The F.I.R.S.T. Frame (Front Impact Reduction SysTem) for Commuter Bicycles
Duncan Stothers
St George's School
Floor Location : M 225 N

Background: In a world facing global warming, cycling is encouraged as a form of transportation that lacks CO2 emissions. A major concern is bicycle safety. Front impact collisions with sudden deceleration are common for cyclists and can result in serious injury. The properties of the bicycle frame are critical in such collisions. In sudden front deceleration in standard rigid frames, riders are thrown from the frame upward off the seat as the rear wheel lifts from the ground. In this experiment a new front impact reduction system for bicycle frames (Front Impact Reduction SysTem = F.I.R.S.T. frame) was designed, constructed and tested to determine if it could outperform current rigid frames in the event of a sudden front impact deceleration. rn rnPurpose: 1. To compare G force impact, rear wheel lift, and angles between the rider and frame during sudden front deceleration at variable speeds and constant rider weight of a standard rigid bicycle frame versus the F.I.R.S.T. frame and 2. to determine optimum spring sequencing for a rider of standard mass suddenly decelerating from typical riding speeds. rnrnHypothesis: A front fork incorporating adjustable sequences of double torsion springs will reduce G force experienced by the rider and reduce lift from the seat allowing the rider to stay with the bike in the event of a sudden deceleration compared to a rigid frame (control). rnrnMethods: The F.I.R.S.T. frame was constructed in metal and incorporated a cylinder and catch design for a sequence of up to 3 double torsion springs. A crash mechanism incorporating a track, a wooden rider of standard mass, weights and pulleys was built to reliably reproduce front impact using drop weights of 34 and 22 kgs. Quantitative (G Force) using an accelerometer and slow motion photography (240 frames per second) measured lift of the rider and rear wheel and demonstrated mechanism of action. Photography was analyzed with online protractors to calculate angles of change of the rider relative to the frame. N=20 trials per spring sequence. rnrnResults: The F.I.R.S.T. frame provided for a statistically significant reduction in front impact G force (reduction of 48% ( t test p<0.05)). The mean change in lift of the rider was reduced from 9.4 cm (mean) in the control to 1 cm (mean) (t test p<0.000001). Compared to vertical, rider angle after impact was reduced to 21.3 degrees from 33.8 degrees (t test p<0.00001). The amount the rider tipped forward on the bike was 1.4 degrees compared to 14.5 degrees in the control (t test p<0.00001). The rear wheel rises on average 3.2 cm less in the control, but the rider is thrown forward off the seat by 8.4 cm more at an angle of 12.5 degrees more.rnrnConclusion: Front impact forces can be reduced to the point where rider lift is significantly reduced during sudden front deceleration by use of the F.I.R.S.T. frame design. The design successfully allowed for variable resistance for potential individualization depending on the mass of the rider with a goal to improving cycler safety. rn rn