Gearbox
WIT
Project overview
This semester-long project for Design of Machine Elements focused on designing a single-stage reduction gearbox for an agricultural irrigation pump. The objective was to create a compact, durable gearbox capable of transmitting 9 hp at 1500 rpm while increasing torque through a 3.5:1 reduction ratio.
The project was primarily analytical, focusing on gear selection, load analysis, bearing design, and overall gearbox layout.
Design requirements
The gearbox was designed for agricultural equipment operating in environments where reliability and simple maintenance are critical.
Key specifications:
Input power: 9 hp
Input speed: 1500 rpm
Reduction Ratio: 3.5:1
Output speed: approx. 430 rpm
Bearing life requirements: 4000 hours
Gear type: 20° spur gears
Gear selection and design
The gear pair was selected from Boston Gear catalog components to meet the required ratio while maintaining manufacturability.
Gear: YF70
Pinion: YF20
Diametral pitch: 10
Face width: 1.25 in
Pressure angle: 20°
Load and stress analysis
System loads were calculated using the input power and gear geometry.
Tangential force: 567 lbf
Radial force: 206 lbf
Bending and contact stresses were evaluated using standard gear design methods. The pinion experienced the highest bending stress approx. 42 ksi, which remained within allowable limits for the selected materials.
Bearing selection
Radial ball bearings were selected to meet the project’s life requirement.
Pinion bearings: 1640-2RS
Gear bearings: R16-2RS
Predicted bearing life significantly exceeded the 4000 hour requirement, confirming adequate reliability for the system.
What I learned
Gear stress analysis and torque transmission
Bearing life calculations
Mechanical layout of gearbox systems
Applying analytical design methods from Shigley’s Mechanical Engineering Design
