Comments by "Gort" (@gort8203) on "driving 4 answers" channel.

"People hate to think." Truest thing ever said in a YouTube video.
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Actually turbojets do struggle more at high altitude than at low altitude. Air density is the prime determinant of how much thrust the engine can develop, so thrust drops with every foot the aircraft climbs. Transport aircraft get around this by flat-rating their engines. At low altitude the engine can actually produce more thrust than than it internals can withstand, so the throttle is only advanced as far as that limit. As the airplane climbs and air density and thrust drop off you can increase the thrust lever setting to work the engine harder and continue to produce sea level thrust with reduced air density -- up to a point of course. It is somewhat analogous to managing manifold pressure in a supercharged piston engine. At low altitude the turbo can deliver more MP than the engine can withstand, so you have have to throttle the engine back until you reach the critical altitude where you are working it at max capacity.
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@makantahi3731 Your sentence is unintelligible, but if I read it correctly you are mistaken. Air from 12 km high is less dense than sea level, but it is colder, not hotter.
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Your videos are fantastic. I've never seen such clear and easily understandable explanations of the subjects you cover.
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@makantahi3731 You have it backwards. The air below is forced to be denser by the weight of the air above it. Air is compressible, you know. Try looking up density altitude.
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If this engine turns out to be suitable for UAVs it might also be suitable for light aircraft, at least in the homebuilt/experimental category. The acquisition cost would have to be competitive, which could happen if these engines get mass-produced for other applications. Durability is an issue, but since many civil light aircraft spend far less time in the air than UAVs the short time between overhaul might not be a serious limitation.
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Yes, that is just one example of a few techniques he said "don't work" that actually do, but are not practical because they are either dangerous or increase wear and tear on the vehicle. Another one is that starting a warm engine uses more fuel than idling at a stop light. That is not true for the length of time spent idling at a typical stop light in a congested area. But I still wouldn't do it because the small amount of fuel saved is not worth the various downsides to shutting off your engine.
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Agreed. "Centrifugal force" is what the occupant of the car feels as he is pressed against the side of the side of the car/seat that is accelerating him in the direction of the turn. Centripetal force is what pulls the car toward the center of its turn radius. It is a continuous lateral acceleration.
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What a great video. This channel really shines in comparison to all the slipshod drivel on YouTube. Subscribed!
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@Rob-pf6yl It's amazing how a person can take a statement out of context and then slavishly adhere to their misconception despite all evidence to the contrary. And this isn't even politics, it's science.
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Because it has a centrifugal rather than axial flow compressor, and a single stage turbine.
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Great video. Even though I already understand this material, I enjoyed and admire your most excellent and coherent explanation. I have forwarded a link to others who I know will find this video very helpful.
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Great video. I would love to see you do a video explaining the balance of a radial piston engine as used in aircraft and some armored vehicles.
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I thought I understood 2-stroke engines, but I have not kept up with them and missed a few things. This excellent video was more than worth watching.
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I think what he is calling cornering force is usually called centripetal force. It is generated by the slip angle of the tires, although I'm not sure I follow his representation of how friction generates this force. Also, he must have assumed it is self-evident, because he didn’t mention how the rear tires obtain the slip angle necessary to general lateral acceleration either. I also don’t think he adequately explained that this force is imparting a lateral acceleration that changes the path of the car, perhaps because he sees it as self-evident. But of course the fundamental issue is that it takes a lateral force to accelerate the car in the direction the road is curving away from the straight path, because without that force inertia would keep the car on an unaltered trajectory. I thinking the terms inertia and acceleration should not be absent from this discussion.
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@richardconway6425 Yes, and a piston engines driving propellers is still the most fuel-efficient powerplant for slower aircraft as well. They fell out of favor for most commercial aircraft due to requiring more maintenance and being less reliable than turbines. That, and their higher fuel consumption was partly outweighed by jet fuel being less expensive than high avgas, even though you have to carry more fuel. I wonder if that is that is still the tradeoff it once was, as I remember when diesel used to be cheaper than gasoline as well.
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The low slip angles of modern tires may make the 4-wheel drift seem mythical, but it is very real. And with skinny bias ply tires it can be done at quite a dramatic angle. That, and the perfect rev-matched downshift while trail braking, are the two most rewarding experiences I've had while driving an automobile.
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Professor D4A, another great video, thank you.
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By military jet engines you mean for high speed aircraft, not transports, and they will always be less efficient. The low bypass ratios and afterburners needed for high speed flight can never be as efficient as a high bypass turbofan. The humble 4-stoke engine can't even play in that high-speed arena.
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Yes, fun and informative, thank you.
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It would seem that a mechanically practical of extracting the energy remaining in the burned air-fuel mixture is a turbo-compound engine like the R-3350. Engines like that have been quite successful. How does their efficiency compare to a 5-stroke engine?
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Another superb video.
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There is good reason for the San-Ti to not trust us.
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Great job, as usual!
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No, a gas turbine is not basically a turbocharged piston engine.
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The discussion of pressure within the engine was a bit unclear to me. If it helps, a turbojet creates thrust by increasing the velocity of the exhaust, but there is also a pressure difference between the air entering the compressor and exiting the turbine. The maximum engine pressure ration (EPR) an engine is capable of is an indicator of its efficiency. For a turbojet the actual EPR indicated at any given moment is the primary method of setting engine thrust to the value desired for takeoff or climb. Turbofan engines are different and typical set thrust by the fan RPM (N1) because much or most of the fan air bypasses the turbine, making pressure ratio a less useful indication of thrust setting.
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Thank you for working to dispel this myth. And yes, video games have misled many players, who then spread their misconceptions on YouTube. This is especially true of people who play air combat video games and then think they understand the realities of air combat. I wish you had a counterpart in that arena.
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Just don't forget that the light weight of the turbine engine is offset the extra fuel you have to carry to go the same distance as the more fuel-efficient piston engine.
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It works the same way. The difference is that the first row of blades is larger and called the fan because some of the air bypasses the engine compressor. Everything after that point is essentially the same. Turbofans take more energy out of the turbine section to power the fan. Turbofans are more efficient than turbojets at lower speeds and altitudes.
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If you hold the steering angle all 4 tires remain at an angle to the direction that car wants to continue in due to inertia. The slip angle continues to accelerate the car laterally off that straight path
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