The steering shaft enters the cockpit through a firewall bearing.
Obviously, the steering on your race car is important to your well being. Many race cars today have to use universal joints (U-joints) in the steering shaft assembly in order to clear various parts while keeping the steering wheel where the driver needs it to be.
A good bit of thought must be given to what is between you and the steering box. This is true of a Bomber, a Street Stock, and all classes above. All racers need to give some thought to safety, but don't turn the page just because I talked about safety. Race car safety is what allows you to race long enough to learn how to go fast.
There are tracks that don't allow Bomber/Street Stock cars to have bracing in front of the firewall. I believe this is a less-than-intelligent and dangerous rule. It costs racers by allowing more front clips to be bent. Without front bracing, the car is more easily folded up front. Obviously, when the front of the car is bent backward, the steering box gets closer to the driver.
Universal joints should operate at a maximum deflection of 30 degrees.
There is usually a rag joint where the stock shaft connects to the steering box. It's called a rag joint because it has a fabric- and rubber-layered washer that connects the shaft to the box. This washer provides the flex necessary in the OE application. The rag joint is not always bad, but it does have a limited ability to work at an angle.
There should be some way for the shaft to get shorter during a frontal impact. One of the easiest ways to achieve this effect is to have U-joints in the shaft at enough of an angle that fore to aft movement of the steering box allows the shaft between the U-joints to jackknife out of position, taking up the movement.
When using U-joints to accomplish the crush, or just to fit the shaft to the car, they should run at a minimum angle of 20 degrees and a maximum of 30 degrees. Having only one U-joint in the system does not allow for the folding action necessary for driver safety.
U-joints installed on the same shaft must be properly phased.
You must have support bearings when using multiple U-joints. For every unsupported length of shaft (with a U-joint on each end), the adjoining shaft will need two support bearings. Large rod ends are commonly used for this purpose. When purchasing a rod end, make sure it is designed for steering shafts. The shaft tubing is often exactly on size or even over-sized by a thousandth. The standard rod end will be exactly on size, making the shaft a press fit. Sometimes a firewall bearing is used. These are properly sized. Don't use a firewall bearing for the steering shaft if the body is still rubber mounted to the frame. Any steering shaft bearing should be rigidly mounted.
Although I like to use no more than three U-joints in a system, the use of four U-joints seems to be OK when positioning the steering wheel to the driver's liking. Remember, slack in worn joints will be multiplied throughout the steering system, so all U-joints must be in good condition.
This is Coleman's aluminum steering shaft with a U-joint attached on each end.
Many of the steering shaft units put together by racers use steel weld-on U-joints. These work well if care is taken to keep the joint cool during the welding process. If too much heat is put into the U-joint, the grease will be forced out, leading to premature failure. How often do you check the grease in the steering U-joints in your race car? A welded-up assembly in a crashed car might need to be destroyed in order to remove it
If you are welding the joints to the shaft, you might consider using the stubs from Woodward Machine. These pieces weld into the shaft tubing, and the outer end is splined for a U-joint so that no welding heat is put into the joint. The splined U-joints can be assembled to the shaft in the car. Mistakes don't need to be rectified with a cutting torch. Bearings and rod ends can be moved as needed, and replacing individual parts is possible.
In this cutaway view of the Woodward SCA700 you can see the working of the shaft.
On our Fastruck project racer, we opted for the Coleman 71/48-inch diameter aluminum steering shaft. Used with Coleman's aluminum U-joints, the shafts and joints are cross-bolted at each joint. The entire unit slips together for a firm fit. These parts can be assembled or disassembled as needed. The aluminum shaft and joints are also lighter than steel. The lighter weight keeps its strength by using a larger diameter shaft, 71/48 inch versus 31/44 inch. The Coleman unit is furnished with all the necessary hardware to finish the assembly.
Anytime the project concerns assembling U-joints to a shaft, you must correctly index them. This means the yokes should be in the same position on each end of the shaft. This is true of driveshafts as well as steering shafts. Viewed from the side, the yokes of the U-joint would assume a symmetrical "U" shape. U-joints assembled incorrectly to a shaft will cause their speed to vary as the shaft is turned. This can present an uneasy feeling to a driver who is trying very hard to be very smooth.
This is a D&M quick steering box.
The rag joint common as an OE item should be replaced with a U-joint splined to fit the steering box. Old rag joints could be soaked with engine and power steering fluids, which can soften and ultimately destroy the joint. Rag joints have the disadvantage of limited angularity. In other words, they don't have a lot of flex.
Another way to keep you from coming face to face with the steering wheel hub is to use a collapsible steering column. Woodward Machine makes just such an item. Internal splines covered by a rubber boot provide the impact absorption movement to protect the driver.
Many short-track steering installations include a steering quickener. This device usually incorporates a 2:1 step-up ratio. The driver turns the steering wheel one turn, but the shaft at the steering box moves two turns. This acceleration of steering on a short track can be of great assistance to a driver's ability to keep up with the car. These units are usually used in conjunction with power steering. Lighter cars may not need the power steering. My daughter and I have raced Pinto-derived Mini-Stocks with no power steering assistance while using a 2:1 quickener.
This blue anodized Pro Lite quickener from Coleman is machined from billet aluminum.
There are two types of steering quickeners. There are those that use gears for the ratio change. The other type uses a chain and sprocket arrangement inside a housing. Today, nearly all quickeners are made in a factory. The first one I ever saw was one I built in 1964. It was made of available chain, sprockets, and industrial pillow block bearings. The darn thing probably weighed 30 pounds. As I recall, it had a ratio of about 2.23:1. With no power steering, all the muscle I had was required to drive the 3,500-pound tank on a rough clay track.
ConclusionsPut some thought into fabrication of the steering shaft and its parts. Keep the U-joint angles in the 20- to 30-degree range. If you use weld-on joints, keep them from overheating. Phase the joints properly on the shaft, and replace the rag joint with a real U-joint. Steering quickeners are good things to have on a short track.