What could be the reason having (larger or smaller) steering wheels, explain in detail?

Discussion Vehicles with Power Steering Mechanism

When you grip a vehicle’s steering wheel with both hands, a couple moment is applied to the wheel.
Would older vehicles without power steering have larger or smaller steering wheels? What could be the reason having (larger or smaller) steering wheels, explain in detail?

A power steering is a mechanical device equipped on a motor vehicle that helps drivers steer the vehicle by augmenting steering effort needed to turn the steering wheel, making it easier for the vehicle to turn or maneuver at lower speeds.

Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver can provide less effort to turn the steered wheels when driving at typical speeds, and reduce considerably the physical effort necessary to turn the wheels when a vehicle is stopped or moving slowly. Power steering can also be engineered to provide some artificial feedback of forces acting on the steered wheels.

Hydraulic power steering systems for cars augment steering effort via an actuator, a hydraulic cylinder that is part of a servo system. These systems have a direct mechanical connection between the steering wheel and the linkage that steers the wheels. This means that power-steering system failure (to augment effort) still permits the vehicle to be steered using manual effort alone.

Electric power steering systems use electric motors to provide the assistance instead of hydraulic systems. As with hydraulic types, power to the actuator (motor, in this case) is controlled by the rest of the power steering system.

Other power steering systems (such as those in the largest off-road construction vehicles) have no direct mechanical connection to the steering linkage; they require electrical power. Systems of this kind, with no mechanical connection, are sometimes called “drive by wire” or “steer by wire”, by analogy with aviation’s “fly-by-wire”. In this context, “wire” refers to electrical cables that carry power and data, not thin wire rope mechanical control cables.

Some construction vehicles have a two-part frame with a rugged hinge in the middle; this hinge allows the front and rear axles to become non-parallel to steer the vehicle. Opposing hydraulic cylinders move the halves of the frame relative to each other to steer.

Electric systems

An EPS module with a partially disassembled steering column
Electric power steering (EPS) or motor-driven power steering (MDPS) uses an electric motor rather than hydraulic system to assist the driver of a vehicle. Sensors detect the position and torque exerted inside the steering column, and a computer module applies assistive torque via the motor, which connects to either the steering gear or steering column. This allows varying amounts of assistance to be applied depending on driving conditions. Engineers can therefore tailor steering-gear response to variable-rate and variable-damping suspension systems, optimizing ride, handling, and steering for each vehicle.[20] This new technological feature also gave engineers the ability to add new driver assistance features. This include features such as lane assist, wind drift correction, etc.[21] On Fiat group cars the amount of assistance can be regulated using a button named “CITY” that switches between two different assist curves, while most other EPS systems have variable assist. These give more assistance as the vehicle slows down, and less at faster speeds.

Click here to ORDER an A++ paper from our Verified MASTERS and DOCTORATE WRITERS: Discussion Vehicles with Power Steering Mechanism
A mechanical linkage between the steering wheel and the steering gear is retained in EPS. In the event of component failure or power failure that causes a failure to provide assistance, the mechanical linkage serves as a back-up. If EPS fails, the driver encounters a situation where heavy effort is required to steer. This heavy effort is similar to that of an inoperative hydraulic steering assist system[citation needed]. Depending on the driving situation, driving skill and strength of the driver, steering assist loss may or may not lead to a crash. The difficulty of steering with inoperative power steering is compounded by the choice of steering ratios in assisted steering gears vs. fully manual. The NHTSA has assisted car manufacturers with recalling EPS systems prone to failure.[22]

Electric systems have an advantage in fuel efficiency because there is no belt-driven hydraulic pump constantly running, whether assistance is required or not, and this is a major reason for their introduction. Another major advantage is the elimination of a belt-driven engine accessory, and several high-pressure hydraulic hoses between the hydraulic pump, mounted on the engine, and the steering gear, mounted on the chassis. This greatly simplifies manufacturing and maintenance. By incorporating electronic stability control electric power steering systems can instantly vary torque assist levels to aid the driver in corrective maneuvers.[23]

In 1986 NSK put the EPS for battery fork into practical use.[24] In the subsequent 8 years Koyo Seiko (current JTEKT), NSK developed a column system exclusively for minicars, sold only in Japan such as Suzuki and Mitsubishi Motors.[25] However, this simple method was noticeable due to the inertia feeling of the motor at the time of rapid steering for danger avoidance in low speed running, at the time of high speed running at which the steering force became small, returning to the manual steering. As a result, that system was not adopted. In the late 1990s, a direct full control system of a rack assist without clutch to a regular car was put into practical use in the Honda NSX (initially, automatic only) Since then, there has been a transition from a brush-attached motor to a brushless motor in the rack type of ordinary vehicles and this method has become mainstream.

Electric power steering systems appeared on the Honda NSX in 1990,The MG F, the FIAT Punto Mk2 in 1999, the Honda S2000 in 1999, Toyota Prius in 2000, the BMW Z4 in 2002, and the Mazda RX-8 in 2003.

The first electric power steering system appeared on the Suzuki Cervo in 1988.[26] The system has been used by various automobile manufacturers, and most commonly applied for smaller cars to reduce fuel consumption and manufacturing costs