Drag factor for a sliding motorcycle

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MSI
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Drag factor for a sliding motorcycle

Post by MSI »

Saw a recent question on sliding friction for motorcycles on their side.
Then saw an article posted which included the following
  • Data from the studies reviewed here (along with a few additional studies) was compiled in a spreadsheet and illustrative decelerations were calculated for different motorcycle types on asphalt and concrete road surfaces. All test types were combined, and no attempt was made to adjust for different test procedures (i.e., drop versus drag). Means and standard deviations of these decelerations are reported in the table below. These decelerations exhibit a mild dependence on motorcycle type.
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  • This first table does not address motorcycle-to-motorcycle differences or characteristics that could influence the decelerations (i.e., whether the motorcycle was fully or partially faired and what components were present to scrape and gouge the road surface or prevent scraping and gouging, for instance). These characteristics are addressed in the next table below. As this table shows, there is strong dependence between the certain characteristics of motorcycles and the sliding deceleration. Motorcycles with fairings produce decelerations lower than those without fairings. Crash bars reduce the decelerations even further, to levels below those produced by fully faired motorcycles.
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REFERENCES
  1. Day, T. and Smith, J., “Friction Factors for Motorcycles Sliding on Various Surfaces,” SAE Technical Paper 840250, 1984, doi:10.4271/840250.
  2. Lambourn, R., “The Calculation of Motorcycle Speeds from Sliding Distances,” SAE Technical Paper 910125, 1991, doi:10.4271/910125.
  3. Baxter, A.T., Motorcycle Crash Investigation, Institute of Police Technology and Management, Jacksonville, FL, 2017, ISBN 978-1-934807-18-7.
  4. Hague, D., “Calculation of Speed from Motorcycle Slide Marks,” Impact: The Journal of the Institute of Traffic Accident Investigators, Spring 2004.
  5. Wood, D.P., Alliot, R., Glynn, C., Simms, C.K., Walsh, D.G., “Confidence Limits for Motorcycle Speed from Slide Distance,” Proc. IMechE Vol. 222, Part D: J. Automobile Engineering, 2008.
  6. Walsh, D.G., Wood, D.P., Alliot, R., Glynn, C., Simms, C.K., “Motorcycle Capsize Mechanisms and Confidence Limits for Motorcycle Capsize Speeds from Slide/Bounce Distance,” 18th EVU Conference, Hinckley, UK, 2009.
  7. Donohue, M.D., “Motorcycle Skidding and Sideways Sliding Tests,” Accident Reconstruction Journal, Vol. 3, No. 4, 1991, ISSN 1057-8153.
  8. Raftery, B., “Determination of the Drag Factor of a Fairing Equipped Motorcycle,” SAE Technical Paper 950197, 1995, doi:10.4271/950197.
  9. Carter, T., Enderle, B., Gambardella, C., and Trester, R., “Measurement of Motorcycle Slide Coefficients,” SAE Technical Paper 961017, 1996, doi:10.4271/961017.
  10. Medwell, C., McCarthy, J., and Shanahan, M., “Motorcycle Slide to Stop Tests,” SAE Technical Paper 970963, 1997, doi:10.4271/970963.
  11. Bartlett, W., et al, “Motorcycle Slide-to-Stop Tests: IPTM Data through 2006,” Accident Investigation Quarterly, Spring 2007, ISSN 1082-6521.
  12. McNally, B., Bartlett, W., “Motorcycle Sliding Coefficient of Friction Tests,” Presentation at IPTM Special Problems in Accident Reconstruction, 2003.
  13. Peck, L., Focha, W., Gloekler, T., “Motorcycle Sliding Friction for Accident Investigation,” Proceedings of the 10th International Motorcycle Conference, Institute for Motorcycle Safety, Essen, Germany, pp. 62-67, 2014.
  14. DiTallo, M., et al., “3 Different Methodologies for Determining the Drag Factor for Motorcycles Sliding on Their Sides,” Collision: The International Compendium for Crash Research, Volume 12, Issue 1, September 2017, ISSN 1934-8681.
  15. Kaplan, M., Bilek, D., Kaplan, S., Vellos, D. et al., An Examination of Rim Gouging and Its Relation to On-Road Vehicle Rollover (SOARce, Society of Accident Reconstructionists, Spring, 2004).
  16. Tandy, D., Pascarella, R., Coleman, C., and Colborn, J., “The Causal Relationship between Wheel Rim Gouging Forces on Roadway Surfaces and Rollover Crashes,” SAE Technical Paper 2018-01-0556, 2018, https://doi.org/10.4271/2018-01-0556.
Here is the article

Sliding Decelerations of Motorcycles - An Update

Mar 14, 2021, Nathan Rose
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MSI
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Re: Drag factor for a sliding mootorcycle

Post by MSI »

Question and response on another forum repeated here so assembling all information

Q: I am in need of a deceleration factor/deceleration rate for a motorcycle on grass and dirt (yard to be specific).


A: Here's what was posted up:
  • Day and Smith, 1984. SAE 840250. Average on grass earth was 0.70 g's.
  • Medwell, 1997. SAE 970963. For 41 meters on asphalt and 15 meters on grass, the average was 0.45 g's. For a similar run, the average was 0.40 g's. When they hit only asphalt, the average was 0.33 g's. So a little math can be done there to pull out the likely grass value.
  • Carter, 1996. SAE 961017. Two tests on dirt resulted in 1.19 g's and 0.91 g's.
  • Bartlett, Baxter, and Robar. AIQ, Spring 2007. One test on hardpack dirt resulted in 1.1 g's, and one on grassy soil resulted in 1.05 g's.
  • Peck, 2014. IFZ. Paper can be found here: www.lightpointdata.com/ifz-paper. During one test documented with 5 Hz GPS, the bike slid on the asphalt for 116 ft at 0.60 g's, and then hit the grass at 12 mph, resulting in an average of 1.09 g's for that portion of the slide. The bike dug into the grass.
    • One at 10 Hz where the bike slid on asphalt for a while, then hit a lightly grassed area with some underlying dirt and gravel (hard pack) and the result was a very consistent 0.44 g's across both surfaces for 217 feet.
    • They documented two more we at New Jersey Motorsports Park across dirt. The first was at 38 mph across dirt and the result was 1.11 g's. Then another at 27 mph where the decel was 0.61 g's.
    • Most of those bikes didn't tumble, as far as I know. I suspect you're going to see higher numbers for tumbling bikes in soft stuff.
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