Problem 2.2 Loci of Points

Problem 2.2 Loci of Points – O1ABO2 is a Four Bar Chain with the link O1O2 as the fixed link. Driving crank O1A is 30 mm long. Driven crank O2B is also 30 mm long. Connecting link AB is 80 mm long. Distance between O1 and O2 is 80 mm. Two cranks are revolving in opposite direction. Draw the loci of points M and N for one complete revolution of the driving crank. The point M is the mid-point of the connecting link AB and the point N is 30 mm from B on AB extended.

Loci of Points Problems - Engineering Drawing
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Step-1 First draw a horizontal center line of sufficient length.

Step-2 Mark a point named O1 on the horizontal center line & O2 at the distance 80 mm from O1.

Step-3 Draw two circles with center points O1 & O2 with radius equal to the length of the crank O1A &  O2B, which is 30 mm.

Step-4 Divide the circle O1 into 12 divisions and give the notations as A1, A2, A3 etc. to the circle as shown into the figure.

Step-5 With A1, A2, A3 etc. as centers and radius equal to the length of connecting rod AB, which is 80 mm, cut the circle O2 in such a way that if center point of the arc is above the center line than the cut should be below the center line and vice versa as shown into the figure. And give the notations B1, B2, B3 etc. as per the figure.

Step-6 Then connect the points A1B1, A2B2, A3B3 etc. with straight lines. And fins its mid points & give the notations M1, M2, M3 etc. as shown into the figure. These are the mid points of the connecting rod AB.

Step-7 Now draw a medium dark smooth curve passing from the points M1, M2, M3 etc. in sequence, which is the locus of the mid-point of connecting rod AB.

Step-8 To get the locus of the point N, extends the lines A1B1, A2B2, A3B3 etc. in the direction from A to B as shown into the figure & give the notations as N1, N2, N3 etc. respectively.

Step-9 Connects the points N1, N2, N3 etc. into sequence by a medium dark smooth curve, which is the locus of the point N.

Step-10 Give the dimensions by any one method of dimensions and give the name of the components by leader lines wherever necessary.

Author: Vasim Machhar

An Engineering Drawing Geek. Working at Noble Group of Institutions, Junagadh as Head of Mechanical Engineering Department.