SmartTruck offers look inside development process of aerodynamic devices
The end result of a new product seldom resembles the initial design; through trial and error, modifications are made until the best possible outcome is achieved. That process at SmartTruck Systems proved that a meticulous eye could uncover further advantages.
“Production designs are always going to be a little bit different,” said Steve Wulff, the chief operations officer at SmartTruck.
After the initial production design had been completed, trial runs of the product began. It was imperative the team of engineers working on the components of the UnderTray system didn’t damage the performance with the production model.
Tests revealed that performance went down.
“As it turned out, in order to get these parts out of the moulding, they need a draft angle. They needed a little bit of an angle so a part would pop out of the tool. So when the tool designer went ahead and did it, he put a little angle on it,” Wulff explained.
He wasn’t sure what his constraints were, so instead of widening the top, he narrowed the bottom. “We lost area along the bottom of the UnderTray and we lost some performance.”
The result was disappointing to the team, but they went back to the drawing board to iron out the kinks.
“We rattled it out with the group and we finally figured out we needed to poke it back out and make the thing wider, run it and see what happens. We re-ran it and the performance came back. Then we thought, ‘How wide can we actually make it?’ so we went a step further and put a little more width in it,” said Wulff.
“The production, at the end of the day, had better performance than the prototype,” Wulff determined.
The vehicle is more stable, it drives easier and there is less driver fatigue, according to drivers.
“It’s more stable because the wake that is coming off the back of the trailer, which we don’t eliminate but reduce, pulses from side to side,” said Wulff. “The wake from behind the trailer is moving from right to left and when you reduce the wake, you reduce that pulse. It takes out some of the wag of the tail and it reduces some of the driver input and it drives more stable.”
The team has established that optimal performance comes from looking at the system as a whole, and not just in terms of all the parts.
“In order to be consistent with what you’re testing, you have to be at operating temperature for the units because everything in there grows and contracts with heat and cold and so bearing temperatures change, oil viscosity temperatures change – all these things stack up on top of each other and add to the overall drag on the vehicle – and not just from an aero perspective, but from a power perspective. It takes a lot more power to drive it when it’s cold,” Wulff said. “Temperature is a big variable. Fuel mileage deteriorates in the winter – everything gets cold, systems take a lot more power to operate, fuel blends change. We definitely learned more as we went along.”
The group devoted a significant amount of time to component placement. A series of tests were conducted moving the axles back and forth. All the certification testing was done at 40-feet from the axle, according to the California standard rule.
“But we also wanted to know, what is the impact as you move the axles fore and aft and is there a better place to put our component to maximize its efficiency based on where it is relative to the axles?” said Wulff.
A specific series of testing was launched – with each run taking approximately 40 minutes to complete and every time a change occurred, a new run was made – even when it is something as simple as moving an axle one foot forward or backwards.
Each test was then backed with a secondary run.
“What we found was our UnderTray component actually worked a little better further forward than what we had tested at originally,” Wulff said.
The rear bracket works optimally when mounted 23 feet from the back of the truck, but the first tests were done with the bracket at 19 feet.
The work atmosphere is very collaborative and the team welcome new ideas. But the primary idea was developing a technique to manipulate the flow of air in an effort to optimize fuel efficiency.
“Our methodology is to guide the air, not block it,” said Wulff.
While the obvious tests would include monitoring airflow, the team also worked to test the system’s impact on brake temperatures.
“We wanted to know, with a kit on the front, what happens to brake temperatures,” Wulff said. “We did the tests with just a standard unit – no kits, no skirts, nothing. We drove it and collected all the data and then at a pit stop we popped a kit on it. We ran the brakes way up in temperature and got them real hot and then we let them coast at a constant 50-60 miles per hour and didn’t touch the brake to see how quickly they cool. We found the brakes cooled better with this kit than with any other kind of treatment.”
The test results have been largely favourable and in the cases that revealed less-than-optimal outcomes, the team worked to restore the units to outcomes that met high quality standards.
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