Understanding Gear Classification

Gears, also commonly known as toothed wheels, are fundamental mechanical components used to transmit rotational motion and power. They are classified in various ways depending on their design features, how they are manufactured, and how they are used in a system. One important way to classify gears is based on the characteristics of their teeth.

Classification Based on Position or Shape of Teeth

The position and shape of the teeth on the gear surface significantly influence how the gear meshes with another gear and the type of motion transmission. This classification directly relates to the geometry of the individual teeth on the wheel.

• Straight Teeth: Gears like spur gears have teeth that are straight and parallel to the axis of rotation.
• Inclined Teeth: Gears like helical gears have teeth that are cut at an angle (helix angle) to the axis of rotation.
• Curved Teeth: Gears used for connecting intersecting or non-intersecting shafts, such as spiral bevel gears or hypoid gears, can have teeth that are curved along their length.

The options "Straight", "Inclined", and "Curved" directly refer to the form or position of the teeth on the gear surface itself. These are all valid classifications based on the position of teeth.

Classification Based on Shaft Arrangement

Another major classification criterion for gears is based on the relative orientation of the shafts that the gears are connecting. This classification describes the layout of the gear train rather than the individual gear's tooth geometry.

• Parallel Shafts: Connected by spur gears, helical gears, internal gears, rack and pinion.
• Intersecting Shafts: Connected by bevel gears (straight bevel, spiral bevel).
• Non-intersecting and Non-parallel Shafts: Connected by worm and worm wheel, hypoid gears, skew-helical gears (spiral gears).

The option "Non-intersecting and non-parallel" describes the relationship between the shafts connected by the gears, not the position or shape of the teeth on the gear surface of a single gear. This relates to the overall system layout.

Identifying the Classification Not Based on Tooth Position

The question asks which option does not come under the classification according to the position of teeth on the gear surfaces. Based on our understanding:

• "Straight" describes tooth position/shape (e.g., spur gear).
• "Inclined" describes tooth position/shape (e.g., helical gear).
• "Curved" describes tooth position/shape (e.g., spiral bevel gear, hypoid gear).
• "Non-intersecting and non-parallel" describes the arrangement of the shafts the gears connect (e.g., worm drive, hypoid drive).

Therefore, the classification related to "Non-intersecting and non-parallel" shafts is a classification based on shaft arrangement, not the position of teeth on the gear surface.

The option that does not fit the criterion of classification based on the position of teeth on the gear surfaces is the one referring to shaft arrangement.