Ballista Analysis

Reef Sweeney

About The Project

In my Engineering class, I have been been making a medieval Ballista. In this project I will use solidworks simulations and an excel analysis to optimize the specifications for a full-sized ballista model.

Simulations

Create Model

Determine Points of Weakness

Input Fixed, Load, and Material Information

Analyze Stress-Strain Charts

Rail Simulation Results

The stress-strain analysis indicated that this piece would have a breaking point at 2356.3N. We improved the design for greater strength.

Frame Simulation Results

The stress-strain analysis indicated that this piece would have a breaking point at 20603.9N. This ended up being of satisfactory strength.

Analysis

The goal of this analysis is to optimize the length of the arms of the Ballista. This was done by using physics equations to relate the variables and then creating an iterative spreadsheet to eliminate time. The idea was to find exit velocity given different arm lengths to find which one works the best.

Determining Relationships

Final Equation

To create the spreadsheet, I also needed a second equation to relate A and alpha. This was found as the second derivative of the relationship between x and theta.

Creating Spreadsheet

Variable Flowchart

This flowchart demonstrates how each variable is defined in reference to all of the other variables in the spreadsheet. It also shows the equations that will be used to find each one from the previous.

The State of the Project

The incredibly long nature of the equations that were used in my project made it almost impossible to troubleshoot. Ultimately, the acceleration, velocity, and position functions ended up oscillating in a way that they were not supposed to. I was unable to discover what caused this.