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Para-sailing dune buggy. - Adventures in Engineering — LiveJournal
The wanderings of a modern ronin.

Ben Cantrick
  Date: 2008-11-10 18:22
  Subject:   Para-sailing dune buggy.
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A workable flying car has been the inventors’ holy grail for half a century, but the reality has remained elusive. Just ask Paul Moller, the Canadian engineer whose four-seater Skycar is still at the prototype stage after 40 years and more than £100m of development.

Cardozo, a self-taught engineer with a tiny fraction of that budget, thinks he may finally have cracked it. "I’ve been dreaming about making flying cars since I was a boy," he says, "thinking about all the ways it could be done and seeing how all the other people in the world have done it wrong. No one’s ever made one that really does work that you can go out and buy. But here’s the ultimate solution: it’s cheap, it’s safe, it works, all the technology’s already there." Without recent advances in flexible wing technology, the idea would barely have got off the ground. New aerodynamic profiles and materials make it possible to lift a vehicle weighing 1,500lb and passengers without dangerous instability.

Fully road-legal - the car passed the government’s single vehicle approval test last month - and designed to run on bioethanol, Cardozo’s Skycar is powered by a modified 140bhp Yamaha R1 superbike engine with a lightweight automatic CVT (continuously variable transmission) gear-box from a snowmobile. It boasts Ferrari-beating acceleration on land, an air speed of up to 80mph and can swap between road and flight modes in minutes. "The fan’s static when you’re driving around," says Cardozo. "The engineering challenge was getting a really reliable system that will switch power between wheels or fan." If the buggy’s 1000cc engine fails in the air, the machine is designed to glide back to earth for an emergency landing, like any aircraft. But it’s also equipped with an emergency, rocket-launched parachute in case the canopy collapses.


http://www.timesonline.co.uk/tol/driving/features/article5106213.ece

We've had working flying cars since the Taylor Aerocar in 1949. The problem has always been that they're too expensive. The Moller M400 works fine, if you have the $3 million to buy one. I really like this design though, primarily for its simplicity and its (relative) failure-safety. If the motor goes, you just glide back to earth on the parachute that you already have deployed.

The big problem here is the same as it is for any aircraft - weight. Part of it is frame weight, and there's only so much you can do about that. You have to have a frame strong enough to make the car part of things work. But I wonder if he wouldn't be better off ditching the piston engine and going for a small turbine. The power to weight ratio would be a lot better and it could run off biodiesel, which has higher energy density (= more MPG) than ethanol.

A Solar T62-A2 seems like a good one. 20"x26", 71 lbs, 95 hp. When the car's in the air, the turbine can drive the fan. When the car's on the ground, it can spin a generator to drive electric motors. Which are lighter per HP than a piston engine for many reasons, including that you can throw away the transmission. Of course, there goes your budget...

I also wonder if a dual fan design would make sense. I know it won't be as efficient as one big fan, but the fans would have a clearer intake, which might help. Also you could steer by running one fan faster than the other. Putting one fan on each side, up high and behind the car, would also allow for some kind of aerodynamic plastic shell to be put on the thing to reduce drag.
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Ben Cantrick
  User: mackys
  Date: 2008-11-11 05:34 (UTC)
  Subject:   (no subject)
Diesel has a higher energy density but aren't the engines so much heavier that it doesn't actually gain you anything?

That's true of diesel piston engines, but not for turbines. As noted, the T-62 generates 95 HP from a 71 lb engine.

Does this T-62 turbo run on diesel?

Turbines are not usually picky. The T-62 series all run happily on jet-A, kerosene, fuel oil, or diesel.
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tiger0range
  User: tiger0range
  Date: 2008-11-11 15:35 (UTC)
  Subject:   (no subject)
The problem with turbines are that they are extremely finicky and have high failure rates if the situation becomes just a bit unoptimum.

It would take quite an engineering budget to get it working just right in a situation like the above.
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