Australian Unveils Prototype Hoverbike
- Thread starter Earnest Cavalli
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Ducted fans do not provide any, "Lift," by the true sense of the word. They are merely a means of generating thrust. That's it.JSF01 said:
Lift is defined by the following equation:
L = (1/2)*ñ*(V^2)*S*(CL)
Where:
L = Lift (as a force)
ñ = Density of the fluid (air) **Should be lower case ro. It won't display correctly**
V = Velocity of the craft
S = Wing area
CL = Coefficient of lift from the given wing.
Lift is not generated without a lifting surface. That's all there is to it. What you are describing is propulsion. Propulsion =/= Lift.
Ducted fans are a nuscance when it comes to control. They are a means to provide directed thrust on command. There is very little more to them than that. The apparent stability comes from a gyroscopic effect due to the spinning of the blades. However, this can also cause control issues because they want to 'right' themselves. Most of the time though, those effects are minimal. If you tip one, it will go in the direction it is pointed.
I think you are thinking of what is known as, "Ground effect," in your explanation since many older ducted fan designs relied on this to function (except the X-22). Ground effect aircraft are a whole new aerodynamic can of worms as you then have to start worrying more about wingtip vortices and stranger airfoil shapes as well as more unusual wing design. I have not researched ground effect aircraft in depth, but here is a nifty visual describing it. It's essentially that, "cushioning," effect you see in many of the early test demonstrations that make the aircraft appear to be more stable that is really is.
As I stated in my previous post, flight based on propulsive force alone is a bad idea. If your propulsion system should lose power or fail, you are done for, and if the craft in question got more than 50 or so feet off of the ground, the ground effects would be lost and you would essentially be held up by engine thrust alone - NOT good.
EDIT: There should be a lower case ro in that equation. I had trouble making it display correctly.
EDIT 2: Edited for organization and better explanation
From whats shown in the video, I call BS.
Compare the design to this:
http://www.youtube.com/watch?v=SHPedpE70Es&feature=player_embedded
from what I've seen on the homepage, I don't think this would work - even if it did, it would be quite uncomfortable to ride and steer.
Compare the design to this:
http://www.youtube.com/watch?v=SHPedpE70Es&feature=player_embedded
from what I've seen on the homepage, I don't think this would work - even if it did, it would be quite uncomfortable to ride and steer.
- Apr 1, 2009
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not to mention that if you get over 7k feet you start to get into thin oxygen and too long there can mess you up. That lil thing doesn't look pressurized so its pointless to even say it can go that highAgayek said:
- Apr 1, 2009
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yeah I think 12000 is the max but anywhere over 7000 and if your up there for too long then you will start to suffer the effects of oxygen deprivation, and yeah it does get coldtsb247 said:
Total Thrust 295kg, off their website
yeah, i doubt this will really work, 300kg of thrust is considerable in a lateral direction, but not vertical. the actual bike is 105kg, so tough luck if you are over 18 or are relatively muscly/fat.
yeah, i doubt this will really work, 300kg of thrust is considerable in a lateral direction, but not vertical. the actual bike is 105kg, so tough luck if you are over 18 or are relatively muscly/fat.
Well, it's not going to hit 170, or even 100 without a rear fan or rear ducted fan, and honestly it doesn't look like it's got enough control surfaces to fly straight and level in the first place.
I wouldn't hold my breath.
I wouldn't hold my breath.
Gotta be higher than 7000. There's a bunch of places just here in the US that are over that, and the only real effect that's not related to baking is shortness of breath after exercise.Worgen said:
10000 feet? Using fans? Unless those fans are moving at the speed of light or so huge it makes the bike look comical or 10000 if he's dropped out of a plane I don't think that sounds real.
I like the idea of a hover bike, I don't like the idea of my junk being that close to a spinning fan again.
I wonder how loud it is.
Oh, we had to invent this because most of the terrors that stalk us here are ground based, like spiders and snakes. With a hover bike we will be safe, until the spiders and snakes have angry sex with birds...
I wonder how loud it is.
Oh, we had to invent this because most of the terrors that stalk us here are ground based, like spiders and snakes. With a hover bike we will be safe, until the spiders and snakes have angry sex with birds...
i c wut u did tharEarnest Cavalli said:
OT: I hate to be one of those fags on Youtube that yells points "this video is fake and gay" at everything... But I'm a bit skeptic.
Still pretty cool though. I'll keep myself updated on this.
im doubting the stats on the bike (they may be very liberal interpretations without weight or no air drag figured in) but i dont doubt that it exists. i just cant see this machine being very stable or aerodynamic enough for actual flight. the man has it tethered down for a reason
Wouldn't be surprised if you could get enough thrust with those fans.
Currently existing jet packs seem to have a similar amount of surface area for their props.
However I'd be highly skeptical that this thing can keep balanced with a rider. The tethers in the pic could be all that is keeping it stabilized. Right now the design appears extremely top-heavy with the rider.
In addition to the above I doubt that this thing would be able to stay aloft for long. With that design I can't see many places for a big honking fuel tank, which is what you need to stay aloft for a good period of time.
Currently existing jet packs seem to have a similar amount of surface area for their props.
However I'd be highly skeptical that this thing can keep balanced with a rider. The tethers in the pic could be all that is keeping it stabilized. Right now the design appears extremely top-heavy with the rider.
In addition to the above I doubt that this thing would be able to stay aloft for long. With that design I can't see many places for a big honking fuel tank, which is what you need to stay aloft for a good period of time.
looks like were slowly erasing "fiction" out of "science fiction"
Well if the fans can lift it it has enough thrust to lift it and is only then limited to the density of air and its movement (like its much easier to lift it in cold air due to it being more dense thus giving more surface to "push" at). and the air density dissapearing as you go up the atmosphere isnt that fast, afterall, we can breathe in the mountains. im certain that 10 thousand feet is a very liberal untested estimation, but if they can lift it as high as that the lift comes from air resistance and not ground resistance (like seen in the picture) then going up isnt hard to do.FuktLogik said:
I'm a business guy, so I noticed that he was looking for funding. What is interesting is that he hasn't incorporated to allow for him to sell stock. He wants 1.1 million AUD, but he's only asking for donations...
That is extremely suspicious to me. Incorporating does cost some money and time, but isn't really all that hard. It provides excellent personal liability security (which there is a lot of liability involved with a project like this) and gives him an easy way to gain a large amount of capital to complete the project. So, either A) he doesn't want anyone owning any portion of the future profit (which is admirable) or B) He doesn't want to sell stock because that would give those shareholders the right to see the product actually tested and this is b.s..
That is extremely suspicious to me. Incorporating does cost some money and time, but isn't really all that hard. It provides excellent personal liability security (which there is a lot of liability involved with a project like this) and gives him an easy way to gain a large amount of capital to complete the project. So, either A) he doesn't want anyone owning any portion of the future profit (which is admirable) or B) He doesn't want to sell stock because that would give those shareholders the right to see the product actually tested and this is b.s..
I have serious doubts. Considering that a Westland Lynx, the fastest helicopter in the world and a dedicated military helicopter from a dedicated aircraft manufacturer, tops out at 180kts and 12,000' (and that's cruise alt, max hover alt is 10,500'), I can't believe that this home-built, under-engineered one off could perform at (funnily enough, EXACTLY on both counts) eighty-three and a third percent of the Lynx.
I also have major concerns for longitudinal stability considering that the centre of gravity appears to be above the fans, rather than below as in a helicopter, making rollover a near certainty. Lateral stability, let alone any real control, would also be non existent since it doesn't have an anti-torque rotor (normal helicopter) nor the ability to manipulate the angle of attack to make it similar to something like a CH-53 Chinook. I'll bet that if he takes it off the tethers, it will either spin like a top and spear into the ground, or roll over like a labrador and spear into the ground.
Further, look up retreating blade stall and/or dissymmetry of lift for a detailed explaination of why this thing, with fixed pitch blades, will not do 150kts. The fans wont tilt like on a V-22 Osprey, so no comparison there, nor do they have a variable angle of attack like on a conventional helicopter (to tilt the rotor disc forward by creating more lift at the rear), so no comparison there either. The only theoretical method for fast forward flight would be to tilt the entire frame into the approaching airflow, which is still unlike a CH-53 Chinook. And I mean TILT, as in about 45 degrees. It looks like he's trying to design a completely new method of forward flight, not just a new vehicle.
Good luck. It's either a hoax or he has delusions of grandeur, but bless his cotton socks for trying.
I also have major concerns for longitudinal stability considering that the centre of gravity appears to be above the fans, rather than below as in a helicopter, making rollover a near certainty. Lateral stability, let alone any real control, would also be non existent since it doesn't have an anti-torque rotor (normal helicopter) nor the ability to manipulate the angle of attack to make it similar to something like a CH-53 Chinook. I'll bet that if he takes it off the tethers, it will either spin like a top and spear into the ground, or roll over like a labrador and spear into the ground.
Further, look up retreating blade stall and/or dissymmetry of lift for a detailed explaination of why this thing, with fixed pitch blades, will not do 150kts. The fans wont tilt like on a V-22 Osprey, so no comparison there, nor do they have a variable angle of attack like on a conventional helicopter (to tilt the rotor disc forward by creating more lift at the rear), so no comparison there either. The only theoretical method for fast forward flight would be to tilt the entire frame into the approaching airflow, which is still unlike a CH-53 Chinook. And I mean TILT, as in about 45 degrees. It looks like he's trying to design a completely new method of forward flight, not just a new vehicle.
Good luck. It's either a hoax or he has delusions of grandeur, but bless his cotton socks for trying.
If this is real I will program mine to have the sound of the Star Wars Hoverbikes if it doesn't already, it must have it!