SAE MINI BAJA POWERTRAIN By Chris Gilson Spencer

SAE MINI BAJA: POWERTRAIN By: Chris Gilson & Spencer Suggs Advisor: Ho-hoon Lee Instructor: Cris Koutsougeras ET 493

WHAT IS MINI-BAJA? � The SAE mini-baja is an international collegiate engineering challenge to design and build an off-road vehicle � This vehicle will go through various stress tests: � Acceleration � Off-road terrain � Steep incline � Endurance

POWERTRAIN � The Powertrain is the mechanisms that transmit the driving force from the engine of a vehicle to its axles � Includes: � Engine � Continuously � Differential Variable Transmission (CVT)

ENGINE • Model: Briggs & Stratton 10 HP OHV Intek • Cost: $250. 00 • Max Power Output: 10 HP • Max Torque Output: 14. 5 ft. lbs.

ENGINE MOUNT DESIGN • Designed for easy removal & maintenance • Material: T 6 6061 Aluminum • Dimensions: • 9” Length • 8. 37” Frame Rail Span • 1” Thickness

ENGINE MOUNT STRESS ANALYSIS • Max Torque from engine is 14. 5 ft. lbs. = 19. 7 Nm • Torque = F * distance • F = 107. 1 N • W=m*g • W = 275. 6 N

FORCE EQUILIBRIUM +↑ΣFy=0 RA+RB+29. 1− 246. 5=0 RA+RB =217. 4 N +↺ΣMA=0 RB (0. 225)+(29. 1)(0. 015)-(246. 5)(0. 21)=0 RB (0. 225)+(29. 1)(0. 015)-( 246. 5)(0. 21)=0 RB=228. 127 N RA+RB=217. 4 RA +228. 127=217. 4 RA =− 10. 727 N

SHEAR FORCE DIAGRAM 0≤x≤ 0. 015: +↑ΣFy=0 − 10. 727−V 1=0 V=− 10. 727 N 0. 015≤x≤ 0. 21: +↑ΣFy=0 − 10. 727+29. 1−V=0 V=18. 373 N 0. 21≤x≤ 0. 225: +↑ΣFy=0 − 10. 727+29. 1− 246. 5−V=0 V=− 228. 127 N

BENDING MOMENT DIAGRAM 0≤x≤ 0. 015: +↺ΣMb=0 − 10. 727 x−Mb=0 Mb=− 10. 727 x Nm 0. 015≤x≤ 0. 21: +↺ΣMb=0 − 10. 727 x+(29. 1)(x− 0. 015) −Mb=0 Mb=18. 373 x− 0. 436 Nm 0. 21≤x≤ 0. 225: +↺ΣMx=0 − 10. 727 x+(29. 1)(x− 0. 015)+(− 246. 5)(x− 0. 21)−Mb=0 Mb=− 228. 127 x+51. 328 Nm

SOLIDWORKS STRESS SIMULATION • T 6 6061 Aluminum yield strength = 2. 75 e 8 N/m 2 • Largest concentration of stress = 1. 102 e 5 N/m 2 • Material will not fail under load

CVT TRANSMISSION � � The continuously variable transmission is an automatic transmission that can change seamlessly through a range of speed ratios Commonly used in ATV / off-road utility vehicles

CVT • Model: COMET 780 • Price: $250. 00 �

DIFFERENTIAL SELECTION � Independent Rear Suspension (IRS) PROS: Greater suspension travel Better ride quality Greater cornering performance Higher ground clearance CONS: Less power transfer Higher cost Higher chance of

DIFFERENTIAL • Model: Dana Spicer H-12 FNR • Price: $500 - $800 • Specs: • Load Rating: 1500 lbs. • Input Torque Rating: 24 ft. lbs. continuous • Max Torque Rating: 96 ft. lbs. intermittent • Gear Ratio: 12. 58 : 1

DIFFERENTIAL MOUNT • Designed for easy removal & maintenance • Material: T 6 6061 Aluminum • Dimensions: • 12” height • 10” length • . 25” thickness • 4” axle hole

MOUNTING BRACKET MATERIAL SELECTION • • Material: T 6 6061 Aluminum Tensile Strength: 290 Mpa (42, 000 psi) Yield Strength: 240 Mpa (35, 000 psi) Weight: . 098 lb. /c. u. in.

BOLT GRADE SELECTION • Engine bolt size =. 375 m • Max Concentration Force = 246. 5 N • Doubled for Safety Factor = 500 N • Max Shear Force = 228 N • Doubled for Safety Factor = 480 N • Selection using graph: SAE Grade 5 • Tension Cap. = 43985 N • Shear Cap. = 36831 N

TORQUE TRANSFERRED TO WHEELS RPM CVT Ratio (RCVT) Complete Ratio (RC) Engine Output Torque (ft. Torque at the Wheels lbs) (ft. lbs) 1800 2. 63 : 1 29. 11 : 1 13 336 2800 1. 66 : 1 18. 37 : 1 14. 5 235 3600 . 69 : 1 7. 64 : 1 13. 8 98

POWERTRAIN POSITIONING • Simplistic Design • Easy Installation • Painless Maintenance • 45 Degree belt angle • Decreases belt length • Smaller wheel base length

GOING FORWRD � Begin to order parts needed � Machine parts to spec � Begin Assembly � Test