• Defined total gear ratio (~200:1) from torque and speed constraints

• Designed 3-stage compound gear train via iterative gear/pinion teeth pairing

• Modeled gear face widths under both bending and surface fatigue conditions

• Designed shaft to satisfy fatigue and deflection criteria using singularity functions

• Calculated output shaft key length for combined fatigue and static stress

• Applied Goodman fatigue criterion and correction factors (Kf, Kfs, Se)

• Input: 15 HP motor @ 1800 RPM

• Output: ≤ 30 ft/min hoist speed via 12.5 in pitch diameter drum

• Gear System: 3-stage compound train, each stage within 3:1–10:1 ratio

• Material: AISI 4140 (shaft/gear), AISI 4130 (key)

• Key Features:

  • Gear face widths sized for both bending and surface fatigue limits

  • Shaft diameter refined based on stress and maximum deflection criteria

  • Key length calculated iteratively using fatigue-based torque transfer equations

• No FEA was used, but design validation relied on analytical fatigue life simulations

• Gear face width sizing performed using Excel to iterate diametral pitch under both bending and surface fatigue constraints

• MATLAB used to solve nonlinear fatigue equations for key length sizing

• Gear tooth counts were adjusted to reduce volume while maintaining required ratios and safety margins

• Shaft diameter finalized based on deflection limits, overriding initial stress-only sizing approach

• Output RPM: ≈ 9

• Total Gear Ratio: ≈ 200:1

• Final Shaft Diameter: 3.5 in (based on deflection and fatigue)

• Key Length: 2.31 in (computed via fatigue-based MATLAB iteration)

• Key Fatigue Safety Factor: 2.01 (confirmed using Goodman fatigue criterion)

• Key Max Bearing Stress: 20.26 ksi (well below yield limits for AISI 4130 steel)

• Balanced gear tooth counts across three stages to stay within both ratio and volume limits

• Recalculated fatigue strength iteratively for gears based on life-cycle correction factors

• Updated shaft diameter after initial deflection exceeded allowable limits despite stress compliance

• Solved a non-linear fatigue equation in MATLAB to determine key length under alternating load and bearing stress conditions

• Finalized 4-inch output shaft key design by selecting material, calculating required length, and verifying safety factors

• Developed MATLAB code to solve non-linear fatigue equations for dynamic key loading

• Analyzed and documented key stress performance under shear, bearing, and fatigue in the final report

• Supported team in validating gearbox design against torque, speed, and safety requirements

• Achieved a key design safety factor of 2.01, confirmed through multi-mode failure analysis

Gear Train Design · Fatigue and Bearing Stress Analysis · Shaft Deflection Modeling · MATLAB for Mechanical Iteration · SolidWorks Technical Drafting · Excel-Based Parametric Design · Engineering Report Writing & Documentation

This project deepened my understanding of machine element design under real-world constraints. I learned to balance analytical stress models with practical considerations such as shaft deflection, gear volume, and manufacturing tolerances. My focus on key sizing using fatigue analysis helped bridge theoretical equations with component-level design decisions. The experience also strengthened my confidence in collaborative workflows and iterative design which are essential skills in professional mechanical engineering environments.