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comment by kleinbl00
kleinbl00  ·  1027 days ago  ·  link  ·    ·  parent  ·  post: Pubski: June 14, 2017

Turns out bikes and bike parts are fragile.

I ride 120-150 miles a week, depending on whether it's a 4-day or a 5-day week (my schedule is 4 days on, 2 days off, which causes some odd precessing away from traditional weekends). Which means every four days, I put the bike up on the stand, wash it, clean the chain, lube everything and deal with the stuff that's been bugging me for a hundred miles (squeaky front brakes, sticky shift on 8th gear, etc). I put the beastie away at the end of last season having just gotten to 75 thousandths wear on the chain... a chain that gets cleaned and lubed every 120 miles but which also has 3,000 miles on it. The intent was to change the chain when I had time, which was Sunday.

Mmmmyeah.

So now it won't take any power in the bottom two gears 'cuz the cassette is thrashed, apparently, and in attempting to adjust around this I also discovered that the rear derailleur is donezo and that the front tire has cracks in it you could drive a nail file through and my buddy told me he put like 10 miles on it while I was gone and I believe him. Also he lowered the seat an inch and a half and I raised it an inch and kept it there for two days and I'm still saddle sore so apparently I'm rather using this bike.

It also hasn't been that hot and I went through a 24oz bottle of water twice yesterday (thank god for the water fountain at Griffith Park) and since I left my camelbak up in Washington 'cuz I hate riding with shit on my back I'm gonna be one of those doofi with water bottles hanging off the saddle 'cuz it's a good 15-20 degrees cooler this year than it was last year but I remember 115 in Glendale and apparently I need even more water this year than last and that heat wave got legit scary.





ThatFanficGuy  ·  1027 days ago  ·  link  ·  

    a chain that gets cleaned and lubed every 120 miles but which also has 3,000 miles on it

That's three quarters the length of Nile and Amazon, one-point-two times New York to LA and one-point-four times diameter of the Moon at the equator. I'd say that's not "fragile": that's heavily distressed.

kleinbl00  ·  1027 days ago  ·  link  ·  

It's also the oil change interval of most motor vehicles.

ThatFanficGuy  ·  1027 days ago  ·  link  ·  

Most motor vehicles being designed for far more aggressive and strenuous driving.

Not that I know much about either. This is me exercising my knowledge and critical thinking on something that didn't sound right. To be frank, I'm surprised the oil change is so infrequent for cars. Must be quite a substance.

kleinbl00  ·  1026 days ago  ·  link  ·  

And to be honest, bike parts have more in common with jewelry than they do with actual mechanical components. They're delicate. And the shit is all out in the open where it can get abraded by dust, scunge, rust, etc.

But yes. Hydrodynamic bearings are no joke.

ThatFanficGuy  ·  1026 days ago  ·  link  ·  

A wonder, then, why it hasn't been developed to a more endurant level. Humanity starts a "new level" of something whenever there's the abundance of resource and workforce for it, isn't that true? Maybe we're just waiting for graphene to become mass product... but then, we'll just suffer over it not working in zero-G or something. :)

Fluid bearing made no sense to me 'cause it's late and my brain is tired. If you could ELI5 it for me, that would be appreciated.

kleinbl00  ·  1026 days ago  ·  link  ·  

Mechanical objects cannot follow Moore's Law. Newtonian physics has been a settled thing for 200 years now and while we can make improvements in materials science, the equations that govern mechanical design have no shortcuts.

A fluid bearing uses a fluid (in physics terms, this means either a liquid or a gas) to absorb the shock of impact and friction. The design of the bearing is dependent on the viscosity and other properties of the fluid. Basically, if you have two parts that should have friction between them, and put a layer of properly designed fluid in between, the friction between those parts becomes the friction between the fluid and the surface instead of the two surfaces.

The archetypal example is a connecting rod and a crankshaft journal:

In a fluidless scenario, the impact of the exploding gas on the piston is transferred down the connecting rod to the crankshaft and the inner diameter of the rod and the outer diameter of the crankshaft rub together, make lots of heat and wear. In a fluid bearing scenario, the impact from combustion is absorbed by the fluid, which has much lower friction than the two metal surfaces, and which is also under constant replacement by the oil pump. This allows the friction heat of the surfaces to be removed from the site.

That was more ELI10 but that's the idea.

ThatFanficGuy  ·  1023 days ago  ·  link  ·  

It took me a while, but I got there.

Thanks for the explanation - as well as for reminding me why I'm not in engineering.

goobster  ·  1026 days ago  ·  link  ·  

(I will not nitpick that Newtonian physics existed long before Newton. I will not nitpick that Newtonian physics existed long before Newton. I will not nitpick that Newtonian physics existed long before Newton. I will not nitpick that Newtonian physics existed long before Newton.)

kleinbl00  ·  1026 days ago  ·  link  ·  

the equations didn't

goobster  ·  1025 days ago  ·  link  ·  

Well, that's kinda what I was getting at, philosophically.

Technically, the equations just are a way of describing the phenomena or principle. So in a way, Newtonian Physics are only the equations describing the principles. So sure, those principles existed before he described them in mathematical calculations.

I dunno... I'm sitting in a long and boring conference call/training, and my mind is wandering off into the weeds... government contracting, my friends... my brains are leaking out my ears...

bfv  ·  1025 days ago  ·  link  ·  

    I dunno... I'm sitting in a long and boring conference call/training, and my mind is wandering off into the weeds... government contracting, my friends... my brains are leaking out my ears...

I know your pain.

kleinbl00  ·  1025 days ago  ·  link  ·  

That video is appropriate far too much of the time.

kleinbl00  ·  1025 days ago  ·  link  ·  

Philosophically, sure. But if you want to act on it, you have to know it, and that knowledge isn't eternal.

My bicycle has 27 speeds and tires that run at 90psi. None of the physical laws that governed its construction came into being recently. But without the knowledge of metallurgy, chemistry, manufacturing science and materials technology that have been developed in the past 100 years it'd be a velocipede. I mean, carbon fiber spokes. Beat steel in many many ways, but utterly unheard of 40 years ago. Multiply by everything. However, hydrodynamic bearings? That's steam engine shit. Internal combustion has advanced much slower than semiconductors despite the fact that the laws of the universe have been knowable (but unknown) since its birth.

ThatFanficGuy  ·  1026 days ago  ·  link  ·