If there is room, a knee knocker should be installed under the steering column or toward the front of the seat. Both options work well, but still consider that this should not be mounted absolutely rigid. Unlike the leg braces, the knee knocker is designed to keep the knees apart and slow down the motion of the legs. If the knee knocker is mounted absolutely rigid, the leg can wrap around it and create injuries.

Below the dashboard, the only things to stop the driver's feet are the pedals. The pedals need to be mounted solidly to the chassis, and the pedal faces themselves need to be thick enough so as not to slice into the driver's foot or leg if the leg were swung that way in the event of an accident. A thin pedal face is lighter, but it can act like a knife blade when the side of a driver's shoe makes high-speed contact.

Head nets have become a visual staple in many series of motorsports. They first appeared as an additional way to control the motion of the head and arms inside Sprint Cars. They were then utilized in the stock car realm for protection of the driver's head. They were used for the right side excursion of the head when the passenger side of the car impacted the wall.

The common window net provides little protection for the head contacting the track wall in a left-side impact. The addition of the left-side head net provides an extra barrier. However, with the advent of seat-mounted head surrounds, the need for the head net is reduced.

Some seat builders question the use of these head nets when adequate head surrounds are utilized. There is no question of their usefulness when there is no head surround or when a short head surround is used. Short head surrounds are put in some cars because of space limitations in the cockpit. They allow for ease of driver exit.

One industry expert theorized that the correct use of these head nets in conjunction with a head surround could help limit the deflection of the head surround in an accident. To our knowledge, no test results have been published in this regard.

The most complete research related to head nets was done a few years ago by Tom Gideon of GM Racing and published in an SAE paper (#2004-01-3513) titled "Race Car Nets for the Control of Neck Forces in Side Impacts." This paper looks at right-side head nets and their placement and usage in controlling head-and-neck loading during a frontal right-side impact.

Gideon begins by discussing the situations that require the use of these nets. In short, whether a driver wears a HANS Device, a Hutchens Device, or some other head-and-neck system, in the event of a side impact, all of these devices have, at best, only limited control over sideways head movement. In these types of accidents, if a seat-mounted head support system is not in place, only the head nets provide protection for the head.

Gideon ran 16 sled tests at a 50g pulse. Various seats, net designs, and impact angles of 45, 60, and 90 degrees were tested. It is important to note that none of the tests utilized a seat-mounted head support system. Some very interesting conclusions can be drawn from the results.

1. As compared to the control test done without a net, the right-side nets were shown to reduce neck force and head acceleration at all crash angles tested.

2. Gideon found that net geometry and placement in relation to the seat and driver is important. The lower strand should be oriented to support the load of the shoulder. The upper strand should pass along the center of the helmet when viewed from the side. This is the preferred placement because Gideon found that if the upper strand of the net is above the center of gravity (CG) of the helmet, neck compression forces increase. If the upper strand is below the CG of the helmet, neck tension increases.

3. Nets should be designed with consideration of the car, seat and driver.

4. In a non-reinforced seat with no head surround system, it is better to have a net.

5. Right-side nets were tested, but there is no reason to think that left-side nets wouldn't function with similar positive results in left-side impacts.

6. The next level involves testing how the nets can be used in conjunction with a head surround to make up for the limitations of specific cockpits.

The days of using a stripped down passenger car to race professionally have been over for a while. Each Nextel Cup race car is now a purpose-built vehicle that has systems and infrastructure built in to enhance safety. This is not true of the common stock class series in which the race team must carefully provide a design that is safe. When designing the cockpit of your race vehicle, it is so important to look at the mounting of each accessory that goes into the car in regard to what may happen to that piece if you are involved in a wreck.