Ford builds a portable wind tunnel — just not small enough for DIYers (yet) – ExtremeTech
What in an election year could be more appropriate than a portable wind machine? Ford has developed a portable wind tunnel that can be quickly set up and used at Ford factories to test early production cars for wind noise issues, apply tentative fixes, and quickly verify the cars are indeed meeting design specs for quietness. Customers have come to expect much quieter cars, and not just on big, expensive sedans costing $75,000. Ford calls the device a mobile aeroacoustic wind tunnel.
“Portable” is a relative term. The wind tunnel comprises a pair of 53-foot shipping containers plus a 40-foot office and power distribution container. Once the containers are onsite at a new facility, the system can be up and running in just a couple hours. Stationary wind tunnels are often several stories high often with an underground air return level and, Ford says, can cost $50 million. Surprisingly, they are not — unlike some Election 2016 two-legged wind machines — all that noisy.
80 mph of wind delivered to the factory park lot
In North America, Ford has several plants in Michigan, but also in Illinois, Kentucky, Missouri, Ohio; Ontario, Canada, and Cuautitlán and Hermosillo, Mexico. Ford wants wind tunnels onsite for immediate feedback, especially as new production ramps up, rather than shipping early-production cars back to Allen Park (MI) and Ford’s main, stationary wind tunnel. So, Ford engineers conceived and created a mobile aeroacoustic wind tunnel and has even applied for a patent — suggesting either Ford might sell the devices to other automakers, or at least keep them from knocking off Ford’s design without paying royalties.
When the mobile wind tunnel arrives on site, the two 53-foot containers are placed side-by-side on level asphalt or concrete, fastened together, and two roll-up doors between the containers are opened, sort of like creating a double-wide mobile home. Only, inside these units there are aeroacoustic vanes and internal ducting the provide smooth airflow at the car end of the device. There are also doors at each end.
At the back end (away from the airflow) are two six-foot-diameter ducted fans, each with 16 blades. Each fan is driven by a 250-hp electric motor capable of delivering up to 80 mph of evenly directed air, meaning there’s little or no swirling, in order to emulate the air flowing over the car when it’s traveling on a highway.
The smaller, 40-foot container (inset with the white windows) has a small office, power distribution, and controls. To power each fan, there’s a 100-foot cable weighing 1,080 pounds or about 100-pounds per foot. The plug alone weights 40 pounds. Ford says the three containers can be prepared for delivery to a different site in a single day, then set up and be ready for use in a couple hours.
What the wind tunnels do
Stationary wind tunnels test all manner of features in the development stage, such as how the body design, side mirrors, grilles, roof racks, and even windshield wipers affect the car’s coefficient of drag, or cD. They also help engineers measure interior noise on the prototype cars.
The purpose of the mobile tunnel is to take the testing where cars are being built. A Ford technician can drive a car off the production line to the device and run tests to see how close the car meets the design specs for interior noise at speed. The smoke wand in the main photo shows how the wind flows over and around an element of the car; it’s not adding any wind velocity. Using the feedback from the test results, Ford can make adjustments to product processes in real time, as well as provide feedback if a piece of trim needs adjustment or reformulation. Over 50 years, the expectation for quiet in cars has gone from only the most expensive vehicles — Rolls-Royce circa 1960 proclaimed, “At 60 miles an hour the loudest noise in this new Rolls-Royce comes from the electric clock” — to big sedans down to compact cars with base prices around $20,000. The average selling price of a new car today is about $34,000, according to Kelly Blue Book.
One intriguing aspect of a wind tunnel is that it’s not very noisy. Visitors to a wind tunnel can stand a few feet away from the car and converse in almost normal voices. Inside the car it’s only as noisy as a car going 60, 70 or 80 mph. Actually, quieter, because there’s no road (not wind) noise — the wheels, if they’re moving, are on steel rollers, not asphalt or concrete. For the mobile wind tunnel, Ford rates noise a distance of six feet as 75 decibels, or the same as a (landline) telephone dial tone. For those who remember landline phones.