The external enclosure. We'd love to show you the inside, but as we're told this facility doesn't even exist, we weren't exactly welcomed inside... (Photo: RCE)
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It is also worth considering the fact that the Laurel Hill tunnel is just under a mile long - not nearly long enough for a Nextel Cup car to get up to full speed under its own power (even without a restrictor plate), run at a steady state and then slow down to a stop before the tunnel ends. So we can therefore conclude that testing must be conducted at a reduced speed. Either that, or the cars are launched by a steam piston or similar device.
Basic straight line and coastdown testing are also likely applications of the tunnel, though again they would be limited by the 0.86-mile length, and the length of the escape roads and hefty tyre walls at each end suggest that some significantly higher speeds are achieved. Racecar has also leant that turntables are fitted at each end of the tunnel to allow the car to quickly rotate and drive back in the reverse direction to speed up testing.
Being in a tunnel raises some other interesting problems, best illustrated by using the example of an underground train. As the train moves through the tunnel it pushes air ahead of it, acting rather like a pump. Apparently this is not a problem at Laurel Hill though, as due to its heritage as a railway tunnel it has a large cross sectional area and a racecar a relatively small frontal area. It is still likely that some calculations have
to be done to take the effect of the tunnel walls and ceiling into account.
Try as they might, some racing items are necessary to keep outside--tire barriers are in plain sight, and empty fuel barrels have also been spied. (Photo: RCE)
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Some pictures show the tunnel doors slightly open during testing, to approximately the height of a car, but with some sort of film over the gap, perhaps to allow a car to crash through it with minimum damage.
Compared to a full-scale wind tunnel, such as the under construction Wind Shear full-scale tunnel at Concord Airport in North Carolina, a converted tunnel may have a number of advantages, not least in power consumption. Whilst a full-scale rolling road wind tunnel requires an enormous amount of electricity to operate, a converted tunnel can be run with a few generators, like Laurel Hill. Rolling road belts and fans need frequent maintenance, whereas a highway tunnel is somewhat less problematic. But the biggest advantage of all is that the converted tunnel allows you to have the car running under its own power, so the ducting and running temperatures would be realistic, while aerodynamically it's a case of a real car moving through air and over a real road, rather than the air moving over the car and a simulated road.
Whether the full details of the Laurel Hill tunnel will ever emerge is not clear but, whilst researching this feature, reports came through of a similar facility being built elsewhere, so perhaps these tunnels are here to stay.
