Cycloidal Drives

Internal Configuration

Application

Characteristics

The mechanism through which the speed of an input shaft is reduced by a fixed ratio, is known as a Cycloidal Reducer or Cycloidal Drives. The word Cycloidal has been derived from Hypocycloidal, which means the curve traced by a point on the circumference of the circle. This curve tracing process repeats inside the circumference of a larger fixed circle. The path traced by a tooth of a planetary pinion which rotates inside a ring gear, is similar to the curve tracing by a point on the circumference of a circle.

Internal Configuration: Cycloidal Drives
Up to a certain extent, the appearance of the internal configuration of Cycloidal Drives is similar to an internal gear pump, but here the output shaft is driven by an outer gear. A bearing which has been departed from its usual/regular form is driven by the input shaft drives. In turn, the Cycloidal disc is driven by this departed bearing in an eccentric. The cycloidal disc starts to move in cycloidal motion. In compare to a stationary ring gear, the Cycloidal Drives have a larger perimeter. Through out the face of the cycloidal disc, there are output shaft pins or rollers present in series. When the Cycloidal disc starts to rotate, the output shaft is directly driven by these output shaft pins. The radial motion which is generated during the motion of the Cycloidal disc, is not translated to the output shaft.

A closely and firmly attached cycloidal input gear set and a low speed helical output gear set are present in the Cycloidal Drives. This combination represents a very durable, quiet and efficient gearbox. A high speed shaft along with a bearing which has been departed from its usual/regular form and a low speed shaft assembly are the main elements in a Cycloidal drive. It also consists cycloidal discs but number of lobe is one less than the number of ring gear pin. The pins and ring gear roller are fixed in the Cycloidal drives.

Characteristics of Cycloidal Drives
The transmission system provided by the Cycloidal drives are very durable and efficient and having five times more shock load capacity. But, along with this advantage, there are some disadvantages also. Due to their method of transmitting motion, they show inflected torque and speed. The ripples are caused from the eccentric motion inside the drive, and slowed speed is the evidence of it. Industries, where smooth motion is require, problems are generated due to these ripples. To achieve ratio below 50:1 is very hard and also the torsional stiffness of the Cycloidal drives is low. The other disadvantages of Cycloidal Drives are the high initial as well their high maintenance cost.

Applications of Cycloidal Drives
For different applications, the Cycloidal drives are useful. These drives are suitable in boats. These drives turn their propeller blades vertically and generate lift over them. These drive vessels comparatively having deep drafts and therefore, these are not very suitable in swallow water. These drives have proved their reliability and robust capacity in the boat industry.