Dreary, grainy autocross ridealong
DARTMOUTH FORMULA RACING – an overview
June 2012 - May2014
In the summer of 2012, I sat down in a professor's office with six other students, and, unexpectedly, we were given free rein of the Dartmouth Formula Racing team. At the time, it was a well-established program, but one that completely lacked continuity of membership or leadership. So, as rising juniors, we were in charge. With little knowledge but a lot of enthusiasm, we took home a first place trophy in the All-Electric class at the Formula Hybrid Competition in May 2014.
0 - 60 MPH IN 18 MONTHS
Beyond the aesthetic and practical appeal (its simplicity, its instantaneous torque) of an all-electric racecar, we thought (and we still think) that electrical vehicles will play the central role in transportation, racing, and recreation. An early partnership with the brilliant team at Mission Electric established our drivetrain: we built the car around an 85 kW, 120 Nm permanent magnet protoype motor, and now (I'm thrilled to say) the rest is history.
The galleries below are a more in-depth view of the parts of the car I was responsible for.
DARTMOUTH FORMULA RACING – chassis design and fabrication
January 2013 - May 2014
Using the custom suspension geometry developed by the team (and carefully following the Formula Hybrid Competition rules), I designed tubular space-frame chassis constructed from 4130 alloy steel. Optimized for minimal weight and maximum torsional stiffness, the completed chassis came in under 90 pounds and with a theoretically modelled torsional stiffness exceeding 2000 Nm/degree.
Beginning in the winter, I created numerous iterations of the design to account for driver comfort, center of gravity, powertrain packaging, load transfer, and manufacturability, while still meeting the critical weight and stiffness specifications. Design reviews with professors and professionals proved immensely helpful throughout the process – coming at the project without experience meant that every design decision had be researched and cross-checked along the way. It was intensely educational and, eventually, exhausting.
Along with the chassis itself, I also designed an aluminum jig table to fix each major tube in place during welding, both for ease of fabrication and to minimize warping. Each aluminum was rotated and cut to a specific angle to account for the precise position of the tube.
While the design and, later, jig construction was underway, I spent the rest of my time practicing TIG welding. By the time the tubes had arrived (CNC mitred and bent by Catesian) and the jig was completed, I had 50 hours of experience and, with one other experienced welder on the team (the multi-talented Will Jewett) we began the 200+ hour project of welding the chassis in house. The location of the suspension mounts, the critical points for the project, were all accurate easily within an eighth-inch.
DARTMOUTH FORMULA RACING
upright and wheel assembly design and fabrication
Febraury 2014 - May 2014
While the chassis design and fabrication had strict safety regulations built into the rules, the uprights allowed for much more freedom to design and optimize. This time designing with Mr. Jewett, I created an all-new welded steel upright design; in recent memory the Dartmouth Formula Racing team has modelled billet aluminum uprights and sent them out to be machined. Searching for lighter weight and increased stiffness and factor of safety, we turned to steel.
We again designed iteratively, checking in frequently with our advisors, until we finalized a design that kept critical unsprung weight below 3 pounds in each corner while maintaining a 2.5 factor of safety. Forces on the upright were modelled for a worst-case scenario combination of 3g breaking, 1g turning, and 5g bump forces.
The upright consists of four main parts to be welded: the hub (which houses the tapered roller wheel bearings and a hall-effect sensor), the two central plates (which span the upright and form the brake caliper mount), the upper and lower outer rims (which fit around the other components to lend strength), and the machined bottom mount. We had these parts waterjet cut from 4130 sheet steel and bent them in-house. After welding, we sandblasted the uprights and sent them out to be heat-treated. Finally, we machined bearing races and could move on to assembly.
Following the final design of the uprights, we also designed and built the rest of the components for the wheel assembly: the spindles to transfer power from the driveshaft to the wheel, adapter plates between shafts and spindles, adapter plates to mate the rotor and the caliper precisely, and clevis mounts for control arms.