1. DESIGN OF STEERING SYSTEM OF SELU MINI BAJA CAR
Benjamin Genre
Advisor: Dr. Ho-Hoon Lee
Dr. Cris Koutsougeras
ET 493 Senior Design Project I
Spring 2017

2. Goal of Project
Create a C-Program capable of calculating steering error for any Mini Baja design.
Determine the best setup to be used on the two different frame designs.

3. Background
In 2013 a research paper about the steering design of an SELU Mini Baja car was written by Alfred Showers, Dr. Ho-Hoon Lee, and Dr. Cris Koutsougeras.
It was determined that a commercially available Rack-and-pinion system would be best used for a Mini Baja car.
A rack-and-pinion system uses rotational motion of a pinion gear and converts it into linear motion with the rack, moving the wheels of a vehicle left and right.

4. With this design, steering error would become a factor and the placement of the rack-and-pinion would be a design parameter.
The distance from the front axle to the placement of the rack-and-pinion is the main value the program helps to determine.
Rack and Pinion System

5. Ackerman Steering Principle
States that the axial lines of all the wheels should meet at the same point.

6. Steering Error
When the projections of the two front wheels do not meet at the same point on the rear axle’s axis.
By changing the distance from the front axle to the rack, the steering error also changes.
Ackermann Steering Error

7. Flow Chart Program made with Microsoft Visual Studio.
At the start of the program, the user is asked to input the constants of the design. These include:
Length from front axle to rear axle.
Width of car.
Length of the rack and pinion.
Length of steering arm.
Angle between steering arm and wheel.
Maximum displacement of rack.
Initial value of S (the distance between the front axle and rack.)
Maximum value of S.

8. Flow Chart
Everything is calculated as a function of S using the equations derived in the paper.
Prints values of S, lt, θl, θr, and es.
S is increased and then compared to Smax.
If S < Smax, the calculations start over with new value for S
If S > Smax, then the program ends.

9. Output Frame 1 Enter angle between wheel and steering arm in degrees:
16.5
Enter maximum displacement of the rack:
2.25
Set initial value of S, the distance between the front axle and rack and pinion:
2.5
Set Max value of S, the distance between the front axle and rack and pinion:
4.5
Steering Error Calculator
Enter length from front axle to rear axle: 64
Enter width of car: 38
Enter length of rack and pinion: 11
Enter length of steering arm: 4

10. Steering Error Output for Frame 1
Table Frame 1
Steering Error Output for Frame 1
s (in)
lt (in)
Ol (rad)
Or (rad)
es (in)

11. Output Frame 2 Steering Error Calculator
Enter length from front axle to rear axle: 64
Enter width of car: 40
Enter length of rack and pinion: 14
Enter length of steering arm: 4
Enter angle between wheel and steering arm in degrees:
17.35
Enter maximum displacement of the rack:
2.25
Set initial value of S, the distance between the front axle and rack and pinion:
2.05
Set Max value of S, the distance between the front axle and rack and pinion:
3.05

12. Steering Error Output for Frame 2
Table Frame 2
Steering Error Output for Frame 2
s (in)
lt (in)
Ol (rad)
Or (rad)
es (in)

13. Design Comparison Frame 1 Frame 2 Rack Length: 11” S: 3.2” Es: 0.058”
Xr: ”
Xl: ”
Turn Radius: 8.5 ft
Rack Length: 14”
S: ”
Es: ”
Xr: ”
Xl: ”
Turn Radius: ft

14. Cost Analysis Parts List 11” Rack-and-Pinion Steering Quickener
Description
Cost
Steering Rack-Frame 1
(Figure 5)
11” Rack and Pinion Unit
Weights 2.25 lbs
desertkarts.com
$100.00
Steering Rack-Frame 2
14” Rack and Pinion Unit
Steering U-Joint
(Figure 6)
Universal Joint with
5/8” Splines
$28.00
Steering Quickener
(Figure 7)
Howe :1 Quickener
summitracing.com
$86.97
(Optional)
Steering Shaft Coupler
Steering Coupler, Steel, 5/8 in. 36-Spline, 3/4 in.
$19.49
Cost Analysis
11” Rack-and-Pinion
Steering Quickener
Steering U-Joint

15. Accomplishments Future Work
Studied Research Paper
Constructed Flowchart
Created Steering Error Calculating Program
Determined Steering Error for Frame Designs
Estimated Cost for Steering Parts
Determine Steering Column Length for Final Design
Finalized Design Dimensions
Collect All Parts
Assemble Steering System