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THE SNAIL / DROP CAM | ||
V. Ryan © 2006 - 2020 | ||
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Eccentric, heart shaped and pear shaped cams
generally allow for a slow rise and fall of the follower. However, a
snail drop cam is used where the drop or fall of the follower must be
sudden. |
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The diagrams below shows the rotation of the snail/drop cam. When rotating for one complete revolution the follower stays level for approximately the first 120 degrees (diagrams 1 to 4). The follower then rises slowly (diagrams 5 to 6) and then suddenly drops when it reaches and passes the peak (diagram 7). |
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WHAT HAPPENS WHEN A DROP CAM ROTATES IN THE WRONG DIRECTION? | ||
Direction of rotation of the cam profile is very important, especially when a drop cam profile is being used. The example opposite shows what happens when this profile rotates in a clockwise direction. The roller follower, ‘jams’ the mechanism. This will usually prevent the profile rotating any further and can even break of damage the mechanism. |
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The mechanical toy seen below has a snail/drop cam as
its main part. The follower is connected to the characters arm by a wire
link. As the cam rotates, the follower rises and the wire link lifts the
characters arm. This gives the appearance of the character lifting a
fork full of food towards his mouth. |
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QUESTIONS: |
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Another example of a drop cam is seen below. As the cam profile rotates the foot of the model rises slowly and then suddenly drops. | ||
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