The driver is truly in the...
The driver is truly in the hot seat. Enclosed cars like Late Models on pavement can be quite warm, but even those with open driver compartments like Modifieds and dirt cars can still retain heat. There are ways to make the driver comfortable enough to focus on the task at hand.
In any form of racing, heat is an issue drivers and crews have to deal with. From the effect of heat on the health of the driver in the seat, to the prevention of mechanical component failure or fluid system failure throughout the vehicle, the control and dissipation of heat is a major concern in motorsports.
Drivers in any division will sweat during the course of a race and an event weekend. Research has shown that an athlete's (driver's) performance can begin to be adversely affected with a loss of 2 percent of body weight. This would be 3 pounds in a 150-pound driver.
Even without the loss of fluids, the hot environment of a driver's cockpit will affect a driver's concentration and driving performance-not to mention that a driver getting burned on the foot or through the seat can be taken out of a race.
There are three main heat sources in the race car that affect the driver-the engine (including the radiator), the exhaust system, and the oiling system. Each of these has its own specific volume of heat and transfer method to deliver heat to the vehicle.
The engine and radiator, because of location and how they operate, will transfer heat to the firewall and under the car. The heat they release will be transferred in the volume of air that flows across them. The method of shielding most practical for these components is to begin at the parts that are affected. This method works best because there is not an effective way to contain the heat of the engine or radiator.
The heat from the exhaust system will be transferred to the firewall, frame, and undercar sheetmetal. The exhaust contains the most heat, and its transfer is the one of greatest concern. The heat from the exhaust will transfer directly to the surrounding air and to the other elements through conduction. The most effective way to shield exhaust heat is to start at the pipe itself and work your way toward the driver or heat-affected component.
The use of exhaust pipe coating...
The use of exhaust pipe coating is a good way to move the heat away from the driver. The coating can be helpful in improving the performance and durability of the exhaust system.
Heat from the oiling system is a concern throughout the car. In a car with a dry-sump system that has a rear-mounted tank, there are oil lines running throughout. The tank itself is a significant source of heat normally positioned behind the driver. Controlling the heat given off by the oiling system is difficult because each piece is different and the method that will work best depends on the individual component.
Now that we know the origin of the heat, we should look at the most effective theories for shielding the driver and specific components from it. Too many teams take the Band-Aid approach after there's a problem. They add more shielding at the driver's point, not understanding that the problem stems from too little shielding at the source of the heat. If the source of the heat were effectively directed away from the driver, any extra shielding at the driver would be unnecessary.
When looking at insulation products, undoubtedly, the question will be asked or a claim will be made about temperature reduction. Most manufacturers will have an answer for that question. However, there is a problem if the person answering the question doesn't have knowledge of your specific application or the true heat levels involved. These claims would be given more credibility if they were accompanied by test data, thermal imaging, or at least a description of the heat involved as radiant, conductive, and so on.
Collector covers can help...
Collector covers can help provide a layer of protection to the driver.
Level 1: Exhaust Pipe Coating
The best way to slow exhaust heat travelling to the rest of the car is to keep the heat in the exhaust pipe itself. Most often, the way to do this is through the use of coatings. One coating is called Emisshield, which makes use of the properties of emissivity, the ability to absorb and reradiate energy (in this case, heat). This coating is applied to the inside or outside of the exhaust pipes. The key is that it must have a "load" to reradiate toward. With the Emisshield applied, the heat energy is absorbed by the coating and reradiated back into the exhaust gasses as opposed to heat transferring through the metal pipe. Through dyno testing, the Emisshield has shown to maintain a higher exhaust gas temperature and a lower header pipe surface temperature when compared to an uncoated header pipe. The benefits of the Emisshield may be two-fold-protection for the rest of the car from the exhaust heat and its ability to maintain exhaust gas temperature, therefore sustaining exhaust velocity through the primaries.
Working with the emissivity principle (absorb and reradiate), Emisshield would not work the best in all situations. As an insulator from a heat source without any airflow to carry off the heat, the Emisshield would have limited places to reradiate the heat.
The heat-resistant boards...
The heat-resistant boards can help in thermal shielding, especially in short races and lower-heat areas.
Level 2: Exhaust Pipe Shields
The next level after keeping the heat inside the pipe is to mount insulation materials to the exhaust pipe itself. A few years ago, fiberglass header wrap was outlawed by many sanctioning bodies because of its tendency to absorb oils and gasoline during an accident or engine failure. It would then continue to burn and fill the vehicle with smoke. In response to that rule, exhaust-mounted insulations were made by incasing the insulation inside metal such as stainless steel.
A few companies offer these stainless steel exhaust shields. These are made with ceramic and silica insulations. The stainless steel containers have grommets for attachment. They are attached to the exhaust using safety wire or stainless steel tie straps.
As an alternative to the stainless steel shields, 3M came out with an industrial fabric and insulation shield. This ceramic textile is used in place of the stainless steel as the outer shell material. The attachment uses the same methods as the stainless shields. These shields, although built of a high-tech textile, cause concern of absorbing the oil from a blown engine and smoking on the hot exhaust. However, if they do get normal oil drips on them, they can be cleaned.
Tunnel Shield is a composite...
Tunnel Shield is a composite material for insulating the floor or the firewall.
Level 3: Under Floor and FireWall (Tunnel Shield and reflective fabric shielding)
At times, it is impractical to mount insulation onto the exhaust itself. In that case, the next best location for the insulation is on the floor and firewall. There are a few options, including reflective silicone foam, adhesive gold foil, and ceramic insulations. But the product that has taken off the most in the last few years is a composite material called Tunnel Shield. This material consists of an embossed aluminum face backed up with fiber insulation and an aggressive high-temperature adhesive on the mounting surface. This material can be cut and molded to fit any shape underneath the car. The adhesive has been shown to hold to 450 degrees F, but it is recommended that a few safety rivets be used if a large piece is being installed.
Level 4: Floor Coating
Once the heat has reached the sheetmetal floor, it has many paths from which to transfer into the vehicle. It is important to look at the interior sheetmetal as a place to continue to slow the transfer of heat.
A floor mat can serve as a...
A floor mat can serve as a defense against heat entering from beneath the car. Floor mats can be tailored to fit the type of car being raced and provide sufficient protection.
Some teams have sprayed traction materials onto the floor to help prevent the driver's feet from slipping. These materials, similar to truck bedliner materials, can act like hot sugar or hot cheese in that they hold heat as opposed to insulating. It's important to be careful when selecting materials for the inside of the car. A material may work well for a specific task, but may hinder in another area.
One option for direct floor applications is a product like Nomex board. This material is a thin, hard Nomex laminate that provides excellent thermal shielding in short-race and lower-heat areas.
Level 5: Air Gap Insulating
We've talked about the physical means of shielding heat, but you can use air as an insulator. There are two main ways to accomplish this. The first is by building a false floor. This is a fabricated piece that raises the driver's feet from the actual steel floor by 11/42 to 4 inches, depending on the car's configuration and the size of the driver. This gap area does not have any insulation. The air in the gap will effectively slow the flow of heat. Some teams have even added a hose to direct a current of air into and out of this air gap and further help to slow the heat transfer.
Crewmembers may have to crawl...
Crewmembers may have to crawl under a hot race car to do work. Many teams have large fans, but some go one step further since the fans don't fit under the car. This crewmember is kept cool by an air conditioner like the single room units placed in windows.
The second way to use an air gap to insulate a driver is through the use of insulating items that contain a partial vacuum. One of the more popular options is the composite honeycomb board. The outer surface can be made out of the carbon, Kevlar, or other composite materials. The inner core of the board is a honeycomb cell structure that is 11/44 to 31/44 inch thick. Most composite shops can make a board of this type; however, the key to the insulating nature of this board is that it's assembled under a partial vacuum. This processing method leaves a partial vacuum in the honeycomb cells. It is this vacuum, combined with the insulating nature of the carbon or Kevlar, that provides the thermal barrier. It is more difficult for a composite shop to set up and manufacture under a vacuum, so there are only a few shops and retailers that offer this type of board.
Level 6: Floor Mats and Component Shielding
In addition to air gap insulating, which can be expensive or difficult with space limitations, the next layer of protection is a physical layer of insulation directly below the driver's feet. This layer of the insulation has more requirements because of where it's placed in the vehicle. First, this layer will be closest to the driver and must act as a final line of defense. Secondly, the driver's feet are rubbing on it, so the top material must be able to take more physical abuse than other insulation. Next, the floor mats have to fit in and cover complex floor- and transmission-tunnel configurations. Finally, it is the most popular piece of insulation shielding and may be installed when all other levels have been neglected. As a result, it must take up the workload of other items not installed.
Most floor mats use a coated fiberglass top material to provide an abrasion-resistant surface. Most often this coating is a silicone in black or iron-oxide color. The fiberglass or ceramic insulation will be under the top material. The insulation will be as thin as 11/44 inch to as thick as 1 inch, depending on the application and how effective the rest of the insulating system is designed. Special stitching techniques and patterns are used to slow the migration (or bunching up) of the insulation from the driver's feet rubbing against the top material. The bottom material consists of a vapor barrier that is often a reflective material. The vapor barrier is installed so the insulation stays dry. The reflective material is not as effective as when used in other applications because it lays directly on the floor or other insulating materials, but it completes the package and provides a good look to the mat.
The heel boot simply slips...
The heel boot simply slips over the driver's shoe. Many companies have also offered shoes with heat protection built into the heel, but these boots provide protection without distraction. Heel boots gained notoriety when Tony Stewart threw his at Kenny Irwin after an on-track incident in a Winston Cup race a few years ago.
Level 7: Heel Boots
One of the first places most teams begin shielding a driver or a component is the last place they should look. The use of body or component shielding is popular because it is thought to attack the problem at the source of the complaint. A driver suffering burns or the failure of a component gets attention, but the root of the problem should be addressed. Doing this will reduce, if not eliminate, the need for extra shielding at the body or individual components in most cases.
That said, there will always be a place for heel boots and other component protective shielding. Fuel pump covers and reflective sleeves for fuel lines have grown in popularity and will always find their place in the industry.
System Concept Through each of the previous sections, we have tried to describe the system concept of thermal shielding. It is important to first look at the source of heat anytime you try to shield or redirect heat. Next, determine if it's a source that can be shielded in such a way to contain the heat (i.e., exhaust pipe) or a source that is required to expel its heat (i.e., radiator). From that determination, you then look at what is to be protected (such as a driver, fuel line, or carburetor). Once you have identified the source and the pro-tected item, an effective plan can be devised to protect the driver or components. The system used may be made of many parts, which is better than relying on only one method of protection.
Thermal protection is highly important in motorsports. Many companies have spent time researching different methods and techniques to shield heat in a race car. It is important to utilize the resources of these companies and the products they designed in order to thermally shield your race car.