Introduction

Charlotte Gephart

Designing and building gear-based mechanical systems with parametric modeling software and 3D printing.

Week 1

Initial project concept: reciprocating rack & pinion gear as seen here [1].

This gear will be used later as a component of a larger system (current idea is a mechanical hand with finger movements powered by the RR&P gear).

Will be studying gear geometry and designing gear system during week 2.

JOR gears from Mathematica:

Week 2

Studying Gear Geometry:

I was provided a textbook (Shigley & Uicker, McGraw-Hill Series in Mechanical Engineering) by Eric to begin examining the geometry of gears.

The key points were to discover the properties of the gear given information on other properties such as number of teeth, diametral pitch, and pitch diameter.

With a rack & pinion gear, some properties are unique, since a rack isn't shaped as a circle and therefore is imagined to have an infinitely large pitch diameter with infinitely many teeth. Properties of a rack come mostly in straight lines, with the circles present on a spur gear straightened out into lines. Additionally, the involute curves present on a spur gear's teeth are absent in a rack, once again using straight lines as opposed to curves.

Fusion 360 had an add-on spur gear tool that I wanted to explore and see if it might be useful here. After playing with it for a few hours, I feel that it may be somewhat useful, but given the very specific geometry of this particular gear system, it might be the same level of difficulty to design from scratch. I will continue to try to work out the mechanics of the tool for the design of the pinion gear, but the rack will have to be designed from scratch.

Current resources being used: [2], [3],[4], [5], [6].

As well as a cool RR&P gear system of a very different design: [7]

Week 3

This week's focus was creating the model of a basic rack & pinion gear system in Fusion 360.

I used the spur gear tool to create the pinion, then created a set of guidelines to create the rack, as seen below. Tutorial for the process here: [8].

Here is the completed rack & pinion gear system.

The next step is to print a prototype to determine if the design and calculation process was correct, then take it into the next stage of the reciprocating rack & pinion design process.

Week 4

Had a successful print of preliminary gear design!

Continued to work on creating reciprocating rack & pinion system. Will laser-cut a prototype to determine if the design is successful, then begin programming an Arduino board with a step motor to create the powered rotating part.