FAKULTI KEJURUTERAAN MEKANIKAL DAN PEMBUATAN

UNIVERSITI TUN HUSSEIN ONN MALAYSIA

BDA20303MECHANIC OF MACHINE

TEST 1 ( 2 Hour)

Q1 Figure Q1 shows a motor accelerating a hoist with diameter 0.9 m, through two sets of gear reducing system. The number of teeth on gear 1, gear 2, gear 3 and gear 4 are 100, 350, 100 and 450 respectively. Moment of inertia for the motor shaft is 5 kgm2, middle shaft is 20 kgm2 and hoist shaft is 100 kgm2. The rope that is encircled on the hoist must capable to accelerate up a load of M kg that is sliding on a 1 in 50 slope at acceleration of 3 m/s2. Friction on the slope is 1000N and the total torque at motor required to raise the load is 1500Nm. Gear efficiency of gear set 1-2 is 90% and gear efficiency for gear set 3-4 is 95% gear. The friction torque effect at the middle shaft is Nm and at the hoist shaft is Nm. Investigate the mass of the load at the above conditions.

Motor

Gear 1

Gear 2

Gear 3

Gear 4

Hoist

Load

Figure Q1

Q2 A pulley of 150 mm effective diameter running at 1500 rev/min drives a followers of 750 mm diameter, the two shafts being parallel, 1 m apart and the free parts of the belt considered straight. The belt has a mass of 0.4 kg/m and the maximum tension is to be 72 N. Estimate,

1. Maximum tension difference allowing for the inertia of the belt if μ = 0.4.

2. The speed of the driven pulley at the maximum condition and the power transmitted to it if the belt has a cross-section area of 320 mm² and E for the material is 300 MN/m².

Skema Jawapan

SOLUTION TO Q1

Total torque required by motor to raise load

where = Torque to overcome equivalent inertia (refer to motor side).

=Torque to accelerate the load through gear system

Total torque to overcome friction effect.

a) Consider for

For double set of gear reducing system,

1

1

1

1

1

kgm2

For the overall gear ratio,

From , thus, rad/s2

Also from gear ratio, , thus, rad/s2

Thus Nm

b) Consider for as in Figure 15;

2

1

1

1

1

1From

N

Thus, torque to accelerate hoist

Nm

Use gear efficiency to relate with

Nm

c) Consider for

Friction effect can be grouped together to form where;

Nm

RF Mg

1F

θ

Mg sinθ

r

F1

hoist

Figure 18: inclined loading

1

1

1

1

1

1

1

1

2

1

From

Thus kg

Solution Question 2

1

1

25