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Mess with your minds: A wind powered craft going faster than a tail wind speed.
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IanB:

--- Quote from: bdunham7 on December 16, 2021, 12:24:30 am ---Really?  'Everyone' is wrong?  How far are  you willing to go with that?  You never doubt yourself even a little?  ::)

--- End quote ---

You guys do realize we are dealing with a troll here, right?

Have you observed that our friend disagrees with, or contradicts, every statement made in this thread, however basic, and finds a reason to reject every experimental result and every external authority?

Nobody could disagree with 100% of all points made, without doing it deliberately. Every normal person would have at least some points of agreement.
Brumby:

--- Quote from: bdunham7 on December 16, 2021, 12:24:30 am ---
--- Quote ---In any case all those bicycle calculators are wrong so this is a very widespread problem.

--- End quote ---

Really?  'Everyone' is wrong?  How far are  you willing to go with that?  You never doubt yourself even a little?  ::)

--- End quote ---
:-X


--- Quote from: IanB on December 16, 2021, 02:23:37 am ---
--- Quote from: bdunham7 on December 16, 2021, 12:24:30 am ---Really?  'Everyone' is wrong?  How far are  you willing to go with that?  You never doubt yourself even a little?  ::)

--- End quote ---

You guys do realize we are dealing with a troll here, right?
--- End quote ---
It's just about impossible to consider any other alternative.  Even the Dunning-Kruger explanation is at a reach.


--- Quote ---Have you observed that our friend disagrees with, or contradicts, every statement made in this thread, however basic, and finds a reason to reject every experimental result and every external authority?
--- End quote ---
Reason?  Most of the time it seems to be a simple statement of "that is wrong" - with little, if any, valid argument.


--- Quote ---Nobody could disagree with 100% of all points made, without doing it deliberately. Every normal person would have at least some points of agreement.

--- End quote ---
Looking at it from the reverse angle - that's the magic of lying/misdirecting properly.  Have just a taste of accurate bits mixed up in a soup of ignorance.  Then you will be greeted with indignation about the "accurate bits" when you were actually challenging the crap.


I have little interest in correcting our recalcitrant as they aren't interested in proper understanding - but I'm having more fun watch how they dodge the discussion points.

With their clumsy attempts at misdirection and mathematical torture, I keep wondering if they had a failed career as a magician.
electrodacus:

--- Quote from: IanB on December 16, 2021, 02:23:37 am ---Nobody could disagree with 100% of all points made, without doing it deliberately. Every normal person would have at least some points of agreement.

--- End quote ---

If there is something I agree with why will I need to comment on that ?
The thing I disagree with merits the most attention.

I made those points clear

No vehicle without an external energy source or energy storage device can exceed wind speed direct down wind.
I showed the correct equation for wind power that relates to such a vehicle 0.5 * air density * area * (wind speed - vehicle speed)^3

I was thinking that giveing numerical examples will help but it seems nobody is shocked by driving against wind speed on a bicycle in 230km/h = 64m/s head winds.
0.5 * 1.2 * 0.5 * (64)^3 = 78.6kW of drag with just 0.3kW on input power.
How much more extreme you need the values to be in order to seems shocking.
Psi:

--- Quote from: electrodacus on December 16, 2021, 03:15:09 am ---No vehicle without an external energy source or energy storage device can exceed wind speed direct down wind.

--- End quote ---

Then your argument has nothing to do with blackbird, you're trying to argue against the accepted scientific facts about sailing boats.

The fact that the boat achieves sailing directly downwind faster than the wind from point A to B through a series of indirect zig-zags is irrelevant, since the length of each zig/zag has no effect on mechanism causing faster than wind travel. 
If the sail boat could change direction in an instant with no time needed to stop, rotate and move the sails, then it could move downwind faster than the wind through a series of zig-zags that were so tiny that they were imperceptible and it would, in effect, be a straight line downwind faster than the wind.

BrianHG:

--- Quote from: thm_w on December 16, 2021, 12:48:28 am ---
--- Quote from: BrianHG on December 15, 2021, 11:43:50 pm ---Most of that excess power difference is due to rubber tires on asphalt which is really affected by tire pressure.
I know that over-inflated 125psi high pressure narrow racing tires take half the effort compared having the same tires inflated to 80psi.  Even worse compared to fat underinflated mountain-bike tires.

Like a train, if your bike had metal wheels driving on a flat steel beam, then wind preasure would be more dominating.

--- End quote ---

Definitely not half the effort for slightly higher inflated tires.
The difference in rolling resistance for 100 vs 120psi on GP5000 tires at 29km/h is ~0.7W: https://www.bicyclerollingresistance.com/road-bike-reviews/continental-grand-prix-5000-2018
So 80 vs 125psi would be ~3W at most (10-13W total).

Sure fat mountainbike tires will be worse, but, calculator is not using them.

--- End quote ---
The resistance drop on under inflated tires tends towards an exponential curve, not linear and it also depends on the weight of the driver.  I used to be 250lb, an 80psi tire was mushed close to the rip and believe me, I was adding a good additional 50-75 watts just to maintain 25km/h compared to 120psi tires at that weight.
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