Slide 1
An outside wheel travels farther during a turn
In a road turn, the outside driven wheel travels farther than the inside wheel. A differential allows their rotational speeds to differ.
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With rigidly linked wheels of equal rolling radius, one or both would need to slip. That can scrub tyres and load the drivetrain, especially on surfaces with strong grip.
Slide 2
A differential transmits one input to two wheel outputs
A differential gearset combines an input with two axle outputs. Its internal gears accommodate a speed difference while transmitting drive.
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For a conventional symmetric differential, the carrier speed corresponds to the average of the two axle speeds. One side can speed up relative to the carrier while the other slows by the corresponding amount.
Slide 3
Equal wheel speeds need little relative movement inside
When both wheels turn at equal speed, the internal gears need little relative motion. The assembly still transmits torque, the turning effect that drives the wheels.
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During a turn, those gears rotate relative to the carrier to accommodate the difference. The extra internal motion changes wheel speeds without requiring the engine to drive two independently controlled shafts.
Slide 4
Low grip on one side limits an open differential
An ideal open differential supplies similar torque to both sides. A low-grip wheel can therefore limit the useful torque delivered to the other wheel.
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Equal torque does not mean equal power when wheel speeds differ. A rapidly spinning wheel can receive substantial power while the vehicle makes little useful progress.
Slide 5
Locking or limited slip trades speed freedom for traction
Limited-slip or locking arrangements restrict the speed difference under selected conditions. They address traction at the cost of added complexity or tyre scrub.
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A fully locked axle is useful in some low-grip situations but resists the natural speed difference during a tight turn. Choosing a system depends on terrain, handling requirements and how engagement is controlled.
Sources
- How a Differential Works
MIT
- Basics of Mechanical Design
MIT Center for Bits and Atoms