Gears are an essential part of the everyday life in an Industrialized Society. With cars, buses, airplanes and even the watch that ticks and tells time uses gears of one form or another. A Draftsman repertoire of experiences has to include gears and how to draw, engineer and illustrate them. With this course in Engineering Drafting we will be exploring The Involute Spur Gears. These kind of gears are the most widely used in gear systems. Involute means curved from a fixed point and this term will make more sense when you begin how to draw this curved profile from a fixed point.

The function of the gear, and a combination of gears creates a mechanical advantage. Through the use of gear sets, reverse rotation is possible as well as higher output speeds that can be transmitted through a device called a transmission.

Connecting Your Learning

As you work your way through this lesson, you should reflect on the following questions:

What is the function of a Gear?
What is an involute spur gear?
What is the function of a transmission
What is a spur gear?
What gear is used to make 2 gears rotate in the same direction?

The State of Arizona has assembled Drafting standards to make sure that Instruction is thorough and well thought out by the instructor. By clicking on the hyperlink below will upload to your browser window the entirety of these standards. The standards that are addressed in this lesson are below the hyperlink.

1.0 USE BOARD DRAFTING EQUIPMENT, INSTRUMENTS AND MEDIA.

• 1.1 Analyze Drawing surfaces for Drafting
• 1.6 Demonstrate Sheet Setup skills

2.0 DEMONSTRATE SKETCHING, LETTERING, AND LINE SKILLS.

• 2.1 Demonstrate freehand sketching skills for drafting applications.
• 2.2 Demonstrate lettering skills.
• 2.3 Demonstrate line work.

6.0 DEMONSTRATE GEOMETRIC CONSTRUCTIONS

• 6.1 Measure Geometric Constructions.
• 6.2 Develop Geometric Constructions.

8.0 APPLY BOARD DRAFTING SKILLS TO COMPUTER-AIDED DESIGN/DRAFTING (CADD)

• 8.1 Demonstrate computer skills for a CADD system.
• 8.2 Create dimensional CADD entities.
• 8.3 Create 3 dimensional CADD drawings.

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The State of Arizona has also assembled Math standards and many of these apply directly to the vocational subject area of Drafting. Drafting is a very precise discipline and the use of mathematics is integral to design and manufacturing. Below are the math standards that are involved in this lesson

1M-P1. Compare and contrast the real number system and its various subsystems with
regard to their structural characteristics

• PO 2. Compare subsets of the real number system with regard to their properties
  (commutative, associative, distributive, identity, inverse and closure properties)

1M-P2. Construct, interpret and demonstrate meaning for real numbers and absolute

• PO 3. Solve real-world distance problems using absolute value
• PO 4. Determine, among the solutions to a real-world problem, which, if any, is reasonable
• PO 2. Define absolute value as the distance from the origin

4M-P1. Interpret and draw three-dimensional objects

• PO 1. Sketch prisms, pyramids, cones, cylinders and spheres
• PO 2. Classify prisms, pyramids, cones, cylinders and spheres by base shape and lateral surface shape.
• PO 3. Recognize the three-dimensional figure represented by a two-dimensional drawing.
• PO 5. Make a model of a three-dimensional figure from a two-dimensional drawing and make a two-dimensional representation of a three-dimensional object (models and representations include scale drawings, perspective drawings, blueprints or computer simulations)

4M-P4. Deduce properties of, and relationships between, figures from given
assumptions

• PO 1. Find similarities and differences among geometric shapes and designs using a given attribute (e.g., height, area, perimeter, diagonals and angle measurements)
• PO 2. Identify arcs, chords, tangents and secants of a circle
• PO 3. State valid conclusions using given geometric definitions, postulates and theorems
• PO 4. Represent pi as the ratio of circumference to diameter
  

Lesson Objectives

1. Draw using ACAD 2002 the Displacement Diagram and Profile of Cam # 5.
2. Use the Array command to arrange lines that will represent on the Cam Profile the various kinds of motion described in its Displacement Diagram.
3. Understand how to use the commands of : line, copy, move, the @ command and vectoring,
4. Create a region from the Cam Profile and create a 3d model by extruding this region.
5. Use the Rotate3d command and orient the extruded model in Plan View and scale to 1/2.

Key Terms

"click on the key on any of these terms and it will hyperlink to the course glossary"

involute	spur gear	idler gear	dimetric pitch
pressure angle	addendum	dedendum	OD
PD	Root Diameter	Circular Pitch	Circular Thickness

 

Instruction

Your Text Book and Reading Assignments

Summary and Assessment