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Great video, thank you for taking the time to make this!

This was solved recently, a proper mathematical theory was provided

So I understand that to use these you need a special light? I bought one of these really cheap on ebay for a couple bucks years ago (no reserve $1 auction for a new-old-stock item) but don't see any paterns forming when placed on a polished metal surface no matter if viewed under daylight or artificial room light

I would say it's that the propellers are always trying to grab More air than the wheels are turning and the air being the open system source. No wind required

I would enjoy a long discussion with you , John Borton, and Derek from veritasium

The wind is always moving forward across the blade in the direction that the blade is turning and the contact point where are the wind meets the blade is always moving down wind slower than the wind

Wonderful work all of you have done here please watch my video and I'll explain exactly what is taking place it is just like a high-performance ice boat sailing diagonally downwind the wind is always flowing forward across the sale or blade and the contact point is always moving down wind slower than the wind thank youth-cam.com/video/azNTzkPhx1s/w-d-xo.htmlsi=Ml27UxOdkDaDKmVF

th-cam.com/video/azNTzkPhx1s/w-d-xo.htmlsi=Ml27UxOdkDaDKmVF

What a shame if you don't do part 3. It's the best info on optical flats there is.

very helpful tnx

People watching this should consider that peices of granite from ancient Egypt have been found to be absolutely optically flat. How is this?

Can I use an optical flat to check flatness for a surface plate?

Hi there. Rick and I designed and built the Blackbird (with propeller assistance from Steve Morris) and hold the world records together. Your analysis is pretty remarkable in that your simulations and observations are amazingly close to our reality. Your compliment that the Blackbird appears to be set up "near optimum" is appreciated. You should know that I build a massive, gasoline engine powered 'treadmill' upon which we optimized (and broke and broke and broke) the Blackbird before taking it to the desert. Though there were a few issues in our first dirt runs (we'll get to your wheel slip comments), the vehicle performed very close to our own simulations. We did run it in higher and higher winds and at higher and higher speeds until I was begging Rick to slow down in fear of it blowing up (which it eventually did). We approached 60mph several times and regularly took it over 50mph. Of course top speed was not our record goal, but rather a multiple of the windspeed. We were initially working with a $5,000 budget (which included our own custom built ~18ft propeller) so I could spend very little on the chassis. I designed a craft which I felt could be safe at our design point (~25mph ground speed). It was made of wood I beams (TJI) from Home Depot and built up from there with steel, carbon, kevlar and fiberglass reinforcements. Salvaged BMX wheels, etc and other bicycle components you already obviously know about. Some (me) would never call home made propeller tips whipping past the back of the drivers head at over 150mph "safe" in any way. You reference Rick's presentation at the St. Francis Yacht club, so I'm sure you noticed the story of why he was the pilot and not me (recounted at 1hr, 11m and 41s of that video). Our original goal was 2x windspeed. Our thought was that if we could double the speed of the wind it would make it more difficult for skeptics to claim measurement error compared to say 1.1x. Our design point for wind was (as I recall from more than a decade ago) ~9-10mph. Our highest ratio we recorded was around 3.4x, and we often got over 3x, but due to conditions and limited time (and NALSA measurement rules which we found appropriately conservative), we didn't reach that under the constrained record recording conditions. All these numbers fit your simulations very closely. Your observation that an appropriate RC works over a rather broad range of wind velocities was our direct experience. I installed the sprocket cluster just so I would have a range covered, but as I recall we optimized on the treadmill and never moved it after that. Yes, a greater tailwind does deliver more power to the cart, and with a far bigger budget and thus safer and stiffer chassis, we could have raised the bar significantly. As it was, at our top achieved speed, there was something like 600 ft lbs of torque on the prop shaft feeding the propeller blades through a variable pitch hub I designed and machined myself on a mini-mill. As I said, I was literally on the radio begging Rick to slow down at times. I still can't believe it took the abuse it took. As to wheel slip, the first videos you can find of the Blackbird (it was unfaired and called the BUFC ... "Big Ugly fn Cart" at that time) show it with symmetrical rear axle lengths. During our first dirt testing day (see "BUFC blow up run with full audio), Rick exceeded the design point by quite a margin and blew up the top sprocket. He reported an odd "surging" just before the failure (just as you suggested). We closely watched all our video and discovered that he was saved from tipping over (equal and opposite reaction to the aforementioned propeller shaft torque) by one wheel lifting slightly and losing enough traction to create the repeated surge in harvested power. This self limited top speed (and torque reaction) and also hammered the top sprocket (just as you suggested). Before we went out again, I revamped the chassis to extend one axle by several feet which gave the Blackbird it's odd asymmetrical look. BTW, the BUFC version of the craft had a fixed pitch propeller hub (relating to your fixed pitch analysis). It wasn't until Larry Page stepped up with sponsorship that we had the funds to dress up the renamed Blackbird and install the variable pitch propeller hub and controls. As you can conclude, the ability to adjust pitch on the fly doesn't really increase the top performance of the craft, but rather allows it to accelerate faster and 'self-start' in lower winds. If you review the other "BUFC" videos and compare them to the later Blackbird videos, you can see this impact. Overall you did a really great job here. Seeing someone applying good engineering analysis and comparing to actual results was refreshing given the literally tens of thousands of times Rick and I have been called frauds and idiots over the last 15 or so years. I have many, many build pictures if you're ever interested and you might also be intrigued by the upcoming possibilities to truly smash this record given the interest of a certain energy drink company to sponsor such. Composite F1 factory built with truly giant, counter-rotating propellers and generator/motor drive is being discussed. Fun if it were to happen. Thanks and very well done. John "JB" Borton Thin Air Designs team principal.

A couple of questions. In the videos showing this demonstrated, slow down the video. At the start, notice the propeller is turning one direction. But when you see the flag pointing towards the rear of the vehicle showing it is traveling forward faster than the wind speed, you’ll notice the propeller is turning the *reverse* direction. Because the *relative* wind is now toward the rear, this is indeed consistent that the forward propulsion is being provided by the wind. But the problem is with the propeller *directly* connected to the wheels shouldn’t that reverse the direction the wheels are turning? I’ve not seen anything of this nature discussed in the demonstrations. That the wheels turn in the same direction would seem to suggest some type of gear conversion that would allow the wheels to turn in the same forward direction regardless of the propeller spin direction. Also, in the small toy models demonstrating it on treadmills you can see there is no such gear conversion being used. This is puzzling. I like your analysis and demo using a parachute analogue. I’m surprised this worked, but I have to say there is a flaw. You see the “parachute” is not moving faster than the wind speed, even if the car is, as the wind is still pushing the parachute *forward*. If the parachute were moving faster than the wind speed the relative wind would push it *rearward*. This is a key distinction from the actual case. In the actual scenario the *relative* wind is pushing rearward against the propeller. In fact I draw the conclusion your parachute analogue would NOT work if the parachute were made to move faster than the wind speed, since then the *relative* wind would move the parachute *rearward*. Here’s a key deduction you can draw from that fact: it is something about the nature of the propeller itself that allows it to work in that case, but not in the parachute case. Here’s what I think that is. Much has been said about this scenario being different than a sailboat tacking into the wind because the vehicle is moving directly downwind, not an angle. But the thing is the propeller, i.e., the sail, is moving at an angle to the wind! This is because the sides of the propeller are *angled*. I haven’t looked at all the video discussions of this phenomenon but I think this fact is not focused on: it really is the same as tacking into the wind with a sail at an angle to the wind direction. If this fact were stated I think the phenomenon would be easier to understand. Robert Clark

brilliant you deserve more visitors to the videos

Superb, great work!

It's been a while now. Are you still going to make part 3? I hope so. Thanks.

What lighting are you using to get a yellow glow?

tnxs god we have ECM to advance, retard or even compensate cylinder wear.

Nice

Hey, I am currently doing a research paper on this idea Can you share the document of the calculations and graphs please? This would really help me

Wow, fascinating work. Can you share the document of the calculations and graphs please?

I am very impressed with your analysis. I guess Rick is the real deal.

First class content presentation. Many thanks for this.

Fascinating.

Thank you for putting all this together. I look forward to part 3. My Optical Flat light is green for a 10.7 millionths per fringe. I wonder if a light is made that gives 10 millionths per fringe? I prefer the green simply because it is NEARLY 10 millionths.

Please never stop making videos sir, I hope I run across you irl and that I can pick your brain sometime.

I am so excited for the next video in this series, and to continue to learn from your channel. I have been a bit obsessed with flatness as a by-product of restoring antique tools. Mostly hand tools. I know it is orders of magnitude more precision than I need, but after watching your videos in this series I am inspired to pick up a surplus optical flat. Metrology is my second favorite (due to expense) hobby, and before your video I believed this level of precision was unobtainable. If you enjoy making videos, I hope you continue. I am interested in soaking in all the information from you that I possibly can.

Not only is the model very nicely made, but the analysis is excellent. It is surprising that some authors in reputable publications claimed that the temple doors were opened using Hero's aeolipile steam engine. That was not correct, as demonstrated here.

This is a very nice demonstration on PLAN and the effects of engine size and displacement. I have a question which I need to explain in some detail. The Stephenson link and its variants allowed the steam engine operators eg locomotives, to vary the valve timing as needed. They could continue to apply full pressure throughout the whole power stroke (TDC to BDC) when taking off from stationary at low RPM, giving maximum torque for acceleration. Full steam pressure was still being applied when the exhaust valve opened at the end of the power stroke, causing a loud puffing sound. However, after reaching cruising speed it would be inefficient to let full steam pressure escape through the exhaust valve. Efficiency could be improved greatly by shortening the intake by closing the intake valve very early in the power stroke. Then the steam which entered early was left to expand as the piston moved. Then the steam being released through the exhaust valve at the end of the power stroke was at a much lower pressure and less power was wasted. The steam was used more efficiently. I recently went on a tourist trip on the small steam powered launch Earnslaw on Lake Wakatipu in New Zealand. The operator was not making use of the Stephenson linkage provided in the engine. Instead he was partially closing off the steam valve supplying steam to the engine. I tried to explain to the captain that they should use the Stephenson linkage, but he didn't get it. The question is, how much difference does it make? If they only need quarter power they could cut the steam supply to one quarter the pressure. Alternatively, they could have the inlet valve cut off about one quarter way down the stroke. Then during the rest of the stroke the volume would increase 4 fold and pressure would drop 4 fold and exhaust steam pressure would be reduced to one fourth. Thus the exhaust steam pressure is the same as cutting the supply steam to one quarter pressure and keeping the inlet valve open throughout the stroke. On this basis it seems that the two methods are equivalent. This is not what I expected. Thanks for you TH-cam videos! PS. I also went on a very similar triple expansion steam launch in Connecticut.

This is a fantastic channel! He seems to know everything there is to know about engine thermodynamics, construction and measurement.

Great work. I've been following this topic for many years. I'd love to take Blackbird to the next level. A more automated vehicle that can shift between propeller and turbine mode. Telescopic and dynamic aerofoils to extract energy from crosswinds. Roadways and railways that canalize any available wind, passible and dynamically to optimize energy transfer to a (rail)vehicle. And the absolute pinnacle: extracting the speed differential between surface coundary layer air speed and higher altitude air speed to power a ground effect flying craft. With efficient floating wheels or tracks, a vehicle could "roll" on the water similarly to blackbird and sail DDWFTTW. It will ask a lot from the engineering, but Blackbird shows there is some rooms of inefficiencies to be introduced, as it went 3x wind speed with somewhat rudimentary drivetrain adjustments. What would the ideal scale for a Blackbird competitor be, to optimize power and drag? Mass grows with the cube, wind power with the square, sort of. Would a cart manned by a squirrel manage 4X wind DDWFTTW?

So THIS is what Gingery was talking about.

I only watched the introduction. The plane has his own energy source else it will not travel faster than air. Blackbird has no internal energy source so in order to exceed wind speed directly downwind it will need to have an energy storage device (and it has). Since a very limited amount of energy is stored by the blackbird it can only travel above wind speed for a limited amount of time proportional with the amount of stored energy . Energy in case of direct down wind blackbird version is stored in the pressure differential created by the propeller (air is a compressible fluid).

I feel like this conflicts with Derek’s explanation over on Veritasium

I think the units would be a bit more clear if they written as "μin" for millionths of an inch and "μm" for micrometers

Really wonderfully cogent and complete analysis. It's astounding that this is still even being debated. It points to a fundamental flaw in our thinking, in how easily we can let even well-developed intuitions lead to entrenchment. I took a brief look at this back when it was still a thought experiment, had my thermodynamics boots already pulled on and ready to do battle, right until saw where the untapped differential in the system is. Quite stellar stuff. Thank you.

Is weird but helium light is not monochromatic, sodium lamp light is and the wavelenght is 589. Why they say helium in the manual?

I believe the source of monochromatic light you have is a sodium lamp not a helium lamp.

Much appreciate your insight and knowledge of this complex subject

Eagerly awaiting part 2

Awesome explanation , well done ! Subed directly !☆ -One question i always asked myself , but never got answered nl.: -What if we use a monochromatic ultraviolet lightsource , the wave lengte is way shorter. Meaning we could even get smaller measurement scaler ? Or am i misding something ? Grtzz from the Netherlands Johny geerts

Thank you so much for this great series! Are you planning to issue the next video in the series? I've subscribed so I don't miss it if you decide to publish it.

This is the very best explanation of how optical flats work that I have found. I sincerely appreciate all the work you put into this video series. Merry Christmas and Happy New Year!

Wow, great video !

Sir, I like this video pretty much and will wait for your next!

Thank you for making a great easy to understand video. Wish I'd seen this earlier.

Fantastic information, thank you!

Nice video!