Rear Subframe Redesigned and Ready for Fabrication

We have officially completed the redesigned rear subframe, which now meets the EcoCAR 2 requirements for stress and strength factors of safety.

“The redesigned rear subframe is important for a couple of reasons,” said mechanical subteam member Chris Eaton. “First, it contributes to the overall safety of our vehicle by providing structural strength and stability. Second, the redesigned rear subframe allows us to completely package our rear powertrain which is required for all modes of operation.”

While the redesigned rear subframe is just as stiff as the previous model, it is twice as strong. To achieve this, our mechanical subteam had to first determine which locations on the subframe needed the most support and where they needed to add reinforcements. Next, we had to identify which shape or geography would best fit the design criteria. Finally, we performed the required finite element analysis (FEA) to accurately represent the stress and displacement generated within the subframe while under different types of loading. 

Three stages of the redesigning process.

The finished product includes two major modifications from the original. First, we changed the angles at which the front cross member approaches the rest of the subframe from 90° to roughly 140°. This reduces stress. Second, we added a new arching cross-member, which will assist with load distribution across the rear portion of the subframe.

In addition to successfully developing a redesigned rear subframe that meets both competition and team (HEVT) requirements, this project also provided a great chance to learn.

“I have learned an immeasurable amount about the modeling, drafting, and simulation aspects of computer-aided design (CAD),” Eaton said.

We also learned about how a product moves through the design, fabrication installation phases. While working on the subframe, we reached out to professional engineers at companies like GM and Siemens, which was a great opportunity to learn and network.

With the redesigned rear subframe complete, we can now focus on testing the exhaust system to ensure that it does not leak. We will also be working on the refinement and installation of components associated with our fuel system.

“I look forward to seeing how the rest of the semester unfolds and how we favor during competition this summer. I believe that we can place well in competition if we finish out the rest of the semester on a strong note,” Eaton said.

Do you think our new design will work well at final competition? Let us know in the comments below!

#TransformationTuesay with Mary's Rear Wiring Harness

Mary the Malibu has been busy getting herself dolled up for competition lately. 

The team has been working hard on a new trunk wiring harness. Although the wiring has been functional, it was extremely disorganized and made it difficult to diagnose faults. Since we are in the refinement phase of EcoCAR 2, some of our team members suggested that something be done to clean up the wiring for serviceability, consumer acceptability also weight reduction. 

The majority of the old wiring was 20 AWG (american wire gauge) wire with thin-walled insulation. Most of the wiring in the trunk is used for signal transmission - not power - so a smaller gauge wire can be used for these connections. We purchased seven rolls of 22 AWG thin-insulation wire to replace the signal wires to reduce weight and take up less space in our trunk.

Before and after of Mary's rear wiring harness.

"I created an entirely new harness so that wire lengths could be measured away from the car," said controls subteam member Brandon Nash. "This was so I didn't interrupt the work others were doing with other parts of the car. I then created new pin-outs for every connector in the trunk as well as connectors required to make the harness fully removable." 

Once the pin-outs were up-to-date, we started to lay wire for the new harness. The final result is a smaller, lighter and entirely removable rear wiring harness. As we continue preparing Mary for final competiton, we will be able to add new wires and run them through the loom to keep them organized and as short as possible!

Emissions Testing Event Provides Important Data

The Emissions Testing Event (ETE) was a success!

We were one of the first teams to pass Safety Tech inspection out of the six teams that were at the event. The inspectors were impressed with the work we had done, but were still critical and gave us feedback on areas of improvement. 

With the help of a General Motors technician, we solved two of our biggest issues—starting our engine and fixing our brakes. The engine control module was faulting because we had modified some of the signals (e.g., the 12-volt starter) in order to take control of it. 

Mary testing on the chassis dynamometer.

Before last week, the brakes would hold pressure while driving and it was causing a lot of issues with energy consumption and drivability. We learned that the car had originally been equipped with a hill-start assist feature, which had been compromised when we modified components from the stock vehicle. 

With a running engine, the only thing standing between us and series mode is a fully operational P2 generator motor. Series mode means our engine will be running and use our P2 as a large alternator that will help to recharge our batteries while driving. There are some issues with the interference on our CAN (controller area network) bus that we are trying to work out before we can use the P2 to generate electricity. 

With the help of a Transportation Research Center technician, we were also able to test Mary on a chassis dynamometer (pictured above). We tested the electric vehicle (EV) mode on our vehicle with a few different control strategies and collected some engine starts emissions data. We will be able to use this data to validate our models and have an expectation of how we will perform at competition in June. 

A big thank you to all of the sponsors GM, TRC, Argonne National Labs and the U.S. Department of Energy who were able to help us out at ETE! 

Keep up with our Facebook and Twitter updates, and we’ll be sure to let you know when we’re running in series mode.

Innovation Under the Hood: Roanoke's Green Car Show

What is it?
Alongside Virginia Clean Cities, we are hosting an alternative fuel vehicle car show featuring the latest hybrid and electric vehicle models on the market. This will give the Roanoke community the opportunity to compare these new makes and models side-by-side. The event is intended to raise awareness of advanced vehicle technologies and increase buyer consideration of alternative fuel vehicles. 

When and where is it?
Innovation Under the Hood will be March 29, 2014, 10 a.m. - 4 p.m. on the roof of the Church Ave parking garage in Roanoke, Va. In the event of inclement weather, we will move down to a covered floor of the parking garage.

We will have presentations from the Roanoke mayor's office, Virginia Clean Cities and HEVT team leaders at 11 a.m. VCC will have a very important announcement for Roanoke hybrid and EV owners, so don't miss out!

Who will be there?
All Roanoke area car dealerships and have been invited to showcase their vehicles. This will include hybrids and electric vehicles from Chevy, Nissan, Tesla, Ford, Toyota and many more! We will have all of the major alternative fuel vehicles you have been curious about. 

2013 Tesla Model S via greencarreports.com

We are also inviting community members to display their alternative fuel vehicles and give testimonials to their worth. If you would like to put your vehicle on display, then please contact Josh Beckner (joshb1@vt.edu) for registration information.

Where can I find out more?
Like "Innovation Under the Hood" on Facebook for day-to-day updates on participating vehicles, special guests and event updates. 

Contact Josh Beckner (joshb1@vt.edu, 540-206-5937) for event logistics and Chris Bonelli (cbonelli@vt.edu, 804-814-9503) for media queries.

Tweet using #RoanokeCarShow to connect with other hybrid/EV enthusiasts and continue the conversation.

Want to see a specific vehicle there? Let us know in the comments below!

Next Stop: Transportation Research Center

Mary has left the building!

She was shipped earlier this week to the Transportation Research Center in Ohio where she will be inspected by the Safety Tech team. The team is inspecting the entire car to make sure components and subsystems are integrated safely. They will also look to confirm that there are no risks for damaging things like high voltage (HV) cables, coolant lines, etc.

Mary being loaded up for shipping.

Additionally they will inspect the functionality of some safety systems such as our HV ground fault detection, emergency stops (E-stops), charging the HV battery pack and common vehicle functions (horn, lights etc.). Our team will be arriving on site Sunday, and will be able to fix any of the issues the safety inspectors find.

Once we fully pass the inspection we will then be able to move onto the Emission Testing Event where we will set Mary up on a chassis dynamometer — essentially a treadmill for cars. This will allow us to test her different drive cycles and see what kind of tailpipe emissions she produces.

“As a whole, this event allows us to see how well Mary lowers her emissions compared to the stock vehicle” said HEVT team leader Eli White. “It allows us to tweak our control code to change some operating points of components within the vehicle to continue lowering emissions.”

Mary will be returning home to the Ware Lab around March 16th.