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

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.

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.

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

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

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

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.

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.

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

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) 2.500000 12.435833 -2.698303 1.561025 32.791946 2.600000 12.425493 -2.681408 1.542593 27.116013 2.700000 12.415951 -2.664580 1.523945 21.834167 2.800000 12.407207 -2.647819 1.505060 16.904785 2.900000 12.399262 -2.631127 1.485913 12.291878 3.000000 12.392121 -2.614508 1.466477 7.964203 3.099999 12.385782 -2.597961 1.446716 3.894279 3.199999 12.380248 -2.581490 1.426593 0.058311 3.299999 12.375521 -2.565096 1.406059 3.564545 3.399999 12.371598 -2.548780 1.385054 -6.993240 3.499999 12.368484 -2.532545 1.363509 -10.244102 3.599999 12.366177 -2.516391 1.341329 -13.331718 3.699999 12.364678 -2.500320 1.318400 -16.269325

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

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) 2.050000 11.938805 -2.727748 1.595668 41.716309 2.150000 11.924406 -2.709923 1.576939 34.935944 2.250000 11.910830 -2.692160 1.558010 28.682266 2.350000 11.898078 -2.674464 1.538864 22.893677 2.450000 11.886154 -2.656836 1.519481 17.517822 2.550000 11.875060 -2.639279 1.499837 12.509750 2.650000 11.864799 -2.621795 1.479902 7.830841 2.750000 11.855372 -2.604387 1.459646 3.447845 2.849999 11.846783 -2.587056 1.439030 -0.668266 2.949999 11.839031 -2.569805 1.418006 -4.542877 3.049999 11.832120 -2.552636 1.396518 -8.198227

Design Comparison Frame 1 Frame 2 Rack Length: 11” S: 3.2” Es: 0.058” Xr: 102.0” Xl: 102.06” Turn Radius: 8.5 ft Rack Length: 14” S: 2.85” Es: -0.67” Xr: 104.2” Xl: 103.0” Turn Radius: 8.583 ft

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 5224 2:1 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

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