What is Gear Drive and Gear Train ? | Spur Gear Drive - News4u95


Sunday, 31 January 2021

What is Gear Drive and Gear Train ? | Spur Gear Drive

Gear Drive

  • In case of belt drive there is a slipping phenomenon which reduces the speed ratio of a system.
  • In precision machines or mechanisms like watch gear mechanism, definite speed ratio is required which is obtained by gear drive or gear wheels.
  • Gear drive is a positive drive and it is provided when the distance between the driver and follower is very small.
  • Gears are defined as toothed wheels which can transmit power and motion from one shaft to another shaft by means of successive engagement of teeth.
  • It is important to note that, both the gears which are engaged, always rotate in opposite direction.
  • The gear drive consists of two wheels. The smaller wheel is called as pinion and larger wheel is called as gear. 


Gear Drive
Gear Drive

Speed ratio or gear ratio

Speed ratio or gear ratio is defined as the ratio of pinion speed to the gear speed.

It is also defined as the ratio of number of teeth on gear to the number of teeth on pinion or it is the ratio of diameter of gear to the diameter of pinion.

Let, ng and np = Gear and pinion speeds in r.p.m.

dg and dp = Diameter of gear and pinion in mm

Zg and Zp = Number of teeth's on gear and pinion

Gear ratio or speed ratio = np/ng = dg/dp = Zg/Zp


Spur Gear Drive

  • Spur gears are used to transmit motion between two parallel axes shafts.
  • They are the simplest of all the gears and easiest in production.
  • The teeth of spur gears are cut along the periphery and parallel to the axis of gear.
  • Spur gears can be made of steel, brass, other metals and plastics.


Advantages of Spur Gear Drive

  • Spur gears are easy to manufacture.
  • They are made in variety of sizes from less than 25 mm to several cm in diameter.
  • These gears are less expensive.
  • Efficiency of spur gear is high (up to 98 %)


Disadvantages of Spur Gear Drive

  • Spur gears are not used for high speed applications.
  • The operation of spur gear is noisy.


Applications of Spur Gear Drive

  • Spur gears are commonly used in machine tool gear box, automobile gear box, watches, etc.


Gear Train

  • A gear train is a combination of two or more gears which is used to transmit motion from one shaft to another shaft.
  • Gear train is necessary when it is required to obtain large speed reduction within a small space.
  • The nature of the gear train used depends on the required velocity ratio and the relative position of the axes of shafts.
  • Gear trains are commonly used in various machines (lathe, milling, drilling, etc.), automobiles, clocks, ships, watches, etc.


Read More Articles: What is Chain Drive ? | Types, Advantages & Disadvantages

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