Hyper cc Sprint Setups. Asphalt cc. Hyper Lightning Sprint. Hyper Midget. That has led to all sorts of misinformation, which in turn is bad news for the racer.
It should be no surprise to anyone reading this that Bickel has built more than his fair share of championship winning race cars, and he is certainly no stranger to tuning suspension systems.
When a drag car launches, the rear-end wraps up. The purpose of a traction device is to turn that wrap-up into forward motion. This is a simple triangular-shaped device that connects the rear-end housing to the frame. The ladder bar prevents excessive suspension wrap up by pushing up on the frame at the point of forward connection basically the point where the upper and lower bars of the ladder bar intersect. As a result, the forward attachment point is called the pickup point.
If the car has two ladder bars as nearly all do , there are really two pickup points—one on each side of the car see illustration 1 below. Consider what happens when the ladder bars push up on the chassis at the pickup point. The respective bar on each of the car also pushes down on the tires and wheels.
That all makes sense, but over time racers quickly discovered that changes in that pickup point location can have a considerable influence upon the behavior of the chassis. If, for example, the pickup points were short and high, then the launch would prove violent. This regularly resulted in the slicks wadding up at the launch. It definitely looks wild, but it also can result is horrendous driveshaft alignment—the results of which can prove disastrous. So instead of a short, high pickup point, what if you had a long, low pickup point?
Bickel tells us that this arrangement will tend to hit the tires less violently, but it can also create more total load transfer to the rear tires. Bickel notes that this is generally an acceptable situation, but if you go too far, the chassis may squat excessively or worse, rattle the tires. The big question with a ladder bar setup is this: How do you make the ladder bar adjustable so that you can tune it from a range of short, high pickup point to long, low pickup point?
It can be accomplished with several different ladder bars along with several different front ladder bar mounting positions. If you begin with a four-link, Bickel notes that it is entirely possible to create both pickup point extremes short and high versus long and low.
Bickel goes on to tell us that the ideal pickup point locations for a race car are dependent upon multiple factors. But there is one truth: All race cars all have a neutral line that determines how the chassis will behave see illustration 2 below.
If the pickup point is located about this line, the body will separate upon acceleration. If the pickup point is located below this neutral line, the body will squat. In a perfect situation, the front pickup point should be located near the neutral line.
This setup will ultimately work well and prove very stable. The car will neither show squat, nor will it encounter excess body separation. Gas pressure shocks are now commonplace in dirt racing where 10 or 15 years or so ago, they were just being introduced.
This is evidenced by the numbers of new shock companies that have arisen and also the move by existing previously asphalt-only shock companies into the dirt market. Research that has been done to document shock influences on dirt show that there are a lot of gains to be had by concentrating on your shocks. The age old truth is that we need to perfect our setup first before working with the shocks. Dirt cars show a lot of travel as they negotiate the four turns. This extreme degree of wheel travel means that shocks get to do more work than with other types of race cars.
A shock does not have any influence if it is not moving, so dirt shocks necessarily can influence the car a lot. Each corner of the car might need a different shock characteristic. A very soft spring would need more compression rate and less rebound rate, whereas a stiffer spring would need more rebound rate and much less compression rate. Shocks affect the motion of the corners of the car and therefore the placement of wheel loads during transitional periods, and dirt cars are almost always in transition.
Think out your handling deficiencies and plan out how to make shock changes to help solve those problems. Turn entry on dirt is important and dictates how well we are able to negotiate the middle of the turn. So, we need to evaluate our turn entry characteristics related to brake bias. We may want to try to solve turn entry problems with the brake bias on dirt. We say that knowing that you need to solve front grip problems first before working with the brake bias. But if the car is turning well through the middle, but needs help getting into the corner, working with your brake bias might be beneficial.
If there is, try to adjust the brake bias to improve the entry conditions under heavy braking to what it is under light braking.
We could always use more bite off the corners on dirt. The exit portion of the track provides little traction and most corners are usually more flat. We almost always need to develop more rear traction for dirt cars.
To give the car more rear traction, we need to understand a little about the dynamics at work on the car when we are accelerating. There are several ways to do that without changing the handling at other points around the racetrack. We can use lift arms and pull bars with various stiffness of shocks and springs.
More and slower movement is needed for slick conditions and much less movement for the tackier conditions. Another way to gain bite involves the use of a spring-loaded push rod that allows a certain amount of forward right rear wheel movement to steer the rearend more to the left. It is common to try to increase loading on the left rear tire on acceleration. This can be overdone and the goal of trying to create equally loaded rear tires could actually go the other way with the tires being unequally loaded with the left rear more loaded than the right rear.
Be careful not to overdue the loading of one tire. Racers discovered the need for better aero designs some years ago. Just look at the dirt late model cars and how they have evolved. The frontends are wedges that scoop the oncoming air up and over the car. The wheel wells are shaped to route air out and away from the front tires creating downforce.
Dirt modifieds are also using better hoods and roofs that will make use of any aero downforce. The available area to use for this is admittedly smaller, but any gain in downforce is useful. The degree that you need to get involved with aero for your car depends a lot on what you run and where. Eubanks Garcia White Caretti Pike Miller Fielding Walter Painter Indoor Nebelung Roch Borneill Cockerill Lewis Morales J.
Wuller Zambrzycki Russell Ledun Benson YZ4SF - Manual.
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