This document discusses steering gear mechanisms used in vehicles. It introduces the basic principles of steering mechanisms, including that the front wheels turn to change the vehicle's direction while the back wheels remain straight. It describes two common steering mechanisms: Ackermann steering uses linkages to ensure the inside and outside wheels follow different radius circles during a turn. Davis steering is also an exact mechanism but has more sliding components, increasing wear and reducing accuracy compared to Ackermann steering. The key difference between the mechanisms is that Ackermann steering is behind the front wheels while Davis is in front, and Ackermann uses turning pairs while Davis uses sliding pairs.

1. Topic:- Steering Gear Mechanism
by
Tarique Siddiqui
131MC00216
Submitted to :- Mr. P. Jagan Mohan

2. INRODUCTION
 The steering gear mechanism is used for changing the
direction of two or more of the wheel axles with
reference to the chassis. Usually, Back wheel axle is
fixed in direction with reference to the chassis and the
steering is done by means of the front wheels.
 When the vehicle takes turn, the front wheels along
with the respective axles turn about corresponding
pivoted points.
Also, the back wheels remain straight and do not turn.
Therefore, steering is done by means of the front wheels.

3.  In order to avoid skidding(slipping of the
wheels of sideways),the two front wheels
must turn about the same instantaneous centre
which lies on the axis of the back wheels.
 if this does not happen, the skidding on the
front or back wheels will definitely take
place, which will in turn produce more wear
and tear on the tyres.

4. Basic geometry
The basic aim of steering is to ensure that the wheels are
pointing in the desired directions. This is typically
achieved by a series of linkages, rods, pivots and gears.

5. Steering principle
A C
E F
B
a
b
If q
cot
cot
cot cot
EI EF FI a FI
AE AE b
FI FI
CF b
a FI FI a
b b b
q
f
q f
 
  
 

    

6. PRINCIPLE OF WORKING
 Ackermann steering mechanism
Ackermann steering geometry is a geometric arrangement
of linkages in the steering of a car or other
vehicle designed to solve the problem of wheels on the
inside and outside of a turn needing to trace outcircles of
different radius.

7. When the vehicle moves along straight path, the longer links AB
and CD are parallel and the shorter links BC and AD are equally
inclined to the longitudinal axis of the vehicle.
When the vehicle moves left, the position of the gear is shown by
dotted lines in fig.

9. Davis Steering
This is an exact steering gear mechanism. This
mechanism fulfils the above steering condition. But due
to presence of more sliding members, the wear will be
increased and this eliminates the accuracy.

10. (i)
(ii
)
(iii)

12. Difference between Ackermann
and Davis mechanism
• The whole mechanism is on back of the front wheels ,
whereas in Davis ,it is in front of the wheels.
• It consists of turning pairs, whereas in Davis, it consists
of sliding pairs.

13. Thank
You