The term "5th wheel" in the context of a platform truck is a bit of a historical misnomer. The name "5th wheel" actually originates from the early days of horse-drawn carriages and later early automobiles. Here's a brief explanation:
Historical Origin: The original "fifth wheel" was a mechanism that allowed the front axle of a carriage to pivot or swivel, enabling it to turn more easily. This pivot point acted as an additional "wheel" in terms of functionality, even though it wasn't a wheel in the conventional sense.
Modern Adaptation: When this concept was adapted for use in platform trucks and other vehicles, the term "5th wheel" stuck, even though these vehicles typically had only four wheels. The "fifth wheel" now refers to the pivoting mechanism or the turntable that allows the front wheels to swivel, enhancing maneuverability.
Terminology Persistence: Over time, the term has persisted, and "5th wheel" continues to be used to describe platform trucks with a similar pivoting front axle design, despite the actual number of wheels being four.
So, a 5th wheel platform truck is named for its pivoting mechanism that allows for better steering and maneuverability, not because it has an additional, physical fifth wheel.