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5. Mechanisms
Understand
44.
Study the cam above. When it rotates, what motion will its follower make?
Analyse
45.
Study the three cams on the right. What type of motion will each cam produce in its follower?
CHANGING THE DIRECTION OF MOTION
There are various ways to change the axis of rotation or the direction of rotation.
Here are two examples:
❚❚
We can use pulleys that are connected by a belt at an angle to each other. This
changes the axis of rotation. We can also cross the belt to change the direction of
rotation.
❚❚
We can put two gears at a 90 degree angle. We use wheels made of chipboard
with nails in them. These nails interlock like gear teeth.
45º
MAKING A CAM
It is quite simple to make a cam:
1.
Draw a cross with two perpendicular lines on a piece of plywood.
2.
Use a compass to draw a circle. The centre must be at the intersection
of the two lines. Draw two more lines to divide the circle into eight
equal parts.
3.
Put the compass needle on point A and the compass pencil on point
C. Then draw an arc. Repeat with the needle on point C and the pencil
on point A.
4.
Put the needle at D and the pencil at E. Draw a line between E and F.
5.
Cut out the cam and sand the edges to make them smooth.
A
C
F
B
E
D
O
MAKING A CARDAN JOINT
As we have seen in this unit, Cardan
joints (or universal joints) transmit motion
between two axes at an angle.
Study the illustration. Prepare the wire
cross, the washers and the two pieces of
tin. Then assemble the pieces.
piece of tin
wire
cross
washers
piece of tin
ADVANCE
EDITION
