2: Drawing an Escape Wheel

I am currently using an IBM with Windows and a drawing program called KeyDraw. If you have AutoCAD, you are well equipped. The most important features you need are the ability to draw lines and circles on a grid, and the ability to rotate the lines by angles that you determine. You may have a different method. This is just one way to do it.

First, draw a large circle. A diameter of 6 inches worked well for me. Draw another circle of 4.5 inch diameter and center it inside the first. Draw a horizontal line across this circle, bisecting it. Draw a tooth on one side until you are satisfied: I chose a line at 15° and another at 25° from horizontal, positioned to fit, and with a small gap to allow for tooth thickness. Duplicate, rotate, and place a tooth on the other side. Remove the line and mark the center of the circle. Your drawing should look like this.

Move the inner circle outside. Group the outer circle with the line and the two teeth, duplicate and rotate by 12°. Duplicate the new group and rotate it by 12° again. Repeat this until you have thirty teeth. Ungroup all the elements and remove the outer circles, one at a time, until only one is left. Place the inner circle in its original position, and group all the teeth and circles. The reason for placing a tooth in a circle before rotating is because the circle makes the tooth rotate about the center of the circle, in order to achieve the desired result.

Rotate the groups by 12° at a time because there are 360° in a full circle, so if you want a 30 tooth circle: 360 / 30 = 12°. If you want a 48 tooth circle, divide 360 by 48 to get 7.5°. Thus escape wheels with different numbers of teeth could easily be made. Escape wheels with the teeth pointing in the other direction could be made by flipping the image, or with teeth of different shapes, such as the club-tooth escape wheel in Swiss watches.

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