what is weight transfer in a race car?

The moment equilibrium analysis will be the same here, but we will substitute the moment from the inertial force about the CG, , by a generic moment, . The following information applies to NASCAR-style Stock Cars; it may also be useful to production-based sports car racers with the engine in the front and the drive wheels in the back. In other words, it is the amount by which vertical load is increased on the outer tyres and reduced from the inner tyres when the car is cornering. 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. b The major forces that accelerate a vehicle occur at the tires' contact patches. Bear in mind that the lateral acceleration obtained from a specific fraction load transfer value will not necessarily cause the correspondent load transfer on the axle. While the skills for balancing a car are commonly taught in drivers schools, the rationale behind them is not usually adequately explained. Substituting the values on the terms inside the brackets, we have: But if we assume that front and rear roll centers have the same height, then the moment arm will be given by: Substituting into the weight transfer equation yields: This shows that when weight distribution and roll rate distribution are equal, for a horizontal roll axis, the sprung weight load transfer component will be independent of roll centres heights. Weight Transfer for Driving, Racing, and Rally - YouTube Dynamic Load Transfer - OzeBiz It is what helps us go fast! Inside percentages are the same front and rear. If that is the case in the front axle, the car will understeer, if it is in the rear axle, it will oversteer. The change in this arm with roll centre heights will depend on the wheelbase and weight distribution. e If changes to lateral load transfer have not significant effects on the balance of the car, this might be an indication that the tyres are lightly loaded, and load sensitivity is small. Ducky Johnson's Cobra Mustang Drag Car Undergoes Unbelievable Weight The analysis procedure is as follows: The potential diagram is a benchmarking of the performance that can be achieved by a pair of tyres. Turning in to a corner brings the car's momentum forward . "The ride height is meant to be in one spot you should look to move weight, adjust the shocks . If you compare figures 13 and 8, you will see that, while lateral weight transfer changes with roll centre heights along contours defined by lines that have the same inclination, the effect is different with respect to roll stiffnesses, as the lines that limit the contours have different inclinations. Notice that this is just one possibility and other parameters might be investigated as well. As fuel is consumed, not only does the position of the CoM change, but the total weight of the vehicle is also reduced. 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). The softer the spring rate the more weight transfer you will see. By the methods presented here, the simplest solution would be shifting roll rate distribution to the front, by either stiffening the front antiroll bar or softening the rear. 2. draw the ground line ,vehicle center line and center of the left and right tire contact patches. The car should be at minimum weight, using ballast as needed to make the proper weight. The total weight of the vehicle does not change; load is merely transferred from the wheels at one end of the car to the wheels at the other end. Another example would be the effect of ride stiffness on wheel hop frequency. Lateral load transfer or lateral weight transfer, is the amount of change on the vertical loads of the tyres due to the lateral acceleration imposed on the centre of gravity (CG) of the car. Briefly, the reason is that inertia acts through the center of gravity (CG) of the car, which is above the ground, but adhesive forces act at ground level through the tire contact patches. Often this is interpreted by the casual observer as a pitching or rolling motion of the vehicles body. The Trackmobile Weight Transfer System is a hydraulic system developed to implement this idea in an intuitive and easy-to-use way. Another method of reducing load transfer is by increasing the wheel spacings. Check stagger at each tire, even if using radials. This is multiplied by the cosine of the reference steer angle, to obtain a lateral force in the direction of the turning centre. The weight distribution is usually quoted in terms of percentage at the front vs back. Figure 14 can lead us to very interesting conclusions. If , and will have the term inside brackets resulting in . Weight transfer in a car is a function of Lateral Acceleration, Track Width, Centre of Gravity Height (CG Height) and Weight. Balancing a car is controlling weight transfer using throttle, brakes, and steering. One thing we can tell without any deep analysis is that increasing the roll centre height in one axle decreases the lateral weight transfer on the opposite axle, everything else kept constant. Car Handling Basics, How-To & Design Tips ~ FREE! Putting weight on the front is achieved by lifting, turning, and/or braking. f Weight Transfer - Formula 1 Dictionary Weight . Ride stiffness can be altered by either changing springs or tyre pressures (tyre pressure affects tyre stiffness, which contributes to the overall ride stiffness). The weight shift component for a single axle will be: Substituting roll angle on the expression above, we have: The total moment from roll angle on a single axle will then be: The lateral load transfer from this moment is obtained by dividing this by the axle track width, t: The three components of lateral load transfer should be added in order to obtain the total lateral load transfer on an axle: The expression above can be utilized to calculate the load transfer on each axle, which can then be used to improve handling. Braking causes Lf to be greater than Lr. The hardest one would be to change the bar itself, though there are some antiroll bars that have adjustable stiffnesses, eliminating the need to replace bars. 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. is the total vehicle weight.[7][8]. In general, it is almost safe to say that the Indycar weighs less than a Formula 1 car. In a drag racing application, you want to narrow down the rate of the spring to the softest one you can run without having any coil bind. This fact can be explained at deeper levels, but such an explanation would take us too far off the subject of weight transfer. Effect of downforce on weight transfer during braking - posted in The Technical Forum: Apologies if the answer to this is obvious, but I am trying to get a sense of whether weight transfer under braking is affected by how much downforce a car has. The rear wheels don't steer, or don't steer as . 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. Weight transfer (better called "load transfer") is not a technique, it's a natural phenomenon due to the existence of inertia, that happens whenever you try to change the state of motion of the car. These effects are good for tightening up the car when winged down, but opposite for roll right. Under heavy or sustained braking, the fronts are . But it must be considered that the Mustang at this time does not mount the carbon bottles, and there's no driver inside. 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. A. Weight (or Load) Transfer Explained (Actionable Tutorial) Driver61 988K subscribers Subscribe 2K Share 93K views 5 years ago Welcome to tutorial five in our Driver's University Series. The vehicle mass resists the acceleration with a force acting at its center of gravity. What would you do, in order to solve the problem? Your shock absorbers are considered after your ride and roll stiffness have been selected. The views are along the roll axis. These lift forces are as real as the ones that keep an airplane in the air, and they keep the car from falling through the ground to the center of the Earth. w On limit conditions, this will translate in one of the axles breaking loose and skidding before the other. any weight added, ballast, may not extend over the front or rear of the car's body or tires, and must be permanently attached to the vehicle, and there may be a maximum of 500 lbs ballast with a maximum of 100 lbs of that being removable. A flatter car, one with a lower CG, handles better and quicker because weight transfer is not so drastic as it is in a high car. Also, when the chassis rolls, the CG of the sprung mass will be shifted sideward, and that will give rise to another moment that will add to lateral load transfer. Newtons third law requires that these equal and opposite forces exist, but we are only concerned about how the ground and the Earths gravity affect the car. Front-back weight transfer is proportional to the change in the longitudinal location of the CoM to the vehicle's wheelbase, and side-to-side weight transfer (summed over front and rear) is proportional to the ratio of the change in the CoM's lateral location to the vehicle's track. Weight transfer is the result of acceleration, braking or cornering. The net loss can be attributed to the phenomenon known as tire load sensitivity. The input data were based on the manuals from the manufacturer of an important formula category. Weight Transfer Part 3: It's All About the [ROTATION] Learning to optimize weight transfer allows us to optimize the grip of the racecar. weight transfer - Everything2.com These objects would have a tendency to tip or rotate over, and the tendency is greater for taller objects and is greater the harder you pull on the cloth. Transient lateral load transfer is an important aspect of vehicle setup, but lets leave the discussion on that for another day. t 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. For example, if you investigate what would happen to the weight transfer in both axles if you held rear roll centre height constant at 30 mm while increasing the front roll centre height, you would see opposite effects happening on front and rear tracks (weight transfer would decrease in the rear axle while increasing in the front). usually, production based race cars will not have any front bar at all, and rely stricly on proper spring rates . This leads some to think that increasing roll centre heights will actually decrease weight transfer because it reduces roll. Referring back to the total load transfer equation, we see that the total weight transfer will be caused by inertial forces acting upon the entire mass of the car. One g means that the total braking force equals the weight of the car, say, in pounds. The location of the components of a vehicle is essential to achieve an ideal weight distribution and it depends on the following factors: Location of Components (Engine-Transmission-Pilot-Mechanical Components, fuel tank). We wont consider subtleties such as suspension and tire deflection yet. How to find weight load on each car tyre during cornering? I have heard of many cars running well outside of these parameters and winning. Load transfer causes the available traction at all four wheels to vary as the car brakes, accelerates, or turns. You divide the center of gravity height by the width of the contact patches, and then multiply that by the acceleration and weight of the vehicle. The added axle weight will slow the release of the stretch in the tire and help hold traction longer. The car has turned in towards the apex. Weight Management for Speed - Playland Speedway 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. It is easy to modify through the components and is where engineers usually make more adjustments specially between sessions or before the race. This conclusion is somehow trivial, as we know that roll moment arm decreases as roll axis gets closer to the sprung mass CG and roll rate distribution only affects the roll angle lateral load transfer component. [2] This would be more properly referred to as load transfer,[1][3] and that is the expression used in the motorcycle industry,[4][5] while weight transfer on motorcycles, to a lesser extent on automobiles, and cargo movement on either is due to a change in the CoM location relative to the wheels. Use a 1/4 to one scale. Lets say that you are a race engineer and your driver is having trouble to go around the slowest corners on the circuit. Before we start this analysis, lets make some important definitions: Load transfer from direct force is one of the two components related to the lateral force acting upon the sprung mass. Where is the roll angle caused by the suspension compliances and K is the suspension roll stiffness. Here they are the real heavyweights! The front wheels must steer, and possibly also drive. Then, a series of steer angles in the range of interest is selected. 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. Figure 4 shows the forces and moments acting on the sprung CG. Before we start, its worth to give a note on units. Term 2 always leads Term 3. Roll stiffnesses were input in the form of roll rate distribution, varying from 0 to 1. {\displaystyle m} As stated before, it is very difficult to change the total lateral load transfer of a car without increasing the track width or reducing either the weight or the CG height. The following weight transfers apply only to the sprung mass of the race car:-Sprung weight transfer via the roll centres (WTRC): Again, weight transfer is seperate for front and rear. Bear in mind that lateral load transfer affects the balance through tyre load sensitivity (the tendency of the tyres to generate higher lateral forces at a decreasing rate with higher vertical loads). Antiroll bars are generally added to the car to make it stiffer in roll without altering the ride characteristics. C. Despite increasing the steering angle, the car has taken a line which is not tight enough to take the turn. 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. h Put an R-compound DOT tire on the same car and raise that force to 1.05 g of cornering force. Weight transfer of sprung mass through suspension links, The second term is the weight transfer of the body through the suspension links, Weight transfer of sprung mass through springs, dampers, anti-roll bars. For the trailer, the chain pulls down . The analysis begins by taking the moment equilibrium about the roll axis: Where is the roll resistance moment, and is the roll moment. "Right now, none. The term between brackets in the equation above is the roll rate distribution or roll stiffness distribution for a given axle, and it will ultimately control the elastic lateral load transfer component. Postby BillyShope Wed Aug 22, 2007 5:48 am. An exception is during positive acceleration when the engine power is driving two or fewer wheels. Weight transfer is generally of far less practical importance than load transfer, for cars and SUVs at least. What happened here? Balancing a Dirt Stock Car Part 1 - Hogan Technologies This article explains the physics of weight transfer. a thick swaybar is not a good idea for the front of a FWD race car. Then if the car is still loose on entry we start moving the weight, at the new height, to the right. 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. Weight transfer is one parameter that is minimized - to aim for even loading on all four tires; resulting in maximum grip during cornering. Likewise, accelerating shifts weight to the rear, inducing under-steer, and cornering shifts weight to the opposite side, unloading the inside tires. Front lateral load transfer is not necessarily equal to the load transfer in the rear side, since the parameters of track, weight and height of the CG are generally different. Since springs are devices that generate forces upon displacements, a force on each spring arises, and these forces generate a moment that tends to resist the rotation of the body. This makes changes in roll moment arm to control roll angle component useless. The vehicle's weight is transferred forwards and the front suspension compresses: 'compression'. During cornering a lateral acceleration by the tire contact patch is created. Left Rear Axle Weight for Dirt Racing Take 2 - Hogan Technologies Bickel explains how the way the 4-link plays into how you adjust the car. Weight transfer happens when a car's weight moves around its roll centre when braking, turning or accelerating. In the post about lateral force from the tyres, we discussed tyre load sensitivity, the property that makes lateral force from a tyre to grow at a smaller rate with increasing vertical load. Lets now see how these components affect each other and how they affect load transfer together. Roll is simply the effect of a suspension reacting to weight transfer. The more the body rolls and the faster the body rolls, the more rotational . From: Dr. Brian Beckmans The Physics of Racing. g The secret to answer this question is to focus not on total lateral weight transfer on the car, but instead, on how it is distributed between front and rear tracks. This is balanced by the stiffness of the elastic elements and anti-roll bars of the suspension. It is always the case that Lf plus Lr equals G, the weight of the car. 2. Most autocrossers and race drivers learn early in their careers the importance of balancing a car. How Weight (or Load) Transfer Affects Handling of a Race car - OzeBiz The moment can be divided by the axle track to yield a lateral load transfer component: Where is the unsprung weight on the track being analysed. 20 - 25,000 (15 - 18,500) Formula SAE. So a ride height adjustment to your race car, or a roll centre geometry . By simply raising or lowering the couplers, our machines can gain thousands of pounds for traction. In order to determine the crossweight, calculate the sum of the right front and left rear weights, then divide this number by the total weight of the car. So lets try it with a 1200 kg vehicle with CG height varying from 100 mm to 1 m (which is ridiculously high even for a road car).