Why do you need a jig?

In the bike world, geometry is king. It decides if your bike is suited for pedaling up a road or flying down a rocky decent. Even the slightest change in head tube angle (a degree) can change the whole feel of a bike. Designers use specific industry accepted dimensions to tailor bikes for certain applications.

When it comes time to fabricate, it is crucial that all tubes lie in the exact positions decided during design. Without a rigid jig, it would be impossible to TIG weld everything accurately.

Design verification with Excel

I wanted verification that the jig would work for any type of bike we would want to make. To make this happen I created a design table in excel that controlled the bike geometry in the model. I could input as many bike geometries as I wanted from manufacturer websites and see how the jig would change to fit these different bikes. I tested everything from BMX bikes to downhill bikes to road bikes.

Precision Locating

In order to make our jig accurate, we had to implement techniques into the design to locate parts in precise locations. For example, we used dowel pins to line up parts whenever attaching parts with screws. We also spent a lot of time designing the sliding mechanisms to slide in only one axis (no wobble or play). All of this is to ensure our bike designs are fabricated with minimal defects, uncertainty, and guesswork.

Fabrication

We are currently in the fabrication stage. I take pride in fabricating on a manual mill and lathe. I believe fabricating your own design is an invaluable experience for any engineer. Unfortunately, fabrication progress on the jig has halted due to our machine shop being closed (COVID-19).

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