Mechanical Design

 

This class focused on the many steps involved in designing mechanical systems, analysis of loading, stress concentrations, fatigue, part interfaces, material properties, tolerances and failure theories. Utilizing Excel to rapidly calculate the changing specifications of a part and gain a better understanding of how slight changes in design can affect the strength of a part. As well as the use of Solidworks Finite Elements Analysis to get detailed insights into how a part may actually perform. The final project for the class was to design a single-stage reduction gearbox, the primary task was designing the shafts and then finding stock bearings, gears and other parts from various manufacturers.

Gearbox-1.png

Initial Design

This is the Solidworks model of the gearbox assembly minus the enclosure as there was not enough time in the semester to properly design one on top of the other requirements of this project. To design this we started by calculating the forces that would be generated from the given input speed of 1800 RPM and 7 Horsepower. Using those calculations we were able to find gears that could withstand those forces above the factor of safety and within the necessary gear ratio. Next preliminary calculations were done to find bearings that would be capable of supporting each shaft. Next the forces on the shaft could be calculated using the bore of the gears as an estimate for the diameter and the widths of the gear and bearings. Starting from this estimate a minimum diameter could be calculated and the resulting adjustments made to each part.

 
FOS-Gearbox2.png

Simulations

To check the calculations done in excel and by hand Finite Element Analysis simulations were run on the shafts. To the right is a minimum Factor of Safety plot, all areas in blue show that the part meets the required factor of safety of 2. This was achieved after multiple refinements of the original design as first calculated. Other simulations (von-mises stress distribution, deflection and resonant frequency) were run to ensure that the shafts wouldn’t fail in other ways and to identify weak spots that needed to be corrected.

Von-Mises Stress Distribution

Von-Mises Stress Distribution

 
 
Deflection FEA

Deflection FEA

Part of the Excel document used for calculating the forces on the shafts

Part of the Excel document used for calculating the forces on the shafts