Indianapolis Motor Speedway was the leader in the move to get the SAFER barrier on the rac
In the last few years, the term soft walls has entered the racing vocabulary, but how much do we really know about them? A better question is, How do they apply to short-track and local track racing? Understanding the physics behind the soft walls (or Energy Dissipating Barrier) provides a better appreciation of their application in motorsports.
There are a few types of soft walls. Some have been in design for more than 10 years, while others have been a reaction to current problems.
Crash energy would be dissipated without the soft wall in place. The key element of the soft wall is where and how quickly the energy is dissipated. Without the soft wall, the energy is dissipated by the crush of the race car and takes the minimum time possible. It is the high crash energy, or impulse, over a short time that causes the most injury to the driver.
With the soft wall in place, the crushing of the race car and the energy-absorber material dissipates the crash energy. The benefit is that the energy absorber (usually foam) is crushed over a large surface area. Increasing both the impact area and the amount of crushable mass will increase the duration of the accident while reducing the kinetic energy of the accident. This combination will provide a less intense impulse felt by the driver.
These large wall sections use a honeycomb structure for energy dissipation. The individual
The standard concept of a soft wall features an inner wall design that is used to dissipate the energy of the car crashing into it. Most of the soft walls in the industry currently installed at Richmond, Indianapolis, Talladega, Phoenix, and Loudon are of the SAFER (Steel and Foam Energy Reduction) style. A group headed by Dr. Dean Sicking at the University of Nebraska-Lincoln's Midwest Roadside Safety Facility designed these walls.
"The total emphasis is on driver safety," says Sicking, professor of civil engineering. "We put in thousands of hours with computer models and on the test track to develop a barrier that would decrease peak forces applied to the car by elongating the impact event, which allows the occupant restraint systems more time to operate optimally and reduce driver injury."
Ken Bell's Supermodified sails into the foam blocks at Oswego (New York) Speedway. Bell es
The SAFER walls consist of a tubular steel wall with tremendous bending strength. The bending strength of the wall element will prevent it from wrapping around the front of the car and virtually eliminate the pocketing. The tubular steel is coated on the surface of this barrier with zinc rich paint. The zinc provides a lubricant, which further reduces the friction between the vehicle and the barrier. By reducing the friction, longitudinal deceleration is also reduced. This longitudinal deceleration pulls the car into the barrier, increasing the acceleration of the driver. Behind the tubular steel, the barrier incorporates spaced foam energy absorbers. These absorbers are made from polyethylene foam.
The early versions of the wall had solid sheets of polyethylene behind the steel, but the energy management properties of that design were not satisfactory. After more computer modeling by Sicking and his group, the spaced absorber design was developed. Through testing, this design showed superior energy management properties and reduced the amount of absorber material required.
The cost of this SAFER system is estimated to be a minimum of $175 per linear foot of wall. On longer, sweeping corners, the cost is closer to this figure. On shorter tracks, the tubes will actually have to be rolled to the radius of the racetrack, a procedure that will somewhat increase the cost. As you get to smaller and smaller tracks, the radii become tighter, and cost of the work required to get the tubular steel to fit increases.
Foam buns are created as the working material for a soft wall system.
Another type of soft wall is called the Impact Protection System (IPS). Eurointernational has developed a soft wall made of layered PVC material placed on a honeycomb structure. This inner piece of the wall is then wrapped in a rubber casing. The barrier walls come in segments that are 5 feet 9 inches long, 3 feet 9 inches tall, and weigh 475 pounds. To install these segments, holes are drilled in the concrete wall and cables are used to tie the segments to it. The individual segments are tied together with strong nylon webbing material to form a continuous wall.
The IPS is the result of many years of research, studies, tests, and modifications. This barrier has the official approval of the FIA and has also been approved by the FIK (Karting) and FIM (motorcycles).
According to the manufacturer, this barrier is able to receive three impacts at the same place without needing to be replaced. The barrier returns to the original configuration after each impact, with an equal amount of energy absorbed each time. The barrier segments for racetracks come in two configurations-standard and reinforced. The reinforced barrier is identical to the standard barrier except it is wrapped in a double layer of smooth rubber material; the standard barrier is wrapped with just one.
Another popular soft wall is the block foam-style wall. As opposed to the other two types, this wall uses only the absorber foam to make up the walls. Some tracks have used large blocks of Styrofoam or polyethylene as the absorbing foam.
A group of NEMA winged Midgets tangle and scatter foam during a race at Oswego Speedway. N
This is certainly the least expensive way to accomplish the soft wall, but it has some drawbacks. The first drawback is that the absorbing foam takes serious abuse during the crash because there is no facing wall. This abuse usually leads to the destruction of the foam while spreading it all over the track. The result is a cleanup problem-and in some stock car tests, large chunks (5-20 pounds) have broken off and flown into the stands.
In addition to Styrofoam and polyethylene, other types of foam are being considered for use in both the block and engineered systems with facing walls. These foams are engineered specifically for energy dissipation. Styrofoam and other foams were used because they were readily available. These engineered foams can be custom made to the needs of the wall systems. A bun of the engineered foams can come as large as 4 feet high by 6 feet wide by 210 feet long. Although it's next to impossible to move a bun that large, it shows that the material is there for a more engineered application.
The End Users A survey of racetracks has found that there are many different approaches to keeping drivers safe through the use of energy dissipation.
Stafford Motor Speedway is a half-mile asphalt track in northern Connecticut. The track employs a more traditional energy-absorbing barrier. The outer wall consists of steel guardrails with down posts that go deep into the ground. Though many tracks have gone to cement in the corners, Stafford has stayed with the guardrail in all but one corner. In fact, Stafford is replacing the guardrail with steel I-beams. "I have seen our wall move 4 feet to 5 feet to dissipate the energy of a crash," says Stafford's General Manager/ CEO Mark Arute. "Our system moves more than a SAFER barrier wall. This system requires a lot of maintenance, but we have never had a failure. Every so often, we will have to take some equipment and reset the wall and tamp in the dirt behind it." Arute says Stafford is investigating the installation of the SAFER barrier in the corner with the cement walls.
"Everyone is impressed with how well the soft walls are working throughout the industry," says Andrew Gurtis, Darlington Race- way's president. "Darlington will be getting soft walls [SAFER barrier]. It is not a question of if, but a question of when. From our conversations with ISC [International Speedway Corporation], we both understand that every track is different, and designing a soft wall system that will work with our track configuration will take time and engineering."
"Incredible-the single most effective way to reduce driver injury and cost of equipment [race cars]," George Caruso, Oswego Speedway owner-in-transition says of the Styrofoam blocks used at his speedway. "Since the installation of the blocks, we have had no serious injuries.
"The blocks are 4 feet tall, 8 feet long, and 3 feet thick, and only cost about $130. The cleanup is a little different from before the blocks. We have a large safety team that goes to the accident site. The larger chunks are picked up, the blocks themselves are moved back into place, and we have a vacuum truck that gets the little pieces."
Caruso credits the late Bill Colton Sr. for the idea behind the walls: "Bill had the idea to use these blocks at Lancaster (New York) Speedway. Some of our Supermodifieds had run down there, and some had hit the blocks. When the message came back to my brother and me, we felt that we had to look into these blocks.
"The only downside I have seen is that our drivers are a little braver. They know the soft wall is out there, so they might try things they normally wouldn't."
Late last year, Phoenix International Raceway President Bryan R. Sperber announced that installation of the SAFER wall system would be completed by the first event of the '04 season.
The barriers run continuously for 1,550 feet from Turn 1 through Turn 2, and for another 1,650 feet starting again at Turn 3 all the way through Turn 4. The walls are 4011/42 inches high and contain steel tubes and 22-inch-thick blocks of Styrofoam that are placed between the original wall and the new wall.
"We have spent the past year making PIR a safer place to race," Sperber says. "Last fall, we moved the Turn 2 wall out 12 feet in order to make it safer for the drivers and promote better racing action on the track. In my eyes, the installation of SAFER walls just finishes the overall project. We want the drivers and teams to understand that we are doing everything we can to make their experience at PIR a positive one."
Even though the results and experiences of the soft walls are positive, there are also some limitations that make it understandable that more tracks do not currently have them installed. The first and most obvious reason is money. At $175-$400 per foot, it is very expensive to install these systems. Most tracks that host a weekly series and a few special events throughout the year do not generate enough money to install a system.
Physical space limitations provide another difficulty in installing a system. The racing line around each track is different. For tracks in which the racing line is up at the outside wall (such as Darlington), this must be considered when designing the system. The track will either move the outside wall out or force the race line farther down on the track.
NASCAR has stated a goal to install SAFER barriers in every track by the end of 2004 where it has been recommended (tracks that appear on Nextel Cup, Busch Series, and Craftsman Truck Series schedules). When this major push is over, the resources should then filter down so that short tracks will have access to the technology.
Soft wall or energy dissipating wall systems have proven their worth. The decision to install the system at a track, or at least investigate how the system would fit into the track, should not be difficult. The decision to go with an engineered system or a block system should be based on budget as well as space. But no matter the choice, it is the safety of the drivers that remains the primary motivation.