One of the most defining characteristics of a Formula SAE Racecar is their impressive acceleration. As these cars are primarily designed as autocross cars, acceleration out of tight corners is a critical performance metric, since the cars will not have much opportunity to build speed before reaching the next corner. As a result, FSAE cars tend to have relatively low top speeds (in the range of 70-100 mph) with relatively fast acceleration (0-60 often between 4 and 5 seconds). Due to the strict air restriction rules for the powertrain, the maximum power output of an internal combustion car is limited to around 80-90 horsepower (a range which many teams at competition are able to reach), so the transmission and shifting setup will ultimately be what separates a slower accelerating car from a faster, more competitive one.

A perfect case study for the difference which a fast transmission can make is with our team's TR24 car. Thanks to my work on the system, this was our team's first ever car to feature (and exclusively rely upon) an electronically controlled shifting system rather than a more traditional hand actuated lever. Due to the car's intake design, we only produced around 60 horsepower at the wheels whereas some our competitors made over 80. Despite this, thanks to the speed of our shifting system the car was able to place 15th in the acceleration event (out of 120 teams) and was only 2 tenths of a second off of the winning time. Compared to TR22 (the most recent comparable Terps Racing car with a shifting lever setup), the system resulted in a 0.583 second or 11.5% improvement.

TR25 featured further refinements to the shifting system including more aggressive ignition cut timing and longer gearing, combined with an estimated power output of 75-80 horsepower, and TR26 targeted reliability improvements to the pneumatic system to reduce leaks that would occasionally happen in the actuation system.

Pneumatic Shifting was a system the team had been attempting to implement for several years before I joined. For the duration of their attempts, the system had seldom if ever worked properly, typically due to electrical issues regarding how the system was controlled. When I took charge of the project, the system was being controlled using an Arduino, with separate connections to the steering wheel's paddle shifters and to the car's ECU. This system had numerous issues, most notably that the Arduinos had a tendency to completely burn out or otherwise behave unpredictably, making the system unreliable at best and dangerous to the car at worst.

The key change I implemented was to migrate the system to be controlled entirely by the ECU. The unit's digital inputs detected the paddle shifters on the steering wheel, and its digital outputs were connected to a set of mechanical relays which actuated the 24V air solenoid, performing the mechanical action of changing the engine's gear. This also worked much better than the previous system for implementing ignition cuts during upshifting, allowing the driver to shift without removing their foot from the throttle. Running the system this way also allows the implementation of automatic-upshifting, meaning that the car can automatically change gears at a pre-determined RPM, making acceleration even faster and more consistent.

All of this only works due to our engine's combination of sequential gearbox and dog-tooth transmission, meaning that shifting can be performed with a simple forwards/backwards piston and with no clutch operation required (if set up properly).

Moving forward with TR25, I further refined and tuned the system in tandem with the powertrain team. This included a closer analysis of engine power output vs RPM and a redesign of our final drive ratio. Our new intake and exhaust design meant we made almost 20 extra horsepower (from ~60 to ~77), which meant that our gearing needed to be longer. This meant that fewer shifts were needed over the course of an acceleration run, which means there is less opportunity for the system to malfunction and less time spent cutting ignition due to needing to shift. 

In addition to performance, one of the largest motivating factors for pneumatic shifting comes down to space and volume. Lever-based shifting systems require hardware strong enough to withstand an adrenaline-filled driver frantically moving their hands to/from the shifter. This system has to be both physically accessible to the driver and unintrusive when not in operation. Our team tends to use a very small cockpit/chassis space, even as far as the small footprint of an FSAE car goes, meaning that fitting such a system in the cockpit is a very difficult challenge. This means that a working paddle shifter system is as much of a necessity as it is a performance benefit, as it allows us to save the space required by a bulkier lever (plus the driver can keep their hands on the steering wheel while changing gears).

I also chose to implement a wired steering wheel quick-release to go along with the shifting design, as previous steering wheel electronics had been handled by a cable attached to the wheel externally. The introduction of a wired quick release allows the electronics in the steering wheel to be disconnected along with the rest of the steering wheel, rather than a separate cable which needs to be unplugged each time the wheel is removed. Implementation required a modification of the car's steering column to allow for the wires to exit, and on TR25 this "modification" became a fully considered element of the column design.