bnd ts tire envelope swept volume

BND TechSource

Tire Envelope Swept VolumeUsingCATIA V5 DMU Kinematics

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

To create the correct tire clearanceenvelope, there needs to be anunderstanding of basic suspensiongeometry.This example will touch upon areas suchas Ackermann Steering, Front/Rear Steer,Jounce/Rebound, Clearance Zones andTurning Radius.The result will be a swept volume usingCATIA DMU Kinematics.Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Certain parameters were set in this particulardesign.

Track: Front/Rear = 1490/1510mmWheelbase = 2489.2mmTire Size: (http://www.csgnetwork.com/tireinfo4calc.html)

Front = P245/45ZR-17(Tire Radius = 326.15mm)Rear = P275/40ZR-18(Tire Radius = 338.60mm)

Wheel Size:

Front = 17 x 8.5 in, Offset = 56mmRear = 18 x 9.5 in, Offset = 63mmPrepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Parameters (contd).

Scrub Radius = +10mmoSteering Axis Inclination = 8.8oCaster Angle = 6.5SLA Ratio = 1.43:1Brake Rotor Offset (Hub face to Rear Rotorface) = 38mmAckermann Steering = 82.5%Shock Extension/Compression = 48.7/48.7mm

All of these parameters affect Tire ClearanceEnvelope.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Ackermann Steering Principle.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Rear Steer is used with Recirculating BallSteering Gear.(Projected Steering Axis)

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Front Steer is used with Rack & PinionSteering Gear.(Projected Steering Axis)

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Ackermann angles set up the Tie Rod Ends.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

100% Ackermann angles and the resultantTurning Angles.

Curb-to-curbturning radiusset at 17.5 ft.

100% Ackermann willconverge at the samepoint along the rear axlecenterline.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

82.5% Ackermann angles and theresultant Turning Angles.

Notice the divergencefrom the true center ofthe Turning Radius.This will cause scrubbingof the inner tire as thevehicle makes the turn.

Curb-to-curbturning radiusset at 17.5 ft.

Center ofturning radius

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Less than 100% Ackermann is a normalcompromise in todays passenger vehicles.Due to packagingconstraints, 100%Ackermann is notalways achievable.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

The worst condition is at full jounce and fullturning angles.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

The jounce (full up) and rebound (full down)must be determined.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Measure the jounce (full up) and rebound(full down).

Jounce = 63.8mm

Rebound = 65.8mmPrepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Another parameter is the clearance zonerequired around the tire.

The clearance zone seton this one-off sports caris 19 mm.A mass produced vehiclewould need to consideradditional clearance dueto tire chains.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Now there is enoughinformation to get an accurateSwept Volume representing theTire Clearance Envelope.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Step 1: Create a Rigid Joint for the Tire ClearanceZone in the current Kinematic Mechanism.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Step 2: Create a Simulation in DMU Kinematics.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Step 3: Compile the Simulation in DMU Kinematics.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Step 4: Generate the Swept Volume in DMUKinematics.

Prepared by: Bill Harbin Technical Director 1-Jun-09

BND TechSource

Step 5: Add the Swept Volume into the Product.

Prepared by: Bill Harbin Technical Director 1-Jun-09