19 August 2017

Involute gear Vs Cycloidal gear

The involute tooth profile is generally used almost everywhere and given preference over cycloidal tooth profile. First, you should know what is involute and cycloidal gear tooth profile?

What is involute gear? 

All the gear teeth have a top flat portion and two side curves. The side curves for the involute gears are in the form of the involute curve of the circle. 

It can be generated by the locus of an endpoint of an imaginary taut string unwinding from the circle.

What is cycloidal gear?

The cycloidal is a curve generated by a locus of any point on a circle which is rolling around another circle gears whose teeth profile is made of cycloidal curves is called cycloidal gears. 

The produced curve is called epicycloid if the second circle rolls outside the first circle. 

The produced curve is called hypocycloid If the second circle rolls inside the first circle.

Let us have a deep insight into the difference between involute and cycloidal gear. 

Involute gear :

  • Pressure angle remains constant throughout the operation this leads to smooth-running operation of the gears. 
  • It involves a single curve for the teeth resulting in simplicity of manufacturing.
  • Teeth have radial flanks thus are weaker. 
  • It is simple to manufacture due to the convex surface and thus are cheaper. 
  • The velocity ratio is not affected by a little variation in the centre distance.
  • Interference takes place.
  • Due to two convex surfaces are in contact, more wear and tear takes place.
  • Line of action is straight. 
  • Suitable for motion as well as power transmission. 

Cycloidal gear :

  • Pressure angle keeps on changing varies from a maximum at the beginning, reduced to zero at the pitch point and again increases to maximum this result leads to less smooth-running operation of the gears.
  • It involves a double curve for the teeth resulting in the complication in manufacturing.
  • Teeth have spreading flanks thus are stronger.
  • It is difficult to manufacture due to the requirement of hypocycloid and epicycloid and thus are costlier. 
  • To transmit a constant velocity ratio, an exact centre distance is needed.
  • There is no interference.
  • Due to concave surfaces are in contact, less wear and tear takes place.
  • Line of action is curve. 
  • Suitable for motion transmission only.