Caroline Walczak

ABSTRACT

Ski patrollers go through significant amounts of training and refreshers in their careers, and during the winter season especially they focus on ski and toboggan skills. During this training, they take toboggans down some of the most difficult terrain in their mountains which, due to initial inexperience, has resulted in many crashes and injuries for the patrollers. This project aimed to provide a safer way for patrollers to train on unfamiliar terrain by modifying the toboggan to have an emergency braking system. This braking system utilized a metal edge in the uphill end (angled towards the downhill/front end) that would be inserted into the snow or ice with a hinge if the leading patroller lets go of the handles. A two-way quick release system was designed so that the activator was attached to the patroller's glove and keeps two cables taught. The cables keep the metal edge flush with the bottom of the toboggan, thereby deactivating the system. If the patroller's hand goes outside the range provided by the activator, the cables are released and so is the brake. The edge was able to work on powdered snow by gathering it like a shovel and was able to work on hard pack conditions with the sharp edge.

GRAPHICAL ABSTRACT

Research Proposal

BACKGROUND

Members of the National Ski Patrol have assisted many skiers and snowboarders in cases of injury or illness, but their assistance can only go so far. As first responders, most Patrollers’ main objective is to stabilize the patient and transport them downhill in a toboggan. Toboggans are sleds in which the patient can be laid prone inside. They have handles (18) operating on a pivotal mount that are extended outside the sled and locked in place (26) for patient transport (Sawatsky, 2001). When transporting a patient, a patroller will lead the toboggan down, holding onto the handles with the goal of controlling the toboggan’s fall down the slope. On intermediate to advanced terrain, it is expected that a second patroller follow the sled, “tail roping” to keep it in the fall line of the lead patroller and further control the toboggan’s fall (preventing “fishtailing” of the toboggan, which can result in it flipping over). There is also a chain that acts as a brake on flatter terrain and is kept down for more challenging slopes in order to reduce speed.

Figure 1: The common
design of rescue toboggans used by Ski Patrol (Sawatsky, 2001) — Figure 1: The common design of rescue toboggans used by Ski Patrol (Sawatsky, 2001)

Operating a toboggan is no simple feat and requires significant training to even get to the most basic level of certification. Even when the Ski and Toboggan class is completed, patrollers continue to either refresh their skills annually and/or advance them. In most programs, it is necessary to train on the most difficult trail on the mountain because skiers and snowboarders could get injured on them (and in fact are more likely to), so Patrollers need to be capable of rescues on these slopes. Other programs also exist for patrollers to train at other mountains, allowing them to practice on more difficult terrain. Due to initial inexperience, however, this training can be dangerous. Toboggans weigh 23.6 kilograms (Cascade Toboggan Model 100 “The legend”), with even more weight added depending on who is riding the sled. The steep slopes and the resulting speeds could lead to the patroller losing control of the sled, leading to a crash or a runaway toboggan. Both could be caused by the toboggan “fishtailing” and flipping over or around, the patroller themselves catching an edge and falling, or the patroller being unable to stop when necessary due to speed or icy conditions. While accidents have occurred with actual patients in the sled (Editors, 2009), these incidents are rare because of the sheer amount of training Patrollers go through. Most toboggan crashes are due to training, presenting a need for safety measures being taken for less experienced Patrollers as they strive to improve. To achieve this, an emergency brake must be added to the toboggan that will activate before a crash.

THE SYLVAND-ALLAIS SYSTEM

Previous attempts have been made to add another brake to the toboggan. Sylvand and Allais were granted a patent in 1952 for a ski patrol toboggan brake that had steel claws attached at the base of the handles. When the patroller pushed the handles down, the claws were pushed into the snow or ice, effectively stopping the toboggan (Sylvand, 2020). While these were popular in the 80s and 90s for patrollers, they were soon removed from most training programs because of their bulkiness and weight. Patrollers usually need to lead toboggans down long trails, especially if they are on larger mountains, and it was exhausting to lead the sled while also holding the handles up. There were also issues with the frontal braking force, as it allowed the sled to spin around when the brake was activated.

THE BOBSLED

Like the toboggan, the bobsled travels on packed snow and requires a safe way to control its path, which is accomplished by steering from inside the sled. At the end of a bobsled race, it is also necessary to brake so the bobsled doesn’t crash past the finish line. As seen in Figure 2, the brake is activated with a brake lever (18) that is pivotably mounted within the back of the sled. It connects to a cable (19) and pulley (20) that turn a pivotally mounted brake spud (21) that will dig into the ice below (Stevens, 1982).

Figure 3: The Olympic Bobsled Brake (Stevens, 1982)

BACKGROUND INFOGRAPHIC

METHODOLOGY

The majority of this project was done independently, but I received advice from Dr. Crowthers at Mass Academy and Jim O’Connor, the national director of toboggan training in Ski Patrol. Jim O’Connor helped me acquire my toboggan for testing and advised me on my project direction and potential pitfalls I might meet. I spent 4 months on this project.

EQUIPMENT AND MATERIALS

This project did not need significantly difficult-to-obtain resources or equipment to construct. To model components of the emergency brake, Onshape, a free online software that can be used for CAD models, was used. The CAD models for the metal edges were inputted in a Shop Saber software that allowed the Computer Numerical Control (CNC) machine at Mass Academy’s robotics lab to cut two pieces of quarter inch 6061 aluminum. The actuator was also modeled and ran through Ultimaker Cura, a software that translates 3D models into printable files. These files were printed on my Elegoo Neptune 3 Plus 3D printer with PLA filament. The fixed pulleys for this system were purchased on Amazon, and the nylon rope at Lowes

METHODOLOGY INFOGRAPHIC

FIGURES

Figure 5: The maximum sled velocity in meters per second versus the stopping distance when stopped via the traditional method of a hockey stop. This test was performed with myself leading the toboggan and 30 kg of weights in the sled. I went down a part of the hill, in between two ski poles that acted as a marker, and as soon as I passed them, I did a hockey stop. This was recorded with a tripod, and later was run through Tracker, a graphical analysis tool that measured the sled’s velocity from the videos. There was also a measurement taken between the front of the sled and the poles to see the stopping distance.

Figure 6: The maximum sled velocity in meters per second versus the stopping distance when stopped via the emergency brake. This test was done with the same procedure, but this time the brake was activated at the pole marker. This was compared with the results of the previous test, but the data not found to be statistically different.

Figure 7: Technique type vs. the amount of times the brake remained deactivated as well as the number of time the toboggan fishtailed, defined by a rotation of more than 30 degrees. To see if the brake would be accidentally activated during training, it was led down by me while practicing the main techniques. The activator was attached to my right glove and each test was done 5 times.

Figure 8: A picture from testing of the activated brake and the resulting stopped sled.

DISCUSSION

This objective of this project was successfully met – through testing it was found that the braking system effectively stopped the sled in an emergency. By comparing the varying stopping distances and their maximum velocities, the modified sled was shown to have a smaller distance compared to the traditional method and control of stopping manually, although it was not statistically significant. For the goal of the brake only being activated in an emergency, data was found by bringing the sled down with common techniques used in Outdoor Emergency Transportation classes, finding that most did not unintentionally activate the system. This could, however, result in issues for patrollers with longer or shorter arms, as the former could activate the brake unnecessarily and the latter would not activate it soon enough. The “outside the handles left” technique was shown to be more likely to accidentally activate the brake, so this could be solved by lengthening the activation string or switching which hand it is attached to depending on which version of “outside the handles” the patroller intends to use. Some limitations of this testing were due to the location of the tests. They were done on a small hill in my backyard on ungroomed snow. The shorter distance failed to account for the accumulation of velocity a patroller and their sled would get on a steep, long trail. There was also a lack of variability in the snow – conditions vary drastically from day to day, and because testing was done over only one weekend, warmer snow and hard pack conditions were not addressed. The snow conditions on the day of testing included a layer of ice over slight hard pack, but this can be much looser than groomed snow. Because the brake did not completely lie flush with the bottom of the toboggan, some drag was created that slowed the toboggan down. Future prototypes will address this issue. The design does need to be cleaned up, for example the ropes should be secured more firmly rather than with knots. The ropes themselves caused too much friction along the edges of the sled so another type of rope might be considered. Future tests should start having patients sit in the sled and should be done on longer, steeper trails with different conditions. As the objective for this project was to create an emergency braking system, I feel that this conclusion should be short. The braking system was able to effectively stop on icy and looser snow. It was shown to not activate when practicing common toboggan techniques, but this may vary with size of the patroller so the activation rope length may need to be varied. With this toboggan modification, patrollers can more safely practice their skills on unfamiliar advanced terrain without a severe fear of injury. Making the mountain safer for patrollers makes it safer for all skiers.