ClassX Video Lessons Youtube Channel The Engineering Mindset Differential explained – How differential works open, limited slip
Have you ever wondered how cars manage to turn smoothly without the tires slipping? The secret lies in a fascinating component called the differential gear train. Let’s dive into how it works and why it’s essential for vehicles.
A differential gear train is a system of gears that allows the wheels of a vehicle to rotate at different speeds. This is crucial when a car turns because the wheels on the outside of the turn need to cover more distance than the wheels on the inside. Without a differential, both wheels would rotate at the same speed, causing tire slippage and making the car difficult to handle.
In a rear-wheel-drive car, the differential is located between the two rear wheels. In a front-wheel-drive car, it’s between the front wheels. Four-wheel-drive vehicles have differentials at both the front and rear. For simplicity, let’s focus on rear-wheel-drive cars.
When a car moves in a straight line, the engine sends power through the drive shaft to the differential, which evenly distributes this power to the rear wheels. However, when the car turns, the differential allows the wheels to rotate at different speeds, preventing tire wear and improving handling.
An open differential allows the wheels to rotate at different speeds but can cause problems on slippery surfaces. If one wheel is on ice, it will spin freely, and the car may get stuck. This is where a limited slip differential comes in handy. It uses a clutch system to limit the slip of the wheel with less traction, ensuring power is distributed to both wheels.
The differential consists of several key components:
The engine’s power is transferred through the drive shaft to the pinion gear, which rotates the ring gear. The ring gear, in turn, rotates the casing and the attached spider gears. When the car moves straight, the spider gears don’t spin on their axis, and the side gears rotate at the same speed, propelling the car forward. During a turn, the spider gears allow the side gears to rotate at different speeds, accommodating the different distances each wheel travels.
To truly grasp how a differential works, building a model can be incredibly helpful. You can 3D print the components or have them printed by a service like PCBWay. Assembling and experimenting with the model provides hands-on learning that enhances understanding.
The limited slip differential includes additional components like clutch packs, which consist of friction plates and discs. These components work together to limit the slip of the wheel with less traction, ensuring power is distributed more evenly, especially on slippery surfaces.
In summary, differentials are crucial for vehicle performance and safety, allowing wheels to rotate at different speeds during turns and providing better traction on slippery surfaces. Understanding how they work can deepen your appreciation for automotive engineering.
For more insights into automotive systems, explore additional resources and videos on related topics.
Engage with an online simulation of differential gears. Observe how the gears interact during turns and straight-line driving. Pay attention to the differences between open and limited slip differentials. Reflect on how these mechanisms affect vehicle handling.
Build a physical model of a differential using a 3D printer or a kit. Assemble the components and demonstrate how the differential allows wheels to rotate at different speeds. This hands-on activity will solidify your understanding of the gear train’s mechanics.
Analyze real-world scenarios where differentials play a crucial role, such as in off-road vehicles or sports cars. Discuss the advantages and limitations of open and limited slip differentials in these contexts. Present your findings in a group discussion.
Create a short video explaining the function of a differential. Use animations or diagrams to illustrate the differences between open and limited slip differentials. Share your video with classmates to enhance collective learning.
Visit a local automotive workshop or a university lab with a focus on automotive engineering. Observe the disassembly and reassembly of a differential. Ask questions to deepen your understanding of its components and operation.
Here’s a sanitized version of the provided YouTube transcript:
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If this gear rotates in this direction, then which direction will this gear rotate? Tell me your answers in the comment section down below, and I’ll show the answer towards the end of this video.
We’re going to understand how the differential gear train works, as well as where and why we need it. You can even build your own model to fully see and understand it. You can download my design files for free and have them 3D printed by PCBWay, who have kindly sponsored this video. Links down below for that.
A differential gear train looks something like this, and we usually find them located between the back two wheels of a rear-wheel-drive car. On a front-wheel-drive car, we find it between the front two wheels, and we find one at the front and another at the rear of a four-wheel-drive car. However, we’re going to stick with a rear-wheel-drive car in this video for simplicity.
So why do we need it? When a car moves in a straight line, the engine provides power through the drive shaft into the differential, which divides the power between the two rear wheels. This propels the car along, and so the wheels will all rotate at the same time and speed. However, when a car turns, the front two wheels change direction, but the rear wheels remain in position. The wheels are now following different length paths; the inner path is shorter than the outer path, so the outer wheels must cover a longer distance in the same amount of time, which means they need to rotate faster. Thus, the rear wheels need to turn at different speeds.
The differential allows the wheels to rotate at different speeds. If this wasn’t installed, then both wheels would rotate at the same speed on corners, causing the tires to slip and wear out. The car would become harder to handle, and the forces could even snap the axle. Therefore, we allow the rear wheels to rotate at different speeds to prevent that from occurring.
We can see from this basic model differential that if I hold one of the wheels, the other can still rotate. This is known as an open differential. The problem we face is that if one of the wheels travels over a slippery surface, such as ice, almost all of the engine’s power will transfer to the wheel with the least resistance, causing the car to become stuck. To solve that, we use a limited slip differential, and we will see how that works later on in this video.
By the way, you can also learn how a car generates electricity in our detailed alternator video. Links down below for that.
Let’s look at the main parts of a rear differential. First, we find the main housing, which surrounds all the internal components. Somewhere on the casing, there will be a removable plate allowing access to the internal gears. The casing stops debris from the road damaging the internal gears, and it also retains oil within the housing to lubricate the gears and reduce wear.
If we remove the housing, we can see the various gears attached to the axles, supported by a number of bearings to ensure smooth rotation. The engine provides power via the input gear, known as the drive pinion gear. The pinion gear connects to the ring gear, which is much larger. Notice the gears are spiral cut; they could be straight cut, but a spiral cut increases the contact surface area. In this example, we have 43 ring teeth and 11 pinion teeth, giving a ratio of about 3.9 to 1. A low ratio increases fuel efficiency but decreases acceleration, while a high ratio decreases fuel efficiency but increases acceleration. Car designers need to take this into consideration.
The ring gear is mounted to the differential casing, which then supports two smaller internal gears known as the spider gears. The spider gears are often joined with a small metal shaft. When the ring gear rotates, the spider gears will travel around the same axis; however, the spider gears can rotate on their own axis. We use two spider gears to distribute the forces evenly. The spider gears connect with two other gears known as the side gears—one connects to the left wheel axle and the other connects to the right wheel axle. The spider gears allow the axles to rotate at different speeds while still transferring torque and rotation to the wheels.
Let’s understand how the open differential works. The engine provides power through the pistons moving up and down, which rotates the camshaft. This transfers through the clutch and into the transmission. The power then transfers through the selected gears within the transmission and out to the drive shaft. The drive shaft transfers this into the differential at the rear of the car, from where it is distributed to each of the rear wheels.
Looking inside the differential, the drive shaft is connected to the pinion gear, which is directly connected to the ring gear. The drive shaft rotates the pinion gear, which rotates the ring gear. As the ring gear rotates, the casing must also rotate, and as the spider gears are attached to this, they rotate with the casing. If the car is traveling in a straight line, the force is equal on both rear wheels, so the spider gears will not spin on their axis. As they rotate with the casing, they transfer the torque into the side gears, causing them to rotate, which rotates the axles and tires, propelling the car forwards.
The side gears and the spider gears will rotate at the same speed and direction as the ring gear. If the car was lifted up, we could see that all the gears are able to turn on their own axis when needed. If you turned the wheels by hand, you could turn one wheel and the other wouldn’t move. You could also turn both wheels together or even turn them in opposite directions. When the car turns right, the left wheel axle and side gears must rotate faster, while the right wheel axle and side gear must slow down.
So while turning, the wheels are both rotating forwards; the left gear is just rotating faster, causing the spider gear to rotate and slow the right gear down. The difference in speed between the side gears is inversely proportional.
The best way to understand is to build your own model version so you can see it all in action. I’ve made this design myself, and you can download my design files for free. You can just 3D print them or even easier, upload the files to PCBWay, who have kindly sponsored this video, and they will print your parts and ship them directly to you. Their website shows a preview of the component, and then you just choose the material and submit your order. The component then arrives in the post, and just look at how good this one has come out, especially in comparison to my homemade 3D printed version. I’m really impressed with this.
So we just assemble the components, and then I can play around with the model and see exactly how it works. Nothing beats learning hands-on. So I’ll leave a link for you in the video description. Do check them out; they offer everything from 3D printing, CNC, injection molding, and even sheet metal fabrication. Just click the link down below to get started and build yourself a model differential.
The problem with open differentials is that they send power to the wheel with less friction, which causes the wheel to slip, and that’s not good when the car travels across a surface such as ice. So we need a slightly different design that limits the slip of the wheel with less friction, which is where the limited slip differential comes in.
The clutch-based version is probably the most common, so we will learn how this works. With the limited slip differential, we have the same main components: the drive pinion, the ring gear, the casing, the spider gears, the side gears, and the axles. However, we do have some additional parts. Behind each side gear, we find a clutch pack, which consists of multiple layers of two different discs: the clutch friction plates and the clutch discs.
The clutch friction plates have a special textured surface that increases friction. Part of the disc extends outwards and slots into the grooves of the differential case. When the ring gear rotates, it rotates the casing, and so the clutch friction plates will also rotate. The clutch discs are sheets of metal with teeth around the inner edge, which will slot into the splines of the side gears, interlocking the two together. When the side gear rotates, the clutch disc rotates as well; however, the clutch friction plates do not interlock with the splines of the side gears, so they will rotate around it.
These two discs are stacked alternately to form the clutch pack. On each side, a spring is then inserted into the middle, providing a light pushing force, so the side gears will slightly compress the clutch packs. The friction material of the clutch plates will grip onto the clutch discs, temporarily joining them together so they will rotate together. However, if a certain amount of force or torque is applied to the wheel, then the two discs will break this temporary joint and slip past each other.
So when the car turns, the wheels have to change speed. This will provide enough force to break the temporary joint, allowing the side gears to rotate at different speeds, while the main casing continues to rotate at the same speed. When the car travels in a straight line, the friction between the clutch packs temporarily locks the side gears so that they rotate at the same speed. The main casing will rotate with them and provide the pushing force.
With the limited slip differential, when a car travels across a slippery surface such as ice, the power of the engine is distributed to both wheels, allowing the car to gain some traction and continue moving forward. This isn’t possible with an open differential, and so the car will become stuck.
Okay, so at the beginning of the video, I asked you if this gear rotates in this direction, then what direction will this gear rotate? The answer is this. However, we have learned in this video that this is an open differential, and so this gear could also be held in place while all the other gears would still rotate. Did you get that correct? Let me know in the comment section down below.
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This version removes any informal language and maintains a professional tone while preserving the content’s integrity.
Differential – A mechanical device that splits the engine torque two ways, allowing each output to spin at a different speed, commonly used in vehicles to enable the wheels to rotate at different speeds while turning. – The differential in a car allows the outer wheel to rotate faster than the inner wheel during a turn, providing better traction and handling.
Gears – Mechanical components with teeth that mesh with each other to transmit torque and change the speed or direction of motion in machinery. – Engineers designed the gearbox with multiple gears to optimize the vehicle’s performance across various speeds.
Traction – The frictional force between a surface and a moving object, which prevents slipping and allows for controlled movement. – The new tire design significantly improved traction on wet roads, enhancing the vehicle’s safety.
Slip – The relative motion between a surface and an object in contact with it, often resulting in a loss of traction. – Engineers tested the anti-lock braking system to minimize slip during sudden stops on icy surfaces.
Vehicle – A machine, typically motorized, used for transporting people or goods from one place to another. – The engineering team focused on reducing the vehicle’s weight to improve fuel efficiency and performance.
Power – The rate at which work is done or energy is transferred in a system, often measured in watts or horsepower. – The electric motor’s power output was sufficient to propel the vehicle at high speeds while maintaining efficiency.
Wheels – Circular components that rotate on an axle and are used to facilitate movement in vehicles and machinery. – The design of the wheels was optimized to reduce aerodynamic drag and improve the vehicle’s overall efficiency.
Handling – The manner in which a vehicle responds to driver inputs, particularly in terms of steering, braking, and stability. – The sports car’s handling was praised for its precision and responsiveness during high-speed maneuvers.
Engineering – The application of scientific and mathematical principles to design, build, and maintain structures, machines, and systems. – The engineering team utilized advanced simulation software to model the stress distribution in the bridge design.
Model – A representation or simulation of a system or process used for analysis, design, or prediction in engineering and physics. – The computational model accurately predicted the thermal behavior of the new material under extreme conditions.
