* There is no wind
* The propeller is powered by a battery
If the speed of the propeller wash is 1m/s, do you agree that the vehicle will move forward at around 1m/s?Replacing the moving sail with a propeller will not be the same thing if the propeller is not powered by something.
So propeller will still rotate but slower and slower same thing that actually happens after the vehicle used all the pressure differential and vehicle starts to slow down.
You keep forgetting 1 thing . This type of propeller has an integral clutch . Which means it can spin Free
with just wind force . only . so it can be used as a sail .(kind of ) When the clutch engages it can ether give
power to the wheels or from . Depending on the setting of the pitch angle of the Blades .
I believe we can analyze, or at least demonstrate this with a fixed-pitch, fixed-gearing propeller. That's how the treadmill model is built. I don't know if this model can start from a full-stop, but it does accelerate once past windspeed.
You keep forgetting 1 thing . This type of propeller has an integral clutch . Which means it can spin Free
with just wind force . only . so it can be used as a sail .(kind of ) When the clutch engages it can ether give
power to the wheels or from . Depending on the setting of the pitch angle of the Blades .
I believe we can analyze, or at least demonstrate this with a fixed-pitch, fixed-gearing propeller. That's how the treadmill model is built. I don't know if this model can start from a full-stop, but it does accelerate once past windspeed.
I believe we can analyze, or at least demonstrate this with a fixed-pitch, fixed-gearing propeller. That's how the treadmill model is built. I don't know if this model can start from a full-stop, but it does accelerate once past windspeed.
That model will be able to start from a full stop assuming high enough wind speed so that power based on vehicle equivalent back area can overcome vehicle friction.
The thing you (all) seems to be ignoring is that air speed relative to vehicle is what can power the vehicle and so when air speed / wind is equal with vehicle speed in exact same direction then there is no way for the air to push the vehicle.
And somehow you imagine that propeller can push air backwards but that will require an energy source and wind is no longer there to help when vehicle is at or above wind speed.
You just think that you can take energy from the wheel but the problem with that is that when above wind speed that wheel no longer takes energy from the wind but will need to take energy from the vehicle kinetic energy and so vehicle will just slow down if you ignore a energy storage device like the pressure differential witch continues to push the vehicle basically taking the role of the wind for a few seconds or minutes depending on the design.
Yes the propeller to push back against the air and thus the wind does require some power and an energy source. So this sounds like you agree that with a given power (from a battery or whatever source) the prop can drive the vehicle a little faster than the wind speed or at exactly windspeed (this is the case that is a bit easier to calculate).
Now comes the slightly tricky question: how much power is needed for the prop to create a given thrust (force) to overcome friction ?
The thing you (all) seems to be ignoring is that air speed relative to vehicle is what can power the vehicle and so when air speed / wind is equal with vehicle speed in exact same direction then there is no way for the air to push the vehicle.
[... fixed-pitch propellers ...]
I am not sure how this can be done as both these propellers have totally different properties .Your know about boats . It would be like saying a life raft is the same as a boat or worse still a Ship . They both travel or go in water . (spot the difference)
Do you understand 2+2? Then why don't you understand 2 - (-2)?
No, the battery is still driving the motor. It is simply a combination of 1 and 2: wind blowing in the sail, sail being moved along the vehicle.
Do you agree the vehicle ground speed would be close to 3m/s?
Yes but this just proves my point that an energy storage device is needed to exceed wind speed.
OK, so now we go back to scenario 2 and replace the moving sail with a static propeller. Recall that:
* There is no wind
* The propeller is powered by a battery
If the speed of the propeller wash is 1m/s, do you agree that the vehicle will move forward at around 1m/s?
Replacing the moving sail with a propeller will not be the same thing if the propeller is not powered by something.
And since you do not have a battery and you do not accept there is an energy storage device (pressure differential) then there is nothing that can power the propeller other than the kinetic energy of the vehicle but taking energy from that will result in reduced vehicle speed. So propeller will still rotate but slower and slower same thing that actually happens after the vehicle used all the pressure differential and vehicle starts to slow down.
OK, so now we go back to scenario 2 and replace the moving sail with a static propeller. Recall that:
* There is no wind
* The propeller is powered by a battery
Against the wind already would be possible with a craft like this, as long as the drag force of the blades is higher than the craft, it would be working like a windmill,
The thing you seem to be ignoring is that the propeller is part of the vehicle and is blowing its own wind backwards. The effective wind speed is both.
Do you understand 2+2? Then why don't you understand 2 - (-2)?
Mate, why did you create a strawman? Well, obviously, it was to knock him down but, really, it's so blatant. You even quoted me where I said:QuoteOK, so now we go back to scenario 2 and replace the moving sail with a static propeller. Recall that:
* There is no wind
* The propeller is powered by a battery
Can you grasp that? The propeller is using B.A.T.T.E.R.Y. power to turn, so the rest of your post knocking down your strawman is completely irrelevant.
So, once again and PLEASE don't jump ahead, make things up or change the subject:
With a propeller fixed in position, powered solely by battery and with no wind, if the prop wash is thrust back at 1m/s, do you NOW agree that the vehicle will move forward at around 1m/s?
Also, please bear in mind that this actual experiment is carried out across the world at all times of day an night, so if you still disagree I will be expecting an extraordinary explanation as to why.
Why include a battery in the equation
For the vehicle to maintain 3m/s with a 2m/s tail wind the battery will need to provide enough power to cover all frictional losses.
Trust me, it is a fucking HUGE battery. But if it pleases you we can make it nuclear-powered instead, just in case you're worried about the thing running out of charge.
So, are we at this point agreed that, ignoring how the propeller is powered, the vehicle with a 1m/s prop and a 2m/s tail wind will move forward at close to 3m/s?
Trust me, it is a fucking HUGE battery. But if it pleases you we can make it nuclear-powered instead, just in case you're worried about the thing running out of charge.
So, are we at this point agreed that, ignoring how the propeller is powered, the vehicle with a 1m/s prop and a 2m/s tail wind will move forward at close to 3m/s?
It is obvious I will agree. You can drive at almost any speed you want if you have a battery.
That's not the point. The question is *how* *fast* will the vehicle move under the conditions above. 3 m/s, right? We are trying to find agreement on forces and speeds.
What powers the propeller when vehicle is above wind speed ? It is a simple question for with you have no answer.
That's not the point. The question is *how* *fast* will the vehicle move under the conditions above. 3 m/s, right? We are trying to find agreement on forces and speeds.
We just agreed on an arbitrary number of 3m/s and I said yes it will be possible. What else will you want me to answer ?
Battery is an energy source and since there is no electrochemical battery on Blackbird I look forward to see what that will be replaced with.
Trust me, it is a fucking HUGE battery. But if it pleases you we can make it nuclear-powered instead, just in case you're worried about the thing running out of charge.
So, are we at this point agreed that, ignoring how the propeller is powered, the vehicle with a 1m/s prop and a 2m/s tail wind will move forward at close to 3m/s?
It is obvious I will agree. You can drive at almost any speed you want if you have a battery.
So what is next ?
The energy which is extracted from slowing down the wind.
On blackbird, the propeller is not a windmill, it's a literal propeller exactly like on an airplane that pushes the air backwards. Effective airspeed speed at the propeller is higher than windspeed, causing the airmass to slow down, which results in excess energy which is used to push the vehicle forwards.
You agreed that the yoyo toy can move faster than the string. Earlier I replaced a hand pulling the string with a sail system that is basically infinite. Sails always move slower than the wind, but the vehicle itself is faster. That model should be perfectly clear.
The next step is slightly more tricky: how much power is needed to drive the prop to create the 1 m/s air speed ?
The power would obvious depend on the size of the prop. In ideal world this would be comparable (maybe smaller by some factor somewhat smaller than 1, as neither the wind turbine nor prop are 100% efficient) to the power a wind turbine could produce.