After building my steel gravel bike I fell in love with riding my bike. Simultaneously, I wanted a faster bike and a new challenge for my design and manufacturing skills. Inspired by many other bike builders, I decided to build a primarily carbon fiber bike. 

I went through many different iterations of CAD. Originally I planned on using all aluminum lugs and carbon fiber tubes, and a standard seat-stay top-tube joint. However, as the design grew the seat-stay separated from the top tube and dropped down, and the head tube was changed to a carbon fiber design.  The CAD was constructed in Solidworks primarily using surface modeling tools as a single body, and then split up into the individual parts afterwards. 

through the design process, I 3d printed dozens of parts and a couple full frames to ensure that the design is exactly how I wanted it. working with aesthetic models like this is difficult in the computer,  and holding it in person makes it much more clear. 

The machining for the bike parts was not trivial, requiring many different techniques. The seat mast topper (above) was  machined on the 4th axis on the tormach, and then the center was cored out on the lathe with a boring bar. The bottom bracket (bellow) was machined in the EMCO using a manual dividing head by swapping around to different angles for each area of the part.  For the second operation of many of the parts, 3d printed soft jaws were used to hold and locate the part. One note is that as the part heats up, the PLA soft jaws will soften, so in the fuitre I would resin print the jaws to prevent this 

The chainstay and head tube where both made in the same way, machining an aluminum mold and then laying prepreg carbon fiber into it. The layup is then compressed against the outside of the mold with an inflatable bladder that is pressurized while curing. The molds where machined with a 3d steep and shallow toolp ath and sanded afterward to 400 grit finish. 

The carbon fiber tubes for the top tube, downtube, seat stays, and seat tube where all made using a CNC filament winder. This device lays a continuous carbon fiber filament down as it rotates the tube mandrel to accurately place each strand of fiber. The mandrel for this process where made on the late, except for the top tube of the bike witch is triangular in cross section. For this, a 3d printed mandrel was used. 

The rear dropouts would have been extremely difficult to machine, and for that reason, they where metal 3d printed in aluminum using PCBway's online services. 

Once all the parts were manufactured, they where assembled in the frame jig. The frame jog allows you to fine tune the fit of all the parts before they go together. It also ensures accuracy of the final bike by holding each of the datums of the bike in the proper location while building. To connect all the parts, 3M DP 420 epoxy was used, with microscopic glass beads used in the aluminum to carbon fiber joints to prevent galvanic corrosion.  

The final bike is exactly how I wanted it to turn out. Compared to my last bike, it is stiffer, lighter, and better looking. I could not be happier with the final result 

Funded and supported by the Invention Studio at Georgia Tech student organization