Problem 2.7 Loci of Points

Problem 2.7 Loci of Points – A four bar chain mechanism has a fixed link O1O2 130 mm long. The O1A 30 mm long is a driving crank revolving in clockwise manner. The driven crank O2B 60 mm long is oscillating about the center O2. The link AB 110 mm long is attached with the driving and driven crank. Draw the locus of the point P which is midpoint of the link AB.

Loci of Points Problems - Engineering Drawing
Click on Image to Zoom


Step-1 First draw a horizontal center line of sufficient length.

Step-2 Mark a point named Oon the horizontal center line & O2 at the distance 130 mm from O1.

Step-3 Draw two circles with center points O&  Owith radii  equal to the length of the crank O1A &  O2B, which is 30 mm & 60 mm respectively.

Step-4 Divide the circle O1A  into 8 equal 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 the connecting rod AB, which is 110 mm, cut the circle O2B in such a way that the cuts should be on the side which is above the horizontal center line.

Step-6 Then connect the points A1B1, A2B2, A3B3 etc. with straight lines. And fins its mid points & give the notations P1, P2, P3 etc. as shown into the figure.

Step-7 Now draw a medium dark smooth free hand curve passing through the points P1, P2, Petc. in sequence, which is the locus of the mid-point of connecting rod AB.

Step-8 Give the dimensions by any one method of dimensions and give the name of the components by leader lines wherever necessary.