What’s scarier? Ghosts or Vampires? Trick question. The scariest thing is driving without a functioning car steering system. Without it, you can’t tell your car to move to the left or right. Scary, right?
So what exactly is a car steering system and how it works?
A car steering system consists of (i) steering wheel, (ii) steering column assembly, and (iii) steering rack. These 3 components work together to give you the ability to steer your car. As an added bonus, the steering system also makes steering our car easier with what we call a “gear reduction” (more to that later).
In this article, we will be looking at each individual component that makes up our car steering system. Feel free to jump to any section below to find out more about a particular part.
Car Steering System Overview
There are many different types of car steering system. Some runs purely on mechanical, some runs on hydraulic, some runs on electric, some runs on both. But forget all of that. Today, we are going back to basics and only look at purely mechanically car steering system to help you understand steering system at the most fundamental level.
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A basic car steering system will have 3 main components: (i) Steering Wheel, (ii) Steering Column Assembly and (iii) Steering Rack. To help paint a picture in your head, imagine this.
Imagine that you are sitting in the driver seat, you would hold onto the steering wheel. Just below the steering wheel is the steering column housing, where you have your signal switches, headlight switches and etc. What you don’t see, is that it also hides a steering column and an intermediate shaft that runs down your foot rest and into the underside of your car, where it meets the steering rack. Finally, the steering rack have two ends that goes into the knuckle on both our car wheels.
That is the entirety of a (simplified) car steering system.
As you can see, all these parts are connected mechanically. So it make sense that when you move the steering wheel, the others will follow and somehow the car wheels will turn to where we want it to turn. But how exactly does it do that? To answer that, it would be very helpful to break it down one by one and find out what they do individually.
Steering Wheel
Let’s start with something we are all familiar with – the steering wheel. This part needs no introduction. It is the circular object that we always holds and turns when driving. If you’re not doing that, then you probably should!
You will find your car horns, turn signals and window wiper switch here.
We are also beginning to see more functions added here in modern vehicles, designed to keep driver’s hands on the wheels. These includes audio system, cruise control and many others.
The steering wheel is responsible for taking our steering input, while the rest of the steering system responds accordingly to this input to change the car’s trajectory. It’s like the keyboard to our computer. It just accepts whatever we do because it’s all mechanical, and then it relays the information (how much have we turn, how fast are we turning, etc) to the rest of the steering system.
Fun fact of the day – The larger the steering wheels, the easier it is for you to turn your car.
This is because…
Torque = Force * Distance
Or in another words,
Turning Power = How hard we turn * How big the steering wheel is.
Yes, while that is true. Our steering wheels have actually become smaller over the years. This is because of the introduction of power assisted steering rack. It allows us to use a smaller steering wheels while still keeping it easy to turn. Less space taken up by steering wheel gives more flexibility to the car manufacturer to design and optimize for comfort and safety.
The steering wheel then mounts directly onto the steering column assembly.
Steering Column Assembly
Steering column assembly is a fairly complicated part and it carries a multitude of functions. To simplify it, we can break it down into three main parts, namely (i) steering column housing, (ii) steering column, and (iii) intermediate shaft.
In essence, here’s basically what they do:-
- Steering column housing houses all the electrical wiring and mechanisms of the switches that you find on your steering wheel.
- Steering column is a solid metal shaft that transfers your steering effort from the steering wheel to the steering rack.
- Intermediate shaft allows us to connect the steering column to the steering rack at a slight angle.
Speedkar made a really great Youtube video disassembling a steering column and explaining how a steering column work. It’s so informative, it’s the best 9 minutes of my life. Have a go at it!
As you can see, steering column assembly is just the whole thing. Let’s slow things down a little bit and take a look at them one by one.
Steering Column Housing
Steering column housing is the upper portion of your steering column assembly. As the name suggests, it’s a house that keeps all the internal wiring and inner mechanisms of your steering wheel switches.
If you open it up, you will find:-
- Airbag module
- Multi-function switch
- Window wiper switch
- Ignition switch
- Car headlight
- Turn signal
- Car horn
Steering column housing is one of the most overlooked part of our car steering system because it typically requires little to no maintenance. Hip hip, hurray!
Steering Column
Steering column is the lower portion of your steering column assembly. You will find it just below the steering column housing, somewhere near your foot rest.
The primary purpose of a steering column is to take the rotational motion from the steering wheel and then pass it down to the steering rack located below it.
It’s nothing fancy really, just a simple metal shaft. This metal shaft is structurally connected to the steering wheel at the top, and the steering rack below it. So when you turn the steering wheel, the steering column will turn accordingly, which also turns the steering rack.
Well, it doesn’t just stop there. Did I tell you that steering column saves lives too?
Invented by Bela Barenyi, the steering column has a collapsible mechanisms that collapses during heavy frontal impact. It prevents the steering column from impaling through the steering wheel and (possibly) the driver’s head like a spear.
The collapsible design features an inner and outer sleeve. Outer sleeve is bigger, hollow tube. Inner sleeve is a smaller tube so that it can fit inside the outer sleeve. Steel bearings are placed between the inner and outer sleeve to maintain firm contact between the two sleeves. Finally, a special kind of resins glues the steel bearings to the sleeves.
Here comes the exciting part!
The resins are basically glue, and so they naturally holds the steel bearings in place by absorbing and redistributing any vibration / force. But, the special resins glues are designed to withstand only a specified amount of pressure. When the pressure exceeds the specified level during an unfortunate frontal collision, the special resins absorbs as much impact as they can and then shatters into tiny pieces. Without the resins holding the steel bearings in place, the inner sleeve falls down the bigger hollow sleeve like a telescope.
Let’s back up a bit here. The steering column just did two things very quickly and beautifully. First and foremost, the resins themselves absorbs a significant amount of the steering column’s thrusting force, which reduces the amount of force that’s going to hit you. Secondly, when the inner sleeve retracts like a telescope, it effectively slows down the time of impact. When all of these add up, it could mean the difference between a minor injury or a devastating death.
Based on statistics from National Highway Traffic Safety Administration, collapsible steering column helps to prevent 1,300 fatalities and 23,000 non-fatal injuries on an annual basis.
Pretty remarkable, are they not? Anyway, the bottom part of the steering column is directly connected to the intermediate shaft.
Intermediate Shaft
Okay, if steering column can already transfer the steering wheel rotations to the steering rack, why do we need another shaft to do the job? So why then, do we have such a complicated looking mechanism here? With all the universal joints and whatnot? Why not just stick to using a simple, straight shaft like a steering column?
Those are perfectly valid questions. A simple straight shaft is indeed good enough to transfer the rotational motion. But, it would be very awkward to drive with a steering wheel that’s lying flat on a horizontal plane, instead of standing upright. The picture below speaks for itself.
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There is no arguing that the steering wheel on the left looks 10 times more comfortable and 20 times cooler. To achieve this level of awesomeness, we deploy two universal joints which you can find on the intermediate shaft.
Universal joints are these mechanical hinges that can rotate freely, while being inclined at an angle. Using these properties, we are able to connect the steering column and intermediate shaft together at an angle while not losing any of the rotational energy from the steering wheel. It’s a win-win.
The intermediate shaft then goes into the steering rack.
Steering Rack
Steering rack is essentially an enclosed metal casing with rack and pinion gears inside of it. It is connected to the bottom part of intermediate shaft.
The main reason why we need steering rack is to:
- Helps to convert rotational motion to lateral motion
- Makes steering easier through gear reduction
Okay, so a quick recap.
When the driver turns, the rotational motion gets transferred from the steering wheel, through the steering column, then the intermediate shaft, and finally arrives at the pinion gear of your steering rack.
Steering rack is where the rotational motion of the steering wheel gets converted to a lateral motion (left or right movement). How? Through its rack and pinion gears. The pinion gear meshes with a straight row of teeth, known as the rack gear.
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When the driver turns, the pinion gear forces the rack gear to move side to side. As the both ends of the rack gear is connected to the car wheels, the car wheels will move side to side as well.
That’s exactly how cars changes direction when we turn our steering wheel.
But…
A car generally weighs around 1,500 kg. Steering an object of this magnitude is just now going to be easy, especially if you car is stationary. So as usual, the engineers try to make things more convenient and better.
They came up with what we call… power assisted steering rack, or power steering in short. Power steering rack works the same way as how a non-power assisted, rack and pinion steering rack would, but with added components. These could be either an engine-driven pump (hydraulic power steering) or computer-controlled electric motor (electric power steering). They provide the additional power to help you turn the car.
Regular Steering:
Car Steering = Driver’s Steering Effort + Gear Reduction
Power Steering:
Car Steering = Driver’s Steering Effort + Gear Reduction + Additional Support (Hydraulic / Electric)
If you’re wondering how they work, that would be a whole new chapter of story and we won’t be discussing it today. But, we’ll be writing an article about that soon, so stay tuned!
The Finish Line
A car steering system is basically just steering wheel, steering column assembly and steering rack. They work together in harmony to make turning your car possible and comfortable.
Car steering systems are usually very robust. In another word, they are built to last. But if you feel that you have any problem with your car steering system, don’t hesitate to get them inspected because it can take away your ability to steer your car.
If you’re not sure whether your steering system is faulty, we have written an article about the Top 7 steering rack problems you can identify [with Videos!]. Give it a read, it might just steer you in the right direction.
Until then, drive safe and drive smart!
