Reverse Engineering of Steering System

Reverse Engineering of Steering System with Developed Equation for Steer Angle Abstract ? This paper deals with the steering mechanism In detail.

As the design component, various equations were derived from the fundamentals. A computer program was made on C language, which calculates all the data relating to steering I. E. (Ackermann angle, length of tie rod, steer angle).

The program was simulated under different Ackermann angle, and various inferences were drawn from it.CAD models were also created to demonstrate the various components used in steering systems. Keywords- Steering, Rack and Pinion. Steering Column, Tie Rod, Gear System, Steering Wheel.

PRINCIPLE The relative motion between the wheels of a vehicle at the road surface should be of a pure rolling type so that wear of the tires Is minimum and uniform. When the vehicle is moving on a curved path, as shown in Fig 2, the steering gear must be so designed that the paths of the point of contact of each wheel with the ground are concentric circular arcs.For proper steering the axis of rotation of all the wheels should meet at G I. E. The instantaneous center of rotation of the vehicle. To satisfy this, the inner wheels would be turned through a greater angle as shown in Fig in which B is greater than ˜, when the vehicle Is turning towards the right side.

INTRODUCTION The intention of the steering arrangement is to permit the driver to manipulation the association of the vehicle by curving the wheels.This is completed by way of steering wheel, a steering column that transmits the rotation of the steering wheel to the steering gears, the steering gears, that rise the rotational power of the steering wheel so as to send larger torque to the steering linkage, and the steering linkage that transmits the steering gear movement to the front wheels (See Fig 1) . The steering arrangement configuration depends on vehicle design (the drive train and suspension utilized, whether It Is a traveler car or a commercial vehicle).Steering Arm / Track Arm f. Spindle A. Steering column The automotive steering column is a mechanism chiefly aimed for relating the steering wheel to the steering mechanism by input torque given by the driver from the steering wheel.

The steering column is an extremely convoluted mechanism. It is projected in such a method that it collapses in an encounter so as to protect the driver. B. Uses of adjustable steering column 1. In the event of a frontal encounter utilized as power dissipation management. 2.

Provide climbing for assorted mechanism: the multi-function switch, column lock, column wiring, column shroud(s), transmission gear selector, gauges or supplementary instruments in addition to the electro motor and gear constituents. Figure 3: Steering wheel This steering wheel is specially designed for BAJA SEA 2012 (See Fig 3). The dimensions are as per specified in the rulebook. The Diameter = CACM.

The steering is specially designed this way so that it can act as a damper during rough terrain. B. Steering Rack 3. Offers height/length adjustment to suit driver preference.

C.Steering Gears The steering gearbox gives the driver of the vehicle alongside maximum impact to enable him to exert a colossal power at road wheel alongside minimum power, to manipulation the D. Calculations for lock-to-lock steering If a car has a steering ratio of 18:1 and the front wheels have a maximum deflection of 250, then at 250, the steering wheel has turned 250x18, which is 4500. That's only to one side, so the entire steering goes from -250 to plus 250 giving a lock-to-lock angle at the steering wheel of 9000, or 2. 5 turns (9000 / 360).

Figure 4: Steering rack C. Pinion Gear Figure 5: Pinion Gear D.Rack and Pinion Assembly Figure 7: Ackermann Principle B. Design Component of Ackermann- Deriving equation to calculate steering angle Determining the steering angle of the vehicle when experiencing a turn.

That is to say that we have two components moving together - the left and right steering knuckles, but the relationship between their motions changes as we move them. It's a bit like having a bowling ball in a dark room and spinning other bowling balls in an attempt to locate it by listening of its impact. Figure 6: Rack and Pinion Assembly As per the SEA BAJA handbook, Fig 6, is a inch rack and pinion system.Fig 4 and Fig 5 illustrates the rack and pinion gear. Taking other features into account Rack and pinion also comes out to be cheap, easy to repair and reduces the overall weight of the car compared to other steering gearboxes.

Hence it's preferable for BAJA Figure 8: Derivation of steer angle 1 STEERING GEOMETRY A. Ackermann Geometry Ackermann steering geometry (See Fig 7) 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 out circles of different radius.The general equation to calculate the Ackermann angle is given by, at the important angles and distances. The two most fundamental distances are the wheelbase of the car and the kingpin center-to-center distance, which can be seen from the Fig 8 above. Drawing two lines representing the wheelbase and the distance from the car's centerline to one of the kingpins, we can make a triangle.

By design, the line that connects through the centers of the Ackerman arm forms the hypotenuse of this triangle. See Fig 9 below. To Bob - cot = PUB turn angle of the wheel on the outside of the turn turn angle of the wheel on the inside of the turn L= track width wheel base b= distance from rear axle to center of mass Figure 9: Derivation of steer angle 2 Note that the angle with its vertex at A is 90 degrees by design, unless the vehicle has been crashed. If this angle experiences an unplanned adjustment due to an impact, the car will dog track. This can be checked using a tape measure and comparing distances from side to side. Also note that the line that forms the Ackerman angle with the hypotenuse is parallel with the wheel base line, again by definition.

Because of this, we can say that angle B and the Ackerman angle are similar, so if we know one angle, we know the other directly. But angle B isn't too hard to calculate. Recall that the tan function gives the ratio between the opposite side and the adjacent side of the triangle. !"#$ ! "# ! #$"% l" tan(S) = we know the distances and we are trying to find angle B. We need the inverse function of tan 0 to get angle B.

So rearranging, we get: tan-1{ } = angle B For example, lets choose a wheelbase of 76" and a king pin to king pin distance of 38". The formula would look as follows: ! Engle B = 14. 0360 So, the Ackerman Angle is 14. 0360. Now we can use this to find the length of the tie rod.

To approach our next problem, which is to find the length of the tie rod, we can divide the trapezoid ABACA into a rectangle and two triangles. See Fig 10 below, SST (14. 0360) = Y/6" Y=6" * SST (14. 360) 0. 243 Y= I .

445" Calculating this gives us the value that its 1. 445" inches shorter at the bottom and 1. 445" inches shorter on the top than the kingpin center-to-center distance. Expressed mathematically: LET = DECK - 2*RA*sin (Ackerman Angle).

......

....

Where: LET is the length of the tie rod DECK is the distance between king pins center to center RA is the radius of the Ackerman Arm Using equation (I), LET = 38" - 14. 0360 LET = 38" - LET = 33. 084" So, for a car configured with this values, the tie rod length needs to be 33. 084". Since we have figured out all of the basic values.

Now the real fun begins. Let's contemplate a turn as shown in the figure 11 in red below. Suppose that the Ackerman arm labeled ABA steers 200 to the left as shown. What angle does the other Ackerman arm transect?You might think 200, but this would result in the wheels being parallel in a turn, which would be unsatisfactory.

In reality, because the car pictured is turning to the left, the right Ackerman arm (CD) needs to steer something less than 200. But the problem is how much less? Figure 10: Derivation of steer angle 3 If you look through the diagram above carefully, you see the length of the tie rod segment BC is equal to the king pin to king pin center distance minus distance Y on each side. So, we have to calculate what is this distance Y? To find out, we have to decide an Ackerman Arm Radius.Purchasing a standard Ackerman arm out of a catalog can choose this, or we can design your own. Either way, this is basically Just a parameter that the engineer chooses by his gut.

Let's pick 6" (as per the catalog) to make calculations easy. So, what is the length of distance Y? If we recall that the sin of an angle is the ratio between the side opposite the angle and the hypotenuse. Let us consider a line drawn diagonally from point D to B (See Fig 12 below). This creates three angles that add together to give the angle of the wheel that pivots at point D.

We'll call the first angle K, the second angle y, and the third angle is of course, the Ackerman angle, which is already been calculated. Now we can start to work on calculating each of them. If you think about angle k, we can determine it because for any steer angle, we know the positions of the ends of the diagonal line. If we assigned point A the coordinate of (assume origin) then point D would have the coordinates (Kingpin Center to Center Distance, O) .

In our case specifically point Do's coordinates would be (38,0). Point Bi's coordinates take a little bit more complexity to find.