When you make hard contact with the wall, or even bump wheels with another race car, you s
Ask any experienced driver and he's likely to tell you he depends on "feel" as much as his eyes to know what the race car is doing on the track. The mystical quality of feel is best described as input transmitted to the driver's body from the car. From his seat, the driver certainly cannot tell if the right-front spring is bottoming out or the rear tires are spinning on exit of the turns, but there's no doubt he can feel it. The driver can feel what the car is doing with his foot on the brake pedal, his rear end in the seat, and most importantly, his hands on the steering wheel. Elementary, right? Of course, but how concerned are you about how well your power steering box transmits information back to your, or your driver's, hands?
Properly setting up and maintaining your power steering system (both the pump and the gearbox) is critical in terms of fielding a car that's easy to drive, and also to eliminate the possibility of a critical failure on the track. A standard gearbox for a race car setup for a drag link steering system may seem like a pretty beefy piece of equipment, and it is. But the pitman arm, idler arm, and tie rods are designed to produce plenty of leverage to help the gearbox steer the wheels. That also means that if the front wheels make contact with the wall or another car, that same leverage is transmitted-often with damaging force-right back to the gearbox.
The valve and torsion bar fits inside the input shaft. If the pin that holds it into place
To get a better idea of how you can use your power steering system to improve the feel at the steering wheel as well, we traveled to Winston-Salem, North Carolina, to the shop of CJR Products. Owned by Ronnie Grayson, who started the business building boxes for Dale Earnhardt in 1988, CJR builds custom gearboxes and power steering pumps for several Nextel Cup teams, including Roush Racing, Hendrick Motorsports, and Richard Childress Racing. The shop also builds more economical units for the Saturday night racer at any level. It turns out that everyone in this four-man shop is a racer, and they understand the real-world economics of local, short-track racing.
Steering gearboxes are manufactured by Delphi. Racing gearbox builders like CJR purchase these boxes from Delphi and then rebuild them to its specifications. Much of the time and attention required is simply to make sure all the parts meet specs, but CJR does other upgrades to make the gearbox a more precise piece of equipment. One major option available to drivers is the "valving" in the box. This is a bit of a misnomer because the valve doesn't change, but the torsion bar on which the valve is attached does. This adjusts how hard the driver has to work to turn the steering wheel before the steering assist kicks in.
Here's a case of severely bent splines on the pitman arm. Still, despite the twist, you ca
The torsion bar actually slides inside the input shaft. One end is pinned to the shaft while the other is pinned to the spool cap. As the driver turns the wheel, he actually twists the torsion bar, moving the valve. Once the bar has twisted a certain amount, the valve is opened completely and the steering assist is activated. You can use different size torsion bars to adjust the amount of effort required to turn the steering wheel. Smaller bars twist more easily, requiring less effort from the driver, while thicker bars do the opposite. According to Jeff McBride of CJR, most short-track drivers prefer a 235 or 250 valve. The numbers represent the thickness of the torsion bar in thousandths of an inch (a 235 valve would mean a torsion bar that is 0.235 inch thick).
"The thicker bars mean the driver has to put more effort into the steering wheel," McBride explains, "but he also gets more feel for what the front end is doing. The lighter it is, the less the driver can actually tell what is going on-where the front wheels are. It seems the younger guys usually want the bigger torsion bars because they really want to feel with their hands what the car is doing. Older guys seem to want less because they have a more developed feel for what the car is doing, and they want to work less.