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.

This clutch has toothed plate which engages when the teeth become enmeshed.
Dog Clutch is also known as Claw Clutch.
It is most commonly used in constant mesh gearboxes. 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 the clutch are designed in such a way that one will push the other and both will rotate at the 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 the 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 of 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 a sleeve having two sets of internal splines. It slides on a splined main shaft with a smaller diameter of splines.
• This type of clutch is generally made of two round plates, one fixed to the drive shaft and one to the shaft being driven.
• These dog clutches have protrusions in its face, similar to battlements on top of the castle wall. The gears in the main shaft to which these dog clutches get connected have like-sized recesses cut into its face.

Working Of Dog Clutch:

• Dog clutches are mainly used to lock different gears to rotating input and output shafts in the manual transmission system.
• When the dog clutch needs to be connected with a certain gear of the main shaft to obtain a certain gear ratio, the dog clutch is slid towards the gear in the main shaft to which it is needed to be connected.
• 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.

Types Of Dog Clutch:

1) Rotating Dog Clutch:-
This is the simplest type of dog clutch in which one component has teeth on its circumference and the other component has slots.
When the two components are brought together, the teeth lock into the slots and hence the clutch is engaged.
The disengage the clutch the two components are moved away from each other.

2) Sliding Dog Clutch:-
It is one of the most common types of dog clutch. In this type of dog clutch, there are two mating components that have interlocking teeth and slide axially to engage or disengage. For engaging the clutch, one component slides towards the other and for disengaging that component slide away from the other component.

Advantages Of Dog Clutch:

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 Of Dog Clutch:

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

Applications Of Dog Clutch:

1) Dog clutches are mainly used in stick shift automobile gearboxes, marine propeller drives and on drives of heavy machinery.
2) Dog clutches are also used in racing cars as there should not be any power transmission loss in racing cars and as there is no chance of power transmission loss in dog clutches so it is best suitable to be used in racing cars.

Maintenance Of Dog Clutch:

1) Regular Inspection:-
The dog clutch should be regularly inspected for any signs of wear, damage or misalignments. Check the wear on the teeth, springs and other components. It is necessary to repair or replace parts in case there is wear or tear so that further damage is prevented.

2) Lubrication:-
The dog clutch should be properly lubricated regularly for proper and smooth functioning of the clutch.
The lubricant recommended by the manufacturer should be used and the frequency of lubrication should also be according to the manufacturer’s recommendation.
Proper lubrication helps in reduces the chance of wear and tear in clutch parts and hence increases clutch lifespan. It also improves the performance of the clutch.

3) Regularly check the shift system:
The shift system should be regularly checked and adjusted to ensure that the dog clutch is moving correctly with full engagement.
Worn cables or linkage will result in a decrease in dog clutch travel which can cause gear jumping under load which will wear the faces of the dog clutch teeth very quickly.