What is a Worm and Crank?
2 Answers
Worm and crank refers to a worm and peg steering gear, where the worm serves as the driving component and the crank peg as the driven component. The steering worm, featuring trapezoidal-section threads, is supported by ball bearings at both ends of the steering gear housing, meshing with a conical peg. Below is an introduction to the principle of the worm and crank: 1. The worm has trapezoidal threads, and a finger-like conical peg is supported by bearings on the crank, which is integrated with the steering rocker arm shaft. 2. During steering, turning the steering wheel rotates the worm, causing the conical peg embedded in the worm's helical groove to rotate on its own while moving in an arc around the steering rocker arm shaft. This drives the crank and steering drop arm to swing, thereby turning the steering wheels through the steering linkage. 3. This type of steering gear is typically used in trucks that require greater steering force.
As a veteran driver with over 20 years of experience, I'm quite familiar with the worm and sector mechanism. It's actually a crucial component in automotive steering systems, particularly common in older vehicles. Simply put, the worm is a spiral-shaped part fixed to the steering column shaft. When you turn the steering wheel, the worm rotates accordingly; it then drives a sector arm (a rocker arm-like component), which connects to the wheels, thus converting your steering input into actual wheel movement. This design was widely used in vehicles from the 70s and 80s, like the classic Santana or Jetta models - the steering felt somewhat heavy, but the structure was robust and reliable. When worn out with excessive play, the steering would become loose, unresponsive, or even slip, compromising driving safety. That's why during routine maintenance, I always remind technicians to inspect the steering mechanism to prevent potential hazards. Modern cars have mostly switched to rack-and-pinion steering systems which are much lighter, but understanding this older technology helps you better comprehend how vehicles operate.
