cool toys
Tam links to a sort of hover-cycle thing.
Looks like it woud be a hoot; it’s always a pity that the laws of physics are such an undiscovered country to most inventors like this.
Speaking of stupid high speed craft, I once did some work for a manufacturer of airboats. I wrote a family of programs that cut the poly skid plats that got bolted onto the bottoms of the boats, and they took me out and let me drive one around.
Let me tell you, those suckers are not easy to drive. The center of gravity is about six feet over your head, and it’s as easy to flip one over as it is to trip over an untied shoestring, Still, I kind of got the hang of it, eventually.
Riding oin it was even more fun, though. And there was precious little alcohol involved when the owners of the company invited me to jump out of the boat onto an alligator, and i complied.
The gator in question was small, about five or six feet, (which is a very small gator) and it probably felt- to the gator- as if a house had fallen on it. It was in far more danger from me than I was from it. And I grabbed it’s face while my companions laughed and wrapped.
This being prior to digital photography except among the very wealthy, no camera was available at the time, but I will always have the memory of having that unhappy gator on my lap in the bow of that airboat, then slicing the electrical tape off it’s snout and lowering it headfirst over the side.
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I think Pissed had it first….
http://theferalirishman.blogspot.com/2011/06/ofgbbq-do-want11eleventy.html
Hope yer doing ok.
The hover cycle looks like it would work for mowing your back yard as well as being a fun toy.
Especially for the tall grass, right?
As an aerospace engineer by training, if not by employment; let me just say say, there is no reason why is CAN’T work…
… but there are plenty of reasons why it WON’T work.
Just to head off the questions, the first and most important being, it will exhibit negative static AND dynamic stability.
Unless it’s got a control suite like an F35, the damn thing is going to be impossible for a human being to control in flight.
They had to run a cable to ENIAC to keep this thing in the air…
Alright, now that’s funny right there.
If they had microprocessors of any ability, and could have used them to stabilize those mothers, these would be more common than flatfender jeeps now. Actually, if you think about it, about any twelve year old could run one, my daughter has the reflexes of a bat, and could probably do this based on playing video games.
I would really like to see the concept explored by someone who had some real grasp of the engineering required. Like, I’ve been waiting for someone to start selling Skycar M400’s, but no dice yet.
In all seriousness, all the various “sky jeeps” did eventually fail, because they had stability problems. Check out the videos of them posted on youtube. Hilarious stuff.
The big issue with this sort of configuration, is that when an HOG (hover out of ground effect) type vehicle with the thrustline below the center of gravity diverges from stable flight, it will naturally continue to diverge.
What you want, is a vehicle where divergence naturally tends to return to a stable attitude (that’s positive stability).
The thing is balanced on the top of a moving column of air; and it’s really very easy to “fall off”; tipping off the side of the stable column and sliding or falling sideways at an off kilter angle. At the same time, the vehicle is continuing to provide considerable thrust, on its new rotated vector, which increases the tendency to slide and tip (especially as the riders weight is concentrated well above the center of gravity… and the thrustline datum… of the machine).
Eventually, after considerable unintentional aerobatics, it just rolls into a downward thrusting attitude, which is stable (and therefore resists control efforts to correct it); and powerslams itself into the ground.
Now, the bigger, and wider spaced the fans are, the more stable the craft is going to be (presuming the fans can be effectively controlled).
Multiple fans can reduce the tendency to “fall off” the air cushion. A single fan is the least stable, 4 or so in a “four corners” configuration are reasonably stable, unless one fails. 8 independently controlled, but coordinated fans seems to be the ideal from the experiments conducted from the 50s through today, but of course has a complicated control and power system.
Also, if the thing stays in ground effect, it’s like to be remain stable enough to be controllable. Making it a lifting body and adding stabilizing surfaces would help a lot too, as would raising the thrustline.
As of now, the design has most of the mass of the vehicle right on the thrustline, and the entire mass of the rider above it. If they were to raise the fans to say, chest level on a rider, with most of the mass of the vehicle hanging below the thrustline, that would DRAMATICALLY improve stability.
The problem with the two center-line fan “sky bike” is that its stability is derived almost entirely by the gyroscopic effect of the two spinning rotors, like a motorcycle’s is from the wheels. (As the inventor notes, in his tethered flights thus far, merely leaning doesn’t upset the vehicle much; you actually have to push down on the bar to get it to tilt appreciably.)
Unfortunately, with only the two rigidly-mounted fans you don’t have any means of directional control other than tipping the bike, and the difference between tipping it a little bit and turning and tipping it a lot and crashing is going to be a knife edge, and no amount of computing power will help that because there are no control surfaces or thrust vectors that HAL could take control of to right the thing and prevent auguring in.
Plus, at the in-ground-effect altitudes levels these things will operate best in, the lack of positive braking is something of a downcheck.
(Another big drawback to the Piasecki AirGeeps: It’s one thing to put a helicopter pilot behind the controls, versus Private Snuffy from the motor pool…)
As a practical vehicle for power line surveying and cattle droving, it’ll never fly (pardon the pun), but as a recreational toy for lunatics bored with street luges and wingsuits? There’ll be a small market there for people looking for ever-more-audacious ways to catch an adrenaline buzz…
Ducting those fans and adding some control surfaces will do the job quite handily, of course,a la harrier, but I’d still like to see more smaller fans than two biguns, and being able to vary those fans to stabilize properly. Shit, that’s how they keep oil rigs planted in one place, after all.