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Kinematics and Dynamics of Machines

by Kurumurthy SKurumurthy S
Type: NoteInstitute: Sbtet Course: B.Tech Specialization: Mechanical EngineeringViews: 22Uploaded: 7 months ago

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Kurumurthy S
Kurumurthy S
EXPERIMENT NO. 7 AIM :- To perform the experiment for static balancing on static balancing machine. APPARATUS USED:- Static Balancing m/c. THEORY :- A system of rotating masses is said to be in static balance if the combined mass centre of the system lies on the axis of rotation. Whenever a certain mass is attached to a rotating shaft, it exerts some centrifugal force, whose effect is to bend the shaft and to produce vibrations in it. In order to prevent the effect of centrifugal force, another mass is attached to the opposite side of the shaft. The process of providing the second mass in order to counteract the effect of the centrifugal force of the first mass, is called balancing of rotating masses. The following cases are important from the subject point of view : 1. Balancing of a single rotating mass by a single mass rotating in the same plane. 2. Balancing of a single rotating mass by two masses rotating in different planes. 3. Balancing of different masses rotating in the same plane. 4. Balancing of different masses rotating in different planes. PROCEDURE :- Remove the belt, the value of weight for each block is determined by clamping each block in turn on the shaft and with the cord and container system suspended over the protractor disc, the number of steel balls, which are of equal weight are placed into one of the containers to exactly balance the blocks on the shaft. When the block becomes horizontal, the number of balls N will give the value of wt. for the block. For finding out Wr during static balancing proceed as follow: 1. Remove the belt. 2. Screw the combined hook to the pulley with groove. This pulley is diff. than the belt pulley. 3. Attached the cord end of the pans to above combined hook. 4. Attached the block no.-1 to the shaft at any convenient position and in vertical downward direction. 5. Put steel balls in one of the pans till the blocks starts moving up. (upto horizontal position). 6. Number of balls give the Wr value of block-1. repeat this for 2-3 times and find the average no. of balls. 7. Repeat the procedure for other blocks. OBSERVATION :S.no. Mass (m) kg Radius ® Cent. Force ÷ Distance Couple ÷ ω2 m ω2 from plane (m.r.l) (m.r) kg-m x(l) m kg- m2 CALCULATION :- The balancing masses and angular positions may be determined graphically as given below: First of all, draw the couple polygon from the data which are calculated in table to some suitable scale. The vector distance represents the balanced couple. The angular position of the balancing mass is obtained by drawing, parallel to vector distance. By measurement will be find the angle. Then draw the force polygon from the data, which are calculated in table to some suitable scale. The vector distance represents the balanced force. The angular position of the mass is obtained by drawing, parallel to vector distance. By measurement will be find the angle in the clockwise direction from mass. PRECAUTIONS :1. Couple should be represented by a vector drawn perpendicular to the plane of the couple. 2. Angular position measure carefully in clockwise direction. 3. Vector diagram should be represent with suitable scale.
EXPERIMENT NO. 2 Aim: To find the effect of varying mass on the centre of sleeve in governor and governor effect. Apparatus required: Governor set up, Voltage regulator. Technical specification: ➢ Drive D.C. Motor – H.P – ¼, speed = 1500RPM. ➢ Speed control unit: 0 - 230 V, 0 – 2 Amps, Single phase auto transformer, ➢ Separate linkage for watt governor, Porter governor, proell governor,(Governor arrangement) ➢ Sleeve displacement is to be noted on scale provided, ➢ Speed measurement is done by the Tachometer. Description: The drive unit consists of a small flange mounted electric. motor connected through differential pulley system to main shaft. The optional governor mechanism can he mounted on spindle. Precise speed control is afforded by the speed control unit and an extension to the spindle shall allows the use of a hand tachometer.To determine the speed, a graduated scale is fixed to the sleeve and guided in vertical direction. The centre sleeve of the porter and proell governors incorporates a weight sleeve to which weights may be added. The Hartnell governor provides means of varying spring rate and initial compression level and mass of rotating weight. This enables the Hartnell governor, to be operated as a stable or unstable governor. The apparatus is designed to exhibit the characteristics of the spring leaded governor and dead weight governor. The apparatus is driven by a D,C. Motor with special variable speed control unit, The apparatus can perform following experiments Watt .Porter, Proell, Hartnell type governors. The governor mechanism under rest is fitted with the chosen weights and spring, where applicable, and inserted into the drive unit. The following simple procedure may then be followed. The control unit is switched on and the speed control slowly rotated, increasing the governor speed until the centre sleeve rises off the lower stop and aligns with the first division on the graduated scale. The sleeve position and speed are then recorded_ Speed may be determined using a hand tachometer on the spindle, The governor speed is then increased in steps to give suitable sleeve moments, and readings repeated at each stage throughout the range of sleeve movement possible. The result may be plotted as curves of speed against sleeve position, Further tests are carried out changing the s aim of one variable at a time to produce a family of cures.
Operating conditions: For obtaining the graphs as mentioned above following instructions may be followed. ✓ Arrange the set up as a Watt / Porter / proell governor as shown in figure. This can be achieved by removing the upper sleeve on the vertical spindle of the governor and using proper Linkages provided. ✓ Make proper connections of the motor. ✓ increase the motor speed slowly and gradually. ✓ Note the speed by tachometer and sleeve displacement on the scale pros ided. ✓ Plot the graph of speed vs sleeve displacement for all governors.

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