ever wonder what is a track bar is and does?

[bigbadbrother]

Trackbar

In 1887, Rene Panhard and Emile Levasor created the car manufacturer Panhard (originally Panhard et Levassor). Panhard is credited with the first modern transmission and provided cars for some of the very first automobile races, like the Paris-Rouen Rally. As part of their R & D effort, they created the Panhard rod, which was used to help make the suspension behave better.

The Panhard bar is a bar connected to the chassis of the car on one end and to the rear end housing on the other end, as I’ve illustrated to the right. The purpose of the trackbar is to control the left-to-right offset of the rear axle. The attachments at the left and right side of the trackbar allow for up and down motion, but not side-to-side motion.

http://i0.wp.com/buildingspeed.org/blog/wp-content/uploads/2012/07/Trackbar2.png?w=684

A trackbar has two mounting points – one on the frame and one on the rear-end housing. The position of the mounting on the rear-end housing is usually fixed during assembly of the car. I’ve drawn a slot in the right-hand side of the chassis mount in the rear-view drawing to indicate that you can adjust this position during a race. By raising or lowering the right side of the trackbar, you move the rear axle left or right with respect to the car’s centerline.

Each stock car has three places where a wrench can be inserted during a race: two places in the right-hand side one on the left-hand side. Two of those are for wedge, which I’ll explain in a future column, but this third is a threaded rod that raises and lowers the trackbar mount. Usually clockwise turns lower the track bar while counter clockwise turns raise the track bar. If you raise the trackbar on the right-hand side, you move the rear wheels to the right. This makes the car looser when accelerating and tighter when braking. Conversely, moving the trackbar down on the right-hand side pushes the wheels to the left, tightening the car under acceleration and loosening the car during braking. Moving the rear axle left/right is essentially adding stagger (“rear steer”) to the car because the distance between the front and rear wheels isn’t the same on both sides of the car due to the offset.

During a race, only one side of the trackbar gets adjusted; however, you can change the height of both sides of the trackbar when you’re initially setting up the car. The overall up-and-down position changes the weight distribution and thus the way the body rolls when the car goes around a corner. If you raise both ends of the trackbar, you make the rear roll center higher and the car gets looser. If you lower both ends of the trackbar, you lower the rear roll center and the car gets tighter.

The trackbar itself is generally 1-1/4 to 1-1/2 inches in diameter and it’s essentially just a long bar with Heim joints on the ends.

I hope that gives you an idea of what’s happening when you hear the announcer talk about trackbar being adjusted during pit stops on Sunday!

[bigbadbrother]

Wedge adjustment simply refers to adjusting the amount of force that bears down on a tire's spring. So before we go any further, we should emphasize how springs are used in a NASCAR race car's suspension system.

*What makes jumping on a bed so much fun? Unlike a hard floor, the springs inside a bed make the most out of the downward force you exert when you jump -- in fact, they give it back to you in upward force, allowing you to jump even higher. You can push down on a floor all you want -- it won't push back. Springs, however, do. The reverse happens when you try to pull the ends of a spring outward -- they'll try to pull back. Springs are such stubborn and resilient things, in fact, that the harder you compress or stretch them, the harder they will push or pull back. In physics, this is called Hooke's Law.

Car engineers are able to take advantage of a spring's unique qualities in a car's suspension system. This system is meant to combat the negative affects of bumps on a road. When a car is moving and encounters a bump, that bump spends energy by transferring some of the car's forward force to upward force. It can also make the tires lose their grip on the road. If you ever got a tire stuck in the mud, you know how important grip is. Although NASCAR racetracks may not have any mud, even the slightest loss of grip can affect a car's performance.

Springs are a great way to absorb the energy that tires encounter with bumps. With a spring at each tire, these suspension systems transfer the energy of the jolting tire to its spring, which pushes back. This keeps the tire in constant contact with the road as the springs continue to push wheels downward.

Even using springs, maintaining grip between the road and the tire can still be difficult when taking a turn at a high speed. This is what happens during NASCAR races. If weight shifts off of a tire during a turn, the tire will lose grip with the road and the driver will have less control of the vehicle. It turns out that the amount of tension on a spring can alter how much of the total weight bears down on a given wheel. When adjusted appropriately, the amount of tension on the individual springs can help attain proper weight distribution and grip during a turn.

*But here's how things get tricky: When you adjust the tension of a spring on one wheel, it can affect the other three wheels in interesting ways.

We've seen how important it can be for suspension springs to help tires maintain a sturdy grip with the road. It's especially important on a racetrack where every second counts and accidents can end in disaster. To accommodate such delicate conditions, pit crews perform wedge adjustments to alter the tension on the springs. But if you notice, these crews adjust the wedge only on the rear wheels. Actually, it turns out that adjusting the pressure on just one rear wheel is often all a race car needs. That's because, as we mentioned earlier, adjusting the tension of one spring can affect the weight distribution on all tires.

*To understand why this happens, think of a stable, four-legged table where the weight is evenly distributed among the four legs. If you tuck a small piece of folded paper under one of the legs, the table will wobble. Now the wedged leg and its diagonal leg carry more of the weight than the other two legs

The same thing happens with a race car.* Compressing the spring of a left-rear wheel or adding wedge puts more of the car's weight on that corner. This adds pressure to that end of the car just like putting the paper wedge underneath the table leg. As with the table, the corresponding diagonal corner of the vehicle gets more of the car's weight. So if you increase the tension in the left-rear wheel, the left-rear and right-front wheels will hold a larger share of the car's total weight than the right-rear and left-front wheels.

The reverse happens if you reduce the tension on the left-rear wheel's spring or subtract wedge. In our analogy, that would be equivalent to cutting short a table leg. It would increase the weight on the right-rear and left-front wheels. This is why a crew may need to adjust only one wheel when a race car needs to add or subtract wedge.

The diagonally related weight between the left-rear and right-front wheels is referred to as cross-weight or simply wedge. It is often measured as a percentage of the vehicle's total weight. When more than 50 percent of the car's weight is on the left-rear and right-front wheels, the car is said to have more wedge.