Understanding Your Car?s Steering System
You spin the steering wheel and the car turns. Simple, right? Well, not exactly. When it comes to cars, many drivers don’t think twice about how the movement of the steering wheel is transferred into movement of the wheels, but ask a mechanic and they’ll explain to you that there’s actually a lot going on down there. In this article, we’ll take a look at two different steering systems — the rack and pinion system and the recirculating ball system — to give you a better understanding of how it all works. We?ll also look at the role that power steering plays in modern vehicles.
The basics of steering
You might not realise it, but when your car turns, the front wheels will not be pointing in exactly the same direction. The reason for this is simple: the outside wheel is always going to be following a circle with a larger radius and, as such, it will always be making a wider turn than the other. As a result, the steering needs to be designed in a way so that the outside wheel turns a little less than the inside wheel. This is the most fundamental consideration when a steering system is being designed.
The rack-and-pinion system
A rack-and-pinion steering system, commonly used in smaller vehicles such as sedans, is made of the following parts:
- The steering shaft, which is attached to a…
- Pinion gear, which is connected to a?
- Rack, which has at each end a?
- Tie rod, which connects to a?
- Steering arm, which helps turn the wheel.
Here?s how it works. When you turn the steering wheel, the steering shaft causes the pinion gear to spin, which in turn moves the rack, providing the linear motion necessary to turn the wheels. Because the rack is connected to both wheels, running across the length of the car (from side to side), it is able to control the angle of each wheel depending on which way and how hard the vehicle is turning.
The re-circulating ball system
More likely to be seen in larger vehicles such as trucks and 4WDs, the re-circulating ball system actually isn’t that much different to the rack-and-pinion system. The steering mechanism has a worm gear within a gear-teethed block containing a threaded hole. The gear teeth cut into the outside, engaging the sector gear, which then works to move the Pitman arm. When the steering wheel is turned, the shaft rotates the worm gear inside of the block. The worm gear is fixed so that, when the wheel is turned, it moves the entire block instead of screwing further into the block. The turning block transmits the motion through the Pitman arm, allowing the wheels to turn.
Power steering
In both the rack-and-pinion system and the re-circulating ball system, the rack has a cylinder with a piston in the middle, with two fluid ports each side of the piston. By adding high-pressure fluid to one side of the piston, the extra power is gained when turning. In order to work, the system will also need a rotary-vane pump to control the hydraulic power, and a rotary valve to help sense the force on the steering wheel. During a car service, your mechanic should check for hydraulic fluid leaks to ensure power steering remains efficient.
