Pure tech and opinion for this posting
I look at what's available on Youtube about
bike ball bearing care and replacement.
I find...not much is there at present.
We tend to think that ball bearings are the defacto standard for lowest friction and longest life.
On bikes, this is certainly true. But, briefly, what about the other kind of bearing? The plain bearing.
Well, plain bearings are hardly "plain" if well made. Many or most small motors employ plain bearings.
When well fitted (close tolerance), and run on a super-thin oil film at a speed which permits "hydrodynamic lubrication",
there is NO wear of plain bearings, and less running friction, often, than from ball bearings. Ball bearings have a long but finite running life. They are hard steel against hard steel and this is good and proper, but, if loaded, as heavily as, say,
in auto wheel bearing applications, the ball bearing eventually must begin to to fail by "flecking" off of its surfaces: a metal fatigue sort of process. Even more rarely these days, a ball (very hard and tough steel) may split, then cause fast and certain death for the remaining balls and for the races. Plain bearings, otoh, are not so great at all for bikes, but do serve
better than ball bearings for other applications, such as for high speed fan motors and IC engine connecting rod and main bearings, etc.
They make no "rrr, rrrrr' noise, ever.
Here is a picture of an attic ventilation motor. It is in my garage attic. I put it there in 1983.
This a plain bearing, GE brand, 1//4HP motor. It has been running (barring power outages), 24/7 for fully 25 years now.
I look up at it every day because it's visible to me from my shop-located computer chair.
Fan sound. No bearing knocks or whines. I've oiled the motor (it has cups to accept a few drops of oil),
two times in 25 years; the last oiling job was about seven years ago.
The plain bearing offers many types of high speed machinery a no-metal-contact running platform:
the parts float on oil, "hydrodynamic lubrication", and so, do not wear, period. Such bearings far outperform
"antifriction" ball or roller bearings..
But for bikes?
Ball or roller bearings are the thing they use, and for good reason:
at low speeds, in ball bearings, no "hydrodynamic" lift-and-separate is possible.
The pure fluid friction of the high-speed hydrodynamic, plain bearing, is, instead, in the low speed ball or roller bearing, supplanted by the
small rolling friction (and wear) of hard steel balls or rollers or needles, against, usually, hard, precision-ground steel.
Here is a proud fellow showing off his super high tech ceramic ball bearing bottom bracket's freedom of action:
http://www.youtube.com/watch?v=4B2eUt9D1TE
("we" are not overly impressed).
Q: does his silky-smooth, rubber-lip-sealed cartridge bearing really spin so very freely?
Q: the still photos of my old school bike's bottom bracket ball bearings (1900 style bearings)
show: very poor quality balls (some are surface-fissured), incredibly bad quality balls, those,
working in a fabricated, soft steel cage, against which they lightly rub; and these caged bearings
roll in cups of mere pressed steel (not precision ground cups) bearing a thin layer of (hard) chrome plating.
Point: the cups cannot be truly round. The balls, too, are suspect. Yet, I was able to obtain a running fit
about as free in action as the $$$ "ceramic bearing" guy's cartridge bearing. Imagine that if my bike's bearings
were of higher quality, yet of the identical construction? They'd not only equal, but exceed the "cartridge bearing"'s
freedom of action, PLUS, be serviceable for an indefinitely long life.
Perhaps today I will get into the rear coaster brake bearings. I "feel" factory grit in them. OR the balls and races are not truly high precision-manufacture. They will be "loose" balls in this case, not caged.
A perfect bearing, with perfect balls, runs without shake, without binding, and without hardly a hint of "rolling ball" sound.
The devil, a small devil, is in the details. "Sealed" bearings, with few exceptions, are not truly sealed; they are only "shielded".
So, if our bike bearings, especially of the old fashioned, obsolescent cup and cone type, cannot be truly sealed,
then what is the secret by which to keep them clean(er) and happier over the long and dusty, wet road?
Ans: regular servicing: clean and re-grease seasonally. Or, perhaps, inject fresh grease on occasion,
just a bit of new grease, at whatever intervals you care for: the bearing will eject the excess, older grease, and need wiping-off.
And so, we might, if we so-design (grease fitting) push an ever-fresh supply of grease through the bearings, ejecting dirty (water and gritted) grease out, to the outside world, ready for a swipe-off of your wiping rag.
No lip seals, no lip seal "drag", however slight. Fear no stream fjording then; when you get home:
pump into the bottom bracket, some fresh grease.
There
are advantages to new bearing constructions. These bearings are not the be-all-end-all, however;
for example, if you like to ride your bike across streams....a "sealed" cartridge bearing will not endure that exercise for very many seasons.
Point: boat trailer bearings. How are they lubricated and sealed? What sort of grease do they employ?
How does their greasing system save the boat trailer bearing (the trailer that goes into salt water to launch the boat).
Salt water. Sand. Silt. How to keep old tech ball bearings running clean and like-new for the life of the bike......
tbc.
more to come in this form:
Let's clean and service the coaster brake (for my first time) and see what is in there?
And while I am at it, I will be lowering the steel Wald brand rack by about one inch, to gain more seat-bottom clearance
and to lower the center of gravity of the bike, just a bit, for the benefit of the 16 pound, 36V, 20Ah,
PING LIFEPO4 battery , which is winging in from Shanghai to Miami next week.
