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Kinematics

Kinematics

 

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Bump Camber

Negative camber gain exhibited. Although static camber was designed to be at 0, graph shows it as -1 deg.

  • 1in jounce leads to about -.7 deg camber gain

  • very slightly progressive

 

 

 

Bump Toe

For a given jounce, the toe angle displacement exponentially increases, at an inch bump, about .075 positive toe is indicated.

  • Although it is nearly negligible

  • goal was for 0 toe or toe-in (pos toe angle) at static

 

 

Bump Caster

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Motion Ratios

Goal right now is for a progressive wheel rate, so I realized we do not need a progressive motion ratio.

  • need to adjust geometry for a regressive MR

  • currently a progressive MR, for increased jounce, our MR getting bigger (at an increasing rate)

 

 

goal was for a higher roll gradient, compromising some stiffness. Still did not want a roll rate of >6deg similar to comfort of passenger vehicles though.

 

 

 

 

Bump Kw - Bump Wheel Rate

Goal is for a progressive wheel rate during bump with MR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Roll Camber

Rolling left makes left wheel gain positive camber and the right wheel gains negative

  • although, the left wheel still remains at a negative camber through -2 deg body roll to the left, which may indicate more straight line acceleration stability when a lateral force is applied - because both wheels will be somewhat still aiming for the center of the vehicle

  • similar to steering camber behavior

 

Roll Toe

Probably want to minimize this, because we dont want unnecessary toe angles from body roll unless from steering, but good to have some for stability purposes

  • honestly need a better understanding

  • resulting scale indicates a bigger toe-ing response than ideal from roll

 

 

 

 

Roll Caster

Follows typical behavior - want increasing roll deg to right to make caster on right wheel to dec and left to inc (more neg)

  • indicates 0 roll to be ab -5 deg caster

  • means scrubbing more in steering on the “inside” tire of roll - deg caster getting more negative away from 0

  • seems to be typical cornering caster behavior

 

 

Roll Migration - Front view instant center

exhibits typical migration of roll center when roll initiated

  • inside tire of roll has an increasing IC height

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Roll CPx migration

 

 

 

 

 

 

 

Roll CPy

Outside tire of roll has contact patch migrating inward (camber negative on outside tires)

Inside tire of roll has contact patch migrating outwards, makes sense because the wheel has pos camber so the patch moves in x direction positively

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Roll Kr - Roll Rate

typical behavior exhibited

Roll rate increases as car rolls, so the response gets quicker - high roll rate is better for driver comfort in roll

 

 

 

 

 

 

NULL

 

 

 

 

Steer Camber

When steering, the outside wheel has neg camber gain and the inside has positive at an increasing rate

  • Less acceleration ability but seems okay for our purposes, while inducing less tire wear

Steer Camber

As we increase our steering angle in one direction, the outside tire gains more negative camber while the inside gets more positive

  • reduced acceleration capabilities but good for reduced tire wear

  • maintaining decent cornering tire contact patches

 

 

Steer Toe

Steering degrees to wheel toe degrees correspond to one another-> steering left makes wheel turn left toe out (neg) and right wheel toe in (pos)

 

 

 

Steer Caster

Caster increases slightly for both wheels no matter what direction you are turning / steering

  • zoom into the mid of graph for relevant scope

 

 

 

 

Roll KinRCz

  • Matches EV trend

  • height is at max at 0 roll, any roll in any direction causes RC height to lower slightly

 

 

 

 

 

 

Roll KinRCy

  • Matches EV trend

  • roll neg then y migrates positively, vice versa

  • whatever direction you roll in, the KinRC migrates the opposite way (bc roll deg CCW is positive)

 

 

 

 

 

 

 

 

 

Roll Scrub

Our scrub radius is set at 1in at static

When body roll is induced, the scrub radius increases or decreases minimally, the behavior graphed is assumed to be within target range for our purposes

 

 

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