Cam Size
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

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To measure the Cam with a Measurement FB, we will click different Points.
If necessary, to select Points only, use
Basic Circle
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
Cam Lift
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. |
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