ClassX Video Lessons Youtube Channel The Engineering Mindset How Manual Transmission works – automotive technician shifting
Manual transmission is a crucial component in vehicles with combustion engines, from everyday family cars to high-performance sports cars. But how exactly does it work, and why is it necessary? Let’s dive into the mechanics of manual transmission and explore its significance in automotive engineering.
In a typical rear-wheel-drive vehicle, several key components work together to transfer power from the engine to the wheels. These include the engine, clutch, transmission, drive shaft, differential, axle, and wheels. While front-wheel and four-wheel-drive vehicles have slight variations, they all rely on a transmission system.
The engine burns fuel to move pistons and crankshaft, creating rotational energy. The clutch connects or disconnects this energy to the transmission, which houses various gears. These gears adjust the speed and torque, ultimately driving the wheels. The drive shaft transfers power to the rear differential, distributing it to the wheels and propelling the vehicle forward.
In vehicles with manual transmission, the driver plays an active role in gear shifting. They must decide when to change gears, which gear to select, and operate the clutch pedal to engage or disengage the engine. In contrast, automatic transmissions handle these tasks automatically, allowing the driver to focus on steering and acceleration.
Think of riding a bicycle. Starting in a high gear is challenging, so we begin in a low gear to gain momentum. As speed increases, we switch to higher gears. Similarly, when climbing a hill, we shift to a lower gear. In cars, low gears provide high torque but low speed, while high gears offer high speed but low torque.
Torque is the force that causes rotation. Imagine using a wrench to loosen a stubborn nut. A longer wrench provides more torque, making the task easier. For example, applying 90 newtons of force with a 30-centimeter wrench yields 27 newton meters of torque. Doubling the wrench length to 60 centimeters doubles the torque to 54 newton meters.
Gears work in pairs, with one gear driving the other. If both gears are the same size, they have a one-to-one ratio, meaning they rotate at the same speed. If the driven gear is smaller, it rotates faster, and if it’s larger, it rotates slower. Gear trains, which include additional gears, can change the direction and speed of rotation efficiently.
The transmission consists of several components: the input shaft, output shaft, counter shaft, and gears. The input shaft connects to the engine via the clutch, causing it to rotate. Gears on the counter shaft mesh with those on the output shaft, transferring power. Helical gears, with angled teeth, reduce noise and stress compared to straight-cut gears.
Synchronizers ensure smooth gear shifts by matching the speed of the gears. A synchronizer hub and sleeve lock onto the output shaft, while a blocker ring prevents gear engagement until speeds are synchronized. This mechanism allows for seamless transitions between gears.
To reverse, the car must be stationary. An idler gear engages with both the output and counter gear, reversing the output shaft’s rotation. This setup allows the vehicle to move backward.
Understanding gear ratios helps in calculating RPM and torque. For instance, if gear A has 8 teeth and gear B has 10, the ratio is 1.25. If gear A rotates at 150 RPM, gear B rotates at 120 RPM. Similarly, torque calculations reveal how gear size affects rotational force.
Manual transmission offers a hands-on driving experience, allowing enthusiasts to control speed and torque. By understanding the mechanics of gears and torque, drivers can appreciate the engineering behind their vehicles. Whether you prefer manual or automatic, the choice depends on your driving style and preferences.
For further exploration of automotive engineering, consider checking out educational platforms like The Great Courses Plus, which offer a wealth of knowledge on various topics, including engineering and technology.
Engage in a hands-on activity where you calculate gear ratios and torque using different gear sizes. Use a set of gears and a torque wrench to measure and compare the effects of gear size on torque. This will help you understand the mathematical relationships and mechanical advantages in manual transmissions.
Utilize a virtual simulator to practice shifting gears in a manual transmission vehicle. This activity will allow you to experience the timing and coordination required for smooth gear transitions without the need for a physical vehicle. Focus on understanding the role of the clutch and the impact of gear selection on vehicle performance.
Participate in a group discussion where you share personal experiences and challenges faced while driving manual transmission vehicles. Discuss the differences between manual and automatic transmissions, and explore the reasons behind personal preferences. This will enhance your understanding of the practical aspects of manual driving.
Work in teams to construct a simple gearbox model using LEGO or similar building blocks. This activity will help you visualize and understand the internal workings of a transmission system, including the arrangement of gears and the function of synchronizers. Analyze how different configurations affect speed and torque.
Conduct an experiment to measure the torque produced by different lengths of wrenches. Use a force gauge to apply consistent force and calculate the resulting torque. This will provide a practical understanding of how torque is generated and its significance in manual transmission systems.
Here’s a sanitized version of the provided YouTube transcript:
—
[Applause] Manual transmission in automotive vehicles is an essential part of every combustion engine vehicle, from standard family cars to highly tuned sports cars. So how does it work and why do we need it? That’s what we’ll be covering in this video, which is sponsored by The Great Courses Plus. Visit the link in the video description to start a free trial and get access to some truly great online courses.
In every rear-wheel drive combustion engine vehicle, we find the following parts: the engine, clutch, transmission, drive shaft, differential, axle, and wheels. Front-wheel drive and four-wheel drive vehicles are slightly different, but they all require a transmission. The engine combusts fuel, which moves the pistons and crankshaft, creating rotation. The clutch engages or disengages the engine’s rotational energy to the transmission. The transmission contains a number of gears that transfer the power of the engine towards the wheels and enables us to change the speed and torque of the vehicle. The shaft transfers the power to the rear differential, which distributes this power to the wheels, causing them to rotate and propel the car along.
Manual transmission requires the driver to know exactly when to change gear, which gear to change to, and also to operate the clutch pedal to disengage and then re-engage the engine. We can also get automatic transmission vehicles, which will automatically do all of this for us. The driver simply needs to put the vehicle into drive, and the car will take care of the rest.
By the way, you can download a personal copy of this video and help support the channel. I’ll leave a link in the video description down below if you would like a copy. Which do you think is better and why: manual or automatic? Let me know your thoughts in the comment section down below.
If you have ever ridden a bike, you’ll know it’s very difficult to start pedaling in a high gear, so we need to start in a low gear to get the bike moving. At a certain point, our legs are spinning very fast, but we can’t go any faster, so we need to change to another higher gear. Once we reach a steep hill, we need to move to a lower gear. The same applies to a car; we start in our lowest gear and work our way up as the vehicle increases in speed, then we change down as we drive up a hill. A low gear provides low speed but high torque, while a high gear gives high speed but low torque.
Torque is a measurement of the force that causes something to rotate around a point. Think of a wrench and a nut that has seized up. Using a small wrench is very hard to free the nut, while using a long wrench will make it much easier. That’s because of torque. If we use a 30-centimeter wrench and apply 90 newtons of force, we have 0.3 meters multiplied by 90 newtons, which gives us 27 newton meters of torque. However, if we apply the same 90 newtons of force to a wrench that is 60 centimeters long, then we would get 0.6 meters multiplied by 90 newtons, which gives us 54 newton meters.
From this simple formula, you can see we have more force acting on the nut by using a longer wrench. We’re using a larger circle to turn a smaller circle. By changing the size, we change the speed and the torque. If we connect two gears and rotate one of them, the other gear would also rotate. If we attach the engine to the first gear, then this will be the driver gear, and the other gear is therefore the driven gear. When the two gears are the same diameter, we have a one-to-one ratio, which means every time the driver gear completes a full rotation, the driven gear also completes one rotation, so the output speed is the same as the input speed.
If the driven gear is half the diameter of the driver gear, then we have a one-to-two ratio, which means for every full rotation of the driver gear, the driven gear completes two full rotations. This means the driven gear is rotating much faster. If the driven gear is twice the diameter of the driver gear, then we have a two-to-one ratio, which means for every one full rotation of the driver gear, the driven gear rotates only half a turn.
To make the output rotate in the same direction as the input, we need to insert another gear, creating something known as a gear train. The middle gear is known as an idler gear. We could add many gears side by side to change the speed and also the output direction, but this will take up a lot of room. Instead, we can mount gears to the same axis and create a compound gear train, which will do the same job but take up far less space.
Looking inside the transmission, we have the main housing, which protects all the internal components and holds them in place. Inside, we have the input shaft, output shaft, and a counter shaft. A number of gears are fixed to the counter shaft, which will rotate together. On the input shaft, we also have a gear that is in constant mesh with the counter shaft. The gear teeth are at an angle known as a helical cut, which distributes the stress on the gears and makes the gear mesh much quieter than straight cut spur gears.
At the end of the input shaft is the clutch, which connects to the engine and forces the input shaft to rotate. Anytime the clutch is engaged with the engine, it causes the input and counter shaft to rotate. There are also a number of different size gears on the output shaft that are in constant mesh with the gears on the counter shaft. When the counter shaft rotates, so will the output gears. However, the output shaft does not rotate with the output gears because each output gear sits on a needle bearing, allowing the gear to rotate independently from the shaft.
The output shaft has a number of spline sections, which are grooves cut into the metal. A synchronizer hub fits over the splines, locking the hub in place so that it rotates with the shaft. Another component called the synchronizer sleeve fits over the hub. The outer surface of the hub and the inner surface of the sleeve are both splined, interlocking the two components. The sleeve can move forwards and backwards on the hub.
When the output shaft rotates, so will the hub and the sleeve, but not the output gears attached to the channel. On the outside of each of the sleeves is a shift fork and a shift rod. The rod connects to the gear shifter, which moves the rod backwards and forwards, moving the fork and sleeve accordingly. On each of the output gears, we find additional straight cut teeth that align with the spline teeth inside the sleeve. When the gear is selected, the teeth inside the sleeve align and interlock with the straight cut teeth on the gear.
The gear is now interlocked with the sleeve and the output shaft, so when the input shaft rotates, this rotates the counter shaft, which rotates the output gear, and this now rotates the output shaft. When the gear is disengaged, the sleeve returns to its default position, allowing the output gear and the sleeve to rotate independently from each other.
To overcome the problem of the output shaft and the sleeve rotating at different speeds, we use a synchronizer blocker ring. It prevents or blocks the gear from changing until the sleeve and the gear speeds are synchronized. The inner edge of the blocker ring is angled and matches the cone on the gear, allowing the blocker ring to slide on and off the gear easily.
We also have small struts inserted into the slots of the hub, held in place by a radial spring that pushes them outwards. The sleeve sits over the struts and the hub. A ridge on top of the strut interlocks with the sleeve, allowing the sleeve to move the struts back and forth. The blocker ring rotates with the hub and the sleeve. When a gear is selected, the sleeve moves towards the gear, pushing the strut against the blocker ring. The blocker ring rubs against the cone of the gear, causing it to synchronize speed and rotate together.
Once synchronized, the sleeve moves across, allowing the teeth on the sleeve to engage with the straight teeth of the gear. The gear is now synchronized, and the clutch can be engaged. To reverse the car, we need to bring the car to a complete stop. An idler gear is then pushed into position with both the output and the counter gear. All three gears are straight cut, allowing the idler gear to slide into position when the car has stopped. Now the output shaft will rotate in the opposite direction.
This is how we use the engine to propel the car along and use gears to go faster. If you are ready to step up a gear, then you should check out The Great Courses Plus. All of our viewers can get a free trial right now by visiting thegreatcoursesplus.com/engineeringmindset. The Great Courses Plus is an on-demand learning platform that lets you binge-watch lectures and courses. They have over 13,000 videos by industry experts on everything from science to math, history, and even cooking. Personally, my favorite is their engineering lectures and their course on inventions that changed the world.
As a fan of this channel, I’m certain you’ll also find these interesting. They add new content every month, and you can watch as many videos as you want from your TV, tablet, laptop, or phone. Just click the link in the video description down below to start your free trial today.
Let’s look at how to calculate the RPM and torque of simple gear trains. By the way, you can download an Excel sheet of these calculations; links can be found in the video description for those. We’re going to use the formulas: ratio equals the output gear teeth divided by the input gear teeth; RPM output equals the RPM input divided by the ratio; and finally, torque output equals the ratio multiplied by the torque input.
For example, if gear A has 8 teeth and gear B has 10 teeth, the ratio is 10 divided by 8, which is 1.25. If gear A rotates at 150 RPM, then 150 divided by 1.25 equals 120 RPM. If gear A has a torque of 20 newton meters, then 1.25 multiplied by 20 gives us 25 newton meters. This gear will rotate in the opposite direction to gear A; it will rotate slower because it is larger but will have more torque.
If we add gear C with 20 teeth, the ratio is 20 divided by 10, which gives us 2. The RPM output is 120 RPM from gear B divided by 2, which gives us 60 RPM. The torque will be 2 multiplied by 25 newton meters from gear B, giving us 50 newton meters. This gear will rotate in the same direction as gear A but will rotate slower because it is larger, although it will have more torque.
If we were to add gear D with 8 teeth, then the ratio is 8 divided by 20, which gives us 0.4. The RPM is 60 RPM from gear C divided by the ratio of 0.4, which gives us 150 RPM. The torque is 0.4 multiplied by 50 newton meters, giving us 20 newton meters. This gear will rotate in the opposite direction to gear A, but it is the same size, so it will rotate at the same speed and the same torque, although this doesn’t take into account any losses we would see in the real world.
This setup lets you visualize how gears manipulate speed, torque, and direction. What if we had a compound gear train like this, which has the same size gears, the same input torque, and the same rotational speed? Again, links in the video description for the Excel sheet calculator for this.
With this setup, we have four gears: A, B, C, and D, but B and C are compound. If gear A has 8 teeth and gear B has 10 teeth, then the ratio is 10 divided by 8, which is 1.25. Gear A rotates at 150 RPM, so gear B is 150 RPM divided by 1.25, which gives us 120 RPM. Gear A has a torque of 20 newton meters, so gear B is 1.25 multiplied by 20 newton meters, which is 25 newton meters. This gear rotates in the opposite direction to gear A; it will rotate slower because it is larger but has more torque.
If gear C has 20 teeth, then the ratio is 20 divided by 10, which is 2. The RPM is going to be the same as B, which is 120 RPM because these two gears are compound and share the same shaft. The torque is also going to be the same as B, so it’s 25 newton meters. This gear also rotates in the opposite direction to gear A; it will rotate slower than gear A because of the size of gear B and will also have less torque than gear A, again because of gear B.
If gear D has 8 teeth, then the ratio is 8 divided by 20, which is 0.4. The RPM is 120 RPM from gear C divided by 0.4, which is 300 RPM. The torque is 0.4 multiplied by 25 newton meters from gear C, which equals 10 newton meters. So this gear rotates in the same direction as gear A; it rotates faster but with less torque.
We need to consider the application of the gearbox, how many gears are connected, and what torque and speed we require.
That’s it for this video! To continue learning about mechanical and automotive engineering, check out one of the videos on screen now, and I’ll catch you there for the next lesson. Don’t forget to follow us on Facebook, Twitter, Instagram, LinkedIn, as well as theengineeringmindset.com.
—
This version removes any unnecessary filler words and maintains a professional tone while preserving the essential information.
Transmission – The mechanism in a vehicle that transmits power from the engine to the wheels. – The transmission system in modern cars often includes both manual and automatic options to optimize fuel efficiency and performance.
Gears – Rotating machine parts having cut teeth or cogs, which mesh with another toothed part to transmit torque. – Engineers must carefully design the gears in a gearbox to ensure smooth and efficient power transfer.
Torque – A measure of the force that can cause an object to rotate about an axis. – The torque produced by the engine is crucial for determining the vehicle’s ability to accelerate and carry loads.
Engine – A machine designed to convert energy into useful mechanical motion. – The internal combustion engine has been a fundamental component in automotive engineering for over a century.
Clutch – A device that engages and disengages the power transmission, especially from a driving shaft to a driven shaft. – The clutch allows the driver to smoothly change gears without damaging the transmission.
Vehicle – A machine, typically one powered by an engine, that is used for transporting people or goods. – Engineers are constantly innovating to improve the safety and efficiency of vehicles.
Ratios – The quantitative relation between two amounts, showing the number of times one value contains or is contained within the other. – Gear ratios are critical in determining the speed and torque characteristics of a vehicle.
Power – The rate at which work is done or energy is transferred in a system. – The power output of an engine is a key factor in assessing a vehicle’s performance capabilities.
Mechanics – The branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements. – Understanding the principles of mechanics is essential for designing efficient and safe engineering systems.
Driving – The controlled operation and movement of a vehicle. – Driving simulations are used in engineering to test vehicle dynamics and driver responses under various conditions.
