Problem Set-1b Week 11Challenge : Basic Handling parameters

1. Ackermann steer angles for 500, 200 and 50 ft radius

ackerman angle=L/R

case-1=100.6/500*12=0.96deg

case_2=100.6/200*12=4.24deg

case_3=100.6/50*12=9.56deg

2. Understeer gradient

interpolating the cornering stifness data

c_front=(1125-950)/(1125-900)=(257*x)/(257-225)

x=232lb/deg

c_raer=900-776/900-675=225-x/225-171

x=195lb/deg

k=(950/232)-(776/195)=0.11deg/g

3. Characteristic speed=sqrt(57.3lg/k)=374.98ft/sec

4. Lateral acceleration gain at 60 mph=(v^2/57.3lg)/(1+kv^2/57.3lg)

=0.474deg/g

5. Yaw velocity gain at 60 mph=(v/l)/(1+kv^2/57.3lg)

= 9.95deg/sec/deg

6. Slideslip angle at the CG on an 800 ft radius turn at 60 mph.

weight distribution front=1900/1900+1552=0.55

cg to rear axle=0.55*100.6=55.33

sideslip angle=57.3*c/r-(wr*v^2)/(c_alpha*g*r)

=-0.8668 deg

7. Why is the calculated understeer gradient quite low (usually it is around 3-4 deg/g)

ans:- cornering compliance of front and rear is nearly equal so the vehicle is nearly neutral steer.