One bolt to go.
Just getting the wrench on the bolt was tough enough with the crowd of people around the 2016 Chevy Camaro. Two team members were holding the door in place, and a third was crouched under them, using her cellphone as a flashlight to illuminate the bolt head. Squeezed between all of them, grad student Andrew Huster couldn’t get enough torque on the wrench to get the bolt to turn.
Power tools to the rescue.
With a pneumatic torque wrench in hand, followed by that pit-crew whine of turning metal, the door was free. The guys who’d been holding it up carried it out of the garage for storage. For the next few weeks, teams will be tearing out the muscle car’s electronic and mechanical systems, so those doors would just be in the way.
Staying on top
On a cold Saturday morning, when fellow students were sleeping in, about 40 students crowd the garage at The Ohio State University’s (OSU) Center for Automotive Research (CAR) with one goal in mind – tear apart the Camaro so they can rebuild it as a plug-in hybrid. If all goes well, the green muscle car will show that energy efficient, fast, and affordable fit together. That’s the goal of the EcoCAR 3 challenge, a collaboration between General Motors and the U.S. Department of Energy that pits college teams against each other to design efficient vehicles of the future.
The OSU team won EcoCAR 2 in 2014, converting a Chevy Malibu into a plug-in hybrid model. And they won the first year of the four-year EcoCAR 3 challenge last year. M.J. Yatsko, team leader with experience from EcoCAR 2 and internships with GM Cummins under her belt, leads the effort, knows that the pressure is on to repeat 2014’s win.
“Everybody has a real sense of urgency to get this put together. We have a legacy to defend,” Yatsko says.
At first glance, the team’s approach appears similar to what it did with the Malibu – add electric motors, a battery pack, and control systems to the vehicle so it can operate as an electric car some of the time and as a gas-electric hybrid model when the battery runs out of juice. But the differences between doing that in a Malibu and a Camaro are significant, Yatsko says. Customers don’t expect wheel-spinning performance from a family sedan. The Camaro, on the other hand, demands performance.
“If the customer wanted to flip the switch and floor it, they’ll get that acceleration they’re expecting from a Camaro,” Yatsko says.
The team’s target is zero to 60mph in 5.6 seconds, while keeping the car as affordable as possible.
Learning by doing
“Here’s the problem,” says the engineering student who had been using her phone as a light and now has the bolt that didn’t want to turn is in her hand. “It looks like they covered it in Loctite or something to keep that bolt from moving.”
Turns out that she was right.
GM spokeswoman Erin Davis explains that the check-link bolt is what stops the door from swinging a full 180º and hitting its own fender. GM coats all such bolts with adhesives to ensure a good connection and avoid any potential rattles.
“The average customer would not be taking off the door. Body shops, dealerships, and the plant have training and tools to do so if needed in process or for repair,” Davis says.
No matter how much theory they learn in the classroom, getting the hands-on feeling of a sticky bolt drives home the detail-oriented nature of the field the students are pursuing.
Once finished, OSU’s EcoCAR Camaro will have two propulsion systems – a 2L, 4-cylinder gasoline engine mated to a 32kW belt-alternator starter (BAS) from Denso, creating a hybrid electric mode, and a 150kW electric motor from Parker Hannifin (double the power output of the 2017 Chevy Volt) with energy storage from an A123 Systems 18.9kWh battery.
Andrew Huster, electrical and innovation team lead and a second-year grad student in electrical engineering, says the two electrical systems allow the team to use different propulsion systems for different tasks. The BAS provides start-stop capabilities, allowing the engine to shut off at stoplights or in stop-and-go traffic. That leaves the big electric motor to handle vehicle propulsion at higher speeds.
“The power demands we have drove some decisions. It was easier to do a rear-wheel drive system because our only high-current path is from the battery to the electric motor,” Huster says.
Yatsko says unlike EcoCAR 2, teams rebuilding the Camaro can use different drive modes, and the OSU team plans to make the most of that change. In performance mode, drivers can mash down the accelerator and get neck-snapping leaps off the starting line. In economy mode, they can keep the car in electric mode for virtually all daily driving tasks, avoiding the need for gasoline.
One enabler of that design was a 5-speed manual gearbox from Tremec that the team plans to automate.
“We want to tune our shift maps for the different driving modes. We couldn’t do that on the automatics,” Yatsko says. “The manual that we chose is very simple, so it gives us a lot of control.”
The bolt is free from the vehicle, so what to do you do with a car door? It’s not going back onto the Camaro until powertrain, electrical, and instrumentation changes are finished, and that’s going to take months.
“Do we have any blankets we can wrap it in?” one student asks.
With no long-term solution, they prop it against a desk in the CAR classroom.
It’s not an ideal resting place. Students filter in and out of the room, dropping off backpacks, bringing in Chipotle from a lunch run, and just hanging out to talk. Any one of them could accidentally knock it over. A few minutes later, the passenger-side door enters the room and gets propped up against another desk.
“Where’s the bubble wrap? We should have a big roll of bubble wrap in the warehouse. It’s pink or purple,” Yatsko tells a student. Minutes later her cell phone buzzes. “It must be on one of the top shelves. Get a ladder.”
Covered in layers of pink bubble wrap, the doors are ready for storage.
Solutions for every problem
Having electric motors and batteries take over engine functions minimizes fuel use, but it creates weight problems. GM engineers designed the Camaro with a 50-50 weight balance, with half of the vehicle’s weight over the front axle and half over the rear. For performance drivers, that makes the car easy to whip around curves.
Adding massive batteries and a 150kW electric motor to the rear end of the car throws off the weight distribution.
“After we added the batteries to the rear end, the balance was closer to 53-47,” says Brielle Reiff, team lead for vehicle dynamics and suspension and a mechanical engineering student in a combined graduate/undergraduate program. “The premise of the project is to have a performance car, so handling is very important.”
Reiff’s team plans to add bigger tires to the rear wheels, and they’re redesigning a sway bar in the suspension to handle the weight and leave room for the motor and battery pack.
“It’s a lot easier to accommodate batteries when you can put them through the floor of the vehicle,” as Chevy is doing with the Bolt and Volt and Tesla does with its vehicles, Reiff adds. “Retrofitting an existing design has its challenges.”
In a nearby lab filled with electrical equipment, another team works on the controls for the BAS and electric motors. Programming the supervisory controller that will handle the hand-offs between different propulsion systems will be one of the team’s biggest tasks.
Dennis Kibalama, an electrical engineering master’s degree student from Uganda and electrical propulsion subteam leader, turns the electrical drive unit in the BAS by hand to get power output data that will be used in programming.
“We need to get the BAS to communicate with the power inverter, so we can program the system to our needs,” Kibalama says. “We have to understand the capabilities and the performance of every component before we get it all working together.”
Putting it all together
Weeks of testing components and studying the performance of each switch are done. This is what the team’s been waiting for since it got its car in December - tearing the Camaro apart and rebuilding it.
Every Saturday, they’ll be back in the garage. The team’s goal is to have the car put back together and functional by the spring, when the engine, transmission, batteries, and other powertrain components should be in place. They’ll test power output at CAR labs and start tweaking various systems.
“We have a couple of weeks of testing set aside in our schedule,” Yatsko says between delegating tasks to team members and answering questions from students with significantly less automotive experience than she’s earned. “We have another two years in the program to refine everything and get as much performance as we can out of the car.”
The Ohio State University EcoCAR 3
U.S. Department of Energy
About the author: Robert Schoenberger is the editor of TMV and can be reached at 216.393.0271 or firstname.lastname@example.org.