
New Greaseless Bearings Spin with 10 Times Less Friction - SwellJoe
http://www.popularmechanics.com/technology/gear/a15603/super-efficient-greaseless-bearings/?click=welcome-ad
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FlyingAvatar
ArduinoVsEvil made a video about this, explaining how the demonstrations gifs
are pretty meaningless:

[https://www.youtube.com/watch?v=uD7Lzv5fWhs](https://www.youtube.com/watch?v=uD7Lzv5fWhs)

In general, the concept doesn't make sense, or at least it's being
inadequately explained. It is probably a hoax.

~~~
HCIdivision17
I was thinking something similar. I immediately thought, "wait, doesn't a
speed change imply a force on the bearing, and wouldn't that necessarily imply
friction between the bearing and track?" Under load (and I've no idea how
much), I just imagine this applying a subtle little ba-dump-ba-dump-ba-dump to
the bearings as they spin around.

Their innovation seems to suggest that this is such a small change that it has
less of a bump and more of a very slight shape change effect. So there may
actually be something there - I've certainly seen stranger topological
results. But until I see one after a few thousand hours in a high speed motor,
I'll be on the fence.

~~~
ars
> doesn't a speed change imply a force on the bearing .... imply friction

Not necessarily. A speed change could also be because the track is longer.
That's how trains stay on the tracks, the wheels are slanted, and if they turn
off the track the length of the wheel changes, which changes the speed
(relative to the wheel on the other side) and steers it back onto the track.

Feynman explains it:
[https://www.youtube.com/watch?v=y7h4OtFDnYE](https://www.youtube.com/watch?v=y7h4OtFDnYE)

~~~
function_seven
> and if they turn off the track the length of the wheel changes

But is doesn't actually change. A different part of the wheel comes into
contact with the rail, but that different part always had a higher linear
speed. It just wasn't in contact with the rail until the turn.

But with these bearings, it appears that the balls themselves actually do
speed up or slow down to maintain separation from one another. In that case,
there must be a force coming from somewhere to effect those changes.

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snowwrestler
> Bearings work to help one surface slide along another by minimizing the
> points of friction between the two. Imagine sliding a book across a desk.
> There's friction at all points where the book is touching the surface. But
> if you put that book on top of some pencils, there's only friction where the
> book touches the pencils and where the pencils touch the desk. Suddenly that
> book is practically racing across the table if you so much as nudge it.

This description of why bearings work is terrible. If the advantage is just
reducing surface area, then that would be a runner: pushing the book along the
pencils long-ways. This actually does not reduce friction, since the equation
for the force of friction does not include a term for surface area. (There are
some real-world exceptions--runners on ice for example.)

Bearings work because they replace sliding friction with static friction.
Static friction is actually higher than sliding friction (otherwise things
would never stop sliding), but it never comes into play because the load-
bearing surfaces don't slide relative to one another. This is also why
antilock brakes tend to reduce stopping distances for cars.

Bearing cages do experience sliding friction, but not on load-bearing
surfaces. Since the normal force is therefore much lower, so is amount of
sliding friction.

It's true that in theory, eliminating the cage would reduce overall friction
in a bearing. However bearings have to live in the real world, where materials
are ductile or friable. Small indentations in the load-bearing race will only
be durable if the load at that point is well under the yield strength of the
materials. Otherwise the balls or the race will just deform and lose the
advantage.

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tlb
The friction under zero load is rarely a factor in a real design. You wouldn't
use a bearing as big as the one in the video unless you had thousands of
pounds of radial force, in which case it's the rolling friction that
dominates. (Rolling friction is due to the balls compressing as they roll).

If you don't have large forces, you could just use a small bearing with
correspondingly low friction.

Possibly there's some application that needs large bearings to handle high
peak forces, but where it's otherwise spinning at high speed with near-zero
forces and friction matters, but I can't think what it is.

~~~
Retric
Something like Aircraft jet turbines might qualify. They are designed to
handel a mid sized bird stike or the loss of a blade which is way outside the
normal force range. Though, I suspect they are heavy enough that rolling
friction still dominates.

~~~
tim333
A lube free jet bearing could be a major plus for preventing Aerotoxic
syndrome.

~~~
FreeFull
Or have cabin air intakes that are separate from the engines.

~~~
PhantomGremlin
The Boeing 787 Dreamliner does this.
[https://en.wikipedia.org/wiki/Bleed_air#Bleedless_aircraft](https://en.wikipedia.org/wiki/Bleed_air#Bleedless_aircraft)

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modzu
My understanding was that a retainer or cage for bearings simply allows you to
use less bearings -- otherwise typically the bearings fill the cup and are all
touching.

In other words I'm not sure I even buy the premise...

Also the grease used also has a huge impact on the speed of the bearings (for
example a really light grease is fast while the heavy stuff is reserved for
conditions that demand it)

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Someone
I don't understand how this works, but the description made me think of shapes
of constant width (example at [http://mathsgear.co.uk/products/shapes-of-
constant-width-in-...](http://mathsgear.co.uk/products/shapes-of-constant-
width-in-acrylic-set-of-4))

I think one could get the effect by slightly undulating the in- and outside
tracks of a ball bearing and use balls that are slightly non-spherical. I
expect making such ever-so slightly non-spherical balls to great precision
would be extremely expensive.

This may (corrections welcome) be something similar, but with spherical balls,
getting a similar effect by varying the point of contact of the balls with the
outer track of the ball bearing.

Does it work for ball bearings? I wouldn't know. I do suspect that there will
be more wear and tear on those varying points of contact, though.

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jkot
Nice, but:

\- If there is bump, does it not rub down over time?

\- balls might jump differently when pressure changes (vehicle weight
changes).

\- How about vertical orientation when gravity is pushing balls in one
direction?

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gr3yh47
wouldn't that graphene + micro diamond thing be great for a bearing?

edit: this [http://arstechnica.com/science/2015/05/tiny-diamonds-
wrapped...](http://arstechnica.com/science/2015/05/tiny-diamonds-wrapped-in-
graphene-get-rid-of-friction/)

~~~
stephengillie
Taking from tlb's currently-top-rated comment:

> Rolling friction is due to the balls compressing as they roll

So I'd assume these have extremely low rolling friction?

~~~
abakker
Ceramic balls and races are currently used in some high end bicycle parts.
They have exceptionally low friction. See chris king bike hubs for an example.

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malkia
As kids we used to make carts with ball bearings, here are some examples:

[https://www.google.com/search?q=лагерна+количка](https://www.google.com/search?q=лагерна+количка)

I'm not sure whether kids in other countries did them, but being in possession
of 4 ball bearings was essential (they were not sold at the stores, or what
did I know - I was just a kid, most of them we had to ... ahem steal them).

