# Designing A Better Steering System

Sept. 26, 1996
Designers often simply assume that 90° angles between the front wheel spindles and the steering levers provide proper steering.

DANIEL D. FRITZINGER
Mechanical Engineer
Grabill, Ind.

Edited by Paul Dvorak

 Poor steering systems are designed on an assumption that a 90° angle between spindle and lever arm provides proper steering action. However, the design causes the front axle centerlines to intersect the rear axle centerline at two different points, producing different turning radii. This produces poor steering action and excessive wheel wear as the front wheels tend to fight each other. Programming the equations into a spreadsheet lets users step through the 0.0090 tions to find values for Tlength and Tt that are nearly equal. For the assumed values, the ideal occurs at about 23.5°.

Small vehicles with inexpensive steering systems often show high tire wear. This is because the front tires most likely do not use the same point for their turning radius. Users may notice that such vehicles do not negotiate corners well and front wheels tend to fight each other.

Designers often simply assume that 90° angles between the front wheel spindles and the steering levers provide proper steering. They do not. The crux of the problem is finding the proper spindle-lever angles. The following procedure does so.

A common steering system for simple vehicles such as grain wagons, toy cars, and low-cost go-carts consist of a spindle-lever arm and a member that moves the tie rod to produce steering action. A wagon tongue connected to a steering column serves the purpose in a towed grain wagon. When a properly designed steering system turns, the centerlines of the rear axle and both front axles intersect a single point, the center point of the turning radius. With such designs, vehicles smoothly negotiate turns.

Before designing a steering system or troubleshooting an existing one, calculate the tie-rod length from:

Tlength = W + 2Lsin(φ)

where W = spindle-to-spindle center distance, in.; Tlength = tie-rod length, in.; L = center-to-center lever arm length, in.; and = angle between lever arm and vehicle centerline, degrees. Estimate this angular value to begin the calculations.

For a required turning radius, calculate the angles through which the inner and outer spindles must rotate for their centerlines to intersect the rear axle centerline at the same point. These angles are not equal and are labeled l and r for left and right. For a left turn, l will be greater than r. Find the angles from:

and

where M = front to rear centerline length, in.; and R = a turning radius, in.

Determine new positions of points A and B on the steering lever arms from:

Ax = Lsin(φ r)

Ay = Lcos(φ r)

Bx = Lsin(φ+ l)

By = Lcos(φ+ l)

Calculate the length of the tie rod in turn mode, Tt, which is the hypotenuse of triangle ABC in the diagram with

The tie-rod length does not change, but the geometry that defines its length does. Consequently, the best value for lets Tlength = Tt. But it is unlikely that the correct value of will be selected on the first try. Ambitious users can solve for after setting the equation for Tlength equal to Tt. Users can also put the equations into a spreadsheet or other math package and solve for a range of values. From the sample spreadsheet, a usable value for comes when the difference between Tlength and Tt approaches zero.

### Paul Dvorak

Paul Dvorak - Senior Editor
21 years of service. BS Mechanical Engineering, BS Secondary Education, Cleveland State University. Work experience: Highschool mathematics and physics teacher; design engineer, Primary editor for CAD/CAM technology. He isno longer with Machine Design.

Email: [email protected]

"

Paul Dvorak - Senior Editor
21 years of service. BS Mechanical Engineering, BS Secondary Education, Cleveland State University. Work experience: Highschool mathematics and physics teacher; design engineer, U.S. Air Force. Primary editor for CAD/CAM technology. He isno longer with Machine Design.

Email:=

### Pumps Push the Boundaries of Low Temperature Technology

June 14, 2024
As an integral part of cryotechnology, KNF pumps facilitate scientific advances in cryostats, allowing them to push temperature boundaries and approach absolute zero.

### The entire spectrum of drive technology

June 5, 2024
Read exciting stories about all aspects of maxon drive technology in our magazine.

### MONITORING RELAYS — TYPES AND APPLICATIONS

May 15, 2024
Production equipment is expensive and needs to be protected against input abnormalities such as voltage, current, frequency, and phase to stay online and in operation for the ...

### Solenoid Valve Mechanics: Understanding Force Balance Equations

May 13, 2024
When evaluating a solenoid valve for a particular application, it is important to ensure that the valve can both remain in state and transition between its de-energized and fully...