MEC240 - Dynamics Of Machine Assignment - University of Southern Queensland

Assignment Task

In each question of the assignment, there are several parameters of different values for each student via allocation number. Allocation number and data will be sent to student’s UniSQ email address. Please check your UniSQ email box for your assignment 2’s data.

1. A vibrating screen machine operates using a four bar mechanism as shown in Fig. 1. Crank OA rotates clockwise at a constant angular velocity ω (rpm). The parameters of the mechanism are given as follows: OA = 200 mm; AB = 940 mm; DB = 450 mm.

Notes:

• The values of other parameters including PB, PC and ω are sent to each student at his/her UniSQ email box.
• The diagram of Fig. 1 is reproduced to scale but not necessarily 1:1. At the position and instant shown, determine:

1. The absolute velocity of points: A, B, C, and D

2. The angular velocity of link AB and link BC. 

3. The acceleration of point A. 

4. The acceleration of point B and the angular acceleration of link BC

2. Regarding the design of a clutch system, a disc A is rotating at an angular velocity ωA (rpm) and has a mass moment of inertia of 4.0 kgm2 . It is dropped on to disc B which has a mass moment of inertia of 5.5 kgm2 . Disc B is initially rotating at ωB (rpm) but in the opposite direction to A as shown in Fig. 2.

Notes: Values of ωA (rpm) and ωB (rpm) will be sent to each student at his/her UniSQ email box.

1. Determine the common velocity of the two discs when all slipping ceases. Also calculate the energy lost to the system.

2. Determine the frictional torque between the two contacting surfaces if slipping stops 5 seconds after initial engagement.

3. A drum (D) rotates anticlockwise as shown in Fig.3 The drum is braked by a band brake as described in the figure. The parameters of the band brake are given as follows: n = 0.8 m, m = 1.0 m. A brake force F (N) is applied at A.

Note: Values of F (N) and r (m) are given to each student at his/her UniSQ email box. Determine:

1) The brake torque applied on the drum.

2) What is the least value of the ration n/r for which the brake is not self-locking?

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