Sake, FINAL (SESSION SEPTEMBER 2022) Mechanics of Machine TME21303 LECTURER SEPTEMBER 2022 TIME : 3 HOURS Instructions : 1. Candidates must read all questions carefully. 2. The examination script consists of the followings: Part ayPes of | instruction Duration lauestions a | ESSAY ‘Answer ALL question. 45 Minutes (Compulsory) ESSAY 2 Hours 18 8 | Onion Answer 3 out of § questions. tourMechanics of Machine PARTA (25 Marks) Duration : 45 Minutes INSTRUCTION This part consists of ONE (1) COMPULSARY question. Answer the question in the answer booklet provided. (Question 1) A kinematic diagram or kinematic scheme illustrates the connectivity of links and joints of a mechanism or machine rather than the dimensions or shape of the parts as shown in Figure 1. Figure 1 (a) Draw the kinematic diagram of each mechanism in Figure 1. (15 marks) (b) | Compute the mobility of each mechanism in Figure 1. (10 marks) 25 marks PART B (ESSAY Option) (75 Marks)Duration : 2 Hours 15 Minutes INSTRUCTION This part consists of FIVE (5) questions. Answer THREE (3) questions only in the answer booklet provided. (Question 1) A belt is a loop of flexible material used to link two or more rotating shafts mechanically, most often parallel. (a) Draw FIVE (5) types of belts that are commonly used in industries. (5 marks) (b) Explain the FIVE (5) types of belts mentioned in your answer according to Q1(a). (20 marks) 25 marks(Question 2) Chain drive is a way of transmitting mechanical power from one place to another. A single-strand roller chain drive connects a 10 hp engine to alawn waste chipper/shredder, as shown in Figure 2. As the engine operates at 1200 rpm, the shredding teeth should rotate at 240 rpm. The drive sprocket has 18 teeth. Figure 2 Determine: (a) an appropriate pitch for the chain. (4 marks) (b) the number of teeth on the driven sprocket. (5 marks) (c) _ the pitch diameters of both sprockets. (8 marks) (d) _ the chain speed. (8 marks) 25 marks(Question 3) Balancing of several masses rotating in different plane is one of the types in balancing field. Four masses 150 kg, 200 kg, 100 kg and 250 kg are attached toa shaft revolving at radii 150 mm, 200 mm, 100 mm and 250 mm; in planes A,B, C and D respectively. The planes B, C and D are at distances 350 mm, 500 mm and 800 mm from plane A. The masses in planes B, C and D are at an angle 105°, 200° and 300° measured anticlockwise from mass in plane A. It is required to balance the system by placing the balancing masses in the planes P and Q which are midway between the planes A and B, and between C and D respectively. If the balancing masses revolve at radius 180 mm, find the: (a) (b) magnitude of the balance masses. angular positions of the balance masses. (Question 4) (22 marks) (3 marks) 25 marks Arotating mass, or rotor, is said to be out of balance when its center of mass is out of alignment with the center of rotation. (a) (b) » =3ke 4 MANE oot Ory 02m m | Figure 3 What are the bearing reactions for the system shown in Figure 3 if the speed is 750 rev/min? (16 marks) Determine the magnitude of a balancing mass if itis to be placed ata radius of 0.25 m. (9 marks) 25 marks(Question 5) Acam is to be used for a platform that will repeatedly lift boxes from a lower conveyor to an upper conveyor. This machine is shown in Figure 4. When the follower motion sequence is as follows: L ii. iii iv. v. (a) (b) (c) (d) rise 5 inches within 3 seconds. dwell for 0.6 seconds. fall 2.5 inches within 0.9 seconds. dwell 0.6 seconds. fall 2.5 inch within 0.9 seconds. = @) Figure 4 Determine the time for a full cycle. (2 marks) Find the required rotational speed of the cam. (4 marks) Determine the cam rotation for each follower motion interval. (10 marks) Plot the displacement diagram. (9 marks) 25 marks END OF QUESTION