by Cassie Gannis
NASCAR racers are surrounded by safety equipment both in the car and out of the car. Originally I was going to write about the personal driver equipment but I thought it may be better to break some the equipment down into individual blogs. Over time I would like to talk about all the safety equipment used in racing and I will. To begin the discussion of safely today, I would like to start with talking about the safety equipment used for a drivers head and neck specifically RACE CAR HELMETS.
The head is probably the most vulnerable human body part for a racer. A driver is strapped in very tightly in a roll cage but the head jerk can be uncontrollable. “The helmet is designed to dissipate impact energy over the entire helmet and prevent debris from puncturing it.”
There are 3 parts to a racing helmets:
- The outer most shell begins with a thin layer of gelcoat. Then a special resin, consisting of several types of glass, carbon, Kevlar and other exotic fibers and weaves, is added to the shell. This all combines to make the hard, glossy outer shell. Racing helmets use to be made out of fiberglass but NASCAR is changing that and now stock car helmets will be made using carbon fiber. Auto racing Helmets must have a fire protection element since racecars catch fire. Auto Racing helmets must also be able to withstand being hit by sharp object.
- The BeadALL liner is a special foam layer found in the crown of the helmet. This lining of the RACE CAR HELMET is the layer that absorbs most of the energy from the outer shell during a crash. It is made from polystyrene.
- The fire proof material on the inner most form fitting layer Is either nylon or Nomex. Nomax is a special fire retardant material made by DuPont. Nomex “doesn’t melt, drip, burn or support combustion.” Along with this inner layer are cheek pads, chin straps and a visor. Visors are made from Lexan, a very tough plastic that is also known as bulletproof glass.
Racing helmets have a narrow field of vision because unlike regular helmets drivers are wearing them on a defined track. Using a racing helmet on a motorcycle on public roads is illegal because of this narrowed field of vision.
Many people don’t know the rigorous amount to tests racing helmets must go through. Even I didn’t know all the tests that were done. This testing is done by Snell Foundation in California, one of the most advanced facilities in the world. These tests are made to mimic things that may happen in a race. But most of the scientists there can also measure the effect the equipment goes through and how it will pertain to the driver. In this state of the art facility helmets are put through a variety of tests to see its performance, ability to stay on a head, handling in difference environment conditions and the helmet must pass all of these!
- Impact: This test involves controlled impacts where the helmet is dropped in a fall on to various surfaces to measure the accelerated Gravitational units. “The impact energy (drop height and mass), or how hard the helmets are impacted is unique to each standard. However, in any valid test, if the peak acceleration imparted to the head form exceeds certain threshold value (around 300 G’s, depending on standard and test type), the helmet is rejected.”
- Positional Stability (Roll-Off Test): From a stand with the face of the helmet heading down and all straps fastened, it is dropped at an angle of 135 to 180 degrees with a 4kg insert to simulate the brain. Each time the helmet drops it must be able to keep the insert inside or it fails.
- Dynamic Retention Test: The helmet is placed on the head form and fastened into place. The jaw area is loaded with a 23 kg weight. During testing there is a simulated abrupt fall and the straps much all hold or not stretch more than 30mm.
- Chin Bar Test: A full force is applied to the face with the helmet facing upward. A 5kg weight is dropped onto the chin bar and the area must be able to hold the hit.
- Shell Penetration Test: The helmet is attached to a base and 3 kg sharp objects are hurled toward the helmet to see if they penetrate. Not objects should be able to get to the head form.
- Faceshield Penetration Test: The face shields are hit objects or pellets from an air rifle. None of these objects should be able to penetrate the shield.
- Flame Resistance Test: Propane flame at 790 degrees is applied to the other shell, trim, chin strap and face shield for a number of seconds and it must self extinguish or the inside temperature must not exceed 70 degrees.
A very important part of a drivers head gear is the HANS device. Jim Downing and Dr. Bob Hubbard, who earned his Ph.D. in engineering studying the mechanical properties of skull bones, invented the “head and neck support” now known and marketed as the HANS device.
A HANS device also known as a head restraint, is a safety item compulsory in many car racing sports. It reduces the likelihood of head and/or neck injuries, such as a basilar skull fracture, in the event of a crash. Serious head and neck injuries happen at impact speeds as low as 35mph. On short tracks with tight turns it is easy to be “Q-balled” almost straight into the wall. The HANS device works as a sort of airbag but it doesn’t inflate. It is a raised collar with 2 polyester fabric tethers attached to the driver’s helmet. The 2 driver’s shoulder belts hold the collar in place.
“The tethers link the sides of the driver’s helmet to collar anchor points. When g-loads build during a forward impact, the HANS device assures that the driver’s helmeted head moves with his torso so vulnerable neck and skull bones aren’t overloaded.” With only a neck to restrain it, a 15-pound helmeted head lunges forward at 107 g during a 40-g head-on collision.
Resulting “shear” (two opposing forces perpendicular to the neck’s axis) and “tension” (pulling force along the neck axis) loads vastly exceed the injury threshold, making death more likely. The restraint provided by the HANS device reduces neck tension by 81 percent, shear by 72 percent, and the total neck load by 78 percent. “The head experiences a tolerable 62 g.
Because the driver’s head and neck motion is now in synch with his torso’s movement, chest g-forces rise slightly, though chest compression is reduced.” http://www.caranddriver.com/features/the-physics-of-how-the-hans-device-saves-lives-feature
One last little piece of equipment that goes on a drivers heads is the simple Nomex Balaclava or “head sock”. The firesuit doesn’t protect all of the neck. To protect a driver’s neck and lower face from fire coming up into the helmet many of NASCAR drivers wear a head sock. Along with protecting against fire it also helps keep small objects from getting into the helmet and into the eyes of the driver.
I hope you enjoyed learning about racing head safety and helmets. I must admit I learned a lot in doing my research. Please let me know what you think and if you have any question. I look forward to hearing from you.