Headquarters Air Mobility Command Enabling the “Global” in “Global Vigilance, Reach and Power!” Cornering 101

2 Enabling the “Global” in “Global Vigilance, Reach and Power!” The information presented here is for informational use only Many references were used to develop this presentation Not all possibilities are covered Use the given information with proper respect to ORM Note: Do Not Remove “For Official Use Only” From Any Slide FOR OFFICIAL USE ONLY Note: This Slide is Mandatory

3 Enabling the “Global” in “Global Vigilance, Reach and Power!” Forces acting on a motorcycle in a corner Suspension / Chassis dynamics Basic cornering physics Negotiating corner OVERVIEW

4 Enabling the “Global” in “Global Vigilance, Reach and Power!” Forces General Theory Motorcycle turns via deflection of front wheel/tire  Makes motorcycle lean opposite path of wheel/tire  Motorcycle actually moves opposite intended path first Tires/corner effective radius becomes smaller  Styrofoam coffee cup on its side  Variable depending on many factors Gravity, centrifugal force  Gravity pulls down, centrifugal force pulls outside, state of equilibrium Centrifugal force must overcome gravity pulling down the amount the combined mass is leaned over Limited by traction available through co-efficient of friction between tires and surface

5 Enabling the “Global” in “Global Vigilance, Reach and Power!” Forces Motorcycle and rider are independent of each other with same forces Combined of the two is motorcycle/rider Can be adjusted by rider more easily than adjusting of motorcycle Forces are at equilibrium point of the contact patch of the front and rear tires

6 Enabling the “Global” in “Global Vigilance, Reach and Power!” Forces Rider / Motorcycle Centrifugal Rider / Motorcycle equilibrium point Earth Gravity Combined CG

7 Enabling the “Global” in “Global Vigilance, Reach and Power!” Chassis Dynamic Chassis Rake, is the angle formed by:  Line drawn from center of steering head through tire to ground  Vertical line drawn through center of front wheel axle  Rake determines steering response Trail is:  Distance between vertical line through front axle  Line drawn to the ground from center of steering head  Trail determines moment of self-righting (straight-line stability) As suspension compresses on fork-equipped motorcycle, effective rake and trail get smaller, thus steering quickens stability decreases

8 Enabling the “Global” in “Global Vigilance, Reach and Power!” Chassis Dynamic Chassis: Rear suspension comprised of swing arm, torque arm, chain pull  Line through all three comprise pole of moment (PoM)  Swing arm comprised of wheel and pivot location  Torque arm usually attached to brake caliper Maybe a rod to frame Maybe rod to swing arm or large caliper mounting plate  Chain pull is line made through the top of the chain  Angle produced by all three determine effect of compression under braking and extension under acceleration  Larger torque arm angle, less compression during braking  Larger chain pull angle, greater extension (lifting) under acceleration

9 Enabling the “Global” in “Global Vigilance, Reach and Power!” Chassis Dynamic Wheelbase  Effect of wheelbase determines diameter of the turning radius a motorcycle may have  Shorter allows for smaller turning radius

10 Enabling the “Global” in “Global Vigilance, Reach and Power!” Chassis Dynamic Single track vehicle is unstable Gyroscopic force created by turning wheel/tires creates stability  Greater the speed, greater the stability  Larger the diameter, greater the stability All chassis and suspension dynamics affect amount of force needed to move stability created by turning wheel/tire combination

11 Enabling the “Global” in “Global Vigilance, Reach and Power!” Chassis Dynamic Steep, small, short Gradual, large, long Rake, Trail, Wheelbase AgileLess Agile

12 Enabling the “Global” in “Global Vigilance, Reach and Power!” Review Key points: 3 forces acting on a motorcycle when cornering Less rake mean quicker steering Less trail less self righting Acceleration causes back to rise All can vary and must be controlled by rider Weight transfer under braking and accelerating changes suspension geometry, thus changing M/C attitude Centrifugal forces keep suspension compressed through corner  Changing centrifugal forces when cornering changes motorcycle attitude  Constant centrifugal force keeps suspension stable

13 Enabling the “Global” in “Global Vigilance, Reach and Power!” Examples Compression Extension

14 Enabling the “Global” in “Global Vigilance, Reach and Power!” Cornering Physics Tires F friction = f x C  f is theoretical coefficient of friction whose max value is 1  C is vertical load bearing on the wheel Represented by the cross of X and Y As long as tire’s contact pitch-black oval) has some part on top of the intersection, friction (traction) is available Y X

15 Enabling the “Global” in “Global Vigilance, Reach and Power!” Cornering Physics Braking Front tire  Weight transfers forward  Tire deforms, contact patch gets bigger  Contact patch moves backward Rear tire  Smaller contact patch from weight transfer  Contact patch moves backward faster then front tire Y X

16 Enabling the “Global” in “Global Vigilance, Reach and Power!” Cornering Physics Accelerating Front tire  Weight transfers rear  Contact patch smaller  Contact patch moves forward Rear tire  Bigger contact patch from weight transfer  Contact patch moves Forward slower then front tire Y X

17 Enabling the “Global” in “Global Vigilance, Reach and Power!” Cornering Physics Cornering Both tires  Tire deforms  Deflects opposite intended path of wheel  Contact patch moves toward intended corner Y X

18 Enabling the “Global” in “Global Vigilance, Reach and Power!” Cornering Physics Braking and Cornering Combined force of braking and Cornering  Maximum available is determined by force of braking and side force of cornering  Intended path is the mean between the two forces  Front tire uses more braking force due to weight transfer Y X

19 Enabling the “Global” in “Global Vigilance, Reach and Power!” Cornering Physics Acceleration and Cornering Combined force of acceleration and cornering  Maximum available is determined by force of acceleration and side force of cornering  Intended path is the mean between the two forces  Rear tire uses more accelerating force due to weight transfer creating bigger contact patch Y X

20 Enabling the “Global” in “Global Vigilance, Reach and Power!” Review Key Points: Traction  Coefficient of friction between tires contact patch and ground Ground surface has constant changing co-efficient of friction depending on what type of surface Contact patch can be smaller due to weight transfer, design of tire, tire deformity  Motorcycle operator must manage these forces within the limitations of the friction circle

21 Enabling the “Global” in “Global Vigilance, Reach and Power!” NEGOGIATING A CORNER Many types of corners 1/3 theory Out-in-Out Vision

22 Enabling the “Global” in “Global Vigilance, Reach and Power!” NEGOGIATING A CORNER 1/3 Envision the lane separated into 1/3  Outside  Middle  Inside Able to legally use entire width of lane Hazard avoidance Entry point selection

23 Enabling the “Global” in “Global Vigilance, Reach and Power!” NEGOGIATING A CORNER Physical movement of a motorcycle cornering

24 Enabling the “Global” in “Global Vigilance, Reach and Power!” NEGOGIATING A CORNER Corner Basics Entry  Beginning of corner Apex  Cornering line closest to inside of curve Exit  Last part of corner

25 Enabling the “Global” in “Global Vigilance, Reach and Power!” NEGOGIATING A CORNER Be at the speed you want to be at to travel around the curve Out-in-Out Start on 1/3 portion of lane which is on the outside of the curve Turn to middle of curve for your apex Exit on outside 1/3

26 Enabling the “Global” in “Global Vigilance, Reach and Power!” NEGOGIATING A CORNER Vision is a fluid, seamless process moving from one step to the next Keep head and eyes up, as level as possible Approaching curve  Look for entry point  Look through entry point to apex Entry Point  Look through apex  Look to exit point and beyond Apex  Look to exit  Look beyond through exit to as far down roadway as possible

27 Enabling the “Global” in “Global Vigilance, Reach and Power!” REVIEW Key Points: 1/3; offers hazard avoidance, entry point selection Have speed at what you want to travel around curve Out-in-Out Vision  Fluid motion  Eyes and brain constantly moving ahead  Body, motorcycle will follow

28 Enabling the “Global” in “Global Vigilance, Reach and Power!” REFERENCES Motorcycle Design and Technology Motorbooks Int’l; Gaetano Cocco, 2004 How to ride a Motorcycle Motorbooks Int’l; Pat Hahn, 2005 Sport Riding Techniques David Bull publishing; Nick Entsch, 2003 Proficient Motorcycling Publisher Unk; David Hough, 2000 Green Knights M/C Club, Hanscom Chapter Gil Besana, President Get the best from your bike, don’t let the bike get the best from you