Snowspeed: Why shouldn’t a sledge go at 150mph?
The world speed record for a gravity-powered snow sledge is currently 83mph (134km/h) but three Norwegian friends who have spent much of their lives messing about in snow have a plan to beat it - by about 70mph. The first step, writes Jorn Madslien, one of the trio of speed freaks, is to make sure the sledge is the right shape.
We're all tense as we enter Toyota Motorsport's cavernous high-performance testing and development facility in Cologne, Germany.
It is an intimidating place, at least for us - three ordinary guys from Oslo.
In the control room, there's a wall of computer monitors, displaying long rows of numbers and complicated graphs.
But the engineers and technicians aren't looking at them. Instead, they watch through large windows as our vehicle is placed on a "rolling road", which simulates travel along an ordinary road.
It's black, sleek and streamlined, adorned with strips of silver tape, which means it resembles the Formula 1 and Le Mans racing cars that are normally tested here - only this is not a car with an engine and four wheels, it's a snow sledge on skis, powered by gravity alone.
Our nerves are calmed by the wind tunnel team's enthusiasm.
"This is the first time we have had a model of a snow sledge in our tunnel," says the man in charge, Antonio Pavesi. "It's an interesting project. All the guys are very excited."
Toyota Motorsport is about to give us some vital lessons in aerodynamics.
Vital, because our sledge, which we've named Snowspeed, has been designed for speeds of around 250 km/h (155 mph - faster than the terminal velocity of a free-falling skydiver in the spreadeagled belly-to-earth position.
The current world speed record in a gravity-powered snow sledge is held by Guy Martin, a British television personality, motorbiker and lorry mechanic known for his love of speed. He reached 134.36km/h (83.49mph) in 2014.
There's a saying that Norwegians are born with skis on their feet, but in truth, sledging comes first.
Norwegian babies are wrapped up warm and placed in a sledges, called a pulk, which is pulled along by parents on cross-country skis.
Then, before they can walk, toddlers are placed on toboggans, squealing with laughter and fear as they are sent flying down snowy hills.
As they get older, they graduate to ski sledges with steering wheels.
"As I child, I loved sledging. For me, that was when the dream was born," says Nima Shahinian, who became an industrial designer after serving with Norwegian special forces in Afghanistan, and designed Snowspeed with his friend and colleague, Anders Aannestad.
"The steering wheel gave me a sense of control, even at high speed. I was always desperate to have the fastest sledge in the world - or at least in our street."
Norwegian children are introduced to skis as soon as they can walk, perhaps when they are two or three years old, but it doesn't stop them enjoying other kinds of snow play.
Where I grew up on the outskirts of Oslo in the 1970s, there was a hill in a forest where we would go sledging, build jumps, or have ski races.
We'd go ice skating too, on the river at the bottom of the hill, and every year one of us would fall through the ice. We were always lucky. Nobody died. And we never told our parents.
As an adult, I have continued to enjoy winter sports, from cross-country ski mountaineering, to downhill and off-piste powder skiing.
Once, back in the 1980s, I rode a mountain bike in deep powder snow down the Grands Montets glacier in Chamonix, a foolhardy venture I decided not to repeat.
Then, in the 1990s, long before kite-skiing became an industry, I used a two-string power kite during a frosty camping trip in Norway's Rondane national park to speed up the journey across a plateau towards the peaks.
Tom Ruud, the third member of the Snowspeed team, shares this passion for speed, ideally coupled with good design, which explains why he's acquired a couple of Riva speedboats over the years.
But for Tom, a serial entrepreneur who has launched and sold several companies, it is mostly about beating records and taking on the role of David challenging Goliath.
"I love the thrill of the race," he says. "I like the rush from being in a challenger's position."
It's taken four years to get from Nima's initial drawings to where we are today.
Three prototypes have been built. A full-size sledge to determine the pilot's position, a 25%-scale clay model to recreate the shapes developed using 3D drawing programmes, and the latest - a 50%-scale model built specifically for testing in the wind tunnel.
The idea is to investigate the sledge's aerodynamic performance by generating a strong wind that passes over, under and alongside it, while measuring drag, downforce and sideforce, plus the three movements, roll, pitch and yaw.
When cars are tested on the rolling road, their wheels rotate while the car remains static. This obviously doesn't work for the sledge, so instead we've covered the base of the skis in Teflon to simulate the sort of minimal friction we expect to experience on snow.
I've seen wind tunnels before, as I've been reporting on the motor industry for some 20 years, but I've never before been inside one during testing.
The sledge is attached to a strut that comes down from the ceiling. The strut contains hundreds of pressure sensors that gather data, as well as "actuators" that move the model during testing.
You can't see the wind moving past the sledge at 40m per second, but all the time the sensors are picking up crucial information about how the sledge responds to the wind, and how the wind moves around it.
Later, the crew injects smoke, which allows the designers to see some of this with their own eyes.
Then they apply a special type of paint that runs with the wind to create streaks and patterns that mirror turbulence and flow.
The process is filmed and photographed for later analysis.
It will take some time to complete the analysis of the test data, but we already know a few things.
For a start, the front end of the sledge, with its broad shoulders and flat surface raised above the snow, provides strong downforce on to the skis, which are fitted on either side with a suspension system. That is a good thing.
But the back end is unstable - it needs to be stretched and flattened further to improve sideways stability.
At high speed this prototype would have been almost impossible to control.
We must also find a way to increase the downforce on the rear ski. A spoiler might provide the answer, says Nima, who has worked on cars of the Lotus/Caterham Seven racing class and the Ferrari-based hydrogen supercar concept Fyk, developed by Norwegian energy company Statoil.
I, for one, like this solution, as it will make the sledge look more like a racing car.
With valuable lessons learned, our time in the tunnel is coming to an end.
We know that we still have a lot to work out, so we quiz the engineers about composite materials, suspensions and aerodynamics.
Together we mull over the choice between short skis, which offer less friction, and long skis, which are more stable at speed.
In turn, they ask enthusiastically about our plans as we move towards an attempt at the world speed record next year.
I would like to see some of them out there on the snow, when I hope our dream will become reality.