Epicyclic Gearing

http://bl.ocks.org/1353700

by llambda • 14 years ago

131 20 14 years ago

bl.ocks.org

bprater• 14 years ago

Quickly clicking thru the options on this webpage will give you an idea on how automatic transmissions work in automobiles -- using the planetary gearset.

The core mechanic is the locking of different combinations of the gears. This is a completely different mechanic than in the standard 'stick shift' manual transmission, which uses traditional toothed gears meshing together.

pkulak• 14 years ago

I think you're thinking of an electronic CVT, like the Prius uses.

majormajor• 14 years ago

Wikipedia tells me that there are some CVTs that use planetary gears, but a traditional automatic uses them too: http://auto.howstuffworks.com/automatic-transmission2.htm

abthomson• 14 years ago

Both "normal" automatic transmissions and the Prius use epicyclic gears. The main difference between the two would be that an automatic transmission in normal operation has one power input (the engine) and one output. As bprater alluded to, any variation in gearing is achieved through fixing different parts of the transmission.

The Prius has two electric motors and a gas engine. It's not a CVT in the traditional sense though, this simulator does a good job of demonstrating how it works(implemented in Flash, not D3...) http://eahart.com/prius/psd/

hencq• 14 years ago

No, he's not. A CVT doesn't have fixed gear ratios (that's where the continuous comes in). A traditional automatic transmission uses planetary gears to have a fixed number of gear ratios.

bigiain• 14 years ago

I (along with nearly everybody I knew) had a bicycle with that gearbox in it back in the '70s.

http://sheldonbrown.com/internal-gears.html

(And I was _so_ jealous of the few kids with the "10 speed racers"!)

aidos• 14 years ago

Oh, that's how they work! I hadn't looked into it but I have one sitting around at home waiting for a spare weekend so I can dissect it to figure it out.

raymondh• 14 years ago

Beautiful website. Fascinating display. Nice source code.

mikepurvis• 14 years ago

Agreed, very nice. I did some demos like this a few years ago, and it was definitely not as clean. Modern JS libs are marvelous things.

(eg: http://sandbox.mikepurvis.com/design/engine.svg)

samlittlewood• 14 years ago

This was how the Model T Ford transmission worked - the foot pedal fixed various parts to get low, high and reverse.

Edit: http://www.modeltcentral.com/transmission_animation.html

jakeonthemove• 14 years ago

That's also how chain hoists work - I'm still amazed at how much you can lift using one!

I actually thought the article will be about Biopace bike chain rings: bikers are using them as an advantage in races (and it really makes sense!).

Terretta• 14 years ago

Supposedly, Biopace was shown to be counterproductive, while the newer Rotor Q-Rings are correctly designed.

The new hotness: http://www.rotorbikeusa.com/science.html

jebblue• 14 years ago

Interesting but it uses 80% CPU time on my system, here is a Java applet showing the same thing - it takes a long time to load but uses less than 10%:

http://www.zfm.ethz.ch/meca/applets/planeten/PG.html

joe_bleau3• 14 years ago

Another good one is the hypoid gearset (http://en.wikipedia.org/wiki/Hypoid) , as used in automotive rear ends. For some reason I've always found them pretty.

Cone drive sets and harmonic gearing (http://en.wikipedia.org/wiki/Harmonic_drive) are neat, too. And then there's the Torsen (http://www.youtube.com/watch?v=Z9iPqIQ_8iM), which I still don't really understand.

From the service manuals I've seen, I think some of the smaller 4 cylinder cars, especially from Japan, use a mainshaft/countershaft arrangement (like a traditional manual transmission) in their automatics, rather than planetary gearing.

HeyLaughingBoy2• 14 years ago

Because the machining is gorgeous

I used to have the hypoid pinion I removed from my Toyota pickup truck rear end (when I changed the gear ratio to compensate for larger tires) as a paperweight on my desk. The flowing curves and polished steel gave it a really Art-Deco look.

It was free, beautiful and weighing close to 10 lbs, very functional. Can't beat that :-)

joe_bleau3• 14 years ago

Speaking of gorgeous, if you're ever in a machine shop and get a chance to look inside the headstock of a top end 1940-1970s vintage engine lathe, do it. The quality and precision makes automotive stuff look like hammered pot metal.

Epicyclic Gearing

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