I promised you guys last time we would be talking about role, centers and that’s, exactly what we’re going to do. So i want to start this out by sort of figuring out how the role centers actually work. What is the role center and then we’re going to move on how you use the role center and as we did with the differentials we’re going to do this in two parts as well? Let’S just jump right into it, we’re going to start out by figuring out how the role center is determined. So when you have a car, how do you figure out where your roll center is so let’s start out with how we determine the roll center? So here is a representation of a car geometry. What you would do is you start out with taking a ruler and drawing a line continuous to the upper link and the light would end up somewhere around here. Then you would do the same thing for the lower arm. You would come here and draw a line and you the line would collide with the line we did from the upper link, and you would have a point here that would be called the instantaneous center. Then what you would do is you would take that instantaneous center. The point where those two lines collide and you take the center point of the tire and then you would draw a line from that center point to that instant center when you’re measuring static roll center.
You would always have the roll center in the center point of the car you’ll be higher or lower, and this information would tell you how the car would handle on the roll. ora, let me show you a finalized. Drawing of this, so here here is that visualize. So the lines are continuous and they collide somewhere here and then you would connect the line from the center point of the tire to the instant center and here in the middle, come potete vedere, we can get the roll center it’s, just basic geometry. And if you draw this up yourself, you can easily see that so, Fondamentalmente, this is how it would work. If you want to do this to your own car, you would measure out the attachment points. You would measure out your tire size, your tire width and also the tire offset, and then you add all these measurements together and you sort of draw this picture on some software and then you can see where your roll center is. If you’re old school, you can use this information to make it into a drawing. I strongly suppose you should use a software for this because we have those tools available, so you could use basic cad for this or you just. There are some softwares that are made for determining your role center. Anche, there are some some of those softwares allow you to see the role center on the movement, which is an added bonus, but we’re gon na.
Go that in the next episode and in this episode, we’re gon na just focus on the role center, where the car is static. Now that we know how to determine our role. Centers let’s start out by going through what this actually means. When setting up the car and then continue to go into how the forces are transferred through the car depending on the role center, Qui, we can see the linkage angles as the upper link is at its lowest position. ora, as we would erase the link, we can see how it affects the linkage angles here. We can see that the change in the linkage angles as we raised up a link from the tower results in the fact that our roll center gets lower. Every change in the geometry will affect the roll center position. So just keep this in mind. What knowing the role center height gives us is the relationship between the role center and the center of gravity. This relationship can be represented with the theoretical lever, so this thing a theoretical lever. This is sort of a tool that we can use to explain how the car rolls okay, so let’s. Now imagine this car would go into a turn that is turning left. The centrifugal force applied to the car would be applied from the center of gravity. That would be here, and that would be this way outside. Ovviamente, the roll center determines how this force is applied to the tire.
This point is sort of a theoretical hinge of the car suspension. One thing that was really key for me was understanding what would happen when the role center would be at the same point as the center of gravity. Let ' s. Imagine a scenario where the role center is exactly at the point of the center of gravity. When you would go into a corner, the car would have zero roll. This would be because of the fact that there is not a lever to roll it it’ll be sort of like pushing a hinge on a door. The door is not going to open. If you push it on the hinge, you would have to have a lever, so you could push the door open. This is exactly the same, it’s just more complicated because there’s more variables here, but this is exactly the same. So what this theoretical lever actually does to the forces is divide the amount of force applied through the linkages and the suspension. Così, come ho detto, when the roll center is at the point of center of gravity, you would have a hundred percent of the force transferred to the linkages. Once you would start to lower the roll center you’ll get a higher percentage of the force transferred through the suspension, which would then cause roll. Così, Fondamentalmente, what we’re doing with adjusting the roll center height, we are adjusting the length of theoretical lever and balancing the force going through the suspension and the linkages to have the desired amount of force ending up on the tire.
Va bene, now that we have a good basic understanding of the roll center and also the theoretical lever and the effects and forces that play out when the car rolls let’s go into how the forces are applied to the tire, because in the end, the grip comes from. Friction between the tire and the ground, so let’s start out with when you would have a lower roll center, which would mean more force on the shocks when more force is applied to the shocks in the springs, the shocks and springs press the tire downwards. The shock presses the arm down and the arm presses the tire down when you apply force through the linkages. The horizontal force coming from the center of gravity would go through the linkages and push the tire and the force pushing tire would be also horizontal. ora, when you have a horizontal force, you would need to have more or the exact amount of friction force that is from the ground and the tire. Così, if that horizontal force to the tire is higher than that friction that will cause slide, because you need friction to be higher or the same amount as the force applied to the tire. ora, when you would add more force through the shocks and springs, the tire would be pressed down instead of pressing pressed out horizontally. This would give the tire more friction, because more force applied to the tire pushing the tire to the ground would cause more friction.
So this is why, in theory, a lower roll center, a longer theoretical lever would give you more grip. Let’S go through some basic things that how you would maybe want to tune your car when you are at the track i’m. Going to start this out by clarifying that, even though i just said that in theory, a low roll center will give you more grip. In reality, that’s not always the case. Due to the large tires we use on rc cars, the added camber gain will, in most scenarios, give you more grip with a higher roll center. Tuttavia, once the friction between the tire and the track surface is very low. To start out with, then most likely a lower roll center will result in more grip. So now i’m gon na go through some basic scenarios you might be facing when you’re at the track scenario. One the track you’re on is fairly high grip and you seem to have issues with the car grip rolling. In this scenario, you would like to lower your roll center. This will make your car much less snappy and aggressive and will reduce grip, rolling scenario. Two the track you’re on is high, speed and bumpy, and you have issues with the car catching ruts and flipping over. In this scenario, you would once again like to lower a roll center. This will put less force on the tire horizontally and once hitting those rods, your car will hit them less intensely and be less prone to flipping over scenario 3.
The track you’re on is smooth and medium grip, and you feel, like your car, is really lazy and going around like a boat. In this scenario, you will want to raise your roll center. This will make your car much more responsive and you will have an easier time rotating the car around the corners all right. So these are just a few scenarios, but i hope these give you a good idea of how to apply the theory of role center into reality once you’re at the track. So one thing to remember from this video is the very very basics, lower role center, more row and also the car will be less prone to flipping over higher roll center less row. But the car will be also more prone to flip over these sort of a very basic key things to know. This works the same on every car it’s, just the geometry very basic at that. So i truly hope i did a good enough job explaining this. Per me, this is the way i understand this and for you, that might be completely different. So if you have something you want to ask, please do because uh for me it’s the best, if i can help the most amount of people and that’s my goal here and making this information available for as many people as possible. So this whole sport can move forward in the long term. Comunque, if you like this video, i hope you like the next one as well we’ll catch up next time.
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