Major Qualifying Project for Worcester Polytechnic Institute
Reverse-Engineering the Parker Fly Vibrato Spring
About the Project
Parker Guitars was a music technology company popular for their electric guitar model, the Parker Fly. It was reveled by an estimated 100,000 consumers for their innovative takes on componentry, including the vibrato system and the piezoelectric pickup option. When they went out of production in 2015, it became difficult and expensive to purchase replacement vibrato springs if they broke due to normal fatigue. This project aims to reverse-engineer the vibrato spring by designing a bending machine and a heat treatment protocol to achieve the geometry and material properties required for its functionality.
This project was advised by Professors Fiona Levey and VJ Manzo of Worcester Polytechnic Institute, and conducted by Imogen Barnes, Thomas Piccione, Chloe Connolly, and I.
Bending Machines
Rotary Press
Rotary Press
Rotary Press
The rotary press is designed to achieve the s-bends on each side of the spring for all spring sizes. Its unique design addresses the >180 degree bend required for the spring to match the specifications after spring back. However, its failure during spring production caused a need for a simpler machine, the bending die, to correctly bend one spring size as proof of concept.
Bending Die
Rotary Press
Rotary Press
The bending die forms the correct s-bend and v-bend for the geometry of specifically the 10-gauge spring.
Heat Treatment
Research conducted by Katherine Burkes, Lanna Delaney, and Andrew Fauerbach concluded that the Parker Fly manufacturers produced a martensitic microstructure through a process of austenitization and quenching. Imogen Barnes and I designed a new protocol under Professor Levey's guidance that utilizes an austempering procedure instead to produce a bainitic microstructure, whose increased toughness could increase the spring's service life.
The image shown is of our spring's microstructure after austempering, taken from an optical microscope at 50X magnification. Its uniform dissolution of the carbides (white) into the ferrite (gray) qualitatively confirms a higher toughness.
