Dog Clutch – Construction and Working

Dog Clutch is a type of clutch that uses interference to couple two rotating shafts or other rotating components like gears.

It is most commonly used in constant mesh gearbox. It functions by mating a set of regularly spaced teeth or protrusions on one half of the clutch mechanism to a set of identical recesses on the other.

This clutch engages not by friction but by interference. It has the benefit of allowing both shafts to turn at the same speed without slipping and with minimal clutch wear.

Dog clutches can not be used to control torque as is the case with a friction clutch.The two parts of clutch are designed in such a way that one will push the other and both will rotate at same speed and will never slip.

This type of clutch is made of two round plates, one fixed to the driver shaft or the gear and other on the shaft being driven.
One of the plates has a series of evenly spaced protrusions machined into its face, similar to battlement on top a castle wall. The other plate has an identically spaced series of like-sized recesses cut into its face.

When the two plates are brought together, the protrusions mate or fit into the recesses, thereby effectively joining the shafts and transferring rotational motion from one to another.
Dog clutches are used when slip and friction are undesirable and the clutch is not used to control torque.

Construction of Dog Clutch:

  • Dog Clutch consists of sleeve having two sets of internal splines. It slides on a splined main shaft with a smaller diameter of splines.
  • This type of clutches are generally made of two round plates, one fixed to the drive shaft and one to the shaft being driven.
  • These dog clutches have protrusion in its face, similar to battlements on top of castle wall. The gears in the main shaft to which these dog clutches get connected have like sized recesses cut into its face.

Working:

  • Dog clutches are mainly used to lock different gears to rotating input and outpit shaft in manual transmission system.
  • When the dog clutch needs to be connected with a certain gear of main shaft to obtain certain gear ratio, the dog clutch is slided towards the gear in the main shaft to which it is needed to be coonected.
  • The dog clutch have protrusions on its face and the gear in the main shaft has recesses of like size.
  • When the dog clutch reaches the gear, the protrusions of the dog clutch fit into the recesses of the gear and hence forming a strong mechanical coupling and transferring the rotational motion from lay shaft to main shaft.

Advantages:

1) No slip or friction involved after the engagement of clutch.
2) Heat generation is very less as no friction occurs.
3) Cost is less than friction clutch of similar torque capacity.

Disadvantages:

1) Shock is caused while engagement of clutch at any speed.
2) Cannot be engaged at high speeds.
3) When both the diving and driven shaft is at rest, some relative motion is required to engage.

Applications:

Dog clutches are mainly used in stick shift automobile gearboxes, marine propeller drives and on drives of heavy machinery.

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