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>> Anyone accustomed to modern practice finds it hard to believe that wood-on-wood could function as a bearing at all. This primitive arrangement was improved in a few cases by the addition of a leather bushing. Lubrication in the form of animal fat or tallow is known to have been used, although the exact composition has not been determined.
You'll notice that your examples involve a lot of power driving the mechanism - a team or horses or a windmill can overcome the kind of friction a wood-on-leather bearing implies. If you've ever ridden a bicycle where the fender was rubbing on the wheel, you'll know that human power is much more limited.
https://www.youtube.com/watch?v=CcvFpbh2fjE [1]
I think people vastly underestimate what you can do with very simple "naive" technology.
[1] Yeah it uses aluminium spacers on the chain, but you can do a bicycle without a chain.
> https://www.youtube.com/watch?v=CcvFpbh2fjE
Your "proof" is unconvincing.
1. The bike looks super wobbly and seems like it takes a lot of effort to just make it function properly. Yes, it is an example of a wooden bicycle, but it is not an example of a useful wooden bicycle. It seems like it probably has a pretty short working life and low speed. In short, it's worse than just running.
2. The bike is being run on a paved road. All of my earlier criticisms get magnified by the stress of taking the bike off road. Yes, dirt roads are a thing. No, they are not nearly as smooth as asphalt. Also, much like carts, a bicycle like that would start to put ruts in a dirt road.
But there were wooden bicycles without ball bearings in real-life history and they worked with the infrastructure they had. How well they worked is a different thing, but still it proves "no tech to build a bicycle" isn't the reason we waited for bicycles for thousands of years.
We had people jumping off towers with wooden wings for centuries before aeroplanes were made after all ;)
It would be perfectly possible for Romans to make bicycles from technological POV. Just wouldn't make sense because 2 slaves with some chair on sticks were cheaper.
BTW - first real world mass-produced bicycle added ball bearings after several years:
> On the new macadam paved boulevards of Paris it was easy riding, although initially still using what was essentially horse coach technology. It was still called "velocipede" in France, but in the United States, the machine was commonly called the "bone-shaker". Later improvements included solid rubber tires and ball bearings.
https://en.wikipedia.org/wiki/History_of_the_bicycle#1860s_a...
Anecdotally, on a bike ride recently, on a modern bike, hopping an inch curb snapped a chain.
https://en.wikipedia.org/wiki/Wooden_bicycle
As for ball bearings these are incremental improvements not a necessity (see horse chariots and carriages with wheels used for millenia before we had ball bearings). For another example see medieval wooden windmills - all cogs and bearings made from wood with some animal fat and skin for bushings and lubrication - worked well enough for centuries.
https://ethw.org/Wheels
> Tutankhamen's chariots give us an opportunity to study the details of wheels and axles. The aspect that is most striking to a present-day engineer is that the axles were made of wood and the wheels bad wooden journals. The favored materials were elm and birch, which were imported because neither wood was native to Egypt. Anyone accustomed to modern practice finds it hard to believe that wood-on-wood could function as a bearing at all. This primitive arrangement was improved in a few cases by the addition of a leather bushing. Lubrication in the form of animal fat or tallow is known to have been used, although the exact composition has not been determined.
https://www.brown.edu/Departments/Joukowsky_Institute/course...
https://vimeo.com/14166672
First mass-produced bicycle (velocipede) had no ball bearings until a few years later.