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1937 film explains how a car differential works (roadandtrack.com)
498 points by oedmarap on Dec 26, 2020 | hide | past | favorite | 144 comments

I work as a diesel engine technician for a small midwestern chain and I whip this video out in the breakroom whenever the apprentice gets an idler/pitman or diff rebuild on a large truck. So many of the guys i work with know about LSD (Limited Slip Differentials) and locking differentials/hubs, but dont entirely understand why they are needed or how they work once the wheels are back on the ground.

if you really want to see something cool, check out interaxle differentials and detroit dfifferentials. https://www.youtube.com/watch?v=e-d-uOYCrRE

torsen differentials are incredible as they can in many cases overcome the traction difference problem https://www.youtube.com/watch?v=JEiSTzK-A2A

I watched those two other videos, the second one twice, but I still don't really understand them. The 1937 video clicked perfectly on the first viewing.

The first video explains differential locks. Basically with an open differential all power would be routed to a wheel that’s getting no traction (for instance if it’s on ice). A differential lock closes it, so it’s as if there were no differential, so both wheels on the axle will turn at the same speed. This is bad if you’re on a normal road (obviously, since that’s why differential were invented) but great in low traction environments like mud or ice.

Most off road vehicles have locking differentials.

Yep, until I'd done off-roading, I never understood why my uncle told me (when driving his vehicle, which had the ability to lock the diff) - "Never ever use this on pavement / normal driving". I obeyed him, but I always thought he was full of it, until I had the money & time & inclination to work on cars, and I learned what was really going on.

"Aaaahhhh... so that's why he told me that..." Thanks Uncle Bill!

Yeah I believe this is how modern cars with traction control work, they brake the slioping wheel so the one with contact can get the traction.

At least this is how it was explained to me by my mechanic friend

Applying the brake on the slipping wheel is one half of traction control. Reducing the power going to the wheel is the other half. I accidentally demonstrated this to myself many years ago when my car suddenly was almost completely ignoring my throttle input for a reason I couldn't explain. It turned out I still had the parking brake on and when I went over a patch of ice and the car lost traction, adding more brake wouldn't do much, so it simply ignored my throttle. Because I wasn't moving more than about 5 miles per hour to begin with, it felt like the car just refused to move, like a stubborn mule.

Thanks for the explanation, I didn't know that!

It is amazingly effective indeed. One time I was driving through ice and snow, and at the traffic light I turned of the ESP by mistake (was trying to plug in my phone charger in the lighter socket beside the button). When I took off I nearly crashed myself off the road, I never realised how slippery it was, and how much the car was covering for my ignorance.

I've tried thinking hard on the second video. I guess most confusion comes from as it doesn't explain why traction situation (where wheel speeds up relatively) is different than the actual turn (where wheel slows down relatively). Here, as speeding up wheel gear can not spin the worm gear, power is captured "back" to the other wheel through the outer locking cage. However, first comment at youtube and an another article (https://www.kmpdrivetrain.com/differentials/torsen-vs-plated...) states that it wouldn't work with 0 traction and can get only the amount of slipping traction torque to the other wheel.

A simple way to think of it is that “locking the differential” could be thought of as disabling it, turning it back into a conventional axle.

So this is useful when you’d prefer a conventional axle: when one one side has a grip and the other side none.

The lack of background music and pace is really interesting to me. Compared to a typical "how it's made" video [1] (which I feel has a similar level of detail), this video feels significantly more digestible. Those moments of silence feel totally alien and out of place in today's style, but I think contributes positively to my ability to understand and process the information.

[1] https://youtu.be/8gno0_emzo8

That's mostly American television. I cannot watch American documentaries because everything is being hyped as largest, heaviest, most expensive, deadliest, etc. and is being narrated in the same sensationalist tone. I cannot convey the tone by text but you certainly know what I mean. The interesting details always get lost because the hype must be there to keep people watching after the next ad break.

European documentaries usually simply follow the process and neutrally explain what is happening.

Not sure if I agree. European YouTube channels are doing the same. It’s a general trend, not specific to American productions. The real reason is the incentives that content producers are subjected to. Notice how YouTube algorithms have promoted thumbnails to include faces. TV, documentaries and the likes are subjected to viewership and engagement metrics. Things have gotten worse over the years.

There are still a lot of great YouTube channels - Applied Science, Tech Ingredients and such. Nationality has nothing to do with this. 1970’s American television was amazing. Watch some Bell Labs videos or how Saul Bass did branding.

I think the opposite is true. There are so many interesting YouTube channels today, it's "quality documentaries" that were unthinkable in my childhood in the 90s.

Technology Connections, Numberphile, 3blue1brown, NativLang, Ben Eater, VSauce, Tom Scott etc.

As a teenager I could watch NatGeo and perhaps another similar channel with 2 hour dragged out documentaries with talking heads edited and narrated by people who don't love the topic the way these YouTubers do.

I think the Internet is still great if you curate what you watch and read, it's better than ever. But perhaps it's worse on the average. The junk is more potent and the intellectual poison is dosed higher than even the worst reality shows used to be on TV.

Both of these can be true at the same time.

Also, you're watching this 1937 docu on YouTube, not on Discovery Channel on TV.

> I think the opposite is true.

Not sure if there is any disagreement, you're resonating with what I said. Both are true - there is some shitty stuff and there are some great channels. Cherry picking examples doesn't actually drive my point so let me try again - It's not so much about specific channels/documentaries, but whether nationality has anything to do with it. I just don't think Americans produce content that's any different than Europeans. That was the point I was trying to convey.

I think the over-the-top style and "dumbing down" is an American influence. Many European countries have or used to have many tax paid productions on public channels, where they didn't have a business mindset at all. Especially before ~2000 in my post-communist country, documentaries were not optimized for engagement, partially because the people making it were not skilled in marketing and just didn't think that way.

Those productions are often actually really boring though. For all the bad stuff we say about History Channel and alien documentaries, it was torture to watch some boring history docus in school history class about some medieval battles with a dry voice detailing the dates and the names etc.

Sure there's a space in between, I just mean that the very commercial-focused documentaries are more an American thing and arrived along with American style cable TV to Europe.

BBC documentaries (especially the nature ones) do a lot of obnoxious foley work.

Also, a very dangerous drinking game is to watch BBC's Planet Earth and have a drink every time they use a superlative ("most," "biggest," "fastest," etc). So that is also definitely not an exclusively American phenomenon.

I've been watching the Free Documentary (I think that's their name) channel on Youtube. They're all European documentaries. They over hype stuff and design around commercial breaks too.

If you’re up for it, go watch an old episode of the show Columbo [1]. Each episode from this 1970’s era TV was over an hour long with no commercials. It’s full of slow, long, quiet scenes. There’s so much time. It’s really amazing to watch. It helped inspire me while making YouTube videos to give more time when cutting things, even if it’s not optimized for algorithmic advancement.


That's a good observation. There is a slow pacing but when it's quiet your mind is still working so it's not 'boring' time.

It's just like in sports now where someone has to be rambling about something the entire game, even though you're watching it. It's still useful, often to find out which player shot or for the added excitement with the crowd. But they ALL feel the need to fill dead space the entire show which I personally would experiment with if I ran the show. There's plenty going on always already. Humans are weird like that.

I'm sure this has applications in Youtube and other educational videos or whatever.

If the losing team wants to win this game, they are going to need to score more points.


> The lack of background music and pace is really interesting to me. Compared to a typical "how it's made" video [1] (which I feel has a similar level of detail), this video feels significantly more digestible. Those moments of silence feel totally alien and out of place in today's style, but I think contributes positively to my ability to understand and process the information.

I think that's because the older movie is an actual educational movie, while the video you linked is really pseudo-educational entertainment. An educational video has the goal of leaving the viewer with actual understanding of something, while the pseudo-educational video only cares to vaguely tickle the viewer's curiosity, and is fine to leave them nearly as ignorant as when they started. While the two movies may have a "similar level of detail," the educational video focuses on fully explaining a specific problem and solution, while the pseudo-educational video only vaguely skims through the high-level steps of some manufacturing process and barely even explains what the product is for.

http://www.engineerguy.com/ makes educational videos similar to this 1937 movie on a lot of similar topics.

Agree. I got quite interested in the topic in the past [1] — it ultimately boils down to optimizing for attention (modern YouTube) vs optimizing for data retention (traditional education).

[1] https://giansegato.com/essays/edutainment-is-not-learning/

That's exactly why this three-hour ‘Intro to synthesis’ series is one of my favorite explanations on musicmaking: https://youtu.be/atvtBE6t48M

Instead of running through all the parameters in ten minutes and one second, the dude keeps twiddling the knobs and lets you hear what they do. He spends ten minutes on dialing just one sound.

As a bonus, since the vid is from the early eighties, you can occupy yourself by guessing exactly how high the man is.

A good thing about that film is that after seeing it if I can't remember how a differential works I usually can remember the steps they took to get to how a differential works and then figure it out myself from there.

That suggests that it didn't just tell me how a differential works. It taught me how someone who needs to invent a differential should think about the problem.

There’s another type of differential called a “spur gear” differential, where none of the gears are at right angles. It’s a much stronger design than a bevel gear differential, but also has a much larger diameter. It’s classic application is in farm equipment.

Yes, this is the first time I’ve seen it explained starting with just two spokes. It motivates the eventual design of the differential and illustrates the mechanism far better than simply showing the full gears of the end product.

This is my favourite way of learning (and teaching) most things. I hate when I'm just told "this is the way it is". I want to know why, what problems does it solve and how was this developed.

Here's the actual film (linked in the article)


Yes, "Around the Corner", one of many Jam Handy films made for Chevrolet. They're all on the Internet Archive, where they can be seen without ads.[1]

There's a whole series. "Spinning Levers" (transmissions), "Down the Gasoline Trail" (fuel), "Just a Spark" (ignition), "Tough Friends" (steel), "No Ghosts" (frames), and more.

[1] https://archive.org/details/0141_Around_the_Corner_M00267_08...

Somebody should use the latest AI libraries available to upscale all these to 4K and maybe even colorize them.

If you enjoy this, don't miss the video lecture on World War 2-era mechanical fire control computers by the U.S. Navy. I learned you can do a lot of computations with gears and shafts.


Another great older film is "Similarities of Wave Behavior" [1] from Bell Labs. It was aimed at college students, and covers in a very clear way these topics: reflection of waves from free and clamped ends, superposition, standing waves and resonance, energy loss by impedance mismatching, and reduction of energy loss by quarter-wave and tapered-section transformers.

[1] https://www.youtube.com/watch?v=DovunOxlY1k

I always use this video to explain how Time Domain Reflectometry finds a broken cable in a wall. Not everyone is familiar with the idea that a cable going to nowhere can have voltage and current.

Thank you so much for linking to this. I knew about many of the concepts in an abstract sense but this cemented them all together for me in an intuitive way.

This one's good too.


The working is explained in a step-by-step manner that makes learning easy. This is characteristic of old instructional films. The other characteristic is the assumption that viewers will sit through tiresome material at the beginning and the end. Still, the 2/3 in the middle is clear and compelling.

This reminds me of a great film on crafting quartz crystals for use in radios: https://youtu.be/wHenisSTUQY

+1, it's an amazing video. Although I'm a daily user of crystal oscillators (right now on my desk there are 6 circuit boards of my own designs, powered by 12 crystal oscillators), previously I just couldn't imagine how they were made by hand without laser cutting and trimming back in the day, and someone directed me to this video, everything is well explained.

I remember the video being posted here a few years back, interesting stuff.

Original discussion here: https://news.ycombinator.com/item?id=15122031

also https://news.ycombinator.com/item?id=8513209 and https://news.ycombinator.com/item?id=1103156

It's worth going through the previous discussions for the recommendations of similar films

I remember playing with a differential engine in those Lego gear sets many many years ago. When you have a bunch of the pieces lying around and free time, you'll probably accidentally make a differential too.

As for this video itself, I've seem it a few times, and it still really does amaze me how much care was put into this. I assume the video is government funded, and it kind of makes me sad to realize that they had the capability to create educational videos of this quality 90 years ago, but it wasn't high enough priority to broadly apply to the general masses.

> government funded

The video was made by the Jam Handy organization. They did videos for several car companies, and sometimes a consortium of them, is my understanding https://en.m.wikipedia.org/wiki/Jam_Handy

That would explain the abundance of available mini-models that they could machine.

That does take the wind out of the sails of the argument that it could've had a broader focus than just the differential engine. In that case I'll shift my dismay to "90 years ago, videos of this caliber were possible, and yet educating people on a broader scale didn't enter the minds of any entity which could've afforded it."

How would films like this be consumed in the 30’s? Would it be shown in theaters before a feature film?

Another comment pointed out that these were made by the Jam Handy Organization[0].

Just hypothesizing, but either GM might distribute these and have showings for staff as part of training. Almost certainly not for the engineers that already learned this but perhaps sales staff so they could better explain the mechanism and benefits to buyers.

[0] https://en.m.wikipedia.org/wiki/Jam_Handy

I believe Chevy contracted his production company for dealers' training material. Notably, he produced the "Hired!" films for dealership salesmen, one of which was riffed by MST3K in their "Manos: Hands of Fate" episode


To me it looks like it's aimed at consumers, from the part at the end. It's as if the movie is intended to overcome worries "but is all this complexity really safe?" by showing how you can load the differential with running people without issue.

It's most likely for personnel training. It would probably have been shown on a small projector in a classroom setting, much like is still done today.

I assumed high school "shop" class. At least when I was in public school they still had "wood", "metal" and "auto" shop classes you could take (I took the wood class one year).

Military conscripts who were assigned to motor maintenance

> Military conscripts who were assigned to motor maintenance

The OP was asking how people might watch a video like this, not who is watching it. In 1937 broadcast television was relatively new and few people owned a tv. For example, the wikipedia page for TV in 1937 notes that by the end of that year 2,121 TVs had been sold in England:


Conscripts in the 30s in the US?

My understanding is US conscription only restarted for WW2 in 1940.

Interesting fact I learned from this video: early cars were one-wheel-drive!

I was surprised by that as well, though in retrospect it makes sense.

I wonder if such vehicles even had a transmission, or if that was a technological advance that came later? And if, before differential car axles were invented, anyone tried solving the same problem by driving two wheels with separate engines?

With modern electric vehicles that lack a transmission, having a separate motor for each drive wheel seems like a reasonable thing to do now. I assume someone's already built such a thing; the Cybertruck is planned to have a 3-motor variant, though I don't know if two of the motors will share a differential or if they'll just each go to a separate drive wheel. Also the Rivian might have separate motors per wheel, I'm not sure.

This was excellent to watch, though the whole time it made me think of this classic engineering video:


Here's a great one by Hitachi from 2005.


That sounds a lot like the schnebber robber from the "Winnebago Man".

This video from 1960 explaining Frames of Reference is amazing.


The "low-center drive" required development of hypoid gearing, versus the spiral bevel gearing used when the drive pinion axis intersects the axle axis. The strength benefits mentioned in the video come from the hypoid gearing, at the cost of efficiency.

AFAIK there isn't currently open-source CAD tooling for designing hypoids.


So whatever happened to "low center drive"? Every car I've been in seems to have that "hump" down the middle where the axis is.

Edit: nice (short) discussion on this on reddit from 2 years ago https://amp.reddit.com/r/cars/comments/9d33os/why_did_the_ch...

Jam Handy, the author, was a genius.


Stumbled onto this explanation of how a Torsen differential works. I'm still trying to wrap my head around it, but it basically uses the one-way nature oh how a worm gear can turn a regular gear but not the other way around (due to the high gear ratio involved).

So in this differential, the housing can turn both wheels simultaneously, but if one wheel slips and becomes free, it can't direct the torque to the free wheel:


Maybe someone has a better explanation?

Oh, that's a clever design. The explanation, even with all those graphics, is poor. The idea is that one wheel can go slower than the speed it would go if the axle was rigid, but it can't go faster.

With that design (which seems to be a Torsen Type A), the faster wheel does all the work of propelling the vehicle on turns, but the wheels lock together if one starts to slip. So it's for off-road vehicles, like the military HUMMV. (But not the civilian Hummer H1. That used a Dana differential more suited to on-road driving at higher speeds.)

There was a Torsen Type A in the B5 platform revision of the Volkswagen Passat 4motion. It was in the center. Front and rear were plain differentials, with the brakes used for left-right issues.

It worked very nicely on highways.

Video says nothing about forces, however.

With this explanation it seems that if one wheel gets slightly stuck, the other wheel gets all the force, causing a dangerous spinning.

> With this explanation it seems that if one wheel gets slightly stuck, the other wheel gets all the force, causing a dangerous spinning.

This is how a (open) differential behaves, though a spinning wheel isn't so much dangerous as ineffective. This limitation can be overcome using a locking differential or a limited-slip differential, or a traction-control system that selectively applies brakes to a spinning wheel to simulate a limited-slip differential.

In the real world momentum dampens how quickly power is transferred between wheels. Further, real world engines have limited RPM ranges which generally don’t damage freely spinning tires.

So, while such simple differentials can get stuck fairly easily, they also work surprisingly well. The obvious trick is to apply some breaking power to the spinning wheel to then apply force to the stuck one, thus traction control. Or to just lock a differential when bouldering etc. More complicated mechanical systems can always provide some power to both wheels, but they aren’t actually necessary.

> With this explanation it seems that if one wheel gets slightly stuck, the other wheel gets all the force, causing a dangerous spinning.

Your comment really shows how great the video is... That is exactly how an unlocked non-limited slip differential works, much to the irritation of anyone who has found themselves stuck in sand or a patch of ice.

The differential (ignoring locking ones) applies the same force (approximately) to both wheels. If you remember your physics course about lever and force, see the video at 5:00, you can see that the lever is pushed by its center, hence both sides have the same length. So the same force is applied to both wheels. But the speed can be different.

Hence, if one wheel is stuck, it still receives the same force as the other, only speed is lower.

What is more annoying is when one wheel is freely slipping (like on ice), the other will have nearly no force applied to it and the car is stuck.

> What is more annoying is when one wheel is freely slipping (like on ice), the other will have nearly no force applied to it and the car is stuck.

i've learned about this the hard way about ten years ago: started my car, put it in first gear (manual), stepped outside and marveled at the freely spinning wheel on a patch of ice.

fortunately got a push from a stranger who happened to pass by.

> you can see that the lever is pushed by its center, hence both sides have the same length. So the same force is applied to both wheels.

This is not necessarily true. Imagine a similar symmetric lever with a weight on one side, and a force on the axis that accelerates rotation. The acceleration of both ends of the lever are equal, but the force is not equal (since the weight is 0 on the other end).

Anyway, the point of my comment was that a thorough analysis of this configuration is more involved than this video of which it was claimed that it "perfectly" explains how this works.

Sorry I do not understand your weight/force analogy. I assume that in a car, both sides have equal weight/inertia.

Anyway, I did write "approximately" to avoid discussing acceleration/inertia of the differential itself. I should have written "in steady state" or something like that. It is true that a complete discussion can be more involved

Not so much dangerous as useless. That’s why Positraction was invented. And why locking differentials are a thing.


Did you say youts?

loved "My Cousin Vinnie". The scene where the relevance of "positraction" is explained is a classic, not just of law but of the application of good science. Thanks for the reminder.

HN discussion of the video from 2017: https://news.ycombinator.com/item?id=15122031

This video has been posted 20+ times, over the years!


The ending on lowering the differential never explained why they didn't just use front wheel drive. Can anyone fill me in?


The idea was around, it just wasn't very practical at the time due to various constraints on engine size and component layout. It was simpler to keep the driving and steering wheels separate. The stereotypical American car with a huge V8 filling the engine compartment and an equally massive transmission wouldn't leave much space to route the driveshafts[1].

Also, FWD requires a differential too.

[1] They later tried to make a big engine and FWD fit, and ended up with this design: https://en.wikipedia.org/wiki/Oldsmobile_Toronado

You need to be able to steer with the front wheels, so a simple differential like this wouldn't work. You need some additional complexity to support driving and steering with the same wheels (CV axles). It just took time for the technology to become cheaper, more compact, better engineered, and paired with smaller engines.

There used to be a youtube channel called WDTV42 that had tons of these old reels, very comprehensive. Shame they took it down.

Ahah, I knew exactly what this was going to be from the post title. My flatmate made a song in 2018-19 and cut together clips from this to make the music video. Check it out: https://www.youtube.com/watch?v=CGU2pfEdJ_o

Suggest changing the title to reflect that this is a General Motors documentary. They are still around! Why not credit them?

The general motors today is not the same company that made this video.

In 2008 the original general motors was effectively dissolved, the current GM simply purchased some of their assets, which happened to include their names and trademarks.

Do you have a source to explains how you're describing this?

I'm aware of government (financial) aid, as well as appointing government officials to "consult" and direct restructuring, but it's much less clear that it was "effectively dissolved" or that a "new" General Motors purchased assets from the old one.


The wikipedia article is fairly extensive.


The main GM article on Wikipedia used to make that distinction, but it was heavily edited to de-emphasize the fact that the original GM was liquidated. The original company was General Motors Corporation. That went bankrupt, and the name was changed to Motors Liquidation Company. If you were a GM stockholder before the bankruptcy, you ended up with stock in Motors Liquidation. If you were a creditor of GM, you were a creditor of Motors Liquidation.

A new company, General Motors Company, was created, and it bought the more useful assets of Motors Liquidation. Not all of them. Motors Liquidation was left to sell off unwanted plants, and such assets as GM's car collection. (GM used to have a collection of one of everything they'd made.) Today's GM is General Motors Company, much smaller than "Old GM".

Having 1937 next to the name of any modern day company would imply such.

Not really, there are plenty of companies founded before 1937 that still exist

But the people are dead, so they are the same or different ‘company’ in a similar vein of argument.

A company is not the people who work for it, or the people that own it. Its its own distinct legal entity.

Great stuff. Making me think how simpler electrocars are: no differentials, no transmission, no complex injection machinery.

I feel it's a bit unfair to those mechanical components to ignore how complicated power electronics are, for example. They are perhaps less inspectable for a layperson (what happens when you break it open to see the insides?) so we tend to treat them as more of a primitive black box building block, but treat the mechanical components as complicated assemblies of primitives.

You need diff and transmission for EVs thought unless you have direct drive on two wheels.

Yes, most current EVs (including Teslas) have single-speed transmissions at each motor driving two wheels via a diff.

Some upcoming models, such as the Rivian R1T pick-up, put a discrete motor at each wheel, allowing each to be driven independently without need for a diff.

But: redundancy.

Does the inner gear rotate at the rate of speed which is the difference of rates of both wheels? (as the name suggests)

Always loved to watch the opening sequence (motorcycles).

Yes, but what about the turbo-encabulator? https://www.youtube.com/watch?v=Ac7G7xOG2Ag

Such a neat explanation!

The style in those old films is so relaxing and pedagogically great.

Has anyone else noticed that today's educational content intended for adults increasingly uses a format that was regionally only used for very young children? There is almost always personality emoting and doing accidentally on purpose funny things and laughing, exaggerating everything to keep people engaged.

This is the subject of an entire book by Neil Postman called "Amusing Ourselves To Death" (1985), including a chapter called "Teaching as an Amusing Activity".

Some excerpts from the book:

> “Dr. Ruth Westheimer is a psychologist who has a popular radio program and a nightclub act in which she informs her audiences about sex in all of its infinite variety and in language once reserved for the bedroom and street corners. She is almost as entertaining as the Reverend Billy Graham, and has been quoted as saying, “I don’t start out to be funny. But if it comes out that way, I use it. If they call me an entertainer, I say that’s great. When a professor teaches with a sense of humor, people walk away remembering.” She did not say what they remember or of what use their remembering is. But she has a point: It’s great to be an entertainer. Indeed, in America God favors all those who possess both a talent and a format to amuse, whether they be preachers, athletes, entrepreneurs, politicians, teachers or journalists. In America, the least amusing people are its professional entertainers.”


> “We may surmise that the ninety million Americans who watch television every night also think so. But what I am claiming here is not that television is entertaining but that it has made entertainment itself the natural format for the representation of all experience. ... The problem is not that television presents us with entertaining subject matter but that all subject matter is presented as entertaining...”


> “Books, it would appear, have now become an audio-visual aid; the principal carrier of the content of education is the television show, and its principal claim for a preeminent place in the curriculum is that it is entertaining.”

> She is almost as entertaining as the Reverend Billy Graham

Can someone explain this to me? Billy Graham is... the last person I’d think of as an amusing figure.

I believe part of the attraction of Billy Graham was that many people found him amusing. Postman characterizes him as principally an entertainer.

In the chapter "Shuffle Off to Bethlehem," Postman compares the 20th century televangelist with 17th-19th century spiritual leaders:

> “Television’s strongest point is that it brings personalities into our hearts, not abstractions into our heads. That is why CBS’ programs about the universe were called “Walter Cronkite’s Universe.” One would think that the grandeur of the universe needs no assistance from Walter Cronkite. One would think wrong. CBS knows that Walter Cronkite plays better on television than the Milky Way. And Jimmy Swaggart plays better than God. For God exists only in our minds, whereas Swaggart is there, to be seen, admired, adored. Which is why he is the star of the show. And why Billy Graham is a celebrity, and why Oral Roberts has his own university, and why Robert Schuller has a crystal cathedral all to himself. ”


> “It would be a serious mistake to think of Billy Graham or any other television revivalist as a latter-day Jonathan Edwards or Charles Finney. Edwards was one of the most brilliant and creative minds ever produced by America. His contribution to aesthetic theory was almost as important as his contribution to theology. His interests were mostly academic; he spent long hours each day in his study. He did not speak to his audiences extemporaneously. He read his sermons, which were tightly knit and closely reasoned expositions of theological doctrine Audiences may have been moved emotionally by Edwards’ language, but they were, first and foremost, required to understand it. Indeed Edwards’ fame was largely a result of a book, Faithful Narrative of the Surprising Work of God in the Conversion of Many Hundred Souls in Northampton, published in 1737. A later book, A Treatise Concerning Religious Affections, published in 1746, is considered to be among the most remarkable psychological studies ever produced in America.”

Thirty five years ago is a long time culturally.

He was so popular he even got to meet the queen of england when he was in the UK:


(This is dramatized in Netflix’s Crown Season 2 Episode 6)

Amusing probably isn't the right word, probably captivating is better. Preaching is a very well developed art; listen to preachers and they're always telling a story of some sort, the story goes to lows and then up to highs, they draw that story back to the lives of their audience and then finish with a call to action to make their lives better. Even details like the preacher's cadence and the songs and rituals are well thought out and tested to keep people engaged. It also helps that the bible is essentially a collection of stories that touch on fundamental themes of the human condition and that Jesus is a universally relatable figure.

I agree that this is definitely a trend, so I feel like highlighting a great example of educational content that is very dense, concise, and with just a touch of whimsy: 3Blue1Brown on Youtube[0]. He has been doing math education videos on YouTube for years. I just watched his latest video on the medical test paradox and redesigning the Bayes rule to address it[1].

All his videos are absolutely phenomenal - the best educational content I've seen on YouTube. I cannot recommend them highly enough. In my experience it is more akin to reading a (very engaging) textbook than watching a video. I often find myself pausing to think things through and can _feel_ myself grasping at new ideas and learning while watching.

[0] https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw [1] https://www.youtube.com/watch?v=lG4VkPoG3ko

No need to highlight this here. 99% of HN readers know 3b1b

I think people drastically overestimate how popular YouTubers they follow are amongst everyone else.

I'm in the 1% that never heard or noticed 3b1b. This doesn't rule out that I could have watched some of those videos, but I still didn't know him. Wrong age group?

Your comment only serves to hinder today’s 10 Thousand: https://xkcd.com/1053/

The down votes are likely due to that as the comment does not contribute to much. If folks don’t want to hear more about 3b1b, it will just not gather upvotes.

I get so tired out by the constant filler in written and video articles of education. At the same time, the internet is becoming harder and harder to search for specific bits of information in lists, encyclopedias or other easily referenced and digestible formats.

Earlier today I was trying to find a list of all Alfa Romeo models to identify a car, and all the top results were ten paragraphs of SEO infused filler bullshit, with some smattering of half or less of the cars. Genuine enthusiasts get crushed under the weight of mighty marketing budgets seeking a pittance of adsense dollars.

I searched for Alfa Romeo models and my top hit was Wikipedia that listed all the models (I think).

Which is what I ended up using then googling each model to find images. Years ago I would expect Google to find a great array of enthusiast blogs that might have them properly catalogued, but nowadays it's mostly content marketing articles. Stuff like this: https://www.motortrend.com/features-collections/most-beautif...

It's an op-ed designed to get clicks and turn ad dollars, in a format that extracts even more clicks once you arrive. That's what's frustrating, all the genuine information is being replaced with content marketing apparatuses. That's not really Google's fault intentionally, it's just how the ecosystem has evolved.

Agree. Children's "science" books today are that way too: "Grossology", "Oh, Yuck!", "Totally Gross Experiments and Activities" to name a few....

Even the ones that are not hit-you-on-the-head scatological are still, as you say, trying to be funny and engaging but in a patronizing way.

Perhaps I am not the target audience but I preferred young science books that made you feel like you were learning real science — learning about the chemistry of plastics for example. The science wasn't a footnote to the experiment, it was the reason for the experiment.

Mae and Ira Freeman's science books for kids were great for younger readers. Kenneth Swezey's books. The classic "Golden Book of Chemistry" is a little slick, but still good (https://www.academia.edu/37919681/The_Golden_Book_Of_Chemist...).

Or maybe I just preferred the presentation of the older books...

It's something that as a French person associate a lot with the USA, although the cultural influence of America is so great that it's been borrowed by many other cultures as a "hip" thing to do. Everything is uh-may-zin in America. Everything is "WOW" and "FLAVOUR BLASTED" and ends with an exclamation point.

I often mock some of my American friends by mimicking them when they say that some rather mundane thing is "AMAZING" or "OH MY GOD I CAN'T BELIEVE IT" or "THIS IS INSANE" and no, Mark, it's not insane, it's just a decent piece of a cake.

Of course my default French blasé attitude towards everything errs the other way, there's probably a compromise to be found. But at least when I say that I found something to be "amazing" my friends generally take note, because it's not something I say lightly.

That's sort of the main issue for me, it's like the loudness wars for music mixing, when people tell you how to unclog your drain as if it was the most amazing thing that ever happened to them the baseline is completely skewed.


You should try watching British Pathé on youtube. They have a series from the 50’s/60’s about how stuff is made and it’s wonderful. Great quality too.

Person-to-person interactions have changed dramatically since those days. Western culture had a sense of duty and progress that is now questioned by the postmodern intellectual elites. The emphasis today is on "enjoying yourself" in your own bubble, and debating "grand moral standards" is even ridiculed.

It's not clear that this phenomenon (if it exists) has anything to do with the relaxing of educational content norms. If anything, the technological advancements caused by that 'sense of duty and progress' have led to a reduction of the average 'Western' attention span to the point of requiring reductive and trivially engaging educational media. That's probably not really the case either, but it seems just as valid of a theory without considerably more rigorous investigation.

Just Coursera has more high quality educational content than all these silly videos that were ever produced combined. Western society moved forward - unlocking education from ivory tower universities and making it freely accessible to students around the world.

Without going down the "moral decay" debate and with all due respect to the coursera content, pedagogically wise nothing touch old video content (check out also the ATT science brief), like wise for the science books. It is only very recently that we have content producer like 3blue1brown or learnengineering that start to match or even exceeds those.

> There is almost always personality emoting and doing accidentally on purpose funny things and laughing, exaggerating everything to keep people engaged.

And to keep videos above a certain length so that the algorithm prefers them over short, concise videos, and that the chance is higher for multiple ad rolls (= more monetization).

Like the stunt riding and log rolling?

Youtube has recommended a few videos from the channel Learn Engineering that have been surprisingly good. For example: https://youtu.be/esUb7Zy5Oio

A lot of 40s videos are so well balanced between basic tangible ideas to full device.

- differentials

- fluid based car transmission

- navy canon driver based on analog computers

- wave principles (using super cute appartus to show impedance)

I was expecting explanations to begin shortly, got bored after the second stunt. The format is, frankly, horrible. This must be the analog of the "You want a tutorial to do X? Lemme record myself writing painfully slowly in "New Document.txt to explain it." style of tutorials.

The explanation, if you get past the 2 minutes of the synchronized motorcycle-riding, is remarkably lucid and to the point. It starts from the most primary considerations and fully explains the concept. It is neither dumbed down nor laden with jargon. I wish more general-audience presentations today strived for the same. What more can you possibly want?

Perhaps the patience level of audiences of that era was much higher than today? But that's OK, now, thanks to modern media technology, you can randomly access any part of the presentation or speed it up at will.

Motorcycles were a much newer concept in 1937 than they are today. The first "modern" motorcycle was released in 1915, according to the Wikipedia article:


Yeah the stunts and music are slow by our standards, but skip past them and you may find it interesting? It's a great video if you don't know about car differentials.

LOL, I think our attention spans are different. Also, we're not the captive audience sitting on folding chairs in the cafeteria with the 16mm projector rolling in the background — we can hit the back button if in a few seconds we are not drawn in.

That "Now This" or whatever it is drivel that trickles out a 250 word article over the span of a 3 minute slideshow is mind numbingly bad.

The music in this video is too pompous.

And now differentials are basically obsolete - not needed in electric cars.

Why is that? Tesla Model 3 for example uses 1 or 2 motors, not one per wheel, so they still need to add variable speed to left vs. right wheels, right?

I don't understand either. Somebody else made the same comment but typical electric cars still have diffs. Examples include Chevy Volt, Nissan Leaf, and Tesla Model 3, Tesla Model S. Where are the electric cars with independent left/right drive motors? Even cheap toy electric R/C cars have differentials.

What's the point of a differential for wheels that aren't driven? Why even connect them at all?

Model S Plaid edition, in theory the top end cybertruck and the new roadster.

https://en.m.wikipedia.org/wiki/Electronic_differential - and it indeed requires separate motors for each driven wheel.

Not true, only if you have each wheel powered can you dispense with a differential. Since that is not efficient (granted it sounds cool - that old pen/paper car wars game cool) most BEVs run one or two engines.

Remember, the idea is to handle the situation when torque on one wheel is not the same as the opposite wheel. Now it can be done with an electronic LSD which applies braking force

They aren’t needed in fossil fuel based cars either if you have an engine for each drive wheel. But most electric cars still employ a differential on one or more axles, even Tesla. Typically, due to cost, packaging, or performance, you have more drive wheels than motors and a differential is necessary.

They are totally needed in (parallel) hybrid cars. Two engines of possibly varying speed moving a car are very much like one engine moving two wheels of possibly varying speeds. Both need a differential.

The alt and title text of the first image seems to be AI generated:

"Line, Grey, Black-and-white, Exercise equipment, Monochrome, Machine, Monochrome photography, Barbell, Circle, Gas, "

Other non-car images on the site have text that's really disconnected from the context, such as an Apple logo on a story about the Apple car called "Christmas shopping in the city of Hamburg" which I guess came from the context of the stock photo being a Hamburg Apple store photographed at Christmas time. Pictures of people seem to be labeled with the events they're photographed at, even when it's nothing to do with the article.

Poor blind people having to figure out that "f1 eifel grand prix" means "George Russell".

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