cornering 101
DESCRIPTION
Cornering 101. FOR OFFICIAL USE ONLY Note: This Slide is Mandatory. 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 - PowerPoint PPT PresentationTRANSCRIPT
Headquarters Air Mobility Command
Enabling the “Global” in “Global Vigilance, Reach and Power!”
Cornering 101
2Enabling 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 ONLYNote: This Slide is Mandatory
3Enabling 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
4Enabling 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
5Enabling 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
6Enabling the “Global” in “Global Vigilance, Reach and Power!”
Forces
Rider / Motorcycle Centrifugal
Rider / Motorcycle equilibrium point Earth Gravity
Combined CG
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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
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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
9Enabling 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
10Enabling 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
11Enabling the “Global” in “Global Vigilance, Reach and Power!”
Chassis Dynamic
Steep, small, short Gradual, large, long
Rake, Trail, Wheelbase
Agile Less Agile
12Enabling 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
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Examples
Compression
Extension
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Cornering Physics
Tires
• Ffriction= 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
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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
16Enabling 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
17Enabling 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
18Enabling 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
19Enabling 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
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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
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NEGOGIATING A CORNER
Many types of corners
• 1/3 theory
• Out-in-Out
• Vision
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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
23Enabling the “Global” in “Global Vigilance, Reach and Power!”
NEGOGIATING A CORNER
Physical movement of a motorcycle cornering
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NEGOGIATING A CORNER
Corner Basics
• Entry Beginning of corner
• Apex Cornering line
closest to inside of curve
• Exit Last part of corner
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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
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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
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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
28Enabling 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• http://greenknights5.com/; Gil Besana, President
Get the best from your bike, don’t let the bike get the best from you