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SAE Baja Senior Design Project
Suspension•Peter Morabito•Michael Paliga•Brian Ross
Drivetrain•Kenny Elliot•Patrick Mooney•Dylan Quinn
Frame•Dan D’Amico•Curtis May•Greg Schafran
Midterm Presentation
IntroductionObjective: To design a vehicle for the SAE Baja Competition
Competition EventsAcceleration Hill Climb Mud Bog
ManeuverabilityEndurance
Drivetrain
Engine 14.50 ft lbs of Torque~10 horsepower
CVT •Gaged GX-9 CVT specifically designed for SAE Baja •3.85:1 initial ratio•0.9:1 final ratio
Gearbox•Double Reduction Gearbox•8:1 Ratio
Gear Design- MethodsOur calculations were based on methods found in Shigley’s Design manual.
[Veh. wt]*[Sin(incline angle)] = Repelling Weight[650 lbs]*[Sin(40 degrees)] = 418 lbs
Rep wt = (tire rad)*(CVT ratio)*(engine tq)*(X min)418 lbs = (1.0 ft)*(3.85)*(14 lb-ft)*(X min) ----->Xmin= 7.7551
Gear Ratio CalculationsGear Ratio: (8.0/7.7551) = 1.0326Vehicle Weight: (650 lbs / 600 lbs) = 1.0833Incline Angle: (40 deg / 37.5 deg) = 1.0667Torque: (15 lb-ft max / 14 lb-ft avg) = 1.0714Total FS = (1.0326)(1.0833)(1.0667)(1.0714) ----->Total Safety Factor = 1.2772
Safety Factor Calculations
After determining the specific gear selections we also analyzed each gear for:• Face Width• Interference• Lewis Bending Stress
• AGMA Stress and Strength• Barth Velocity Factor
Lewis Bending Stress
Barth Velocity Factor
Lewis Factor of Safety
Barth Velocity Factor of Safety
Stage Pitch Teeth Pitch Angle Dp Face
WidthTangential Load
(lbf)Lewis Form
Factor Stress (psi) stress (psi) AISI 1020 Steel Safety
AISI 1020 Steel Safety factor
1 12 20 20 1.6666 1 803.88 0.322 4160.869 10212.609 16.342 6.658
1 12 40 20 3.3333 1 803.88 0.389 6888.431 16907.249 9.871 4.021
2 12 20 20 1.6666 1 1688.148 0.322 8737.826 15092.152 7.782 4.505
2 12 80 20 6.6666 1 1688.148 0.436 25812.660 44584.157 2.634 1.525
Gear Design- Results
Gear Ratio: A minimum ratio of 7.7551 wascalculated and 8:1 chosen to provide extra torque
Top Speed: 35.7 MPH at 3600 RPM.
Face Width Required: 1.0 inches
Gear Material: AISI 1020
Total Safety Factor (torque output): 1.277
Lewis Safety Factor (minimum): 2.63
Stage 1 - 2.0:1Size: 20/40 teeth Pitch: 12Face Width: 1.0 in
Stage 2 - 4.0:1Size: 20/80 teeth Pitch: 12Face Width: 1.0 in
Two Stage Reduction Gearbox (8.0:1)
6.5 inch diameter output gear allows room for differential mounting and selection.
•This year’s more advanced design will incorporate a differential•Added to increase the vehicles maneuverability•Wheels will be able to rotate at different speeds•Better in technical events and in and out of tight turns•Will be a great help since the vehicle lacks reverse•Need to determine shaft size to fit differential
Differential
What Comes Next?
•Gearbox housing and bearings•FEA analysis •Subframe/Mounting
Suspension
Front Suspension•Basic Double A-arm setup•Same overall design as previous years car•No significant changes, just modifying to fit newly designed frame
Rear Suspension•Using a rear trailing arm set up similar to the 2012 car•Eliminating the dynamic toe aspect, but maintaining the dynamic camber•Improving wheel travel and reliability
Shock Selection
Fox Float Racing Shocks: Adjustable air spring, velocity damping control, and light weight. Reduced Cost - $521.25 per pair versus $859 per pair for Custom Works
Shocks. Comparable performance
Optimum K
• Front suspension modeled in Solid Works
• Front suspension modeled in Optimum K
• Front suspension has begun testing in Optimum K
Frame- Methods•SAE standards•Firewall•Front end•Roll cage•Rear end
• The 2012 ODU Mini Baja (55th place) weighed 479 pounds
• Cornell’s car (3rd place) weighed only 306 pounds• Reduce frame size and weight• Eliminate redundant members
Frame- Analysis
Material-4130 steel tubing
Shorter overall length
Lighter than previous ODU cars
Future: FEA using PATRAN
Rollover
Test front/rear/ side impact
Frame- Results
Gantt Chart
Questions?