14 ms·
1937 film explains how a car differential works
- jpswade 6y agoI remember the video being posted here a few years back, interesting stuff. Original discussion here: https://news.ycombinator.com/item?id=15122031 https://news.ycombinator.com/item?id=15122031
- adamjb 6y agoalso https://news.ycombinator.com/item?id=8513209 https://news.ycombinator.com/item?id=8513209 and https://news.ycombinator.com/item?id=1103156 https://news.ycombinator.com/item?id=1103156 It's worth going through the previous discussions for the recommendations of similar films
- elymar 6y agoHow would films like this be consumed in the 30’s? Would it be shown in theaters before a feature film?
- mattlondon 6y agoMilitary conscripts who were assigned to motor maintenance
- privong 6y ago> 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: https://en.wikipedia.org/wiki/1937_in_television https://en.wikipedia.org/wiki/1937_in_television
- chrisseaton 6y agoConscripts in the 30s in the US? My understanding is US conscription only restarted for WW2 in 1940.
- neogodless 6y agoAnother 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 https://en.m.wikipedia.org/wiki/Jam_Handy
- dangerbird2 6y agoI 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 https://www.youtube.com/watch?v=aWIQuvbxu0E https://www.youtube.com/watch?v=aWIQuvbxu0E
- im3w1l 6y agoTo 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.
- JKCalhoun 6y agoI 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).
- retrac 6y agoIt'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.
- ethbr0 6y agoHere's the actual film (linked in the article) https://m.youtube.com/watch?v=yYAw79386WI https://m.youtube.com/watch?v=yYAw79386WI
- ernst_klim 6y agoGreat stuff. Making me think how simpler electrocars are: no differentials, no transmission, no complex injection machinery.
- amelius 6y agoBut: redundancy.
- foobarian 6y agoI 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.
- rightbyte 6y agoYou need diff and transmission for EVs thought unless you have direct drive on two wheels.
- Reason077 6y agoYes, 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.
- natmaka 6y agoJam Handy, the author, was a genius. https://en.wikipedia.org/wiki/Jam_Handy https://en.wikipedia.org/wiki/Jam_Handy
- ashkankiani 6y agoI 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.
- MaxGabriel 6y ago> 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 https://en.m.wikipedia.org/wiki/Jam_Handy
- ashkankiani 6y agoThat 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."
- amelius 6y agoVideo 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.
- wtallis 6y ago> 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.
- Retric 6y agoIn 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.
- refurb 6y agoNot so much dangerous as useless. That’s why Positraction was invented. And why locking differentials are a thing.
- bluenose69 6y agoThe 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.
- TazeTSchnitzel 6y agoYes, but what about the turbo-encabulator? https://www.youtube.com/watch?v=Ac7G7xOG2Ag https://www.youtube.com/watch?v=Ac7G7xOG2Ag
- kumarsw 6y agoSuggest changing the title to reflect that this is a General Motors documentary. They are still around! Why not credit them?
- djbebs 6y agoThe 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.
- mensetmanusman 6y agoHaving 1937 next to the name of any modern day company would imply such.
- djbebs 6y agoNot really, there are plenty of companies founded before 1937 that still exist
- mensetmanusman 6y agoBut the people are dead, so they are the same or different ‘company’ in a similar vein of argument.
- djbebs 6y agoA company is not the people who work for it, or the people that own it. Its its own distinct legal entity.
- neogodless 6y agoDo 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. https://www.politico.com/story/2018/12/19/bush-bails-out-us-automakers-dec-19-2008-1066932 https://www.politico.com/story/2018/12/19/bush-bails-out-us-...
- nabla9 6y agoThe 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.
- CraneWorm 6y agoI 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.
- dmitryminkovsky 6y agoYeah 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.
- crispyambulance 6y agoThe 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.
- MPSimmons 6y agoMotorcycles were a much newer concept in 1937 than they are today. The first "modern" motorcycle was released in 1915, according to the Wikipedia article: https://en.wikipedia.org/wiki/History_of_the_motorcycle#The_First_World_War https://en.wikipedia.org/wiki/History_of_the_motorcycle#The_...
- hawktheslayer 6y agoThis was excellent to watch, though the whole time it made me think of this classic engineering video: https://youtu.be/RXJKdh1KZ0w https://youtu.be/RXJKdh1KZ0w
- keanebean86 6y agoHere's a great one by Hitachi from 2005. https://www.youtube.com/watch?v=xb_PyKuI7II https://www.youtube.com/watch?v=xb_PyKuI7II
- gabrielsroka 6y agoThat sounds a lot like the schnebber robber from the "Winnebago Man".
- ape4 6y agoAnd now differentials are basically obsolete - not needed in electric cars.
- Shivetya 6y agoNot 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
- harperlee 6y agoWhy 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?
- lopmotr 6y agoI 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.
- benlivengood 6y agoModel S Plaid edition, in theory the top end cybertruck and the new roadster.
- jimmaswell 6y agoWhat's the point of a differential for wheels that aren't driven? Why even connect them at all?
- praptak 6y agohttps://en.m.wikipedia.org/wiki/Electronic_differential https://en.m.wikipedia.org/wiki/Electronic_differential - and it indeed requires separate motors for each driven wheel.
- djcooley 6y agoThis reminds me of a great film on crafting quartz crystals for use in radios: https://youtu.be/wHenisSTUQY https://youtu.be/wHenisSTUQY
- segfaultbuserr 6y ago+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.
- lopmotr 6y agoThe 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".
- segfaultbuserr 6y agoIf 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. https://www.youtube.com/watch?v=gwf5mAlI7Ug https://www.youtube.com/watch?v=gwf5mAlI7Ug
- tzs 6y agoAnother 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 https://www.youtube.com/watch?v=DovunOxlY1k
- segfaultbuserr 6y agoI 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.
- ryukafalz 6y agoThank 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.
- tzs 6y agoA 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.
- thechao 6y agoThere’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.
- divbzero 6y agoYes, 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.
- globular-toast 6y agoThis 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.
- durnygbur 6y agoThe music in this video is too pompous.
- deleted 6y ago[deleted]
- A-Jay 6y agoThere used to be a youtube channel called WDTV42 that had tons of these old reels, very comprehensive. Shame they took it down.
- tqi 6y agoThe 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 https://youtu.be/8gno0_emzo8
- dmix 6y agoThat'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.
- geoduck14 6y agoIf the losing team wants to win this game, they are going to need to score more points. https://i.pinimg.com/originals/a8/21/10/a82110b6d53e4089a33e99bb8d2cde7f.jpg https://i.pinimg.com/originals/a8/21/10/a82110b6d53e4089a33e...
- TaylorAlexander 6y agoIf 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. https://en.wikipedia.org/wiki/Columbo https://en.wikipedia.org/wiki/Columbo
- foepys 6y agoThat'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.
- pbrw 6y agoDoes the inner gear rotate at the rate of speed which is the difference of rates of both wheels? (as the name suggests)
- zackmorris 6y agoStumbled 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: https://www.youtube.com/watch?v=JEiSTzK-A2A https://www.youtube.com/watch?v=JEiSTzK-A2A Maybe someone has a better explanation?
- Animats 6y agoOh, 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.)
- souprock 6y agoThere 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.
- nimbius 6y agoI 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 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 https://www.youtube.com/watch?v=JEiSTzK-A2A
- thomasahle 6y agoI 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.
- mattmaroon 6y agoThe 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.
- thr0w__4w4y 6y agoYep, 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!
- Reason077 6y agoInteresting fact I learned from this video: early cars were one-wheel-drive!
- elihu 6y agoI 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.
- anonu 6y agoSo 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_chevrolet_low_center_drive_never_take/ https://amp.reddit.com/r/cars/comments/9d33os/why_did_the_ch...
- jibolso 6y agoSuch a neat explanation!
- Animats 6y agoYes, "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_00_41_00 https://archive.org/details/0141_Around_the_Corner_M00267_08...
- b0ner_t0ner 6y agoSomebody should use the latest AI libraries available to upscale all these to 4K and maybe even colorize them.
- vermontdevil 6y agoAlways loved to watch the opening sequence (motorcycles).
- bacon_waffle 6y agoThe "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. https://en.wikipedia.org/wiki/Spiral_bevel_gear https://en.wikipedia.org/wiki/Spiral_bevel_gear
- thomasahle 6y agoThe ending on lowering the differential never explained why they didn't just use front wheel drive. Can anyone fill me in?
- WillPostForFood 6y agoYou 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.
- userbinator 6y agohttps://en.wikipedia.org/wiki/Front-wheel_drive#History https://en.wikipedia.org/wiki/Front-wheel_drive#History 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 https://en.wikipedia.org/wiki/Oldsmobile_Toronado
- wnevets 6y agoThis video from 1960 explaining Frames of Reference is amazing. https://www.youtube.com/watch?v=bJMYoj4hHqU https://www.youtube.com/watch?v=bJMYoj4hHqU
- HighlandSpring 6y agoAhah, 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 https://www.youtube.com/watch?v=CGU2pfEdJ_o
- gnicholas 6y agoHN discussion of the video from 2017: https://news.ycombinator.com/item?id=15122031 https://news.ycombinator.com/item?id=15122031 This video has been posted 20+ times, over the years! https://hn.algolia.com/?q=yYAw79386WI https://hn.algolia.com/?q=yYAw79386WI