Project summary
As co-mechanical lead of the Tufts Solar Vehicle Project, I co-designed and built a 3.3’x1.7’x11′ negative mold for our carbon fiber chassis. The process from start to finish consists of:
- Constructing a frame out of 1/2″ MDF pieces
- Cutting and bonding polyurethane foam to the frame
- Sending the combined frame+foam to a CNC shop
- Machining out the shape of the chassis
- Laying up and infusing carbon fiber to produce the chassis
Background
Our chassis is a carbon-fiber monocoque design, wherein most of the tensile and compressive loads are carried parallel to the walls of the chassis (carbon fiber is much stronger in-plane than normal to the plane). A carbon fiber chassis is much lighter than the steel space-frame chassis commonly used by formula student teams (crucial for decreasing rolling resistance in a car that only runs on ~1000W of sun power), though it is much more time-consuming and expensive to manufacture.
CAD
As with all of our TSVP designs, we CADed the mold in Onshape:
Fabrication Process
The first step was to cut the MDF pieces and glue them together.
The next step was to screw some 2×4″s underneath to make it transportable, add walls for further integrity, and finally cut and bond the foam to the frame.
Then we were ready to transport it to the CNC shop in Rhode Island!
Update as of Nov. 29: The chassis is currently sitting in the CNC shop, awaiting the next machining slot in mid-December.