Stuff you didn't know about gears (long)

[ImanCarrot]

Read this today and thought it might be of interest:

(Source "Quality World", December 2008, page 12)

"Gears:

As soon as rotating machinery was invented, so were gears. The oldest machine is beleived to be the potter's wheel invented more than 3000 years ago, which used primitive gear technology. The Book of Song, a historical text from China, claims that the differential gear was invented for the South Pointing Chariot of 1050- 771 BCE. In the fourth centure BCE, Aristotle wrote about wheels using friction between surfaces to transmit motion.

Early use of gears focused on the lifting of heavy loads such as building materials, as well as ship anchor hoists and catapult pre- tensioning. They were originaly made from wood with pegs for cogs, lubricated with animal grease. The early Greeks were the first to use metal gears with wedge shaped teeth, but metal became more commonly used as clocks and watches were developed throughout Europe.

With the invention of the bicycle in 1817, the development of gears started to move more quickly as the chain and gear method was introduced. During the industrial revolution metal was more widely used as the invention of electrical and steam motors increased the need for sturdier gears.

More recent developments have focussed on innovative materials. Modern metallurgy has increased the life of equipment and the use of plastic gears in consumer electronics has become more common and reliable."

There you go! my Colchester lathe is the offspring of a catapult.... probably why it keeps launching things at me

[Geof]

On the topic of early gear mechanisms I assume you know about the Antikythera? Or am I one up on you? Not at all likely I think unless you have been asleep for a long time.

[JWB_Machining]

The Antikythera mechanism is amazing, quite the computer of it's time I imagine. They're not really sure what it was used for though correct? Last i heard was they believed it was used to calculate astonomical events. I just want to know how craftsmen back then could make such an instrument and verify it. Must have been an intense project for someone's shop.

[RICHARD ZASTROW]

Actually, it was developed in the future by a "time traveler troll" who deposited in the water some time BC. My investigations/theories (aka BS) indicate that time of development was just slightly more in the future than the present. Just before the last qualified machinist died. LOL

Dick Z

[Geof]

The Antikythera mechanism is amazing,....... believed it was used to calculate astonomical events.....

Astrological events, I think it predates astronomy. Although that is a bit hair-splitting because the two are close to synonymous if you take out the predictive and causal aspects of astrology.

[One of Many]

I can offer the Youtube link to a program here.

"http://www.youtube.com/watch?v=DiQSHiAYt98"]YouTube - Antikythera Mechanism Part 1: by Nature Video

"http://www.youtube.com/watch?v=znM0-arQvHc&feature=related"]YouTube - Antikythera Mechanism Part 2: by Nature Video

DC

[RICHARD ZASTROW]

OK, it wasn't my troll. I'll go with Archimedes. But he was one of us old farts too. LOL

Dick Z

[One of Many]

Talk about gearing. I ran across this little gem in a bit of research on the Antikythera.

Tatjana van Vark

Stunning!

DC

[BobWarfield]

Antikythera is a fascinating mechanism. The fellows on the videos are endeavoring to tell a great story, so I suspect a degree of embroidery.

The ratios of time that govern the prediction of astronomical events such as Antikythera could predict were well understood by a number of cultures during its time. The revolution, appropriately enough for this thread, was the embodiment of those ratios as a gear train and hence an astronomical clock (or orrery if you prefer).

At some point I will set out to build my own such clock loosely based on Antikythera. I wouldn't attempt it without a lot of CNC skill and capability, unlike the old clock maker in the video who did his on manual machinery, or the Ancient Greeks who hand filed their gears.

For those interested, you can see more about the ratios involved on my page here:

http://www.cnccookbook.com/CCOrreryNotes.html

Cheers,

BW

[HuFlungDung]

Truth be told, the antikythera was in the fumbling hands of a more modern sailor, who happened to drop it overboard after which it descended onto the wreck, much to the consternation of the archeologists

I find it interesting to imagine the tooling that was used to make such a device. Granted there are old masters who could do amazing things with hand tools, but indeed, they need drills and files, don't they? Can you imagine patiently laying out and creating 200 something tooth odd gears and filing them with......something? And never having made another gear before or since? Sounds almost too far fetched.

[ImanCarrot]

Ahhh Geof, ya nearly got me! I didn't recognise the name, but I have read about the mechanism in New Scientist a while ago.

Amazing bit of kit just boggles the mind how they could have made the gears... perhaps acid etched?

Or... maybe there's a society of archaological windup merchants who wander about dropping modern stuff onto old sites (after accelerated ageing of course).

Wouldn't surprise me on bit Can you carbon date bronze?

[Geof]

Carbon dating bronze? Good one, but it raises the serious question would it be possible to carbon date cast iron or steel? 5400 year half life, iron has been smelted for a few thousand years, cast iron for a few hundred; should be possible.

The Antikthyera is intriguing because the wreck it was found associated with was well documented I think so it is known where it was from and where it was going. Of course you cannot rule out Hu's theory so you may be correct about a group of nefarious hornswogglers. After all the experts believed Piltdown Man for 46 years before someone fessed up and it is less than 46 years since the Antikthyera was found so there is still time.