 6.35 cm pulley
Pulley
180 Clock wise 345 1 705 172.5
1 360 Clock wise 340 2 1060 170
1 540 Clock wise 336 3 1416 168
2 720 Clock wise 330 4 1770 165
2 900 Clock wise 325 4 1945 72.5
3 1080 Clock wise 323 5 2123 18.5
3 1260 Clock wise 315 6 2475 22.5
4 1440 Clock wise 313 7 2833 23.5
180 Anti clock wise 351 1 711 175.5
1 360 Anti clock wise 359 2 1079 179.5
1 540 Anti clock wise 356 3 1436 178
2 720 Anti clock wise 346 4 1786 173
2 900 Anti clock wise 347 5 2147 173.5
3 1080 Anti clock wise 330 5 2310 75
3 1260 Anti clock wise 33 6 2497 11.5
4 1440 Anti clock wise 335 7 2855 12.5
Questions:
1. Draw the system and label with appropriate names. Also indicate the belt tension side and slack
side by indicating the direction of rotation for both pulleys as clockwise.
Refer Drawing 1.
2. Calculate the theoretical ratio of driven velocity to drive velocity.
2 1
, = = =
1 2
1 12.7 2
= = = = 2: 1
2 6.35 1
3. Calculate the theoretical angle of contact of both pulleys and the percentage of difference
between theory and actual value for both pulleys and state the reason for the occurrence.
1 2
=
6.35 3.175
=
15
= 0.212 .
, = + 2
= + 2(0.212)
= 3.57 .
= 204.55
, = 2
= 2(0.212)
= 2.72 .
= 155.84
= %
a) ,
210 204.55
= 100%
210
= 2.59%
b) ,
180 155.84
= 100%
180
= 13.42%
The percentage difference that have been calculated for both pulleys show that there have been
some errors occurred during the experiment. This is due to systematic error. The instrument is
poorly maintained. Moreover, during the experiment is performed, the belt is not precise in giving
the results. The belt is wear and loose which affect the reading of angle of contact for both pulleys
when taken since it is used in the experiment that is done many times before this. All this has lead
to the loss of accuracy and precision of the experiment result. Parallax error also occurred when
taking the measurement of angle of contact. The measurement of the angle of contact for both
pulleys is not viewed is the right direction which causes error in accuracy.
4. Plot two graphs vs 1 (for clockwise rotation and anti clockwise rotation). Calculate the
slope of both graphs.
Refer graph
