Spur & Helical Gear system for 2 & 4 wheelers

Spur Gear:

  • Easier to manufacture
  • No axial forces to deal with
  • Produce a characteristic whine at higher speeds     
  • Less demanding of lubricant
  • Can slide in and out of connected gear

Advantages of Spur Gear:

  1. Spur gears have high power transmission efficiency.
  2. They are compact and easy to install.
  3. They offer constant velocity ratio.
  4. Unlike belt drives, spur gear drives have no slip.
  5. Spur gears are highly reliable.
  6. They can be used to transmit large amount of power (of the order of 50,000 kW).

Disadvantages of Spur Gear:

  1. Spur gear drives are costly when compared to belt drives.
  2. They have a limited center distance. This is because in a spur gear drive, the gears should be meshed and they should be in direct contact with each other.
  3. Spur gears produce a lot of noise when operating at high speeds.
  4. They cannot be used for long distance power transmission.
  5. Gear teeth experience a large amount of stress.

Applications of Spur Gear:

Spur gears have a wide range of applications. They are used in:

  1. Metal cutting machines
  2. Power plants
  3. Marine engines
  4. Mechanical clocks and watches
  5. Fuel pumps
  6. Washing Machines
  7. Gear motors and gear pumps
  8. Rack and pinion mechanisms
  9. Material handling equipments
  10. Automobile gear boxes
  11. Steel mills
  12. Rolling mills

Helical Gears:

  • Expensive to manufacture
  • Requires thrust bearing to counter axial forces
  • Quieter and smoother
  • Demands good lubrication
  • Less localised tooth stress (Mainly due to increased contact area)

Advantages of helical gears:

  1. As we have discussed in our previous post that in case of helical gear, engagement of helical gear teeth will be gradual and engagement will start from one end of a tooth of helical gear with the other tooth of mating helical gear and spread continuously throughout the tooth as gear rotates. Such gradual engagement of helical gear will provide the silent and smooth operation.
  2. Helical gears are preferred for heavy load applications
  3. Helical gears could be used to transmit the motion and power between two parallel shafts and also between two non parallel shafts.
  4. Helical gears will have more capability to transmit load between two parallel shafts as compared to similar module and equivalent width of spur gears.
  5. There will be less wear and tear in case of helical gear during operation as compared to wear and tear in case spur gears operation as if we consider helical gears operation, load will be distributed between several teeth at any time and that is why there will be less wear and tear in operation of helical gears.

Disadvantages of helical gears:

  1. When a pair of helical gear meshes with each other, there will be creation of axial thrust load on gear due to helix angle of gear teeth and therefore gearbox designer has to select such bearings those are able to absorb and support this axial thrust load.
  2. There will be sliding movement between mating gear teeth in case of helical gear and heat generation will be more as compared to spur gear application. Therefore helical gear requires good quality of lubrication.
  3. One pair of mating helical gear will have less efficiency as compared to efficiency of mating spur gears of similar size.
  4. Power loss in case of helical gear train operation will be more as compared to spur gear train operation.
  5. Manufacturing and designing cost of helical gears will be more as compared to spur gear designing and manufacturing cost.

Applications of helical gears:

Helical gears are normally preferred to work under heavy load efficiently. When we need silent operation such as in automobile applications, we prefer to use helical gears as such gears work silently and smoothly.
Areas of applications of helical gears are very large but let us find few applications here where helical gears are preferred to use.

  1. Helical gears are used in fertilizer industries, Printing industries and earth moving industries
  2. Helical gears are also used in steel, Rolling mills, section rolling mills, power and port industries.
  3. Helical gears are also used in textile industries, plastic industries, food industries, conveyors, elevators, blowers, compressors, oil industries & cutters.

Helical gears are immovable once meshed, spur gears can move about to engage and disengage gears. Due to axial forces more rigid casing, thrust bearing and good lubrication is required. So for cost and weight savings spur gears are used in motorcycle gearbox.

Question :  What types of gear system in used in 2-Wheelers & 4-Wheelers? 

                        A) 2-wheelers use spur gears & 4-wheelers uses Helical gears. 

                        B) Both Spur & Helical gears are used in 2 & 4 Wheelers.

                        C) Only spur gears are used in 2 & 4 wheelers.

                        D) Only Helical gears are used in 2 & 4 wheelers.

                        E) None of the above. 

Answer:        A) 2- wheelers use Spur gears & 4- wheelers uses Helical gears 

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