Alteration of Bicycle Handlebar Grips to Decrease Impact as Measured by Penetration into Ballistic Gelatin

Summary

Impact with handlebars causes abdominal wall trauma, internal organ injuries, and in some instances death. It was hypothesized that a novel grip with a wider contact surface would decrease collision force. In order to test this novel grip, a sliding platform was constructed with a protruding test grip to fall into ballistic gelatin, which approximates human tissue. As a means of comparison a standard (store bought) grip and a reversed engineered version of the standard grip (RE) were also tested using the same method. This testing apparatus was used twelve times on each grip and the depth of penetration was measured in inches using a dial caliper for each of the 36 trials. The mean depth of penetration for the standard, RE and wider contact surface grips were 3.7286 +/- 0.3020, 3.7473 +/- 0.4069, and 1.4932 +/- 0.2878 inches respectively. ANOVA analysis revealed a p<0.0001. Subsequent t-test comparisons between the standard and wider contact surface and the RE and wider contact surface revealed significant p-values of  p<0.0001 and p<0.0001 respectively. Comparison of the standard and RE grips revealed an expected non-significant p=0.897748. In conclusion, the results yielded a significant difference between the depth of penetration of the standard handlebar grip/RE and the novel wider contact surface grip. This suggests that wider contact surface handlebar grips would result in lower impact forces to the abdomen during bicycle accidents, and thus a decrease in traumatic injuries. This will allow petition of the US Consumer Product Safety Commission to require bicycle handlebar testing.

Question / Proposal

Objective: To develop a bicycle handlebar grip that will reduce impact force during direct impact.

This research topic was meant to explore different ways to reduce impact force and hopefully injuries related to bicycle handlebars. This was done by creating a new design that would more widely distribute the force that goes into the abdomen and was tested against a standard handlebar. The test was to determine which handlebar style was most efficient in reducing the impact force. If one can be determined to be significantly safer, many people could benefit and numerous injuries in children and adult alike could be eliminated.

Hypothesis (H1): The handlebar grip with the largest contact surface area will produce a significantly lower impact force.

Null Hypothesis (H0): There will be no significant difference in the quantified impact forces from different handlebar grips.

Research

According to a study published in September of 2015, bicycle accidents are one of the major causes of unintentional traumatic injury in children (Hirose, 2015). Direct-impact injuries from bicycle handlebars lead to worse outcomes than people who sustained an injury by flipping over the handlebar (Nadler, 2005). These accidents normally occur at low speeds, but since the impact force from the fall is transferred to a small area through the end of the grip, it acts similar to a “blunt spear” and can cause a remarkable number of injuries (Karaman, 2009). Impact with handlebars causes abdominal wall trauma, kidney, intestine, liver, spleen, aorta, and pancreatic injuries, and in some instances death.  The number of children under 15 years of age that were affected in the year 2011 was 26,245 in Japan alone (Hirose, 2015). Similar results done in other countries, such as Turkey, proved that this is a prevalent problem (Cevik, 2013). Additionally, in the United States bicycle accidents account for 5-14% of blunt abdominal trauma in children. In a separate US study from 19 states in 1997, an estimated 1.15 per 100,000 children had bicycle related abdominal or pelvic organ injury leading to hospitalization due specifically to handlebar trauma (Winston, 2002). This resulted in an estimated national cost of $9.6 million dollars in hospital charges for that year (Winston, 2002).

This research topic was meant to explore different ways to reduce impact force and hopefully injuries related to bicycle handlebars. This was done by creating a new design that would more widely distribute the force that goes into the abdomen and was tested against a standard handlebar. The test was to determine which handlebar grip style was most efficient in reducing the impact force.

To date, there is no known published research in which others have attempted to change the handlebar grip in order to decrease the aforementioned injuries. If one can be determined to be significantly safer, many people could benefit and numerous injuries in children and adult alike could be eliminated.

Method / Testing and Redesign

Construct a sliding platform apparatus with 12x12x2 inch wooden bases, a 12x12x1 inch sliding platform and 10 foot steel poles as shown below.:

Creation of 3D Printed Handlebar Grips:

  1. Purchase standard handlebar grip from bicycle shop
  2. Dimensions: contact surface diameter: 19 mm, internal diameter: 23.431 mm, external diameter: 28.972 mm, overall length: 133 mm
  3. Create a reverse engineered CAD model using Autodesk® Inventor® of the purchased grip
  4. Dimensions: contact surface diameter: 19 mm, internal diameter: 23.431 mm, external diameter: 28.972 mm, overall length: 133 mm
  5. Create a CAD model using Autodesk® Inventor® with contact surface area being greater than that of the standard grip
  6. Dimensions: contact surface diameter: 51.944 mm, internal diameter: 23.431 mm, external diameter: 28.972 mm, overall length: 133 mm
  7. 3D print both CAD model designs using MakerBot® software

Ballistic Gelatin:

  1. Get a container that is at least 5 inches deep and fits in the bottom of the testing apparatus.
  2. Measure how much water fits into the container leaving room for the added volume of the gelatin powder.
  3. Heat up the amount of water found in the previous step in a pot.
  4. Add the proper ratio of gelatin to the heated liquid depending on volume in order to create a ten percent concentrated solution (this study used a container with a volume of 15 cups and added 12 ounces of gelatin)(Jussila, 2004).
  5. Stir in the gelatin slowly.
  6. Once incorporated remove any foam that formed on the top.
  7. Coat the container with a thin layer of canola oil.
  8. Pour the mixture into the mold slowly.
  9. Put container into the refrigerator for a minimum of eight hours.
  10. Take the container out of the refrigerator and flip it over onto a plate.

Independent variable:  Handlebar grip designs

Dependent variable:  Impact force

Operational definition of dependent variable:  How much the ballistic gelatin at the bottom of the sliding platform contraption was indented. Measured with a dial caliper.

Constants:

  1. Height of platform (1 meter from the top of the ballistic gelatin)
  2. Ballistic gelatin recipe
  3. Relative weight on platform (7 pounds)

Experimentation and Data Collection:

  1. Within the school's research area put a block of ballistic gelatin in the center of the bottom base (on a plate).
  2. Attach one of the handlebar designs to the bottom of the sliding platform
  3. Lift the platform so that there is 1 meter between the top of the ballistic gelatin and bottom of the grip
  4. Drop the platform
  5. Remove the handlebar from the ballistic gelatin
  6. Measure, in inches, the depth of penetration using a calibrated dial caliper
  7. Repeat steps 1-6 for each handlebar trial (12 trials for each of the three grip types)

Results

The mean depth of penetration of the purchased standard grip, reverse engineered version of the purchased grip, and the wider contact surface grip were 3.7286 inches, 3.7473 inches, and 1.4932 inches respectively. This data is shown in table form below along with other measures of central tendency. 

An ANOVA test was chosen as the first statistical analysis in both cases as the data provided three or four groups of values. In order to reduce uncertainty in terms of the different batches of ballistic gelatin used, a ANOVA test was done between the averages of each batch’s trials. The results suggest that there was no significant difference between the ballistic gel batches with a p-value of p=0.476.

Results from ANOVA statistical analysis between handlebar grip types yielded a p<0.0001 suggesting a significant difference between the depths of penetration of the three different groups. Further t-tests between experimental groups suggest that there was no statistical difference between the depth of penetration of the purchased standard grip and the 3D printed reverse engineered model. The p-value between the standard grip and reverse engineered version was p=0.897748. This suggests the material type did not make a difference in determining the impact force.

Further testing showed that there was a significant difference between both the the standard and wider contact surface and reverse engineered and wider contact surface alike both with p<0.0001. This is shown in graphical form below.

Figure 1.

Conclusion

This study demonstrates that a wider contact surface at the end of a handlebar grip results in a statistically smaller depth of penetration into a ballistic gelatin as compared to a standard store bought handlebar grip as well as a 3D printed, reverse engineered version of the store bought grip. The contact surface area of the novel design was 2.7 times greater than that of a standard handlebar grip. The mean depth of penetration was approximately 2.5 times less for the novel handlebar grip compared to the standard design. As there was no statistical difference in mean depth of penetration between the store-bought handlebar grip and the plastic 3D printed grip of the same dimensions, it can be concluded that it is the wider contact surface area of the novel grip that resulted in a smaller mean depth of penetration, and not the change to a plastic material.

Despite the encouraging results, it is unclear whether the force of impact generated by the falling platform is greater than, equal to, or less than that of a typical bicycle accident in which the handlebar grip causes significant abdominal trauma to a child. It is possible that if the experimental force of the falling platform is significantly less than that of a typical accident, the performance characteristics of the wider surface area may not be enough to prevent significant trauma.

theless, the conclusion drawn from the data collected in this study is a direct representation of the study’s original expectations. The wider contact surface area from the novel grip significantly reduced the impact force from the collision between the grip and the ballistic gelatin.

Further experimentation to determine if alternate bicycle handlebar grip designs manipulating the shape or material composition could result in a lower impact force would be a suggestion as to how to expand upon this research. Another expansion would be the validation of the assumption that depth of penetration reflects impact force by experimentation with alternate models (e.g. cadaveric, computer simulation). Finally, this data would support a petition to the US Consumer Product Safety Commission to require the testing and use of safer bicycle handlebar grips so as to prevent serious injury.

About me

When I was eight years old I broke my arm on the school's playground monkey bars. This lead me to later do research on monkey bar safety. More recently, I heard about neighborhood children injuring themselves when the bicycle handlebar grip went into their abdomen. This inspired me to do this research and try to find a way to make riding a bicycle safer for people of all ages.

As a native of New Jersey, I have been fascinated with Thomas Edison. He was an inspiring and prolific inventor that tried to make people's lives better. He was not afraid to fail, and emphasized that much can be learned from one's mistakes.

Winning the Google Science Fair would validate the hard work I put into the project, and shed light on a common safety issue that no one has tried to solve previously.  I would use the prize money to do more research and also try to get a patent on my safer bicycle handlebar grip. 

I have long loved doing research and have never missed an opportunity to do a project. My current high school, High Technology High School, affords me numerous opportunities to do this and encourages me, as a woman, to pursue my interest in STEM. In the future I want to continue doing research and trying to make the world a better place. I am definitely going to go to college and want to be an electrical or mechanical engineer.

Health & Safety

For purposes of constructing the testing apparatus the student researcher needed to utilize the school's tech lab. This area includes a number of power tools that the student researcher needed to pass written and practical exams on before being able to use the area. After passing this test the student researcher was able to construct their testing apparatus while having the adult in charge of the area supervising at all times. During testing, after the apparatus was constructed, the student researcher continued to follow safety protocols which included wearing safety goggles during drops and having an adult in the area to supervise.

Bibliography, references, and acknowledgements

Cevik, M., Boleken, M. E., Sogut, O., Gökdemir, M. T., & Karakas, E. (2013). Abdominal injuries related to bicycle accidents in children. Pediatric surgery international, 29(5), 459-463.

Hirose, T., Ogura, H., Kiguchi, T., Mizushima, Y., Kimbara, F., Shimazaki, J., ... & Matsumoto, H. (2015). The risk of pediatric bicycle handlebar injury compared with non-handlebar injury: a retrospective multicenter study in Osaka, Japan. Scandinavian journal of trauma, resuscitation and emergency medicine, 23(1), 66.

Jussila, J. (2004). Preparing ballistic gelatine—review and proposal for a standard method. Forensic science international, 141(2-3), 91-98.

Karaman, İ., Karaman, A., Aslan, M. K., Erdoğan, D., Çavuşoğlu, Y. H., & Tütün, Ö. (2009). A hidden danger of childhood trauma: bicycle handlebar injuries. Surgery today, 39(7), 572-574.

Nadler, E. P., Potoka, D. A., Shultz, B. L., Morrison, K. E., Ford, H. R., & Gaines, B. A. (2005). The high morbidity associated with handlebar injuries in children. Journal of Trauma and Acute Care Surgery, 58(6), 1171-1174.

Winston, F. K., Weiss, H. B., Nance, M. L., Vivarelli-O'Neill, C., Strotmeyer, S., Lawrence, B. A., & Miller, T. R. (2002). Estimates of the incidence and costs associated with handlebar-related injuries in children. Archives of pediatrics & adolescent medicine, 156(9), 922-928.

 

I wish to acknowledge Mr. Roche, my research advisor, who has mentored me and supervised me throughout my research project. In addition, Ms. Grunthaner who supervised during the construction of the testing apparatus within the school's tech lab.