ME 490 B: SAE BAJA Project: Transmission Design

Luis Martinez, Hani Chalingo, Samantha Moore

Department of Mechanical Engineering

Abstract

Many SAE Baja Team’s need a better functioning transmission. Different options were researched to find one to be work with the continuously variable transmission (CVT) that will be new to this year’s car, lighter in weight and sustainable. The methods used to reach these criteria; was finding the gear ratio (Reduction ratio) , torque for the wheels, the specification sheet for the gear sets as well as failure analysis. Our calculated reduction ratio is 6.63 which will allow the engine power to be used efficiently to maximize the speed of the Baja car. The torque of the wheels found was 249.18 ft-lb. The torque is the turning power of the car and determines how quickly a speed can be reached. We are also working with a gear ratio of 6.63:1. From this data this transmission can work with CVT Gaged (GX9): and can work at a smaller size and less weight from the current working model.

Results

Conclusions

References

Methods Used/Analysis

To find the final reduction ratio for CVT Gaged (GX9):

Reduction Ratio (Rr) = RPM engine ∗ CwheelRCVT high ∗ V Vehicle

Where:

RPM engine = 3800 rpm using Briggs &Stratton Engine

Cwheel (Wheel Circumference) = p * wheel Diameter

Diameter of wheel = 22 in

RCVT high = 0.9 using CVT Gaged GX9

V Vehicle(The required speed for the Baja Vehicle) = 42 mph

Rr = 3800 rpm ∗ π ∗ 22 in∗1 ft ∗1 mile∗ 60 min

0.9 ∗ 42 mph 12 in ∗ 5280 ft ∗ 1h = 6.63

Transmission for the Mini Baja Device that allows the use of Brigs & Straton generator motor’s power to be used efficiently. Use of gear reductions

CVT (Continuously Variable Transmission) Additional gear transmission.

Stress and Failure AnalysisPrototype

Physical3D PrintedTheoretical (SolidWorks Model)

Make BAJA team completive

• Made gear box that is smaller size and less weight from the current working model

• Made Tester to test gears and evaluate stress and failure criteria

• Develop specification sheet for the gear sets

• Gives team the ability to use other CVT options (Gaged Engineering GX9)

• Makes it easily to test and acquire data

• Easily serviceable

• Stress and Failure Analysis

• Testing and Development

• Durability

• Application of Learned ME skills

• Develop Transmission for future cars

• Make new case that incorporates new gears

• Make parts easily to be serviced.

Norton, Robert L. "11." Machine Design: An Integrated Approach. 3rd ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2006. Print.

Gear N Pd F(face width) Y(geometry Factor) Torque Wt (tangantinal load) (φ) cos (φ) W(force) Bending Stress

(1/in) in (lb.in) lb deg lb lb/in^2

1 30 16.9 0.014766686 0.114 153.6 173.3632 20 0.9398 184.477 1743516.136

2 65 16.9 0.014766686 0.135 332.8 173.3632 20 0.9398 184.477 1472302.514

3 33 12.7 0.019685039 0.117 332.8 256.1551515 20 0.9398 272.577 1412487.671

4 101 12.7 0.019685039 0.142 1018.4 256.1049307 20 0.9398 272.524 1163582.092

0

10

20

30

40

50

60

0 1000 2000 3000 4000

MP

H

Engine RPM

Comparison

CVT Gaged Speed

Old CVT Speed

Gear set 1 Gear set 2

Gear 1 Gear 2 Gear 3 Gear 4

Gear Ratio Gr 2.167 3.06

Diametral Pitch, Pd (1/in) 16.93 12.7

Module, m (mm) 1.5 2

Number of Teeth, N 30 65 33 101

Pitch Diameter, d (mm) 45 97.5 66 202

Pitch Diameter, d (in) 1.77165 3.838583 2.59843 7.95276

Pitch radius, r (in) 0.885825 1.9192915 1.299215 3.97638

Center Distance (in) 2.8051165 5.275595

Pressure Angle ,φ (degree) 20

Circular pitch, Pc (in) 0.1855 0.24737

Base pitch, Pb (in) 0.1743 0.23245

Addendum, a (in) 0.059 0.0787

Dedendum, b (in) 0.0738 0.098

Clearance, c (in) 0.0148 0.0193

Working Depth (in) 0.118 0.1575

Whole Depth (in) 0.1329 0.17716

Length of action , Z (in) 0.3 0.41

Contact ratio ,mp (in) 1.72117 1.764

Tooth Thickness (in) 0.0928 0.1237

Outside Diameter (in) 1.88965 3.956583 2.75583 8.11016

Fillet Radius (in) 0.0177 0.0177 0.0236 0.0236

Width of Top land (in) 0.01477 0.01477 0.0197 0.0197

Project Description