Ackerman Steering and Racing Oval TracksMany racers are becoming
aware of Ackerman Steering geometry and are concerned with how it
influences their race cars. Conventional Ackerman Steering was
developed around 1800 AD. Yes, 1800, not 1900. The Ackerman concept
is to have all four wheels rolling around a common point during a
turn. The example above shows that the inside front tire must turn
a larger number of degrees than the outside front tire for this
principle to work. Ackerman Steering TheoryThe theory was
originally developed for wagon designs to keep them from skidding
crushed stone driveways.Modern race cars will use this as a
baseline and then adjust the closeness to true Ackerman in order to
maximize traction. For best efficiency, keep it as close to true
Ackerman as possible. See next 4 slides to help with the
geometry.
Ackerman Linkage Set UpTop ViewRear Mounted Rack with 4
Wheels
Ackerman Linkage Set UpTop ViewFront Mounted Rack with 4
Wheels
Ackerman Linkage Set UpTop ViewFront Mounted Rack with 3
Wheels
Ackerman Linkage Set UpTop ViewRear Mounted Rack with 3
Wheels
Top View of Toe-inPositive ToeZero ToeToe-in angle a is the
angle of how much the wheels point in. Negative toe is when the
wheels point out. Rear wheel production cars have 5-20 of toe in
and front wheel drive cars have up to -20 degrees of toe out to
compensate for drive forces and bushing compliance. For maximum
efficiency with a rigid suspension, toe should be kept to near 0
with slight toe-in if the vehicle steering feels darty.aa
Front view of camber.Negative CamberZero CamberCamber angle c
helps keep the flat part of the tire in contact with the road
during hard cornering. Production cars are generally -3..0 degrees.
For max efficiency keep this as close to 0 as possible.Front
Viewcc
Caster and Caster AnglePositive Caster is the distance that the
contact patch of the tire follows with regard to the point at which
the steering axis contacts the ground. Caster determines straight
line stability as well as self-centering feel. The caster distance
for an has less to do with efficiency but has a lot to do with
steering feel. Try to set caster at 1 in front of the contact
patch. Negative Caster can lead to steering instability.
Front View of Kingpin AnglekrKingpin angle k is the angle from
the front view that goes through the steering axis. Kingpin angle
influences on center feel and straight line stability. r is the
kingpin offset or steering offset. r influences steering feel and
dictates forces applied to the steering during braking. For maximum
efficiency, minimize r, but do not have k above 7 or so degrees.
Large values for k create high steering effort.
