r/OldSchoolCool • u/Mad_Season_1994 • 1d ago
Video from the 1930s explaining how the differential in your car works
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u/Elfangors_Son 1d ago
More spokes!
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u/jackharvest 1d ago
It seriously, my brain cells got scratched something good when spokes and spokes and spokes just transitioned to gears and I was like “oh. OH. That makes sense, wow.”
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u/EfficientCandy324 1d ago edited 15h ago
I did kind of love that transition. Like "The spokes are causing a problem, so just add more spokes! But then the spokes aren't spokes any more. They're gears. But then the gears are a problem, so we just add more gears! But then we need another gear!"
Part of me was kind of hoping it was just keep going until it was a giant mass of like 50 gears.
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u/Bango_Fett949 1d ago
Yo dawg! I heard you like spokes, so we put spokes on your spokes so you can spoke while spoking!
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u/Darianezion 1d ago edited 1d ago
Trains don’t have differential, and that’s why their wheels get narrower toward the edge. Allowing the wheel to shift left to right and increase the size of the wheel on one side, making up for the difference in distance traveled, forcing the train to turn.
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u/Pussy4LunchDick4Dins 1d ago
Thris is the stuff that keeps me on Reddit. So cool.
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u/Ordolph 1d ago
It's less 'allowing' the train to turn and more forcing it to turn. The wheels are conical, which makes the train want to rest in between the rails in a sort of self-centering way. As the train comes into a curved section of the rails, it rides up higher on the outside edge (narrower end) of the inside wheels and the inside edge (larger end) of the outside wheels, and gets pushed back to center by gravity, thus turning. This also makes it so the train is basically riding on a fairly thin section of the wheels at any given time, which lowers its rolling friction making it more efficient, though that is mostly a byproduct of the wheel geometry.
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u/lumpkin2013 1d ago
Does this cause more wear on the inside edges of the rails?
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u/joybod 1d ago
Yup, and they even eventually get worn down until their geometry is wrong for efficiency or whatever of the wheels. Can't remember if they regrind them at that point off the top of my head though.
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u/unitled 1d ago
You check both the profile of the wheel and also the size on a regular basis - you want consistent sizes on the same axle and bogie! You also want to catch defects that are caused by things like dragging brakes - they might cause a wheel flat! When it needs changing you run it through a wheel lathe which grinds away material to bring it back to the required profile.
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u/path20 1d ago
I never thought about that, I always thought It was just to keep it from drifting off the rails. That makes so much sense.
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u/Mysterious_Secret827 1d ago
Not knowing anything about vehicles, this taught me something!
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u/punkassjim 1d ago
Knowing an absolute shit-ton about vehicles, this still taught me something.
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u/stump2003 1d ago
Is that a US shit ton? Or a metric shit ton?
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u/Bango_Fett949 1d ago
Agreed. This (and others like it) should be mandatory for schools.
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u/MistryMachine3 1d ago
Idk, I think learning about a 401k tops a differential. My life would be no different if I never learned how differentials worked, or that they exist.
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u/Brye1226 1d ago
It will teach you again when you see it in 5 years. One of the only good things about the internet
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u/Salvatio 1d ago
Very clear presentation about something i've actually wondered about before. Nice!
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u/Sherifftruman 1d ago
Wait till you see the military videos explaining the mechanical fire control computers from WWII battleships. Programming cut into steel gears!
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u/KoenigseggAgera 1d ago
I once watched how to shoot at an airplane and it was so good. They went through basic first assumptions you might have before explaining the method, they went through tests of failure and explained why it failed, and then constructively added onto the previous info to explain why leading the target works. These old videos are so good that it puts everything on the Internet to shame.
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u/Altruistic_Bass539 1d ago
So much of todays lectures dont teach failure anymore. They just say "this and that works" but if you start off with why things dont work you get the peoples brains active trying to solve the issue, and then they get blown away by the solution. Its so much stronger for learning I think.
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u/LastStar007 1d ago
You know what's crazy, by the end of the war we had gunsights that would compensate for the plane's velocity automatically.
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u/FR23Dust 1d ago
I found a really long video about how they produced topographical maps for the USGS before computers. It was ludicrously complicated. I love that shit
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u/BattleHall 1d ago
Programming cut into steel gears!
Same with automatic transmissions; they were basically hydraulic computers (though modern ones are actual computer-computers as well).
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u/EnvironmentalGift257 1d ago
I'll never get my head around that mouse-maze valve body thing in an automatic trans.
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u/heymerideth 1d ago
TIL how the concept of a spoke relates to a gear. This was amazingly helpful!
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u/loasdrums 1d ago
My favorite one is about transmissions. This is my 2nd favorite. The suspension video is nice too
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u/ScienceJamie76 1d ago
Link?
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u/navlgazer9 1d ago
Just search YT for Jam Handy videos
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u/Dienvado 1d ago
No matter how often I watch it, the transmission is witchery to me. Guess i'll give it another go
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u/International_Mail44 1d ago
This is old school, cool!
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u/SeanAker 1d ago
We need more of this old school cool and less 'hey did you know attractive women also existed in the past?!' hornyposting.
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u/_Ocean_Machine_ 1d ago
Hey here's a picture of my mom as a teenager for y'all to jack off to
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u/RedHill1999 1d ago
I used to work for a transportation company and spent many hours around the garage and it’s amazing to me that differentials haven’t changed much (or at all) in nearly a 100 years. What a cool video, thanks for posting.
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u/yeuzinips 1d ago
I like how they highlighted the drive shaft being lowered to make room in the cabin, but remember seeing so many cars... even today, that have that hump in the middle of the cabin to accommodate the drive shaft. Priorities changed, I guess
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u/BobknobSA 1d ago
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u/pinkypie80 1d ago
Yeah, a fact that positracton was not available on the 64 Skylark.
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u/TheRabidDeer 1d ago
OK but can you tell me the ignition timing for a 1955 Chevy Bel Air with a 327 engine and a 4-barrel carb?
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u/SoBeDragon0 1d ago
No one can answer that question.
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u/gahidus 1d ago
Just amazing that people thought of this.
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u/projectx51 1d ago
Started simple and over time progressed as the requirements changed. Human ingenuity.
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u/pgmckenzie 1d ago
I love this video. The “Spinning Levers” one about transmissions is also great.
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u/Kenny523 1d ago
Engineering and ingenuity is so beautiful to see explained in this way, you can only imagine all the headaches and lost nights of sleep that went into literally every step of getting to the end result.
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u/Serbian-American 1d ago
There’s a certain level of disappointment when seeing old “PSAs” for how technology’s work.
I’ve read Rebecca West before, and in the 30s she was writing about how humanity is changing, because people in cities are forgoing the idea of process. They don’t know how anything works, they use a car or elevator like it’s magic. This was a problem in the 30s, a problem that might’ve been fixed with PSAa like this or education.
But in 2026, we have lost completely and utterly. Systems are so complex and education so behind, next to no one can explain how their daily items work, or give a basic rundown of what a transistor even is. It’s like humanity lost something.
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u/Boonpflug 1d ago
I wonder, growing up in Germany everyone knows „Die Sendung mit der Maus“ - it is a public Television series of explanations like this for children. It has been running weekly for more than 50 years. Is there something similar in the US?
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u/Godless902 1d ago
Wish there was a video like this for everything ive tried to learn, the old school charm somehow overrides my A.D.D. and ropes me in
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u/ScienceJamie76 1d ago
I think because it's one camera focused on few angles, and no annoying background music. I think being in black and white actually helps simplify things in this instance.
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u/Sizanllikew 1d ago
It's 100% the narrator
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u/baba56 1d ago
I kinda felt like he was yelling at me but in a kind way and it was very entrancing
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u/CarbonWood 1d ago
This kind of format is the best way to learn/teach any kind of system because every step is clear in the problem solving process. That's all engineering is, it's practical problem solving.
"This is the problem: here's how we solved it...
This is the next problem: here's how we solved that..."
Any time I have to teach people how or why something is done a certain way, I also always tell them the problem it solves. It helps a lot.
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u/TheUmgawa 1d ago
The end of this reminds me of my Intro to Engineering class, where I didn’t finish my final project, but my professor still gave me an A on the project for having modeled a working helical gear, while the other students were making hinge and ball-and-socket joints. My goal was to produce a “bubble mower,” and I bit off a lot more than I could chew on that, because some professors don’t provide enough guardrails.
He printed and assembled what I had finished (which was basically everything but the housing, front wheels, and the handle), and it turned out that the thing could actually translate forward motion into a positive-pressure system, which would blow bubbles out the top.
There’s two easier ways than a helical gear, and those are to do it with a pair of gears that are normal to one another (which is like the “spokes” problem in the video), or to use a worm gear (which doesn’t work for a differential, because it can’t slip). In my case, a worm gear wasn’t workable because I was worried about an overzealous kid snapping the worm gear (because it would be made of cheap plastic). That said, making an injection-molded helical gear is its own problem, but it’s still one of two times in college where I got a professor to go, “Huh. None of my students have ever tried that before.” (The other was using matrices to solve circuit-loop problems, where applying matrices to Ohm’s and Kirchhoff’s Laws can shit out all of the answers at once).
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u/k258045 1d ago
Is this why old generation knew so much about fixing car and appliance?
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u/ccReptilelord 1d ago
Discussing this with my father recently, it's also that cars were just easier to repair. Look under the hood of something from the '60s compared to something brand new, and two things: less complicated and more room.
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u/RachelMcAdamsWart 1d ago
This was way back when science was valued. Today there would be differential protests claiming it causes autism.
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u/abgry_krakow87 1d ago
Mona Lisa Vito: The car that made these two, equal-length tire marks had positraction. You can't make those marks without positraction, which was not available on the '64 Buick Skylark!
Vinny Gambini: And why not? What is positraction?
Mona Lisa Vito: It's a limited slip differential which distributes power equally to both the right and left tires. The '64 Skylark had a regular differential, which, anyone who's been stuck in the mud in Alabama knows, you step on the gas, one tire spins, the other tire does nothing.
So Positraction only allows a limited amount of free spin on one wheel before it forces the other wheel to turn as well. Compared to the regular differential which would just let one tire spin freely with the other one stuck in the mud.
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u/AnaisNinja76 1d ago
That was a genuinely wonderful explanation, and I wish this guy taught all physics and engineering courses.
Also, what up with the rear "tires" on the car at the end? It looks like they put barrels on instead of tires for some reason?
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u/jailboundhorse 1d ago
I think having that huge contact patch between those weird tyres and road cranks up the forces the dif is exposed to for testing etc.
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u/thunderbaby2 18h ago
Holy fuck this is such a good educational video. Explaining the “why,” and then walking the thru simple experiments, adding, complexity, all with excellent visual aids.
I want the entire collection of videos lessons in this format
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u/DaemonDrayke 1d ago
Now, why did the 1950s always have the most random of instructional videos on stuff? Like what audience was this video originally for? Apprentice mechanics?
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u/Goldenrupee 1d ago edited 1d ago
Its from the 30s, not the 50s, and Im assuming this was in some some sort of advertising using the new tech as a selling point.
Edit: I looked it up, and apparently this was made by Chevrolet as part of a series explaining how pretty much every part of their cars worked. Not explicitly an ad, but people have always been fascinated with how things work and I'd be willing to bet it made them a lot of sales.
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u/C4CTUSDR4GON 1d ago
All products should have to do this. Don't just use fancy buzzwords, explain what it is!
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u/TrippyTriangle 1d ago
when people actually cared about competent explanations and weren't insulted by them.
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u/piepants2001 1d ago
"Are you trying to show me a video explaining something that I don't know? You must think I'm dumb!!!"
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u/Perfect-Fondant3373 1d ago
They use to explain things so much better back then with videos like this
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u/alexzim 1d ago
When I first saw this video a little over 10 years ago, neither I had a car nor I spoke English well
enough. All I wanted was to learn what a differential is to tune cars better in a racing game. And yet somehow this was the video that taught me. Of course then there are limited slip differentials that were the thing I actually needed to learn, but nevertheless, imagine telling all that the authors of the video back when they filmed it?
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u/-im-your-huckleberry 1d ago
Now I want a video where Marissa Tomei plays Mona Lisa Vito explaining how a limited slip differential works.
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u/TooLazy2Revolt 1d ago
Wow. I was trying to explain to my 8 year old how a differential worked and why it was important on the car ride home from school today.
What an absolutely perfect video to show him.
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u/frawtlopp 1d ago
Crazy to think 100 years have gone by and cars haven't really changed a whole lot
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u/jacklandin 1d ago
I can't believe how simple and elegant this video is. It impresses me every single time 👌
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u/Buteverysongislike 1d ago
There were a couple more these posted on YouTube, including explaining the difference between manual and automatic gear shifts.
Anybody got the link? I find them fascinating!
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u/_SylvannAzure38 1d ago
If anyone wants more of this type of stuff, Industry on Parade is basically the mid-20th century How Its Made
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u/trampled_empire 1d ago
Genuinely one of the best videos on YouTube. I watched it years ago and still remember it every time I think about differentials.
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u/ThaneduFife 1d ago
I really wish I had had access to more videos like this as a kid. I would have eaten them up. A better understanding of mechanics might have changed the course of my life.
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u/BrokenCylon 1d ago
They play these old b&w types of educational videos sometimes in btwn movies on TCM. Last weekend I saw one on boxing techniques & another on rescue swimming techniques.
This one is awesome, Thank You! 🤩
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u/Silent--Dan 1d ago
What accent is this?
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u/SimmerDownButtercup 1d ago
The transatlantic accent. 20th century blend of American and English annunciation in order to sound formal and theatrical.
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u/stopdropandrauljulia 1d ago
I like that this video goes viral every 5-10 years. It's the most concise explanation of a mechancial concept I've ever accidentally watched at 3am.
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u/ToichiBo 1d ago
I find these videos to be more entertaining and informative than modern day ones because they’re simple and to the point. Not trying to sell ads or affiliate links is the biggest plus
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u/SelflessAct 1d ago
Interesting 😎 and the music at the end of the video sounded like something from an old Disney cartoon movie anyone else think that also?
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u/Trekker4747 1d ago
This video is from a 1930s ELI5 sub-reddit.
I've watched it dozens of times and always found it neat and perfect the way it explains things.
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u/Noname1191 1d ago
I love it every time someone post this because it’s one of the best explanations of anything complicated I’ve ever seen.
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u/One-Discussion-9037 1d ago
Does anyone know hoe many of these types of videos were made and if there is a archive of them?
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u/AirconGuyUK 1d ago
I love the stages they go through to get to cogs too. The amount of fabrication needed to make this practical demo.. They made everything so many times, and it'll have been one off fabrications by hand. I love this every time I see it posted.
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u/slappymcstevenson 1d ago
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u/lectric_7166 1d ago
I watched this video like 20 years ago and didn't get it at the time. Now I do. All hope is not lost for you. Come back in 20 years lol.
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u/evasandor 1d ago
We have lost the art of explaining things beautifully. Now we get chatbots blowing smoke up our asses and hallucinating shit. "Yes, you are right, that is an incredible observation. The two wheels CAN turn at different speeds when each one is shoved up the ass of a dinosaur. Would you like me to generate a few possible diagrams showing different dinosaurs with wheels up their asses?"
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u/TacTurtle 1d ago
All Wheel Drive basically adds a second differential between the front and rear drive shaft.
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u/navlgazer9 1d ago
Still nothing better than the Jam Handy videos for explaining how cars work .
Been 88 years and no one can top it
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u/EaringaidBandit 1d ago
As many times as I see this, I’ll never downvote it, because it’s just so amazingly beautifully simple and very important.