Technical Drawing 2, WASSCE (PC 2ND), 2018

Question 2

 

 

 

Fig. 1 shows a crank mechanism having F as centre.  The rod PY slides through pivot E and is connected to the crank.  Plot the locus of a point P when the crank makes one revolution.

 

Observation

 

 

This is a question on constructing the locus of a point in a crank mechanism.

The solution to this question lies in making the rod PY slide through the pivot E.

The question was well attempted and good result was recorded.

 

Strength:

Most candidates were able to:

 

  1. copy the given mechanism;
  2. draw circle R40 and divide into 8/12 equal parts;
  3. locate corresponding different positions at rod PY on crank FY;
  4. join points P into a smooth curve.

 

Candidates were expected to:

 

LINK MECHANISM

 

i. copy the given mechanism (crank FY, rod PY, slot E, centre lines);
ii.draw circle R40 and divide into 8/12 equal parts;
iii.locate corresponding different positions of rod PY on crank FY;
iv.mark different positions of point P on rod PY;
v.join points P into a smooth curve;
vi.correct positioning of parts of link mechanism;
vii.neatness and quality of linework.      

 

The solution is shown below: