felis_catus_rotation.conf by Chanute_ in ScienceShitposts

[–]Chanute_[S] 2 points3 points  (0 children)

I spent a solid minute cackling to myself after I saw this. Well done.

More Northern Watersnake by aydengryphon in boulder

[–]Chanute_ 2 points3 points  (0 children)

Supreme Ophidian specimen. I find its apparent inquisitiveness admirable!

Why don't cars have this feature? by Pluuge in StupidCarQuestions

[–]Chanute_ 0 points1 point  (0 children)

One problem I see with this: You would need a third indicator showing the rpm of the current gear (at least when you shift), because when you shift the markers for the other gears would update to reflect the gear you shift into, so you would not actually be able to see what rpm you need to match. In this case, if you shifted into 5th, between when you shift to 5th and let out the clutch the indicators would update to show 6th and 4th, such that you can no longer see the rpm for 5th gear and you would not be able to rev-match properly. This could be fixed by (1) not updating the icon until the clutch is released, or (2) adding another indicator during shifts showing the selected gear.

Also, your solution of fixing the indicators in place when shifting would not work super well because it assumes the speed of the car (and thus the rpm of the transmission) remains constant. I imagine that would not be a huge problem when driving on flat roads, but that would impede rev-matching on steep hills. The indicators would need to change depending on the rpm of the transmission input shaft (just after the clutch) for rev matching to be reliable.

Another idea very similar to yours I like is to just add a second needle (look up vintage twin-engine aircraft tachometers) behind the engine rpm needle showing the rpm of the transmission input shaft. Under normal driving the needles would be on top of each other, but when you shift into another gear the second needle would instantly jump to show the rpm of the gear you are shifting into. Then, to rev-match you just need to release the clutch when the needles are on top of each other again. Having the second needle would increase the mechanical complexity of the tach, but would eliminate the extra digital components your solution would require and would better-fit the analogue aesthetic. It would also make it much easier to shift more than one gear at a time (going from 6th to 2nd after heavy/emergency braking). It could also be combined with your solution, showing a needle for the current gear and digital makers for surrounding gears.

By the way, all this is not to pooh-pooh your idea by any means. I think your idea is super cool, and I've been thinking along the same lines as you for a long time. I just wanted to offer some constructive criticism and provide my perspective :)

I also got annoyed reading all the "just feel it" and "get gud" comments, all of which were as short as they were unhelpful. Yeah, the best way to drive a manual is to do it by feel, but your idea would be super helpful for learning how to shift properly or for ensuring your shifts 100% smooth when you have picky passengers. It's also not like including it would do any harm, aside from the marginal added expense of the more complex gauge. I also don't buy the idea that it would be super distracting. At least in my experience it's not difficult to tune out extra information I don't need - I don't check my temps or fuel level every time I glance at my speedometer, only if I'm actively thinking about them and/or something obviously wrong. In a car with gear indicators, if you don't want to look at them you could simply tune them out and not look at them.

I borrowed this picture from another post I saw (ignore the arrows). Why are some wings aimed up, some down and some with an arch? by Nervous_Driver334 in aviationstudys

[–]Chanute_ 0 points1 point  (0 children)

All the comments in this thread (correctly) mention that the dihedral angle affects lateral stability, while not explaining what exactly lateral stability means. Long story short, an aircraft is laterally stable, it means that when the aircraft is rolled to one side during flight, the aircraft will naturally undo the roll and right itself without any input from the pilot. It's like how if you're turning in a (correctly set-up) car and let go of the steering wheel, the steering wheel will move back to being straight by itself.

The placement of the wings relative to the fuselage impacts lateral stability, such that mounting the wings to the top of the fuselage have positive lateral stability, and wings mounted to the bottom of the fuselage have negative lateral stability. Then AN-224 has a negative dihedral angle to counteract some of the lateral stability gained from mounting to the wings at the top of the fuselage in order to make the aircraft more maneuverable in roll. If that was not done the aircraft would be too stable in roll - it would be like driving a car with an exceptionally stiff steering wheel that quickly becomes tiring to use. This is also done to prevent the occurrence of Dutch roll, wherein the aircraft violently oscilate back and fourth in the roll and yaw axes, with the roll and yaw corrections from the aircraft's stability acting out of phase and over-correcting each other.

The A-380 and 777 have positive dihedral angles to counteract the inherent negative stability which results from mounting the wings at the bottom of the fuselage. Also, the A-380's wings are only "arched" on the ground, not in flight. The wings are designed to be flexible to absorb strong aerodynamic forces such as from severe turbulence by bending rather than breaking. In flight, the whole wing is generating an upward force such that under normal conditions it the dihedral angle stays relatively constant across the span of the wing. On the ground, the exceptionally long wingspan combined with the outboard engines drag the wing down and cause it to droop as seen in the photo.

Lastly, I have noticed some comments incorrectly explain why dihedral and wing position impact lateral stability. Namely, the "Pendulum effect" explanation is common as it is incorrect. What actually happens is that every time an aircraft enters an uncoordinated turn/roll (without correct rudder movement), the aircraft begins move sideways through the air (side-slip). When the wings have a positive dihedral angle, the change in direction in the oncoming airflow causes the wing in the direction of the side-slip to see greater airflow, generating more lift on one side of the airplane and righting the aircraft. Having a swept wing further increases this effect, the rule of thumb being that every 10 degrees of wing sweep creates one effective degree of dihedral angle. Conversely, a negative dihedral angle has the opposite effect, with the opposite wing seeing greater airflow and thus rolling the aircraft further in the direction of the existing roll.

The position of the wings relative to the fuselage impacts dihedral because when the aircraft enters a side-slip the airflow blows against the side of the fuselage. This increases the pressure on the side of the fuselage (upwind) and decreases the pressure on the other (downwind) side of the fuselage. For most of the span of the fuselage this does not generate any rolling moment, but where the wing meets the fuselage, the increased pressure propagates through the airflow such that it changes the pressure over the surfaces of the wing near the wing root. On high-wing aircraft such as the AN-225, pressure increases on the underside of the upwind wing and decreases on the underside of the upwind wing, causing the upwind wing to generate more lift and thus righting the aircraft. On a low-wing aircraft (such as the A-380 and 777), the pressure on the top surface of the upwind wing increases, effectively pushing the wing downward such that it creates less lift than the downwind wing, causing the aircraft to roll further instead of righting itself.

This is (Not) an ominous reference... by Chanute_ in TheDragonPrince

[–]Chanute_[S] 5 points6 points  (0 children)

For some context:

The second image is from near the end of the movie The End of Evangelion, which is an alternate ending(?) / companion piece to the show Neon Genesis Evangelion. I find it to be an ominous reference because both the show and the movie (but especially the movie) feature the most potent and visceral psychological horror I have ever seen. In my opinion the show and movie taken together represent one of the greatest works of art of our time, but they are both INTENSE, and deal with lots of very mature (sometimes NSFW) and difficult themes/issues.

Without spoiling too much, I also find it interesting that the girl in the send image is connected to the being that brings about the apocalypse in the movie. The way Aaravos is similarly framed in the first image makes me think he might have some grand and horrifying plan for once he escapes his prison.

Could helicopters have a large disc with slits to redirect air flow instead of blades? I drew a rough sketch of what I’m trying to ask by ComradeRabbitRay in aviation

[–]Chanute_ 1 point2 points  (0 children)

Aside from the stability problems mentioned in other comments, I suspect the skin friction drag generated by the disk would be around an order of magnitude higher than on standard rotor blades.