How Differential Steering Works (1937) [video] | Hacker News Reader

How Differential Steering Works (1937) [video]

youtube.com

145 pointsPhithagoras41 comments

I wish, in school, teachers would have taught us things like this, how gears are just concurrent levers, how cams introduce asynchronicity to an operation. This is stuff I only started learning from working on and learning about cars.

I remember even when I was in school (a good time ago now), they were already killing off shop classes and the like. How sad that schools couldn't see what values classes like that have in critical problem solving.

They could. The bureaucrats didn't, and moreover didn't care.

I took a hands on physics class in high school (elective at a magnet school) called power and energy, in which we took apart, cleaned, and put back together an engine as our semester project, as well as learning all the math and physics behind the way in which they operated, how to calculate pretty much everything they did, etc.

It was an enormously valuable class in learning, fairly early on in my proper STEM education, how a system could be made up of many moving parts and subsystems - an obvious boon to my work today in software.

Contact your local school board and state education agency. The schools I have taught at still have these classes (automobile mechanics, applied physics, etc) because parents fight for them.

They are probably still able to legally be offered as courses (states usually don't remove entire course from state standards. The just go unupdated). School boards like to remove these courses because they are expensive (among other reasons) and on paper they look unpopular (hard safety caps mean a 15 person shop class looks unpopular compared to a 45 student overfilled history class).

Schools and school boards are parts of the government most susceptible to public pressure.

As a teacher, I want parents and community members to lobby their local schools. They don't listen to teachers but they buckle to parent complaints[1]. Please use your "complaining" powers for good.

[1]Unfortunately, schools can have a bad habit of viewing all parent contact as "complaints" or "whining."

I was in a Soviet school system (it was towards the end). And somehow we had a really fun shop class. We did stuff with electricity. Had a lathe, wood and metal. Remember making our own hammers. Learned to use a coping saw, a wood plane. School was remodeling so they let do demo work. Totally unsafe but loads of fun. Didn't learn about cars much though.

We had so many things there that would be considered unsafe and dangerous these days for US kids here I'd imagine. Same thing with chemistry experiments. Though interestingly there more encouragement here to play contact sports like football which leads to concussions and injuries.

> Though interestingly there more encouragement here to play contact sports like football which leads to concussions and injuries.

Better brain dead than Red ;)

My 7th and 8th grade shop class in the early '60s was a great learning experience. I think I learned more geometry and trig there than in math class. At least more about their practical application.

Of course I found it especially cool because I was shop foreman both years - which meant I got to direct the cleanup at the end of class instead of having to do the cleanup!

The first semester was mechanical drawing, and the second was using the power tools and building whatever we'd designed in the first semester. Whoever scored highest in mechanical drawing would be shop foreman.

It was pretty awesome getting to use drill presses and bandsaws and lathes and all that good stuff as an 11-12 year old.

We did use eye protection, unlike my third grade "special ed for smart and restless kids" class where I told the teacher I wanted to etch a printed circuit board and I needed a tank of nitric acid to do it, and she got it for me! No eye protection back then, I just got to watch the copper dissolve away. (And fortunately, not my eyes.)

Anyway, I think I may have won the shop foreman job because I took great care in erasing cleanly. When you're doing mechanical drawing with pencil and paper and compass and protractor and a French curve and straightedge, a good eraser and that little metal erasing shield are your best friends:

https://www.google.com/search?q=erasing+shield&tbm=isch

That interest in whitespace seems to have carried over into my programming career. I'm a bit saddened by today's popular wisdom that says it really doesn't matter what the whitespace conventions in your code are, as long as you pick some standard and make everyone stick to it now and forever, and if you don't like something about the standard you're just bikeshedding.

I've had the good fortune to mostly work on teams that simply didn't have whitespace standards, so I got to see a variety of styles and learn from them all - which ones helped communicate the structure and meaning of the code, and which ones maybe less so. And also that it really isn't that hard to read code where one person's work has minor variations in spacing from another's.

If I'd been locked into rigid standards all along, I don't know if I would have had the chance to learn any of this.

Don't get me wrong, I'm not talking about sloppy indentation! You gotta get that right. ;-)

My professor showed this video in one of my first upper division mech eng courses

Shop class material isn't on standardized tests, so --- no more shop classes.

All schools have electives though.

It's part of a series for Chevrolet by Jam Handy. The Internet Archive has many more of them. A few:

"Streamlines": https://archive.org/details/0142_Streamlines_M7960_09_08_44_...

"Down the Gasoline Trail": https://archive.org/details/0542_Down_the_Gasoline_Trail_06_...

"What Stops Them": https://archive.org/details/0797_What_Stops_Them_M6850_06_27...

"No Ghosts": https://archive.org/details/0797_No_Ghosts_M7860_06_16_49_00

They were really trying to get across how a car works.

>how a car works

Spinning levers, obviously...

Jam Handy was a national treasure. Another of my favorites from them is "Back of the Mike", a look at how radio dramas and their sound effects were produced:

https://archive.org/details/Backofth1938

Wikipedia on Jam Handy (olympic swimmer as well as educational film maker): https://en.wikipedia.org/wiki/Jam_Handy

The differential stops sliding of the rear wheels, Ackermann Steering Geometry stops sliding of the front turn wheels: https://en.wikipedia.org/wiki/Ackermann_steering_geometry Tires slide during sharp low speed turns on some vehicles due to lowering, lifts, tire changes and even production defects.

You can buy a Lego differential gear to keep as a desk toy: https://www.amazon.com/LEGO-Technic-Differential-connectors-...

Omg, great! I did it with lego technic back in early 90's (without those new fancy gears) when the simplicity and power of the differential struck me :) The simplicity of the differential is just beautiful !

FWIW, there was a differential in the lego technic 8865 Test Car from 1988: http://www.technicopedia.com/8865.html I think this was the first model with a differential. At least, that's what introduced me to it.

The 8865 was the first model with a differential. I wrote about being an adult fan of lego[1]. Over time, I purchased all 7 "super cars" that Lego manufactured. One of each car was sold every ~5 years and each one improved the previous generation's already amazing gears, steering, etc.

Fun fact: who is the largest manufacturer of tires in the world?

[1] https://www.facebook.com/notes/alok-menghrajani/afol-adult-f...

You typoed, you meant the 8860 :) I actually saw it in a catalogue back in the day, but I hadn't realized it had a differential. It was also already old when I was into Lego technic in my teens, at which time the 8865 was new and shiny.

Edit: It also seems both the 8860 and the 8865 were using the same parts for the differential.

Yes, 8860. A few years before the 8865.

My first exposure to a differential was building a Tamiya radio-controlled car kit. Those were great for learning some basic mechanics, and since you built them yourself they were easily repairable.

The training video for old Navy mechanical fire control computers is a similar classic: https://www.youtube.com/watch?v=lr1uK24SND8

The nice thing is, a planetary gearset can do basically the same, and is the building block of automatic gearboxes and Prius power distribution between ICE, electric motogenerator and wheels.

Relevant and amazing link: http://eahart.com/prius/psd/

Did a project based around the Prius PSD in my Mechanical Dynamics and Vibrations class. Very cool, really opened my mind to the power of gears.

Also, a youtube demonstration: https://www.youtube.com/watch?v=dLNDGUISTYM (this is the Toyota eCVT), and a teardown of the Ford version: https://www.youtube.com/watch?v=hHU5xFOBcsU

Same video over and over again https://hn.algolia.com/?query=differential%20gear&sort=byPop...

It's still interesting, and it's still a very good demonstration on how to explain a concept new to people.

https://xkcd.com/1053/ - Ten Thousand

It's like a rubber ball fired out of a cannon into a concrete box. It hits reddit, it hits HN, it hits FB it hits forums, wash, rinse, repeat.

Hey, its the first time I saw it. Nice stuff. Should be recycled.

Wait you didn't see this when it was posted the first time 8 years ago? Then you clearly shouldn't get the chance to see it again.

There's a flood of these mid-century instructional videos appearing the Web just over the past couple of years, right up to the present week. (I quite like the Jeff Quitney account on YT https://www.youtube.com/channel/UCM-kjdrQge9AACfB3MSRyrg , a fairly nice firehose of videos in good quality, which even seems to have some that aren't on the IA.) One thing I've taken from watching them is that US accents seem to have changed a lot in the past few decades: you hear presenters with accents that afaict don't seem to exist anymore. Jam Handy's is one, but there are more dramatic examples.

The TransAtlantic Accent! -> https://www.youtube.com/watch?v=Gpv_IkO_ZBU

But listen to how he pronounces the 'o's (in particular) in "and it couldn't get a good enough grip on the road" and "both rear wheels to the engine" https://youtu.be/yYAw79386WI?t=164 : Handy surely didn't learn that from an elocution class teaching RP-lite. Is it a trace of an Irish accent? a Scandinavian-American "Lutheran" accent?

To be clear, I'm pretty sure the narrator in these films is not Jam Handy. There is an interview with Mr. Handy himself here https://www.youtube.com/watch?v=AlDdE3Q5BWM

Possibly interesting sidenote, to this day a large number of the audio/visual and staging companies in the Detroit area can trace their lineage back to the Jam Handy Organization. Although I have a feeling we may now be a generation far enough removed that many of them may no longer know it.

You're referring to the Transatlantic accent, which was a contrived manner of speaking:

https://en.wikipedia.org/wiki/Mid-Atlantic_accent

Another odd, acquired accent is the manner of speaking employed during air traffic communications, with elongated R sounds, as when pronouncing words like "roger" over poor signal quality.

You can almost hear the air traffic control in mission control's transmission in 2001: A Space Odyssey, but only slightly:

https://www.youtube.com/watch?v=QFSE4dUJYM8

Jam Handy is under-appreciated in my opinion [0]. I wonder how videos like this would be received today.

0. https://en.wikipedia.org/wiki/Jam_Handy

Pretty well given the attention they get whenever they do the rounds.

Ten years ago I also would have wondered. Now I know; there are a lot of fine YouTube channels of a similar nature. It is certainly true that one must filter through a lot of garbage to find them, but they are there. Different topic, but here's just an example to get you started: https://www.youtube.com/watch?v=KfuARMCyTvg

I like how informative these videos are. Some more of these and I'd feel I could make working toyish automobile. I wonder why we dont get this kind of videos for our time's tech. Maybe computers and especially software are too complex to represent like this?

I like how they ghost ride the whip at the end of the video.

Hopefully coming soon "Show HN: I wrote a bot to re-post highly up-voted videos if they haven't been re-posted for a certain time period."

Reply on news.ycombinator.com