Winter snow sports and outdoor recreation are becoming increasingly popular, and there is a strong need for safety gear that will keep winter enthusiasts safe in unsure snow conditions. Every year, hundreds of people die from avalanches and snow suffocation because of a lack of information and little use of safety equipment. The current safety standard for back country winter sports is to never travel alone and to wait for fresh snow to settle; however, many tend to ignore the safety standard because they enjoy the solitude of back country recreation. And because of the dangers associated with back country sporting, there exists a large demand for a reliable and cost effective device that will reduce the danger of traveling in these areas by helping winter sportspeople survive in a snow slide. A solution to this problem is to design an alternative avalanche airbag that is internally mechanical, reusable with no extra cost, inexpensive, and lightweight that will keep prevent users from being buried under avalanches.
Like all current avalanche airbag systems (ABS), our device will work on the principle of granular convection where large particles naturally rise to the surface of a free flowing fluid. Take for example a bag of trail mix, if you shake the bag long enough, the larger peanuts and raisins will end up at the top whereas the small bits can be found towards the bottom. By utilizing this process, our product will essentially maximize the user’s volume without the typical cost and limitations to mobility current avalanche airbag systems (ABS) impose onto the user while keeping the user on the surface of the avalanche.
In order to accomplish this, Team Snow Pack proposed to enclose a large steel spring inside a cylindrical-shaped nylon airbag. Numerous one-way air valves would then be placed at both ends of the device which would allow for ambient air to enter the system once the internal spring is relaxed. Additionally, backpack straps are to be sown onto the pack itself which allows users to wear the device with, or without, a winter sports backpack. A user such as a back country skier would wear the device while the spring is compressed; however, once the spring is deployed it will expand out and inflate the nylon airbag and increase the net volume of the user. This would ensure that the users volume is maximized and decrease the users chance of burial by an avalanche.
In order to successfully develop this concept, the team placed product requirement specifications onto the product. Some of these include:
- Product must be 10 lbs or less,
- Product to cost less than the retail price of $400 per lot
- Deployment time to be less than 4 seconds
- Able to function properly in temperatures down to -15 degrees Fahrenheit
Proof of Concept:
To verify the effectiveness of a spring powered mechanical airbag, the team chose to construct a down scaled prototype. The prototype is approximately a half scale model of the final product. The proof of concept is also without backpack straps and a deployment system since our area of interest was the effectiveness of a spring powered airbag. Additionally, the team built the POC as a standalone unit for testing. The bag shown in fig 1. consist of a nylon shell encasing a cylindrical compression spring. Five intake air valves of different sizes are positioned around the top of the bag. The check valves serve as an intake for ambient air to enter the nylon bag. The air intake is powered by the pressure difference created from the stored energy in the compressed spring. The spring itself (fig. 2) was constructed by the team. 0.187″ thick phosphate coated steel wire was wrapped around a 10″ diameter log and then heat treated over a campfire. The POC is roughly 10″ in diameter and 2 feet tall.
Figure 1: Proof of Concept Figure 2: Internal Spring
All drawings, components, assemblies, etc. where done using Solidworks and can be viewed below with the correct dimensions.
Verification and Validation:
Before the finalization of the product, the team developed a series of tests for the product once it was completed in order to examine it’s completeness when compared to it’s original design. The final product was to be weighed, placed in a freezer, compared costs to similar products, and the deployment time was to be measured. Upon completion, the product was weighed on a scale, tested in a freezer, verified using material specifications from vendors, and deployed several times while measuring the time of inflation. After testing the product weighed 8 lbs and 9oz. Also, the device was tested inside a kitchen freezer with the thermostat reading -20 degrees Fahrenheit. The material strength of the 80 denier nylon ripstop and 1/4″ thick 1080 phosphate coating steel wire was well over the initial specified requirements. Initially, the nylon and steel had to withstand at impact forces of at least 100 N-s. The specifications for these materials were well over what was needed. Nevertheless, the team continued testing with a finite element analysis of the pack. For the purposes of these calculations, the device was assumed to be a pressure vessels with low internal pressure and external pressure expected in an avalanche collision. The results show that the nylon will experience small pressures external which were well below the nylons tensile strength. Figure 3 shows the analysis.
Figure 3: FEA of Nylon Bag
The 1/4″ thick 1080 steel wire was wrapped along a 12′ diameter tree log. It was then heat treated over camp fire until it retained its cylindrical shape. A plastic plate was then glued onto one end of the spring where 5 valves were additionally glued. The nylon bag its self was professionally sown by a Taylor. Once all components were gathered, the spring and valve plate were placed inside the bag through a small opening in the nylon fabric. Finally, the opening was sown and glued by the team.
The images above are the finished product. As seen in the photographs, the system can be compressed to a small volume and expand to a very large volume. It’s total volume capacity when expanded is approximately 80-90 liters. The farthest right image is the compressed state of the system while the other two pictures are when the system is deployed.
The links below show in detail how the device deploys and how it can be repackaged.
Benefits and Features:
- No added cost to reuse
- Adjustable for average men and women
- Can be used with any type of backpack or as a standalone
- Usable for subzero conditions
- Minimal moving parts
- Weighs only 8 lbs 9 oz. (healthy baby boy!)
Future Possibilities and Improvements include:
- Improved material spring design for better efficiency
- Larger volume options
- Improved valve performance
- Incorporate a breathing apparatus in case of burial
In conclusion, Team Snow Pack has successfully proved the validity of a mechanically operated airbag system, found a cheaper solution to an existing problem, and developed a potential alternative to avalanche airbag systems.
Meet the Team:
Peter Gail is a Mechanical Engineering Student at the University of Nevada, Reno. Peter is an avid snowboarder/skier and has worked at four different ski resorts in the Tahoe area during his college career. Along with his various internships in the mechanical engineering field, Peter’s work experience will be invaluable toward designing a successful project.
Craig MacDonald is a mechanical engineering senior at the University of Nevada, Reno. He currently holds a B.S. in meteorology from Plymouth State University, in Plymouth New Hampshire. His passions outside of school are skiing, camping, snowmobiling, and dirt biking. He also likes to work on cars and build various projects when time allows. Once his schooling is completed, his ideal job fields will be working with internal combustion, sporting goods, and weather instrumentation.
Gun Charupoom is a senior student at the University of Nevada, Reno. He is majoring in Mechanical Engineering. He was born in Thailand and moved to UNR from Las Vegas, NV. In his free time outside school, he likes to go golfing, play tennis, and play video games. After graduation, he would like to work in the robotic, and aerospace field of engineering as well as traveling to many places around the world.
Kevin Veliz is a senior student in the mechanical engineering program at the University of Nevada, Reno. His hobbies include: playing video games, reading adventure and sci-fi novels, designing with Solidworks, learning about science, and going to Rhymesayers concerts. At UNR, he spent three semesters as part of ASME’s supermileage vehicle club where he helped senior engineer students design and build a small motor-powered vehicle for the annual SAE Supermileage competition. After graduation, Kevin hopes to work as a CAD engineer where he can best utilize his knowledge of CAD software.