Drive systems
Experiments 2: Angle of Lap.
Aims and Objectives:
To prove the theory of angle of lap.
Experiment setup:
Experiment procedure:
1. Cut two pieces of cord to around 400mm and fit one to the pulley.
2. Add weight to create loads as shown in the blank results table. Each time
you add a load, add effort until the pulley just starts to slip round record
the effort value.
3. Divide the effort by the load to give the force ratio.
4. Repeat for the other angle of laps.
5. For each test, find the average effort/load force ratio.
6. Insert the poulie in the board
7. Attach the pin in the board
8.
Conclusion:
1. The results should show that the effort needed to move the loads (force
ratio) increases with angle of lap. From the results, can you easily predict
the average ratio for two and three complete turns(720and 1080 degrees
of lap)? If not, why not?
2. Examine the figure below. The belt at the driver pulley is given a greater
angle of lap by using the idler pulley. Your results should indicate that there
should be positive outcome in terms of the maximum torque and power
that can be transmitted, but what is this at the expense of?
Please return all the
equipment used to their
places!!!
Efficiency in real machines will always
be less than 100 percent because of work
that is converted to unavailable heat by friction and air resistance.
Friction is another force that energy gets "wasted" on in the dragging. ... Therefore, the
machine gives you less mechanical advantage when too much friction is involved because it
wastes energy. It also makes it less efficient!
From the graph of In (T2/ T1) against θ, the relationship between the ratio of belt tension and the lap
angle is linear while the graph of T2/ T1 against θ depicts a curvilinear relationship between the ratio of
belt tension and the lap angle. Also, from this experiment, the coefficient of friction for flat belt = 0.53.
Which means that the coefficient of friction is influenced by the angle of contact between the belt and
the pulley
he output work is always less than the input work because some of the input
work is used to overcome friction. Therefore, efficiency is always less than
100 percent. The closer to 100 percent a machine’s efficiency is, the better it
is at reducing friction.
8.1 Based on data from TEST 1, plot the graph of T1 versus T2 according the angle of lap on the same
graph paper. Discuss the relation between changes of driving forces with the angle of lap. From data of
Test 1, we can assume when the angle of lap become higher, the driving forces will be decrease. The
value of m1 to stabilized the m2 become smaller when the angle of lap increase
of lap on the smaller pulley, the idler pulley is used. The angle of lap may be defined as the angle of
contact between the belt and the pulley. With the increase in angle of lap, the belt drive can transmit
more power. Along with the increase in angle of lap, the idler pulley also does not allow reduction in the
initial tension in the belt. The use of idler pulley is shown in Figure 3.7
Idler pulleys can be used to improve belt drive performance. Idlers can be used to reduce
belt vibration by supporting a segment of belt that is prone to vibration/oscillation. Idler
pulleys are used in car engines for positive clutching action by running the idler pulley on
the slack side of the flat-belt drive from engine to transmission.
It has been observed that, the graph of load v/s effort is a straight line cuts the Y-axis giving the
intercept „C‟ which indicates the effort lost on friction, when no load is applied. Is must be noted that, if
the machine is an ideal machine, the straight line of the graph will pass through the origin.
The angle of lap may be defined as the angle of contact between
the belt and the pulley. With the increase in angle of lap, the belt
drive can transmit more power. Along with the increase in angle of
lap, the idler pulley also does not allow reduction in the initial
tension in the belt The angle of lap may be defined as the angle of
contact between the belt and the pulley. With the increase in angle
of lap, the belt drive can transmit more power. Along with the
increase in angle of lap, the idler pulley also does not allow
reduction in the initial tension in the belt
The machine whose efficiency is always less than 100 % due to frictional resistance offered by the
different moving component parts of the machine is called as actual machine
