OK, so this one is about 50 years too late.

The Etch-a-Sketch has two controls, one in the X dimension and one in the Y. As everyone knows it takes great talent to draw a diagonal line, let alone a curve or circle. What the device needs is one knob that determines the direction and a second knob that moves the drawing point forward or backwards.

The directional knob should be much larger. This way one revolution can equal the full 360°. The knob should at least have a forward arrow pointing in the corresponding drawing direction, and possibly another mark to show the reverse direction. I’m torn about the idea of the knob snapping into certain positions (e.g., every 45°) as this would make drawing a circle more difficult. Perhaps compass markings around the directional knob would would be sufficient.

The traditional Etch-a-Sketch has a simple design; a fixed rectangle, with two sets of strings and pulleys to move the drawing point. I like the simplicity.

My model is only slightly more complex. It starts with a large underlying disk that is turned (with a string and pulleys underneath) by the directional knob. Spanning this disk is a horizontal frame that holds the drawing point. The frame has its own string and pulleys, which are not directly connected to any knob. A third string goes around the outside of the disk which drives the frame’s string and pulleys from either end of the frame.  This third string leaves the edge of the disk to join with the forward/backward control knob.  It needs to be a distinct string because the disk can be turned more than 360°, so the string needs to be able to disengage from one end of the frame while passing through the axis, while remaining engaged on the other side of the disk.

I do have a couple of design concerns:

  • Since the third string needs to engage/disengage, it can’t wrap around a pulley point, so it might be relying on tension too much.
  • The directional knob could get out of sync with the disk. The solution is to use a timing belt instead of string.
  • Unfortunately my design is a circle. It can be fudged into a square or rectangle by giving it a large bezel, or the new circular design could be embraced as a new-and-improved feature!

Now all I need is the evil business plan for a time machine…