A jet plane on a large treadmill

[DJSapp]

I bet a box fan on a treadmill falls over. And then the server crashes.

No no no. The mice are on the treadmill that powers the server. The fan keeps the mice cool enough to keep running.

[jono]

Is that why there's no surplus box fan to use for the server?

[Brock Landers]

I bet a box fan on a treadmill falls over. And then the server crashes.

I lol’d. Good audible chuckle which I didn’t think I’d get from this thread (aside from certain trollings)

[k2skier112]

Has this been posted before?

It's got treadmills involved in it!

[Harry]

It's got treadmills involved in it!

And a propeller, which is just like a big box fan, right ?

The hive mind of the TRG is way smarter than those physics professor nerds.



Sent from my iPad using TGR Forums

[jono]

That was sofa king cool. Bonus points for quoting Bill Nye's super committed email and NdGT getting concerned about dividing by zero.

It's weird how much the wind seems to screw with intuition, compared to the little geared car being pushed by the slower stick, which just makes sense. I'd love to have seen the reactions of the doubters to those few seconds.

[ötzi]

I kinda sampled it and missed Nye's email, what did he say? I wonder if I could get get Kusenko to bet me that it's impossible for sailboats to go faster than windspeed, I could use the cash.

[Not DJSapp]

I kinda sampled it and missed Nye's email, what did he say? I wonder if I could get get Kusenko to bet me that it's impossible for sailboats to go faster than windspeed, I could use the cash.

The video that sparked the bet


And the explanation that is in there is pretty good but the physics prof was right to question it. He had valid arguments that weren't addressed in the first video. The first video links how sailboats go faster than windspeed to the propeller motion here with cylindrical earth theory (skip to 7:37 if you don't have time). They don't really address why it doesn't work for boats, but the simple answer is drag. Wheels on land vs. a hull in water is orders of magnitude different in drag losses.

My next question is how long until someone starts a racing league of these trikes and aren't built out of leftover parts from Cletus's backyard? Larry could make this a new passtime between America's Cup races.

[From_the_NEK]

They don't really address why it doesn't work for boats, but the simple answer is drag. Wheels on land vs. a hull in water is orders of magnitude different in drag losses.

I would assume that drag eventually catches up with the props thrust?

[Not DJSapp]

I would assume that drag eventually catches up with the props thrust?

It's more likely a question of scalability. The land version required a pretty large prop to overcome a low friction wheel/ground/air resistance drag force. The water version would most likely be impractically large to get to a speed faster than the wind.

I'm sure there is an upper limit to the ground version, but the vehicle they built definitely wasn't going to be the one to find it.

[abraham]

Seems like an appropriate place to add this. Cargo plane lost both engines, ditched into the Pacific at night and both pilots were rescued.

Accident: Trans/Rhoades B732 at Honolulu on Jul 2nd 2021, ditched about 2nm out of Honolulu
By Simon Hradecky, created Friday, Jul 2nd 2021 14:36Z, last updated Friday, Jul 2nd 2021 18:46Z

A Transair/Rhoades Aviation Boeing 737-200, registration N810TA performing flight T4-810 from Honolulu,HI to Kahului,HI (USA) with 2 crew, was climbing out of Honolulu's runway 08R when the crew stopped the climb at about 2000 feet reporting they had lost the #1 engine (JT8D, left hand). Tower cleared the flight for a visual approach to runway 04R. The aircraft began to descend while trying to position for a return to Honolulu's runway 04R. The crew advised they might lose their other engine, it was running very hot, and requested the coast guard out, and then reported: "We have all the Rhoades 810" and requested to turn right towards the airport and received clearance. Tower subsequently cleared the aircraft to turn onto a heading of 020 for runway 04R, the crew reported they no longer had the airport in sight. Tower advised they had a low level alert, tower cleared the flight to land on any runway, all operations at the airport were stopped, emergency services were called out and the coast guard were on their way out. Tower provided a heading of 310 degrees directly to Honolulu's Kalaeloa Airport, in the end tower did not receive a reply from the aircraft anymore. The aircraft did not make it to the airport and needed to ditch in the Ocean about 2.7nm short of the Kalaeloa's runway 29 (last position received from the transponder: N21.275 W158.026 at 50 feet MSL at 113 knots over ground). Both crew were rescued, one pilot was airlifted to a hospital, the other taken ashore by a rescue boat and taken to a hospital. Both pilots received serious injuries, one of the them is in critical condition, the other in serious condition.

ATC further informed rescue services that they had lost communication with the aircraft, the aircraft had lost an engine, no further information was known to ATC.

The FAA confirmed the aircraft developed engine trouble and needed to land in the water while attempting to return to Honolulu.

[jono]

I kinda sampled it and missed Nye's email, what did he say? I wonder if I could get get Kusenko to bet me that it's impossible for sailboats to go faster than windspeed, I could use the cash.

Nye basically said he thought the professor was right and that if this worked sailboats would be doing it. I'd bet watching that little all-wheel model was an aha moment for all of those guys, but Bill Nye's comeuppance is always sweet. He should have stayed in comedy (not a dis on his sciencing).

I think sailboats could do it, just to a lesser benefit. Consider that it would probably work fine if you start with an America's Cup hydrofoil and just add a pair of props. Whether it's worth doing is another question--the logistics of how you'd use it and how to hide it when not in use seem challenging. An AC airfoil would simplify things vs. sails, though.

But to the extent that friction (and water prop drag) slows the boat down, that's a problem for going fast, but does it change anything WRT generating net thrust? Seems like it all still works but with less speed gained.

[Ted Striker]

@10:53 "this fan is powered by the wheels"

Not sure if the three of them knew they were connected at all, or if they just glossed over it, but that's where the mental disconnect was.

[jono]

@10:53 "this fan is powered by the wheels"

Not sure if the three of them knew they were connected at all, or if they just glossed over it, but that's where the mental disconnect was.

They knew. They were discussing equations describing the actual system at the start of "who's right?" If there's an orthodoxy in physics it must be "watch out for perpetual motion machines!" They were a little overzealous.

It seems like we're both seeing it through our most common lenses, too: as a pilot you know a prop can outrun a tailwind. As a degenerate dynamicist I see a system with 1 degree of freedom (like the little wheel/gear car) and it's behavior seems intuitive.

Actually, now I'm even more curious what those guys found convincing. The treadmill is pretty solid, too, given their initial skepticism about it. Kinda funny to guess that a person could "fake" that well enough to overcome friction.

[Ted Striker]

I also raced sailboats, where the fastest way downwind debate was huge.

If they knew, and still got hung up on the math, those are some pretty big blinders they had on. I never watched the original video, just the who's right, and the moment he said the fan and wheels were connected I knew he was going to win the bet. And I just barely got through 200 level physics. It's an especially bad look for Tyson, who is literally selling a course on critical thinking.

It's like those nerds never hung out down by the train tracks when they were kids.

[jono]

^^That's actually why I think the wind aspect is such an easy hang up--lots of physics tests asking whether it helps to put a fan on your boat to blow on your sail. Makes it easy to forget that any difference (voltage, height, velocity....) represents potential energy.

To quote a wise teacher of physics "you don't really understand something until you can describe it mathematically." So I expect they all understood the discussion to be about whether the math accurately described it. In that sense it shouldn't really be a distraction. And in the end the apparent red flag of a "divide by zero" possibility was explained correctly.

I'm kind of glad he wasn't more rigorous up front. $10k troll is not as funny as Mr. Nye used to be, but it's something.

[Toadman]

I just felt like this thread needed a bump.

https://twitter.com/WillManidis/stat...-trial-2023-10

[Ted Striker]

That's pretty funny (intended or not)

[Core Shot]

That video is trippy. CGI?

Sooo. Back on track. And related to the thread.

What about VTOL airplane on a treadmill?

I guess we would need to know the length of the treadmill? If it’s long enough I say it takes off.

[Brock Landers]

I just felt like this thread needed a bump.

https://twitter.com/WillManidis/stat...-trial-2023-10

It’s crazy, I just landed and as we were taking off, I was thinking….i think I want to bump the treadmill thread.

Need to play the lotto!

[Ted Striker]

That video is trippy. CGI?

No. That's legitimately what the SFO 28L approach is like when you've got the speed up, and the guy on 28R is slowing down.

[Core Shot]

No. That's legitimately what the SFO 28L approach is like when you've got the speed up, and the guy on 28R is slowing down.

Cool. I love inside baseball.

But since you’re a pilot. What about VTOL on a treadmill?

[Gepeto]

No. That's legitimately what the SFO 28L approach is like when you've got the speed up, and the guy on 28R is slowing down.

c a n t b e l i e v e u n e e d e d t o e x p l a i n

The Earth is spinning at 1,000 mph while traveling through space at 67,000 mph, and I never miss the toilet.

I do it standing just to impress myself - wow, I am amazing

[Gepeto]

...What about VTOL on a treadmill?

That would be straight up, as in V.
I think you're mean STOL
https://youtu.be/WMVjYT6laKo?si=wU_QnCO44_booN3U

6 feet

[Ted Striker]

The Earth is spinning at 1,000 mph while traveling through space at 67,000 mph, and I never miss the toilet.

Ha! so true. A satellite in geostationary orbit "doesn't move" yet it does.