what is weight transfer in a race car? what is weight transfer in a race car?

The loads in each wheel determine the vehicles maximum cornering, braking and acceleration capability, then the lateral weight transfer is a key factor in a racing car performance. Sprung weight distribution is calculated as the ratio between the distance from the sprung weight CG to the axle opposite to the one being analysed, , and the wheelbase of the vehicle , times the sprung weight . is the center of mass height, The rear wheels don't steer, or don't steer as . Most high performance automobiles are designed to sit as low as possible and usually have an extended wheelbase and track. Bear in mind that all the analysis done here was for steady-state lateral load transfer, which is why dampers were not mentioned at all. This fact can be explained at deeper levels, but such an explanation would take us too far off the subject of weight transfer. Literally, the rear end gets light, as one often hears racers say. As you see, when we increase front roll centre height, the lateral weight transfer decreases on the rear axle while increasing on the front. These numbers are just averages and are very dependent on the class of car and the tires being run. In figure 3 the effect is repeated, but from a different perspective. To obtain these, I created a MATLAB routine to calculate the total lateral weight transfer from our previous discussion, keeping the front and rear roll stiffnesses equal and constant while varying front and rear roll centre heights. You already know from steady-state pair analysis and from the discussion on tyre load sensitivity that lateral load transfer will decrease the lateral force capability of the axle. This puts more load on the back tires and simultaneously increases traction. Taking the moment equilibrium about the point O, of the tyre, we can see that: Dividing the equation by t on both sides, we obtain: But assuming a symmetric weight distribution, , since the left tyre is the outside tyre. We'll assume the car's side to side weight distribution is equal. From our previous discussion on direct force weight transfer component, you know that to change roll moment arm you need to play with roll centre heights, which will ultimately affect that weight transfer component in the opposite way you want. The braking forces create a rotating tendency, or torque, about the CG. By simply raising or lowering the couplers, our machines can gain thousands of pounds for traction. Both of these changes will involve adding, removing or repositioning mass (and therefore parts) within the unsprung part of the car. We dont often notice the forces that the ground exerts on objects because they are so ordinary, but they are at the essence of car dynamics. Literally, the ground pushes up harder on the front tires during braking to try to keep the car from tipping forward. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright . Learning to do it consistently and automatically is one essential part of becoming a truly good driver. This is balanced by the stiffness of the elastic elements and anti-roll bars of the suspension. We derived the equations of lateral load transfer in one axle of the car, showing that its composed of three components: Unsprung weight component not useful as a setup tool because of the effect that it has on ride, specifically wheel hop mode. From the general lateral load transfer equation, we know that this component is changed by modifications to either the weight distribution of the car, or the roll centres height. You must learn how different maneuvers . Note that this component resists only roll angle, and the entire sprung mass is used here, as this is how we obtained the expression for roll angle. For the tow vehicle, the chain pulls up on the weight distribution bar. Then if the car is still loose on entry we start moving the weight, at the new height, to the right. Reference:Dr. Brian Beckman The Physics of Racing, Michelin Raceway Road Atlanta is 2.54 miles long, with 12 turns winding their way through the scenic Georgia countryside. The forces upon the springs are reacted by the tyres, and that contributes to lateral load transfer. The previous weight of the car amounted to 2,425 pounds, while now it is about 2,335 pounds. a thick swaybar is not a good idea for the front of a FWD race car. If that solution doesnt work, you could have roll centre heights that would give a roll axis too close to the sprung CG, as discussed before. A. In the context of our racing application, they are: The first law:a car in straight-line motion at a constant speed will keep such motion until acted on by an external force. Read more Insert your e-mail here to receive free updates from this blog! The analysis begins by taking the moment equilibrium about the roll axis: Where is the roll resistance moment, and is the roll moment. When cornering, the sprung mass of the car will roll by an amount , the roll angle. Hence, springs and tyre pressures should only be changed when other aspects need modification, but not only roll stiffness itself (unless the vehicle has no antiroll bar). One g means that the total braking force equals the weight of the car, say, in pounds. Just as taking Claritin or Benadryl reduces your symptoms without curing your allergies, reducing roll reduces the symptoms but does not appreciably cure weight transfer. Also, the only direct link between the front and rear tracks is the chassis (all-wheel drive cars are an exception), and vehicle behaviour can be evaluated by looking at the relative performance of front and rear tracks. This component of lateral load transfer is the least useful as a setup tool. It is a fact of Nature, only fully explained by Albert Einstein, that gravitational forces act through the CG of an object, just like inertia. This component is the easier to control. Then, a series of steer angles in the range of interest is selected. "Right now, none. Again, if that doesnt work, then lateral load transfer will not be the right parameter to change. For the sake of example, ride stiffness controls ride height, which has strong effects on aerodynamics of ground effect cars (almost every race car with relevant aerodynamics design). One important thing to notice is that its difficult to change total lateral load transfer by setup. Putting weight on the front is achieved by lifting, turning, and/or braking. The article begins with the elements and works up to some simple equations that you can use to calculate weight transfer in any car knowing only the wheelbase, the height of the CG, the static weight distribution, and the track, or distance between the tires across the car. Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects:[1]. Newtons second law explains why quick cars are powerful and lightweight. As long as the tires stay on the car, the ground pushing on them slows the car down. An important attribute of the suspension is the Roll-centre. The inertial force acting on the vehicle CG will generate a moment about the roll axis. We wont consider subtleties such as suspension and tire deflection yet. The added axle weight will slow the release of the stretch in the tire and help hold traction longer. When the driver gets on the brakes, the total remains the same . The term is a gravity component that arises due to the sprung CG being shifted to the side when the chassis rolls. Turning in to a corner brings the car's momentum forward . A larger force causes quicker changes in motion, and a heavier car reacts more slowly to forces. This could affect wheel hop (the ride mode that characterises oscillation of the unsprung mass between the road surface and the sprung mass) frequency and amplitude, reducing the contact of the tyres with the ground and hence, reducing grip. 2. draw the ground line ,vehicle center line and center of the left and right tire contact patches. The trend in dirt racing seems to be leaning toward a left side weight percentage of around 53.5 to 55 and somewhere between 75 and 125 pounds of wedge. In this paper, that issue is discussed with a focus on ride rates, roll rates and simple tire data analysis for a Formula SAE race car. You have less lead to work with. In my time in Baja, I have done calculations of the type for vehicles that had roughly the same weight distribution and wheelbases of approximately 1500 mm. https://www.allenbergracingschools.com/expert-advice/road-atlanta-track-guide/ #Sportscar #racing #motorsport #racingschool #F1 #BeARacer #MichelinRaceway #roadatlanta, Michelin Raceway Road Atlantas multi-purpose racing facility has been a fixture in the motorsport community since its opening in 1970. https://www.allenbergracingschools.com/expert-advice/road-atlanta-track-guide/ #Sportscar #racing #motorsport #racingschool #F1 #BeARacer #MichelinRaceway #roadatlanta, Allen Berg Racing Schools 1835A Centre City Parkway #408 Escondido, California 92025, (888) 722-3220 (831) 272-2844 robin@allenbergracingschools.com Hours Mo - Fr: 8:30 am - 4:30 pm, WeatherTech Raceway Laguna Seca 1021 Monterey Salinas Hwy, Salinas, CA 93908, USA, Michelin Raceway Road Atlanta 5300 Winder Highway, Braselton, GA 30517, USA, Virginia International Raceway 1245 Pine Tree Road, Alton, VA 24520, USA. Learning to optimize weight transfer allows us to optimize the grip of the racecar. The views are along the roll axis. The simplest component of load transfer is the one related to unsprung mass. If (lateral) load transfer reaches the tire loading on one end of a vehicle, the inside wheel on that end will lift, causing a change in handling characteristic. a Closed Wheel Race Cars How much does a NASCAR car weigh? Deceleration Weight Transfer The opposite of the acceleration weight transfer takes place during deceleration. The weight transfer is caused by rotational forces centered at the hitch ball. This law is expressed by the famous equation F = ma, where F is a force, m is the mass of the car, and a is the acceleration, or change in motion, of the car. For context, we are experimenting with carbon-carbon brake discs on a non-downforce car. However, the pitching and rolling of the body of a non-rigid vehicle adds some (small) weight transfer due to the (small) CoM horizontal displacement with respect to the wheel's axis suspension vertical travel and also due to deformation of the tires i.e. The amount the body rolls is affected by the stiffness of the springs/bars, and the speed of the roll is affected by the stiffness of the shocks. Here, the lateral force acting on the sprung mass () will generate a moment on the tyres through the roll centre height that will also contribute to lateral load transfer. Understanding weight transfer is a fundamental skill that racecar drivers need to know. This is given by: Here, is the sprung weight distribution to the axle being analysed and is the roll centre height for the track. g Weight transfer occurs as the vehicle's CoM shifts during automotive maneuvers. This graph is called the, The actual load transfer depends on the track width and the rolling moment produced by the lateral acceleration acting on the fictitious CG height. The thing is, roll is only one part of the equation, and as the discussion on this post will show, increasing roll centre height might either increase or decrease the lateral load transfer, depending on other parameters. The vehicle mass resists the acceleration with a force acting at its center of gravity. *This website is unofficial and is not associated in any way with the Formula One group of companies. Lets say the car is rear wheel drive with a rear weight distribution and large, lightly loaded tyres. NOTE: This information is from an NHRA Rule Book 2019 Addendum. In that case, the tires on the right side of the car are going to be on the outside of the corner many more times than the left side tires. The initial lurch will sink the car. The fact is, by increasing the roll centre height in one axle, you are increasing lateral load transfer from the direct lateral force component, while at the same time you are decreasing lateral load transfer from roll angle component. Most autocrossers and race drivers learn early in their careers the importance of balancing a car. In order words, the goal would be to reduce lateral load transfer in the rear axle in comparison to the front axle. An additional curve might be obtained by plotting the intersections of the lateral accelerations with the lateral load transfer parameter lines, against the reference steer angle. The analysis procedure is as follows: The potential diagram is a benchmarking of the performance that can be achieved by a pair of tyres. I have heard of many cars running well outside of these parameters and winning. If the tyres of the car are lightly loaded, there might not be enough load sensitivity in the tyres, so that even if one end of the car takes all the lateral load transfer, the lateral force performance isnt degraded significantly. For example, if our car had a center of gravity 1 foot above the ground and the tires were 4 feet apart, we would divide 1 foot . Balance of roll damping will further modify the handling during transient part of maneuver. The Trackmobile Weight Transfer System is a hydraulic system developed to implement this idea in an intuitive and easy-to-use way. This is a complex measure because it requires changes in suspension geometry, and it has influence on all geometry-related parameters, such as camber and toe gain, anti-pitch features and so on. f This leads some to think that increasing roll centre heights will actually decrease weight transfer because it reduces roll. This will give: Now consider , the vertical load on the outer tyre in a corner, and , the vertical load on the inner tyre. Put an R-compound DOT tire on the same car and raise that force to 1.05 g of cornering force. As fuel is consumed, not only does the position of the CoM change, but the total weight of the vehicle is also reduced. [6] Weight transfer is an advanced techniqe which can impact the cart in four directions: front, back, and then each side of the kart. The next topic that comes to mind is the physics of tire adhesion, which explains how weight transfer can lead to understeer and over-steer conditions. Weight . In a pair analysis, steady-state lateral force is obtained for the tyres on a track (front or rear pair), through data from a single tyre. The same thing happens on the left . If you accelerate, brake or corner harder, you transfer more weight. {\displaystyle a} If you represent multiple proportions, you will have multiple lines with different inclinations. This will tell us that lateral load transfer on a track will become less dependent on the roll rate distribution on that track as the roll axis gets close to the CG of the sprung mass. Antiroll bars are generally added to the car to make it stiffer in roll without altering the ride characteristics. Try this exercise: pick whatever value you want for rear roll centre height, and imagine an horizontal line passing through the point correspondent to that value in both graphs, and observe how weight transfer changes along this line in both graphs (remember each graph represents an axle). Weight transfer is generally of far less practical importance than load transfer, for cars and SUVs at least. Our system is proven to increase traction, and reduce fuel consumption and track maintenance. These adjustable bars generally have blade lever arms, as the one shown in figure 11. This can be done in multiple ways. The driver has hit the apex but has found the car is starting to push wide of the desired line. b These effects are very important, but secondary. This being a pretty typical "clubmans" type car it sits properly between the road going sports car and the sports prototype figures given in the table. The third term is usually split between springs, dampers and anti-roll bar, and determines the nature of body control and the level of body roll. Tire Offsets. Imagine pulling a table cloth out from under some glasses and candelabra. Figure 10 shows the plot of the roll angle component versus gravity term. More wing speed means we need to keep the right rear in further to get the car tighter. In conclusion, it was a huge effort by Tin . In the automobile industry, weight transfer customarily refers to the change in load borne by different wheels during acceleration. If you analyse figure 2, you will see that an increasing fraction load transfer will come together with a decreasing lateral force potential for the axle. {\displaystyle g} In cases where the performance of a pair of tyres is being analysed without regards to a particular vehicle, the parameter is a convenient way to represent changes in lateral load transfer. The rotational tendency of a car under braking is due to identical physics.The braking torque acts in such a way as to put the car up on its nose. If our car is a little loose going into the turns we may raise all the weight 6 or 8 inches.