How do you show a gear train in an engineering drawing?

Short Answer:

A gear train is shown in an engineering drawing by representing each gear with its standard symbol or detailed profile, arranged to show how they mesh and transmit motion. The drawing includes the number of teeth, pitch circle diameters, gear types, and their relative positions.

Sometimes simplified schematic views show the gear arrangement, while detailed drawings show gear teeth and dimensions. This helps engineers understand how the gears work together and ensures correct manufacturing and assembly.

Detailed Explanation:

Showing a gear train in engineering drawings

A gear train is a set of gears working together to transmit power and motion between shafts. Representing a gear train accurately in an engineering drawing is important for design, manufacturing, and assembly. The drawing must clearly show how gears are positioned, how they mesh, and their critical dimensions.

Types of drawings for gear trains

  1. Schematic or layout drawing
    • Shows the arrangement of gears in simplified form.
    • Uses circles or standard gear symbols to represent each gear.
    • Shows gear centers and mesh points.
    • Often used in early design stages and for general understanding of gear relationships.
  2. Detailed gear drawing
    • Shows the full gear profile with tooth shape, size, and pitch.
    • Includes detailed dimensions like number of teeth, module or diametral pitch, pressure angle, face width, and bore size.
    • Used for manufacturing and inspection.

Key information shown on gear train drawings

  • Number of teeth: Important for speed ratio and gear ratio calculations.
  • Pitch circle diameter (PCD): Diameter of the imaginary circle where gear teeth mesh.
  • Gear type: Spur, helical, bevel, worm, etc., often indicated by the tooth profile and notes.
  • Gear center distances: The distance between shafts where gears are mounted.
  • Direction of rotation: Arrows may indicate rotation direction and power flow.
  • Mounting details: Shaft sizes, keyways, and bearings may be shown.

Representation methods

  • Orthographic views show gear profiles and assembly with adjacent components.
  • Section views may reveal internal gear details or how gears fit on shafts.
  • Isometric or 3D views sometimes illustrate spatial arrangement for clarity.
  • Exploded views can show individual gears separated but aligned for assembly understanding.

Importance of clear gear train drawings

  • Ensures proper gear ratio and power transmission design.
  • Helps machinists manufacture accurate gears with correct tooth profiles.
  • Guides assembly workers on correct gear placement and orientation.
  • Assists maintenance teams in identifying parts and troubleshooting.
Conclusion:

A gear train is shown in engineering drawings by combining schematic layouts and detailed gear profiles. Drawings include gear sizes, number of teeth, types, center distances, and directions to clearly illustrate how gears mesh and transmit power. Accurate gear train drawings are essential for proper design, manufacturing, assembly, and maintenance of mechanical systems involving gears.