rotational motion

Four-position Geneva mechanism

Rotational motion

  • transfer rotational motion from one place to another – pulley(animation) – pulleys are the same size. By crossing the belt the direction of drive can be changed. Two sizes of pulley are used to change the speed of rotation. Drive can be transferred by friction of the belt on the pulley, by using a toothed belt, or chain drive
  • convert rotary motion into reciprocating motion – cams (animation) – As the cam turns, driven by the circular motion, the cam follower traces the surface of the cam transmitting its motion to the required mechanism.
  • convert rotary motion to reciprocating or oscillating motion – crank (animation)
  • Geneva drive (animation) (or Maltese cross) – a gear mechanism that translates a continuous rotation into an intermittent rotary motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel advancing it by one step. The drive wheel also has a raised circular blocking disc that locks the driven wheel in position between steps.

That’s engineering

  • cam – a device that converts a circular motion into a linear motion. It is usually fixed on a shaft or axle. As the shaft turns, the cam pushes against an object (a cam follower) to make it move back and forth in a straight line.
  • cam follower – lever or other machine part which moves back and forth in contact with a cam rotating on a shaft or axle.

Engineering ideas

  • motion, rotation, drive, circular, linear, friction, continuous, intermittent, step

Do it
Here are some challenges for you to work on…

  • Build a Cam Mechanism – Create a simple machine that transfers a rotational motion into a linear vertical motion.

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