Detailed Design

Table of Contents

1 Team Vision for Detailed Design Phase
2 Prototyping, Engineering Analysis, Simulation
3 Drawings & Schematics
4 Bill of Material (BOM)
- 4.1 Indented BOM
5 Risk Assessment
6 Plans for next phase

Team Vision for Detailed Design Phase

Plans during this phase:

Get trained on CNC router and laser cutter
Test different gear profiles
Update BOM
Contract construction of wheel faces to a local woodworker
Determine acrylic mounting
Finalize design

Accomplished during this phase:

Trained on CNC router and laser cutter
Tested five different gear profiles
Updated BOM
Contacted prospective woodworkers
Updated design

Prototyping, Engineering Analysis, Simulation

Iterative activities to demonstrate feasibility, including assumptions you made in your analyses or simulations. Have you completed sufficient analysis to ensure that your design will satisfy requirements? Have you included all usage scenarios in your modeling?

We tested a selection of gear tooth profiles, Because the Trapezoidal Profile was most promising, we decided to test a couple of modifications to the profile.

The two modifications consisted of rounding the edges, and by increasing the steepness of the contact angle.

The rounded edges should decrease the irregularity of the gears, while the increased contact angle increases spacing in between teeth to help prevent binding.

After we were trained on the CNC router and Laser cutter, we cut out a set of 10 gears at half scale for testing. These gears were mounted to an axle to test meshing.

The laser cutter often did not fully penetrate the wood, even after multiple passes, later it was found out that the plywood was pressure treated. This releases toxic fumes when burned and prevented us from cutting out any more sets of gears for testing.

When the gears were added to the model, it was found that the pinions had very little spacing between each other, which may have resulted in interference. To remedy this, more teeth were added to the gear in order to decrease the total diameter and increase spacing.

Final selection consists of 24 and 48 trapezoidal tooth gears. Pitch diameters of 7 and 14 inches respectively. It is essential to leave some "play" in the meshing of the gears so that any expansion will not cause the gears to bind. Drawings documented here.

Drawings & Schematics

Note that drawings are subject to change during construction. To view finalized drawings see Customer Handoff & Final Project Documentation.

public/Detailed Design Documents/CAD/full_assembly_drawing.PNG

public/Detailed Design Documents/CAD/wheel_face.PNG

We were able to keep all holes away from the glue joints. It was later determined that this should not be an issue anyway, as glue is stronger than the wood if joined correctly.