10 Differences Between Ackermann Steering Gear and Davis Steering Gear

The steering gear mechanism is used for changing the direction of two or more of the wheel axles with reference to the chassis, so as to move the automobile in any desired path. Usually, the two back wheels have a common axis which is fixed in direction with reference to the chassis and the steering is done by means of front wheels. The condition for correct steering is that all the four wheels must turn about the same instantaneous center. There are two types of steering gear mechanisms:

1. Fifth wheel steering system
2. Side pivot steering system

Side pivot is further divided into two:

1. Davis Steering Gear
2. Ackerman Steering Gear

The main difference between the two steering gear mechanisms is that the Davis steering has sliding pairs, whereas the Ackermann steering has only turning pairs. The sliding pair has more friction than the turning pair; therefore the Davis steering gear will wear out earlier and become inaccurate after certain time. The Ackermann steering gear is not mathematically accurate except in three positions, contrary to the Davis steering gear which is mathematically correct in all positions. However, the Ackermann steering gear is preferred to the Davis steering gear.

What Is Ackermann Steering Mechanism?

The Ackermann steering mechanism is a geometric arrangement of linkages in the steering of a vehicle to turn the inner and outer wheels at the appropriate angles. When a vehicle is turning, the inner front wheel, the inner front wheel needs to turn at a different angle to the outer because they are turning on different radii.

The ackerman steering mechanism comprises a steering arm, a left steering cross rod, a right steering cross rod, a left wheel and a right wheel, wherein the steering arm, the left steering cross rod and the right steering cross rod are connected together through a traditional method. The left wheel is provided with a left steering knuckle, and the right wheel is provided with a right steering knuckle. The ackerman steering mechanism is characterized in that a steering machine shell body is fixed at the middle of a front shaft, and an ackerman cam plate is fixed on the steering machine shell body. A curvilinear groove is arranged on the ackerman cam plate, and the steering machine shell body is connected with a steering guide rail provided with a through cavity through a steering pin shaft in a rotating mode. The steering arm penetrates through the through cavity of the steering guide rail, and the front end of the steering arm is movably connected in the curvilinear groove in a clamping mode. The steering guide rail receives steering input which is from a steering wheel and then rotates around the steering pin shaft. Therefore, the steering arm is forced to rotate along the steering guide rail as well as slide relative to the steering guide rail under the guidance of the curvilinear groove.

What Is Davis Steering Gear Mechanism?

Davis steering gear is an exact steering gear mechanism. It has two sliding pairs and two turning pairs. In this mechanism, the slotted links are attached to the front wheel axle, which turn about two pivotal points. It has the rod and it is constrained to move in the direction of its length by the sliding two members. These constraints are connected to the slotted link by a sliding and a turning pair at each end. The main drawback in Davis steering mechanism is tear and wear problem of sliding pairs. The drawbacks in Davis steering mechanism are overcome by Ackermann steering gear mechanism

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Ackermann Steering Gear Mechanism Vs. Davis Steering Gear Mechanism

1. Ackermann type steering gear mechanism is placed on the back of the front wheel axle while Davis steering gear mechanism is placed on the front of the front wheel axle.
2. The Ackermann steering gear consists of turning pairs. The Davis steering gear consists of sliding pairs.
3. The Ackermann steering gear mechanism is very much simple and flexible than Davis gear steering. The Davis steering gear mechanism is a bit inflexible when compared to Ackermann steering gear.
4. Skidding is high in Ackermann steering gear mechanism. Skidding is low in Davis steering gear mechanism.
5. The Ackermann steering gear does not require more effort at turning. The Davis steering mechanism requires more effort at the time of turning.
6. Ackermann steering gear is subject to less wear and tear. The Davis steering mechanism is subject to more wear and tear than Ackermann steering gear.
7. Ackermann steering gear mechanism is simple and easy to maintain. Davis steering gear mechanism is costly in terms of maintenance.
8. The Ackermann steering gear requires relatively less space than the Davis steering mechanism. The Davis steering gear mechanism requires relatively large space when compared to Ackermann steering gear mechanism.
9. The Davis steering gear mechanism is less preferable when compared to the Ackermann steering gear mechanism.
10. Ackerman steering gear is an approximate mechanism. Davis Steering gear mechanism is an imperfect mechanism.

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Difference Between Ackermann Steering Geer And Davis Steering Geer In Tabular Form

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Summary

What is the main difference between Ackermann Steering mechanism and Davis Steering mechanism?

• Ackermann type steering gear mechanism is placed on the back of the front wheel axle while Davis steering gear mechanism is placed on the front of the front wheel axle.

• The Davis Steering gear has sliding pair, it has more friction than the turning pair, there fore the Davis Steering Gear wear out earlier and become inaccurate after certain time. This type is mathematically accurate.