We huddled in a tight circle by the finish line, frantically waiting for radio updates on the progress of our team’s rider, Rob “Bullet” Barber, who was miles in the distance and closing fast. Our 11-person team of student engineers and support crew from The Ohio State University could hardly breathe as we got the report: Barber was battling for third place—a podium finish—in the TT Zero class for electric racing motorcycles at the 2014 Isle of Man TT.
Barber was aboard our latest race bike, the RW-2.X, designed and built by the OSU College of Engineering team, known as Buckeye Current. We’d brought it over 3600 mi (5700 km) to the Isle of Man, the iconic road-racing mecca in the middle of the Irish Sea. We aimed to prove our engineering and technology against the best electric bikes on the fast and treacherous public road—37.75-mi (60.75 km) per lap—that is the world’s most unforgiving race circuit.
Finally came a rider, tucked in tight behind the fairing. He whooshed past us almost silently down the front straight—but it was Robert Wilson of the professional Saroleá team from Belgium. He crossed the finish line amidst cheers from his team. Then came an eternity for OSU, as we caught sight of our man Barber approaching. He tore across the line—and confusion reigned.
The TT races pit competitors against the clock rather than against each other, and the timing app coming over the radio had our bike finishing third by a split second, ahead of Wilson. But the Saroleá rider was wheeled into the victory circle. We were shocked. For the next five minutes we waited in suspense. Then came the radio report with the official finishing order—and an immediate fist-pump from our staff advisor: the RW-2.X finished third by 0.37 s, with lap speed of 93.5 mph (150 km/h).
OSU team leader Polina Brodsky remembers the euphoric walk to the winner’s circle as “a mess of embraces and tears and laughs and love." Our underdog college team from Ohio had scored a hard-won third place finish in the TT Zero (so named for zero emissions) for the second consecutive year. We did it on a shoestring budget and beat a number of professional, better-financed teams.
Faster, lighter, smarter
When the Isle of Man TT organizers announced the new all-electric race class in 2010, EV and motorcycle enthusiasts at OSU quickly banded together to form a race team through the Center for Automotive Research. Unfortunately, our first race bike, the RW-1, never made it to the TT due to battery issues (after we showed it to President Obama during his 2012 visit to CAR). Still, we managed to set the East Coast Timing Association’s top speed record at 144 mph (232 km/h) in the flying mile.
With the knowledge gained from RW-1, we again set our sights on the Isle of Man for the 2013 TT Zero, in which electric bikes get a single 37.75-mi lap on one charge. (By comparison the Senior TT race for gasoline-fueled bikes runs six laps, or 236 mi/380 km). In our first appearance there, our new RW-2 with “Bullet” in the saddle shocked the competition with a third-place finish. It was a narrow victory over Kingston University of London, the reigning collegiate champ. Our average speed over the single lap was 90.4 mph (145 km/h), a record for the university entrants.
For an on-bike video of the pre-2013 TT test at the Transportation Research Center in Ohio: http://www.enstroj.si/Videos/videothe-ohio-state-universitys-current-electric-motorcycle-test.html
We returned to the States determined to prove our 2013 podium finish was no fluke. Instead of starting from scratch, our 25-strong engineering team chose to rebuild RW-2 and make it faster, lighter, and smarter. The revised bike was dubbed RW-2.X, a cheeky reference to version control protocol. The new design featured many carryover components, including the Honda CBR frame, which was reinforced to replace the 1.0-L combustion engine that serves as a stressed member in the production bike. We made many other major modifications to the bike's suspension, aerodynamics, electrical systems, and packaging.
SIMba: secret development tool
When designing a racing bike on a limited budget, it is important to understand where the most efficient investment of time and money will optimize performance. In order to analyze the design, the team built an in-house simulation tool, SIMba, to model the machine through the race course. By quantifying the race, we could uncover the critical parameters for success (i.e., weight, energy use, aerodynamics, cooling, vehicle dynamics) and determine what needed to be improved.
SIMba showed us that lean angle, aerodynamics, and energy-to-weight ratio were critical to success in the TT Zero. As Rob leaned the behemoth RW-2 over through the corners in 2013, the suspension bottomed out, causing the road to carve through our bottom fairing and send a shower of sparks. To prevent this and pack more energy on board, we redesigned the battery pack, with additional cells.
The new, more compact design enabled us to increase the bike’s lean angle an additional 9°, which was critical for maintaining momentum through the famous TT course’s 264 corners. To keep all 589 lb (267 kg) of bike off the ground, we used the stiffest racing-grade suspension available. Also, brand new, lightweight fairings shaved pounds while reducing our aerodynamic drag, which SIMba showed to be one of the most critical parameters.
A key to the RW-2.X's powerful, reliable electric drivetrain is its Emrax 228 HV traction motor, designed for an electric glider aircraft. It is supplied by Enstroj, a Slovenia-based e-motor specialist company. This high-voltage, 3-phase, air/liquid-cooled brushless synchronous AC machine features a pancake axial-flux design and a rotor of 228 mm (8.98 in) diameter. The motor is very light (12.3 kg/27.1 lb) and power-dense (both weight- and volume-efficient). Delivering up to 96% efficiency and rated at 120 N·m (88 lb·ft) continuous/240 N·m (177 lb·ft) peak up to 5000 rpm, it allows additional space and weight for batteries for the energy necessary to complete the 37.75-mi lap in a single charge.
One of our team's proudest achievements is the completely custom electrical monitoring system, developed in-house, that regulates and quantifies the bike. The battery pack especially requires careful monitoring to ensure no cell is over-charged or over-depleted. This data is also valuable for analyzing the performance of the pack throughout the race. In addition, the system features an advanced array of sensors that record key information, from suspension travel to coolant temperature.
Much of the RW-2.X build was the result of parts and services provided at little or no cost, including battery-management system hardware from Texas Instruments, and the battery cells from AEE. Other sponsors, including the Honda-OSU Partnership, Lawless Industries, and RRW Engineering, graciously stepped in to provide logistics support and cover other key costs.
In typical college style, the build phase came down to an 11th-hour, sleep-deprived crunch after nine months of design and building. After testing the bike, shipping it was a project in itself. Getting lithium batteries, along with other gear, through customs required meticulous tracking of every tool and part in the crate. Finally, we sent it on its month-long ocean voyage—just in time to cram our neglected coursework for finals—before 11 of us would fly over and get on with racing.
Battling the battery demons
From the moment we arrived in picturesque Douglas, the Island’s main city, to unpack and prep the bike, trouble plagued the team. On the first night, a short in the battery pack, caused by debris during shipping, sent up a cloud of smoke and required a long night of troubleshooting and repairs. The day came for Rob to try the new design against the course for his first practice lap. The bike performed astonishingly well and he placed second. But our excitement turned to dismay as we discovered an issue in the battery pack.
During the jarring ride, several of the 55 lithium nickel-manganese cobalt oxide (Li-NCM) cells were damaged. The team spent the night devising a quick, innovative solution to change the packaging of the cells and prevent a recurrence. Just to be safe, we elected not to run in the two remaining practice laps to spare the batteries from additional harm. Continuing the theme of bad luck, both of our battery chargers broke as we recharged the pack. Luckily, ARC EV, another race team, was kind enough to let us borrow theirs. Even in this competitive field, everybody is still in it for the advancement of the technology and a good race.
A year of hard work came down to one lap. The team assembled and made the bold decision to go all in. Rob was going to run that pack into the ground and squeeze every bit of power out of it, no matter the cost. After thorough analysis, we aggressively geared the bike so that there would be nothing left “in the tank” as Rob crossed the line. We were going to finish third or not cross the line.
Next stop: the 2015 Pike’s Peak International Hill Climb, where OSU hopes to crush the gasoline competitors and beat the Lighting Superbike record of 9 min 52 s, held by a Ducati Multistrada 1200.
Brendan Kelly, a fifth-year graduating senior at Ohio State University studying industrial systems engineering with a minor in entrepreneurship, wrote this article for MOMENTUM. As a freshman he joined the Buckeye Current e-bike team in its inaugural year. He served as Business Manager for the 2013 racing season and Team Lead of Marketing in 2014.Continue reading »