The car is regarded as one of the most influential inventions in recent history, with multiple elaborately engineered mechanisms. Various mechanisms have been used and refined throughout the development of cars, including the engine, the transmission, the brakes, etc. However, one invention stands above these as one of the most crucial developments to let the car effectively perform its function: the differential.
The car’s basic drivetrain is 4-wheeled, but only the hind wheels are motorized. This is done because it's much simpler for the hind wheels to move, and the front wheels to steer. The only limitation of this drivetrain is the inability to turn. To turn, the outer wheel must travel faster than the inner wheel. If hind wheels were motorized by one axle, there would be no way for the hind wheels to travel at different speeds.
This wasn’t an issue for the car’s predecessors, such as a horse wagon, where wheels were on individual axles. A plausible solution to this issue would be motorizing each wheel, which would be too expensive and impractical. Because of this, engineers had to find a solution to maintain motorized hind wheels and have effective turning capabilities.
The differential mechanism can send power at different rates to each wheel, as seen in the image below that shows its basic theory. The source of power influences the two-wheel hubs through the center hub, which pushes the wheels forward or backward. However, the center hub has a separate rotational force that can adjust to each wheel hub. The wheel hubs are independent from each other, which means they can move at different speeds. Because of this, the differential system maintains a single power source while both wheels are on individual axles.
By adding more rods for smoother turning, we see how this system evolves into the 3-gear differential that is seen in modern-day cars. Adding more rods is crucial for functionality, because it allows the wheels to spin and turn consistently, whereas without the added rods the wheel hubs would eventually lose contact with the center hub. With an 8-rod support, there would be a constant connection between the wheel hubs and the center hub, which lets the wheels move with no issues.
Conclusion
The invention of the differential has had a very definite influence on the automobile landscape we see today, and the same concept has been integrated into every modern car design. Beyond usage in cars, The differential has become a staple in educational engineering kits, such as the Lego education line where a custom-made differential is used to teach children about its importance within cars. The differential exemplifies how basic theory can have such an effective application in practice, and how simple mechanics can be used to solve significant problems.
Works Cited
Industry, US Auto. “Around The Corner - How Differential Steering Works (1937).” YouTube, Video, 16 Sept. 2009, https://www.youtube.com/watch?v=yYAw79386WI. Accessed 27 Apr. 2024.
Nice, Karim, and Talon Homer. “How Differentials Work.” HowStuffWorks, 4 Apr. 2023, https://auto.howstuffworks.com/differential.htm. Accessed 27 Apr. 2024.
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