Everyone who wants to begin their career in robotics must have good knowledge on 3 parts of engineering-

  • Mechanics
  • Electronics
  • Programming

In this article, I am going to share with you the basics of mechanics on types of gears which is essential for a beginner in robotics.

Gears are the essential things in a mechanical part for the transmission of motion. They are wheel-like machine elements that have teeth uniformly spaced around the outer surface. They are used in pairs and are a very valuable design tool.

What is a gear?

A gear is a toothed cylindrical or roller shape component of a machine which meshes with another toothed cylindrical to transmit power from one shaft to another. It is mainly used to change in torque and speed of driving shaft and driven shaft.

According to the type of gearing. The gears, according to the type of gearing, may be classified as :

(a) External gearing, (b) Internal gearing, and (c) Rack and pinion.

Let us see each of them briefly:

External gearing

In simple language we can say that gears having teeth over its outer side of the body as shown in the figure below; the gears of the two shafts mesh externally with each other.

Internal gearing

In simple language we can say that gears having teeth over its inner side of the body as shown in the figure below; the gears of the two shafts mesh internally with each other.

Rack and pinion

The rack is a gear of infinite radius. The smallest of the mating gear is known as pinion. It is used to convert the linear motion to rotatory or vice versa.

Lets see the real life pictures of the above types:

Example of both external and internal gears
A rack gear (black) pinion (white)

Some Basic Terms Used in Gears

  1. Pitch circle: It is an imaginary circle which by pure rolling action, would give the same motion as the actual gear.         
  2. Addendum: It is the radial distance of a tooth from the pitch circle to the top of the tooth.
  3. Dedendum: It is the radial distance of a tooth from the pitch circle to the bottom of the tooth.

BASIC FORMULA FOR THE CALCULATION OF SPEED OF GEARS FROM TOOTH RATIO AND VICE VERSA:

T1= number of teeth on 1st gear

T2= number of teeth on 2nd gear

V1= speed of the 1st gear

V2= speed of the 2nd gear

T1*V1=T2*V2

This is simply derived by relation that speed of gear is inversely proportional to the no. of teeth present on it.

LET’S DISCUSS SOME OF THE IMPORTANT GEARS USED IN THE MECHANICAL PARTS OF THE ROBOTS

  • Spur gear: Spur gears are the most commonly used gears due to their simplicity and the fact that they have the highest possible efficiency of all gear types. They cannot withstand higher loads.

  • Double helical gear: A Herringbone gear, also known as a Double helical gear is a special type of gear which is a side to side combination of two helical gears of opposite hands.

  • Bevel gear: Bevel Gears are used exclusively to transmit rotary motion between intersecting shafts. Though commonly seen in right angle drives, bevel gears can be cut to drive any angle.
  • Crown gear:  A crown gear is a gear which has teeth that project at right angles to the face of the wheel.
  • Worm gear: Worm gears resemble screws. A worm gear is usually meshed with a spur gear or a helical gear, which is called the gear, wheel, or worm wheel. It is the best gear to attain high torque and low speed.  It also acts as a brake to reverse spin.
  • Rack and Pinion: Rack is a gear of infinite radius. Pinion is the smallest mating of the gear.

Final Note:

This was very basic introduction about gears used in robots and in next articles I will deal about more mechanical, electronic and programming parts of the robots.

Have fun with the content and feel free to ask any doubts!