






Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
Main points of this past exam are: Shaft Diameter, Belt Pitch Length, Pulley Pitch Diameter, Belt Contact Angle, Belt Static Tension, Aid, Refrigeration, Refrigeration Plant, Required Number, Actual Compressor
Typology: Exams
1 / 12
This page cannot be seen from the preview
Don't miss anything!
Instructions Answer FIVE questions. All questions carry equal marks.
Examiners: Mr. T. A. Farrell Mr. D. Leonard Dr. M. Smyth
Q1 (a) Explain carefully, with the aid of sketches, the following terms in connection with belt drives: (i) Belt pitch length. (ii) Pulley pitch diameter. (iii) Belt contact angle. (iv) Belt static tension. (8 marks)
(b) A compressor in a refrigeration plant is driven by a 10kW AC squirrel cage electric motor, running at 1450 RPM. The compressor runs for 24 hrs. per day, and the required compressor speed is 800 RPM approximately. Design a suitable drive consisting of classical V-belts and sheaves. The design should include: (i) The pulley diameters, and actual centre distance. (3 marks) (ii) Belt cross-section, and pitch length. (3 marks) (iii) The required number of belts. (3 marks) (iv) The actual compressor speed. (3 marks) Assume an initial centre distance estimate of C = D + 1.5d, where D and d are the diameters of the large and small sheaves respectively.
Q2. The rotating impeller section of a ventilation fan is mounted on a shaft as shown in Fig. below. The shaft is supported on two bearings at A and B, and the fan impeller centerline is 320 mm from the face of bearing B. The load due to the impeller weight is 260 N. The material of the shaft is steel, having a yield strength in tension, Syt = 825MPa. (a) If the drive motor generates a torque of 35 N-m in shaft section AB, between the bearings, calculate the shaft diameter ‘d’ required to withstand static yielding due to torsional shear stress in this section. Assume a yield strength in shear for the material, τy = 0.5Syt, and a factor of safety of 2.0. (6 marks) (b) Considering bending only, in the shaft section BC between the shaft support point in bearing B, and the impeller centreline, calculate the shaft diameter ‘d’ allowing a factor of safety on static yielding of 2.0. (6 marks) (c) Considering the combined induced stresses in shaft section BC, due to the torque of 35 N-m, and the impeller load of 260 N, calculate the shaft diameter ‘d’ required to withstand yielding. State any assumptions made. (8 marks) Note: Refer to Fig.1 below.
Q3. (a) Describe, with the aid of a sketch, and briefly explain the function of each of the following three components of a rolling contact bearing: (i) Outer race (ii) Inner race (iii) Rolling element (6 marks) (b) The total mass of the impeller and shaft assembly of a centrifugal fan is 200 kg. The shaft diameter is 40 mm. If the assembly rotates in two roller bearings, one at either end of the shaft, at a speed of 2000 RPM, calculate the basic dynamic load rating for suitable roller bearings to give a life of 100,000 hours, and give the designation of a suitable bearing. (14 marks)