Learning Objective

To develop students' problem solving capability by guiding them through a mechanical systems problem.

Situation

The diagram opposite illustrates a typical brush head that fits onto an electric toothbrush. This brush head oscillates through an angle of 16 degrees.

(Click the start button to view the animation).

The toothbrush system

The known parts of the toothbrush system are:

  • the toothbrush has a battery powered electric motor as the input device
  • the toothbrush has a switch that switches the motor on and off
  • the toothbrush has an oscillating toothbrush head as the output device

Problem solving

  1. Devise a circuit for the electric motor that allows it to be switched on and off
  2. Devise a mechanism that connects the motor to the toothbrush head and converts the rotary motion of the motor into the oscillating motion of the toothbrush head.

Process diagram, electric toothbrush

Electric toothbrush mechanism
Click on the screenshot above to view the electric toothbrush system animation by Laszlo Lipot

An image showing the Flash animation logo SWF Flash logo is a link to a Flash animation.

Flash animations are embedded into the pages of all my D&T Modules but there are pictorial links to the animations on this web site so that devices that cannot play Flash animations will at least show a jpeg screenshot of the animation.

If your PC or personal digital assistant (PDA) can play Flash animations you may click on an image showing the Flash animation logo SWF Flash logo to view the animation in a new window.
(Your browser may require you to click "Allow Blocked Content" to view the animation). See info about viewing Flash animations.

What you must do

  1. Analyse the problem so that you understand it fully.
  2. Devise a circuit for the electric motor that allows it to be switched on and off
  3. Make a list of mechanisms that convert rotary motion into an oscillating motion.
  4. Devise a mechanism that connects the motor to the toothbrush head and converts the rotary motion of the motor into an oscillating motion of the toothbrush head.
  5. Use notes and sketches to record your ideas and to evaluate them.
  6. Draw your best design.
  7. Evaluate your design and modify it if necessary.

You may use research methods to find information about suitable mechanisms, e.g.

  • product analysis
  • library search / computer software search
  • internet search
  • experiments - model your ideas
  • interview - ask an expert.
  

Success criteria

You have:

  • Analysed the problem and have worked independently and with others to find solutions to it.
  • You have used research methods to find information.
  • You have recorded ideas and your research findings.
  • You have used your research and other ideas to develop a solution to the problem.
  • You have produced an accurate drawing or model of your solution to the problem.
  • You have evaluated your solution to the problem and modified it if necessary.
 
 
Click here to view a PDF version of this resource Toothbrush mechanism PDF Toothbrush drive mechanism PDF
Copyright Laszlo Lipot.