by Madison Wood
St. Johnsbury Academy, Concord, VT
Honorable mention
The sport of equestrian eventing sees a great number of both equine and rider injuries, many of which are due to rotational falls in the cross country phase of eventing. Traumatic brain injury, broken ribs, collapsed lungs, or death are all possibilities when a fall occurs in this high speed event, but are seen most commonly in instances of rotational falls. A rotational fall occurs when a horse hits one of the solid, imposing cross country jumps with its front legs or chest, causing the body of the horse to somersault over the fence, while the fence acts as a pivot point. The rider is usually thrown from the saddle and lands on the far side of the fence as the horse continues to somersault, landing, in worst case scenarios, directly on top of the rider (Goldsmith, 2008).
The Transport Research Laboratory in the United Kingdom conducted research that showed that when a horse’s front legs contacted the jump at high speeds, they were pushed backward, causing the horse’s movement to become a downward vertical force around the pivot point of the jump (Goldsmith, 2008). This occurred if the jump did not collapse. However, if the top rail could give way when the horse’s legs or chest came into contact with it with great enough force, the horse would fall straight down instead of flip, a result that is preferable to and less dangerous than a rotational fall (Goldsmith, 2008). Thus, a breakaway device was designed by mechanical engineers, to only collapse if the critical weight was reached. This device is known as a frangible pin.
In 2008, research into frangible technology for eventing was launched by the United States Eventing Association with an engineering team from the University of Kentucky. The press release announcing the research effort stated that the design of this technology must be carefully considered. The statement stressed that “frangible technology, often referred to as ‘breakaway fences’, must be based on sound engineering principles; it is not as simple as making fences that fall down when impacted” (Morris, 2008). Badly designed frangible technology could cause larger problems that those it is intended to prevent. Mechanical engineers working on the project planned to evaluate both prototype and full size jumps designed by course builders to develop the most effective and safest possible technology.
The project consisted of three major areas: development of new concepts and ideas, field testing, and the evaluation of materials. Within those areas were further considerations that engineers faced in developing the frangible technology. In the case of a fence “breaking away” upon impact, there must be little chance that the breakaway itself could cause injury. Engineers had to find a way to prevent flying metal pieces of the fences from impacting either the horse or rider. There was also the potential for these pieces to cause problems for later competitors rounding the course, if metal found its way into a horse’s foot. Furthermore, engineers had to include a support system to the prevent the fence from falling parallel to the ground during breakaway, so that horse or rider would be prevented from being trapped under the fallen fence (Weaver Smith, 2009).
The material that would be used in fence construction was also carefully considered. All material had to be tested for mechanical properties to guarantee the frangible pin would fail at the desired force (Weaver Smith, 2009). There also had to be consideration given to the chance of impacts other than those causing dangerous falls, such as minor hoof impacts.
Design decisions were made based on expense and functionality. It was found that by using one frangible device on a single side of the fence, expense could be reduced. Furthermore, using two devices increased the chance that the device would not work during an impact. Two pins may increase risk, increase required material, increase design complexity with more pieces to maintain, and decrease reliability, as there is a higher chance of defects with twice the number of pins (Kahmann, 2010). Engineers chose to use a more brittle material for the frangible pin, finding that the pin would survive small impacts undamaged, but breakaway as desired with the critical force. A metal sleeve for the pin ensured that the pin fit well, and limited the flight of metal parts during impact (Weaver Smith, 2009).
The initial development of this frangible technology in the form of breakaway pins was a significant achievement for improving safety in the sport of eventing. In December of 2014, the USEA’s Cross Country Design and Fence Construction Safety Task Force released a report on their opinion of and hope for safety in the cross country phase. The task force acknowledged their responsibility to continue pursuing new technology and engineering designs that will continue to make cross country safer. The report stated, “the Task Force feels that… we must endeavor to eliminate 100% of rotational falls… [and] we believe that with the correct application of current frangible technologies, and the quest for new deformable or collapsible design, this is achievable” (Autry, 2014).
There is much work still to be done. There are types of fences for which the use of the breakaway pins is not an option. One of the main types of fences that need to be seriously looked at are tables, wide solid obstacles where mistakes tend to result in unrecoverable falls. While some effort has been directed toward designing and building functional collapsible tables, there has been minimal improvement in the technology implemented for these fences (Autry, 2014). Engineers will continue to be needed for the design, development and building of better, safer obstacles.
The frangible pin has had an incredibly positive influence on safety in the sport. With the work of mechanical engineers and course designers, new ideas and systems can become available for field testing. Testing must also be done in the laboratory and field, of materials that will contribute to the development of new frangible technology. As Denny Emerson, past president of the USEA and World Championship gold medal winner in eventing, said, “You cannot have a sport where the price of a mistake, even a stupid mistake, is flipping and possible serious injury or death” (Kahmann, 2010). The frangible pin is already making a difference. In one case, a horse attempted to jump an imposing obstacle from a standstill, throwing horse and rider over the fence, resulted in no injuries and a quickly repairable fence- thanks to the pin. In another instance, a tired horse failed to make it completely across a wide oxer- both pins broke and both horse and rider “escaped unharmed from an incident that eye-witness accounts suggested would have resulted in significant injury had the pins not been in use” (Goldsmith, 2008). The eventing community may continue to hope that the focus on course safely will result in safer fences, as engineers continue to look for new designs and technology. The frangible pin is one such tool that has already saved the lives of both horses and riders.
Resources
Autry, Jenni. "USEA Safety Task Force Releases Initial Findings & Opinions -."Eventing Nation. 5 Dec. 2014. Web. 21 Jan. 2015.
Goldsmith, Liz. "What Is a Rotational Fall and How Can They Be Prevented?" EQUINE Ink. 18 July 2008. Web. 21 Jan. 2015.
Kahmann, Katherine M., "Engineering Sport Safety: A Study of Equestrian Cross Country Eventing”. (2010). University of Kentucky Master's Theses. Paper 15. http://uknowledge.uky.edu/gradschool_theses/15
Morris, Joanie. "USEF/USEA Launches Frangible Technology Research Campaign in Conjunction with University of Kentucky." USEF Network, 8 Oct. 2008. Web. 21 Jan. 2015.
Weaver Smith, Suzanne. "Frangible and Deformable Fence Technology Study."Review of USEA Safety Studies. USEA Annual Meeting & Convention, 5 Dec. 2009. Web. 21 Jan. 2015. ;