A dog clutch (also known as a positive clutch or dog gears) is a type of

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

that couples two rotating shafts or other rotating components by engagement of interlocking teeth or

dogs The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. ...

rather than by

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

. The two parts of the clutch are designed such that one will push the other, causing both to rotate at the same speed and will never slip. In engineering, a " dog" is a tool or device used to lock two components in relation to each other. Dog clutches are used where slip is undesirable and/or the clutch is not used to control

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...

. Without slippage, dog clutches are not affected by wear in the same way that friction clutches are, but result in

shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emerge ...

when shafts of different speeds are engaged. For this reason they are best used when sudden starting action is acceptable and the inertia of the system is small. Dog clutches are used inside constant-mesh

manual transmission A manual transmission (MT), also known as manual gearbox, standard transmission (in Canada, the United Kingdom, and the United States), or stick shift (in the United States), is a multi-speed motor vehicle transmission (mechanics), transmission ...

s to lock different gears to the rotating input and output shafts. A

synchromesh A manual transmission (MT), also known as manual gearbox, standard transmission (in Canada, the United Kingdom, and the United States), or stick shift (in the United States), is a multi-speed motor vehicle transmission system, where gear change ...

arrangement ensures smooth engagement by matching the shaft speeds before the dog clutch is allowed to engage. Racecar,

motorcycle A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle Steering, steered by a Motorcycle handlebar, handlebar. Motorcycle design varies greatly to suit a range of different purposes: Long-distance ...

, and large

truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...

transmissions, having less need for smooth engagement than passenger cars and higher performance demands, commonly employ dog clutches alone (without the use of synchronizers) to engage gears due to their high strength and durability and low complexity and weight. These unsynchronized gearboxes, also referred to as a dog boxes, allow clutchless shifting. Another example of a dog clutch is in the Sturmey-Archer bicycle

hub gear A hub gear, internal-gear hub, internally geared hub or just gear hub is a gear ratio changing system commonly used on bicycles that is implemented with planetary or epicyclic gears. The gears and lubricants are sealed within the shell of the ...

, where a sliding cross-shaped clutch locks the driver assembly to different parts of the

planetary gear An epicyclic gear train (also known as a planetary gearset) consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates the planet and sun gea ...

train.

References

Clutches {{Automotive-part-stub