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
