## Tools to Learn

### Sketch

Select a Plane, The sketch we are making will be 2 dimensional so you ned to select a plane to draw on. When you click create sketch three planes are kighlighted in yellow. Click on one to select it. usually I will pick the plane that is the x, y axis plane.

### Line

L activates line tool. Click one point then the next, click the check mark when done. esc to leave line tool.

You can type in a value for the length of the line here. In designing the robot the length of the line is usually a distance between holes.

### Circle

Click for center, then drag for approximate diameter. Enter a value to set the diameter. esc to leave circle tool.

### Dimension

D activates dimension tool. Click a feature and drag mouse to create dimension line. Right click to get other options. Click when placed correctly. Enter a value and click enter to finish. This will constrain the size of the feature to that dimension. esc to leave.

### Constraints

Coincident A coincident constraint is made when a new line is started on an existing point. A blue box indicates this. Equal Makes 2 lines , arcs or angles constrained to be equal. Parallel Makes 2 lines parallel Tangent Makes a line and an arc tangent or two arcs tangent.

## Knowledge to Use

### Geometry

Chord of circle. Equal chords give equal arcs. Can use to create gear motions on gear constrained lifts. See DR4B

### Building

#### Vex Parts

Constrain features as a real build. Imagine screws as constraints and lengths of parts fixed.

Hole spacing is ½ inch so try to use lengths in ½ inch increments.

#### Gears

Gears are 24 dp, meaning a 24 tooth gear would be 1 inch in diameter.

So for the VEX 60 tooth gear the diameter would be 60/24 or 2.5 inch.

So when you use gears in Crayola cad use the correct diameter circles. Note that this is the pitch diameter , where the gears mesh. If you measure the diameter at the end of the teeth it is larger. Meshed gears are drawn a circles with the pitch diameter and tangent to one another.

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