Sri ramakrishna institute of technology, coimbatore-10

SRI RAMAKRISHNA INSTITUTE OF TECHNOLOGY, COIMBATORE-10 (Approved by AICTE, New Delhi – Affiliated to Anna University, Chennai) Department of Mechanical Engineering

Class : III Year Semester : V

Subject : Dynamics of Machinery Max Marks :

TUTORIAL 2

1. 
   Determine the input torque on the crank of a Slider Crank Mechanism for the static equilibrium when the applied piston load is N. The lengths of the crank and the connecting rod are 40mm and 100mm respectively and the crack has turned through 45° from the inner dead centre.
   
2. 
   A horizontal steam engine running at 240 r.p.m has a bore of 200mm and stroke of 360mm. The piston rod is 20mm in diameter and connecting rod length is 900mm. the mass of the reciprocating parts is 7Kg and the frictional resistance is equivalent to a force of 500N. Determine the following when the crank is at 120⁰ from the IDC, the mean pressure being 5000N/m² on the cover side and 100N/m² on the crank side.
   

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  Thrust on the connecting rod, Thrust on the cylinder walls
  
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  Loads on the bearings Turning moment on the crankshaft
  

3. 
   A machine punching 38 mm holes in 32 mm thick plate requires 7 N-m of energy per sq. mm of sheared area, and punches one hole in every 10 seconds. Calculate the power of the motor required. The mean speed of the flywheel is 25 meters per second. The punch has a stroke of 100 mm. Find the mass of the flywheel required, if the total fluctuation of speed is not to exceed 3% of the mean speed. Assume that the motor supplies energy to the machine at uniform rate.
   
4. 
   A shaft carries four masses A,B,C and D of magnitude 200kg,300kg,400kg and 200kg respectively and revolving at radii 80mm,70mm,60mm and 80mm in planes measured from A at 300mm, 400mm and 700mm. The angles between the cranks measured anticlockwise are A toB45°, B to C 70° and C to D 120°. The balancing masses are to be placed in planes X and Y. The distance between the planes A and X is 100mmm between X and Y is 400mm and Between Y and D is 200mm. If the balancing masses revolve at a radius of 100mm fine their magnitudes and angular positions.
   
5. 
   The following data apply to an outside cylinder uncoupled locomotive :
   

Mass of a rotating parts per cylinder = 300 kg;

Mass of reciprocating parts per cylinder = 450 kg;

Angle between cranks = 90°;

Length of Each crank = 350mm

Distance between Wheels = 1.6m

Cylinder centers = 1.9 m;

Diameter of Driving Wheel = 2m

Radius of balance masses = 0.8 m;

If whole of the rotating and two-thirds of reciprocating parts are to be balanced in planes of the driving wheels, find":

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  Magnitude and angular positions of balance masses.
  
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  speed in kilometers per hour at which the wheel will lift of the rails when the load on each driving wheel is 35 kN
  
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  Swaying couple at speed arrived at in (ii) above.
  

6. 
   The stroke of each piston of a six cylinder two stroke in line engine is 320 mm and the connecting rod is 800mm long. The cylinder centre lines are spaced at 500 mm. The cranks are at 60° apart and the firing orders are 1-4-5-2-3-6. The reciprocating mass per cylinder is 100kg and the rotating parts are 50kg per crank. Determine the out of balance forces and couples about the mid plane if the engine rotates at 200rpm.
   
7. 
   The lengths of the upper and lower arms of a Porter governor are 200 mm and 250 mm respectively. Both the arms are pivoted on the axis of rotation. The central load is 150 N, the weight of each ball is 20 N and the friction on the sleeve together with the resistance of the operating gear is equivalent to a force of 30 N at the sleeve. If the limiting inclinations of the upper arms to the vertical are 30° and 40°, determine the range of speed of the governor. (Nov/Dec 2006)
   
8. 
   In a Porter governor, the mass of the central load is 18 kg and the mass of each ball is 2 kg. The top arms are 250 mm while the bottom arms are each 300 mm long. The fiction of the sleeve is 14 N. If the top arms make 45° with the axis of rotation in the equilibrium position, find the range of speed of the governor in that position. (April/May 2008)
   
9. 
   The intercepted areas between the output torque curve and the mean resistance line of a turning moment diagram for a multi cylinder engine, taken in order from one end are as follows:-0.35,4.10,-2.85,3.25,-3.35,2.60,-3.65,2.85,-2.6 sq cm. The diagram drawn into a scale of 1cm=700Nm and 1cm = 45°. The engine speed is 900rpm and the fluctuation of speed is not to exceed 2% of the mean speed. Find the suitable diameter and cross section of the flywheel rim if the safe centrifugal stress is limited to 7MPa. The density of the material is 7200kg/m^3. The rim is rectangular with the width 2 times the thickness. Neglect the effect of arms.
   

©Varun B Dynamics of Machinery