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Comparing Bicycle Helmets' Ability To
Absorb Crash Impact |
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Researched by Bradley W.
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The purpose of this experiment was to compare various brands of bicycle helmets based on their ability to absorb impact during a crash.
I became interested in this idea as I was looking at safety equipment in a sports store and noticed helmets. I then became curious about the prices of all the different brands available. I wanted to find out if the most expensive brand of helmet would be the safest in a crash.
The information gained from this experiment could benefit consumers everywhere by showing them which brands of helmets would protect them most effectively. Regardless of price, having the best helmet could save lives.
My hypothesis was that the more expensive helmet brands would absorb nearly the same amount of impact force as the less expensive helmet brands during a crash test.
I based my hypothesis on the Bicycle Helmet Safety Institute program that tests the safety of all market helmet brands. It stated that all of their helmets have to pass a series of tests to go onto the market. Since all helmets meet their standards I thought there would be very little difference in their impact absorption.
The constants in this study were:
- The type of head shape used in the testing of the experiment.
- Mass and shape of object hitting helmet.
- Height the impact weight is dropped from.
- Number of trials for each helmet.
- Impact probe, computer, and software.
The manipulated variable was the brand of helmet used in the experiment.
The responding variable was the amount of impact transmitted to the probe in the “head.”
To measure the responding variable, I used a Vernier accelerometer probe attached to a computer running Logger Pro software to measure the acceleration (m/s2) during each collision and the impact impulse in thousandths of a second.
| QUANTITY |
ITEM DESCRIPTION |
| 1 | Mannequin head shape |
| 1 | Vernier accelerometer probe |
| 1 |
Computer running Logger Pro software |
| 4 |
Bicycle Helmet Safety Institute certified brand helmets |
| 1 |
Pulley |
| 1 |
Weight (2000 grams of sand) |
| 10 meters | Rope |
| 1 | Tape measure |
1. Tie a rope securely to the base of the pulley.
2. Pass the rope over a strong support 3 meters above floor. Pull the rope so the pulley is positioned securely about 3 meters above the floor.
3. Measure 2000 grams of sand into the nylon weight bag.
4. Attach the weight bag to a second rope and run this rope though the pulley so the weight can be raised and lowered easily.
5. Attach the Vernier accelerometer probe to the computer with Logger Pro software.
6. Place the Vernier accelerometer probe inside the mannequin head shape by drilling a hole in the top of it and stuffing the probe inside of the hole.
7. Put the mannequin head shape into one of the four helmets in an upright position on a flat surface that can hold the mannequin head shape into a position where it is not tilted or uneven when it is placed on the flat surface. (If you can’t manage to do this you can always strap the mannequin head shape to the flat surface.)
8. Be sure it is positioned exactly under the weight bag.
9. Check helmet for “square” fit.
10. Hold the rope so the weight is in a fixed position, suspended 2.0 meters in the air directly above the helmet. The weight must not be swinging.
11. Release the rope so the weight will hit the helmet.
12. Record what the Vernier accelerometer probe reads in “meters per second squared” for that individual helmet brand at the moment of impact.
13. Repeat steps 8-12 for a total of 10 trials.
14. Repeat steps 7-13 for each helmet brand.
The original purpose of this experiment was to compare various brands of bicycle helmets based on their ability to absorb impact during a crash.
The results of the experiment were that the various brands of bicycle helmets absorbed nearly the same amount of impact during a crash.
My hypothesis was that the more expensive helmet brands would absorb nearly the same amount of impact force as the less expensive helmet brands during a crash test.
The results indicate that this hypothesis should be accepted. I believe this because the data proved to me that the more expensive helmets absorbed nearly the same amount of impact force as the less expensive helmet brands during a crash test.
Because of the results of this experiment, I wonder if the force rate or amount of force would create a different result in the experiment. I also wonder if the use of different types of padding inside the helmets would have also changed the results in the experiment. Finally I was also curious about the chinstrap tension around the head that possibly would have also created other test results in the experiment.
If I were to conduct this project again I would have had it so that the equipment I was using could read up to 0.0001th of a second instead of just 0.001th of a second. That would have made the data more precise. I would have made more trials for each helmet brand. Also I would have used a more realistic “head” shape rather than having used Styrofoam. Finally I would have had it so that I dropped the helmets more like the “real” professional tests.
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Introduction: Helmets are used in many different human activities that involve danger, whether it is sports, law enforcement, motor cycling, military, or even astronomical use. We need to research more about helmets so we can provide more protection to all of the people who are involved in dangerous activities. Safety: By law it is required to wear a helmet when you are participating in certain sports. The law was created because of all the fatalities caused by head injuries to people not wearing a helmet. This law has largely minimized the death rate in sport activities like bicycling, skateboarding, football, etc. Helmets: We have used helmets in our society since the ancient times when helmets were only made for war. The main reason helmets are used is because they are designed to protect the head from being inflicted with damage. A helmet is usually constructed of metal or other sturdy material that covers the surface of the head. Most consist of a strap and buckle that straps onto your chin and prevents the helmet from falling off. Most also have soft liners inside of them that offer comfort for your head. There are many different types of helmets that we use in sports, the military, construction, firefighting, police, mining, motorcycling, and even astronaut activities. Bicycle Helmet Standards: There are many different legal standards that bicycle helmets have to pass to be able to go onto the market. Many of the standards used today are Consumer Product Safety Commission (CPSC) which has been a United States Law since March 10, 1999, ASTM F1447 (Had been the most used standard, sidelined by CPSC.), ANSI (Replaced by ASTM.), and Snell (Is a premium standard). All of the standards require the helmet to pass a lab test where it is placed on an instrumented head form, turned upside down and dropped for a measured distance onto an anvil of any shape. The drop distances vary but are generally between one and two meters (3.3 to 6.6 feet). For the helmets to pass they have to register less than 300 g’s during the impact, or in some cases 250 or even 200 g’s. There is also always a strap and buckle strength requirement, and sometimes even a “Roll off” test to see if the helmet will stay on the head form when yanked by another object. Collision: The scientific definition of collision is “A dynamic event consisting of the interaction between two or more bodies, usually of very brief duration, resulting in a change of momentum of at least one participating body.” It is the force that happens when two or more objects hit each other. Impact Impulse: “The product of average force and the time it is exerted.” From Newton’s second law, which states that when an object is pushed or pulled on by force it will accelerate in velocity. Momentum: “The product of a body’s mass and linear velocity; the force of motion.” It is the force that makes all objects have motion. Force: “Capacity to do work or cause physical change; strength; power. Power made operative against resistance; exertion.” Summary: We should continue to research in the development of helmets and find a way to dramatically improve the safety of each individual helmet made. It will make the world a safer place to live and work in. |
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“A Visit to the CPSC Lab.” Bicycle Helmet Safety Institute. October 13, 2004 <http://www.bhsi.org/cpsclab.htm>. “Bicycle Helmet standards.” Bicycle Helmet Safety Institute. October 13, 2004 <http://www.bhsi.org/standard.htm>. Gutman, Bill. Bicycling. Minneapolis: Capstone Press, 1995. pp. 25-27. “Short Helmet Standards Comparison.” Bicycle Helmet Safety Institute. October 13, 2004 <http://www.bhsi.org/stdchart.htm>. Raintree, Steck-Vaughn. “Impact.” Illustrated Science Encyclopedia. 1997. |
I would like to thank the following people for helping make my project possible:
- My parents for encouraging me to succeed in this project.
- Mrs. Helms for assisting me in my project.
- Most of all Mr. Newkirk for taking his time after school to help me with this project, for buying the materials that I needed in the experiment, and also for encouraging me to do my very best work on this project
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