Terminology that relates to 'Cam-Size'.
|•||Base Circle: the diameter of the smallest circle that is tangent to the cam surface.|
|•||Prime Circle: the diameter of the smallest circle that is tangent to the .|
|•||Cam Lift (also called Follower Stroke): the difference between the 'Prime-Circle' and the maximum radius of the Pitch-Curve.|
Advantages of a 'smaller' Cam.
A small cam:
|•||reduces material costs (but a 'very' small and 'very' large cam increase manufacturing costs).|
|•||reduces its inertia for rapid starting and emergency stopping.|
|•||reduces out-of-balance forces.|
|•||reduces the number-of-rotations that cam-follower roller makes for each rotation of the cam|
|•||reduces the angular velocity and angular acceleration of the cam-follower roller|
Disadvantages of a 'smaller' Cam.
A small cam:
|•||reduces the flywheel effect. This helps to rotate the cam-shaft at constant angular velocity. However, this effect is usually quite small.|
|•||increases the accuracy required to manufacture.|
Cam Size and the Measurement-Dimension FB
To measure the Cam with a Measurement FB, we will click different Points.
If necessary, to select Points only, use
The radius of the Base-Circle is the minimum radius from the centre of the cam to the contact between the cam and the cam-follower.
|2.||Click the small Point at the contact between the Cam-Follower and the Cam|
|3.||Click the Point at the centre of the rotating Cam|
|4.||Click the graphic-area.|
The Measurement (and the FB) are now in the graphic-area . The Measurement will increase and decrease when you rotate the cam.
When the Measurement is a minimum - you have found the radius of the Base-Circle
The difference between the minimum and maximum values given by the Measurement FB is the Cam-Lift.
You can also use a Stats FB to find the maximum and minimum values.
Prime-Circle (also called the Reference Circle)
The radius of the Prime-Circle is the minimum radius from the centre of the cam to the centre of the cam-follower.
|1.||Click Add Measurement FB |
|2.||Click the Point at the centre of the Cam and then the centre of the Cam-Follower.|