DMTB Engineering

1. DMTB Engineering Mini Baja Gearbox Presentation 1I: Design Presentation March 4, 2014 Colin Rose, Mitch Whelan, Nick O’Reilly, Mike O’Brien

2. Presentation Outline • Restatement of Problem Definition & Design Targets • Design Overview • Gear Properties • Shaft Properties • Old vs New Calculations • Gear Wear • Gear Bending • Cost Analysis • Project Management Plan Update • Questions

3. Problem Definition • Designa simple mechanical gearbox for use in a Mini Baja off-road vehicle. • TARGETS: • Weight – 10% decrease; • Torque – 5-10% increase; and • Cost – on par with previous.

4. Design Overview • 1045 carbon steel gears • Purchased • Aluminum housing • Fabricated • Carbon steel shafts • Fabricated • 11.9:1 Ratio • F/N/R (reverse shaft not shown)

5. GEAR SPECS

6. SHAFT SPECS

7. OLD vs NEW GEARBOX CALCULATIONS • Old Gearbox • Tin = 40.7 Nm • Tout = 455.8 Nm • Gear Ratio: 11.2:1 • ωin = 1750 rpm • ωout= 156.25 rpm • New Gearbox • Tin = 40.7 Nm • Tout = 484.22 Nm • Gear Ratio: 11.9:1 • ωin = 1750 rpm • ωout= 147.05 rpm

8. Gear Wear Life Cycle – Infinite (Calculated Life Cycle – 2.44x1012 Rev) Design Factor – 1.2 Calculated Gear Wear – 213768.9 psi (Calculated from Budynas & NisbettShigley's Mechanical Engineering Design 9th) Force to Cause Gear Failure – 1774.19 lb

9. Gear Bending • Bending Stress – 11224.47 psi • Bending Fatigue • 1. Due to repeated bending stresses. • 2. Stresses that exceed local fatigue strength. • 3. Failure occurs in tensile root fillet of the gear tooth.

10. Cost Analysis • Estimated cost of approximately $1050.00 • Cost of gears has risen ~10% • Bulk of cost is in the Housing.

11. Project Management Plan

12. Questions?