Are you trying to get a CDL driving license and you are interested in learning what are retarders on a truck? Well, if that is the case, then you are at the right place because there will be a lot to cover on this topic where we are going to learn everything when it comes to these types of brakes.
Learning what are brake retarder means and the types of different retarders that are out there is something really crucial because if you don’t know this stuff, you will fail your driving test. Since you are required to understand how these retarders CDL work in order to get your CDL driver’s license.
And also, on top of that, you need to learn this presumably that you haven’t driven a truck for a really long time and you want to repeat the knowledge or further understand how these methods of braking that you are using on your truck work behind the curtain. And this is why we are here, to help you out understand precisely that.
First, we are going to learn what are retarders on a truck. Then we will learn why they are so important and the different types of retarders that are out there. Later on, we will learn more about how each of these systems works individually and see their method of action. So, if you want to learn more about it, follow along till the end.
What Are Retarders On A Truck
Now before we dive into more complex topics like the types of retarders that are out there. Let’s first take a look at what are retarders in general. Knowing this will be really beneficial, especially for beginners who are not into trucks and want to learn more about their brakes on a semi-truck. So, without further ado, let’s introduce ourselves to the topic and learn what are retarders on a truck.
Well, as the name implies, a retarder is something that retards. This means that it slows down on purpose so the vehicle loses its momentum and comes to a stop.
Let’s imagine something spinning fast like a torque converter. The torque converter on automatic transmissions is a clear example of this retardment process. Inside the torque converter, there is a device that is designed in such a way that in order to work it uses hydraulic fluid to slow the speed of the driveshaft and reduce the momentum of the vehicle and help the vehicle to come to a stop.
So, if you have a torque converter automatic car, you clearly have one of these retarders. Every time you remove the foot from the gas, the car loses momentum and comes to a stop. Even without serious braking.
In trucks though, this is a rather different process and actually, there are a few different types of these retarders that are used. Which we are going to cover later on in the article. The important thing for you right now is to know what are retarders on a truck.
These are devices that help your truck come to a stop without creating friction like your standard brake system which is usually a disc or drum brake design.
Why Retarders Are So Important To You
So, we learned what are retarders on a truck and learned that these are devices that make your truck come to a complete stop without using or to aid the friction brakes that are installed on the wheels so the truck comes to a complete stop.
But have you asked why these retarders are so important to you as a truck driver? What makes them so irreplaceable and one of the things that no truck driver should live without? Let’s elaborate more on this because you really need to know the importance of these brake retarders.
If you are a novice truck driver, then you need to pass your driving test. And without knowing what a retarder is, the chances of failing are really big.
Let’s imagine that you climbed over a steep hill and now you need to go down the hill and the truck is full of cargo that weighs a lot.
So, you decide to slam on the brakes and the trailer simply swerves to one side and you end up severely injured or even killed.
Or another situation where you use the standard brakes and you overheat them and the truck doesn’t want to stop anymore and you rear end someone or end up in a ditch. Both of these situations can be dangerous or even deadly.
This is why brake retarders were invented. To slow the momentum of the vehicle when you approach a steep downhill road.
The brake retarder will do this job for you and will slowly but surely slow down the truck, without you engaging the brakes at all.
This is why you should know what type of brake retarders you have on your truck and use them accordingly.
Types Of Retarders On A Truck
Now since we covered what are retarders on a truck, we can move on and learn more about the types of retarders that are on the truck.
There are a few different types of retarders that are used out there. Some of them are dead simple, while some of them are rather complex to explain. But we will make sure that we deliver the best answer to these questions.
In the following few chapters, we will go through these types briefly. But after that, we will cover them more in-depth and understand their method of action a lot better. So, let’s get into it.
1. Exhaust Retarder
So, we learned what are retarders on a truck. Now let’s take a look a the first type of retarder that is most commonly used on trucks.
And this type of retarder is the exhaust retarder. Also known as the exhaust brake. So, how the exhaust can make your car stop?
Well, there are ways that diesel engines use to limit the flow of exhaust gases and this slows down the engine work in the process. Slowing down the rotation of the crankshaft results in the slowing down of the vehicle as well.
These are the most effective retarders out there and also one of the simplest types to understand. Later on, we are going to elaborate more in-depth on how this type works and why is so useful. So, we learned what are retarders on a truck. Now let’s move on to the second type of retarder.
2. Jake Brake
So, we know what are retarders on a truck, now let’s take a look at the second type of retarders that are out there. And these are the Jake brake retarders. So, what is a Jake brake retarder?
Well, a Jake brake retarder is similar to the previous type that we covered. They are both engine retarders. Which means that they reduce the RPM of the engine. But both of these types are achieving this in a different manner. The previous achieved this by stopping the gases to escape from the exhaust, while the Jake brake is doing things differently.
Namely, this system is playing with the exhaust valves. It opens the valves just before the compression stroke ends and releases the compressed gas which is trapped in the cylinders and slows the vehicle in the process. Quite an ingenious design if you are asking me. Later on, we are going to elaborate on this design and we will learn how it works in detail. Now let’s move on to the next system.
3. Hydraulic
We know what are retarders on a truck, now let’s take a look at the next type of retarder which is the hydraulic retarder.
As we noted, a hydraulic retarder is something similar to a torque converter. This component is usually mounted on the driveshaft and the transmission of the vehicle.
So, when stopping power is needed, hydraulic fluid is pumped into this component and then this fluid puts some resistance to the spinning motion of the gear. It creates a viscous drag that the hydraulic fluid creates in order to reduce the spinning motion. And it works. This type of retarder is often used on buses.
What is good about this retarder is that it is really quiet and often you can’t hear it. Meaning that it is much more convenient than the first two types that we covered previously.
4. Electric
So, we know what are retarders on a truck, now let’s take a look at the last type of retarder that is out there. And this is the electric type of retarder.
Electric retarders are quite similar to hydraulic retarders when it comes to their mounting place. It is similarly mounted between the driveshaft and transmission.
The only difference is that this retarder works with the help of electromagnetic induction in order to provide retarding force. These retarders are less frequent but still are equipped for a lot of trucks out there. But why you should know what are retarders on a truck and the types of these retarders? Let’s elaborate more on this next.
Why You Should Know All These Types Of Truck Retarders
Now as we learned what are retarders on a truck and learned the different types of retarders that are out there. We can start discussing why you should know this information. Why is this essential? Let’s elaborate in the following paragraphs and see why this is the key.
The main reason why you should know what re retarders on a truck, the types, and how they are used is because of the CDL driver’s license.
If you opt to get a CDL driver’s license, you just need to know this stuff. Since, how you will operate a semi-truck if you don’t know what is a Jake brake or an exhaust brake?
This is really essential knowledge that you need to have in order to operate a commercial vehicle that has this type of equipment installed on it.
If you don’t know how to operate these features, you could end up crashing if you don’t know how to climb down a steep hill and overheat your standard brakes.
Another reason why should anyone should know what are these types of brakes is common knowledge. Having some extra knowledge didn’t hurt anyone. One day you might even decide to enlist for a CDL. So, knowing this in advance will save you a ton of time when it comes to preparing for these tests and learning how to tackle them. But enough on that.
Now let’s learn in the following chapters, how these brakes work and answer some common questions associated with them. We will focus primarily on engine braking, which includes the exhaust brake and the Jake brakes and sees more about their features and method of action.
Engine Braking Systems
As we mentioned previously, since we learned what are retarders on a truck, we can move on and learn more about the engine braking systems. We will not cover the hydraulic or electric systems. But only the ones used by the engine. Which are the exhaust brakes and the Jake brakes. We will learn how they work and their main features. So, if you want to learn more, follow along.
What Are Retarders On A Truck: What Is Exhaust Brake
Now, since we learned what are retarders on a truck, we can move on and cover the first type of brake retarder thoroughly. Namely, the exhaust brake.
So, what is the exhaust brake? Well, this is a special brake that is located on the hot side of the turbo of the engine. This means that it is located right between the turbo and the exhaust of the car.
So, as you can tell, this system is installed mostly on turbo diesel applications. You will notice the exhaust brake as a big hump right next to the hot side of the turbo.
In some applications, it is even simpler and tidier. More modern applications are rather simplified and more compact when it comes to the engineering of this type of brake. But how this exhaust brake works on an engine?
How Do Exhaust Brakes Work?
Exhaust brakes work with the help of backpressure. So, what is backpressure? Well, backpressure is the situation when the gases are prevented from escaping the exhaust.
If you put something inside of the exhaust, you will notice how the engine turns off. But the exhaust brake does not fully close the gas passage. So, there is enough gas passage for the engine to keep on working and slow down in the process. But what makes the engine slow down?
Well, as we said, the backpressure buildup makes the engine slow down. There should be equal parts intake gases and equal parts exhaust. So, if you block the exhaust partially. Then you will only need 50% less air than usual.
So, less air burnt into the cylinders equals less power produced by the engine. And the engine slows down in the process.
The exhaust brake is simply a butterfly flap that opens and closes. There are different types of actuators that open and close this brake, there is a pedal-operated one, two-stage pressure control, or a pneumatic or hydraulic actuator valve. It really depends on the application.
What is good to know is that these brakes create noise more than the standard brakes used. So, you need to keep this in mind. Now as we learned what are retarders on a truck, let’s move on to the next type of brakes.
What Are Retarders On A Truck: Jake Brake Meaning
Now as we learned what are retarders on a truck, let’s cover the second type of brake retarder that is used most commonly. And that is the Jake brake.
Jake brakes are not something new. They were patented by Clessie Cummins and were first put in production in 1965 by the company Jacobs Vehicle Systems. Thus, they got the name Jake brakes.
These brakes are also known as compression brakes because they are basically playing with the compression of the engine. These brakes are common on trucks. But what is bad with these brakes is that they have some limitations that we are going to discuss later on in the article.
But how this type of brake works in reality? What does all the magic and makes your truck stop when you need this the most? Let’s elaborate more on this in the following chapters and see what is the method of action of these brakes.
How Does The Jake Brake System Works?
As we mentioned previously, the Jake brakes are compression brakes. This means that they play with the compression of the engine in order to make it stop. So, how do they work? Let’s elaborate.
When a driver releases the foot from the gas pedal, the vehicle still has momentum that moves it forward. So, here comes the compression brakes also known as Jake brakes.
This system when activated is opening the exhaust valves of the cylinders. But only at a certain point. And that is the point where the compression stroke ends.
This action releases compressed gas trapped in the cylinders. The compressed air that is generated during the compression stroke is basically acting like a spring that pushes the piston down. And this action helps the engine lose momentum and retard the motion of the crankshaft. Making the vehicle stop in the process.
And these Jake brakes are really effective when it comes to stopping. But they have some limitations that we are going to cover in the following chapters since we learned what are retarders on a truck.
Jake Brake Sound
Now as we learned how the Jake brakes work and what are retarders on a truck, let’s cover another interesting topic and that is the legality of these types of brakes.
If you didn’t know there are engine braking prohibited signs in many areas across the country. So, why is this actually the case and engine braking are banned in populated areas?
Well, it is mainly because of the sound. Exhaust brakes create sounds and Jake brakes also create sounds.
Especially the Jake brakes are really hated by everyone. Mainly because when you put your foot on these brakes, the sound they produce is as if there is someone shooting with a heavy machine gun. And this is not something that’s easy for your ears. No sir. When you hear a Jake brake, it’s like the sky is falling down on your head and the air force bombing your place, it’s that bad, especially if you live close to a frequent road.
So, there are a ton of signs across the country that say no Jake brakes within city limits. And if you use them in the city, it has to be during an emergency situation unless you will be heavily fined.
Facts about Engine, Driveline, and Transmission Retarders for Heavy Trucks
- Engine, driveline, and transmission retarders are systems designed to support the existing braking system of heavy trucks by converting energy from the vehicle’s drivetrain into a braking system.
- Engine retarders work by capturing exhaust from the engine, compressing it, and forcing the engine to work harder to push the gas out of the cylinders, which slows the vehicle, requiring less braking force on the service brakes to stop the vehicle.
- Transmission retarders slow down the vehicle by creating resistance within the transmission. The system consists of a vaned rotating element called a rotor and vaned elements on either side called stators. The cavity between the rotor and stators is pressurized with oil, which slows down the vehicle when the operator asks for retardation.
- Driveline retarders use electromagnetic energy to counter the energy in the rotating driveline, slowing down the truck without using the brakes. The system consists of two rotors attached to the driveline that rotate at the same speed as the driveline, and a stationary stator bolted to the frame rail.
- Retarder systems help to extend the brake life of heavy trucks and are most prevalent in high stop/start vocations like refuse trucks.
- The activation of retarder systems can be set up based on the needs of the operating system. The most popular option in the refuse market is foot control, where the retarder is activated in four different stages with 25% for each stage.
- Companies have other options for activating retarder systems, such as off-throttle control, where approximately 25% or 50% of the power is activated as soon as the accelerator is released, with the additional stages being activated off the brake pedal.
- Retarder systems are beneficial to heavy trucks that operate at high speeds because there is more braking energy going into service brakes (for more insight, check out our guide on service brake assist), and the retarder can absorb that energy instead of the service brakes, extending brake life.
- Retarder systems are necessary for speed control on grades and to provide additional braking to the vehicle that could help save the normal service brakes to extend brake life.
- Braking systems must meet or exceed the National Highway Traffic Safety Administration’s requirements to bring a Class 8 vehicle to a stop within 355 feet from 60 miles per hour. The NHTSA has a nine-step program to reduce the fatalities involved with heavy-duty vehicles by 50%.
Conclusion To What Are Retarders On A Truck
In this article, we have covered quite a bit when it comes to what are retarders on a truck. First, we learned what are retarders and what is their mission. Then we moved on and covered the types of retarders that are out there.
Then we covered why you should know these separate types and that is because you need to know them if you want to get a CDL driving license. Later on, we learned how the engine retarders work and what are their downsides.
F.A.Q To What Are Retarders On A Truck
Now let’s answer some frequently asked questions.
What Are Retarders
Retarders are simply auxiliary non-friction brake assists. They help your truck stop when you go downhill. Using retarders is much more beneficial because you don’t risk overheating your main brakes and still make the truck stop.
What Is The Purpose Of A Jake Brake
A Jake brake in simple terms is an engine brake. It is also known as a compression brake. This type of brake when activated it opens the exhaust valves before the compression stroke ends and releases the compressed air trapped into the cylinders. This makes your truck stop in the meantime.
What Does Jake Brake Mean
Jake brake is a special brake designed to slow down the engine momentum. It is also known as a compression brake as well. It is known as Jake brake because the first company that produced these brakes was called Jacobs Vehicle Systems.
What Does No Engine Brake Mean
This means that trucks are not allowed to use engine braking in the area because this type of braking creates a lot of noise that is disturbing for the people who live around.
What Does No Engine Brake Sign Mean
This sign means that engine braking is prohibited in the area. And by engine braking, we mean using exhaust brakes or Jake brakes. This is the case because these brakes create a ton of noise.
Why Is Engine Braking Prohibited
It is prohibited in many areas because it creates a ton of noise. Jake brakes create the same sound as someone is shooting a heavy machine gun. And this can be really annoying for people living around.
