No, thrust is from speeding up the wind.
I'm shocked that you are in the same boat as Dennis and haven't a clue what's going on here.
I accept the propeller may initially be used as a sail, but once the land speed matches the air speed, only an idiot would think they can still extract energy out of "wind" with a propeller.
You've misunderstood how this works. You may describe the propeller as a turbine until the vehicle closely matches the speed of the wind. After that the propeller generates the thrust which is more than the drag on the wheels that goes to power the propeller.
For a better explanation:
Yes, but that relies on tacking, something you can't do if travelling directly with the wind as in this case.
You are correct, the the thrust is from slowing the wind down. My apologies.
Well, I'm happy I understand it. I don't accept it's a propeller, and I don't accept it generates thrust. It's a turbine. The wind directly pushes against the turbine's surfaces, even when the vehicle is going faster than the wind.
Perhaps you and I have different understandings of some of the words we're using. We probably should just agree that you think I don't understand :)
Thanks
There's no need to tack when your "sail" is whizzing round in a corkscrew motion all the time.
And litter is well into the boundary layer - a sand yachts sails are a lot higher
IN this case Dennis is actually right, and you are not
You need to have the vehicle some way anchored to the ground, but moving.
The propeller pitch simple reverses so that instead of the wind going through the prop from behind and turning it, its actually coming from ahead - the car is 'overtaking' the wind and the propellor provides a frame or reference that is moving at a different speed from the wind so as to extract energy from it. If you like the turbine blades are 'tacking'.
As I said the key is extracting energy from the wind whilst moving faster than it. Simples. Have a propellor blowing back in its face!
In this case the prop is acting as a sail, not as a propulsive device, and is generating enough thrust to move the car forward AND produce the slipstream...
OK, lets assume the "turbine" powers the wheels:
Can you accept that the maximum power produced by this "turbine" is force x (land speed - wind speed)
Can you accept this is less power that require to provide the same force through the wheels which is force x land speed?
If so, why doesn't it slow down?
Another:
To quote the maker ?Skeptics think that the wind is turning the prop, and the car is turning the wheels, and that?s what makes the car go,? Cavallaro said. ?That?s not the case. The wheels are turning the prop. What happens is the prop thrust pushes the vehicle.?
Which is perhaps more helpful.
You and Wodney can stick together. I prefer the explanation from the designer/builder:
And to quote, "Skeptics think that the wind is turning the prop, and the car is turning the wheels, and that?s what makes the car go,? Cavallaro said. ?That?s not the case. The wheels are turning the prop. What happens is the prop thrust pushes the vehicle.?
It just goes to show that neither you or Wodney understand what is really going on. I prefer to accept the words of a keen aerodynamicist and someone whose project is sponsored by Google.
No thanks, because that's wrong. The wheels rotate the turbine.
The turbine doesn't produce power.
To be honest, I'm not completely sure how to calculate the power "produced" by a sail. If a boat is anchored with its sail up, I suppose the power "p roduced" by the sail is zero because the boat's speed is zero. But the for ce produced by the wind on the sail is, of course, significant.
You mean a sail that takes power from the wheels and creates thrust through moving the sail?
Oh dear, you the propeller is pushing the machine? Where do you think it is getting its energy from.
On your explanation, is you decouple the wheels the machine will go even faster!
Yes, it's called tacking.
The sail doesn't create thrust by moving. (That's what a propeller does, which this isn't...) The wind creates thrust by blowing on the sail.
As I keep saying, it's not a propeller - it just looks like one. But anyway, the energy comes from the wind, of course! Where else would the energy come from???
Of course not!
I'm going to leave this discussion here, because (unlike the machine!) we don't seem to be moving forward. Goodbye.
So what you're saying, if I put a sail directly downwind, it can travel faster than the wind?
If the propeller, sorry sail, doesn't provide thrust by moving, how does it provide thrust?
Perhaps you should experiment placing a sail inline with the wind and see if it can travel faster than the wind itself. If you can then you have truly found a source of free energy.
Is it impossible for you to grasp that the propeller is truly a propeller and providing thrust?
Correct, you've got it where so many haven't.
Correct, it's a propeller taking power from the wheels.
There are a stack of equations to calculate propeller and turbine efficiencies. I recall some for wind turbines that I followed but weren't very memorable. I believe the record so far is a land speed of
28mph from a downwind speed of 10mph.I have generally taken prop efficiencies to be circa 50%, but this record implies they achieved rather higher than this.
They are. Having played a LOT with model aeroplanes, cut right and driven right I reckon 75% or better is in fact the name of the game, and in fact since the L/D ratio is what determines it, and that can be 10:1 or better, up to 90% is possible,
My models always outperformed ones that hadn't been 'calculated'
Thanks, that does make the speed "Thunderbird" achieved more believable!
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.