Re: What is "fretting?"

Alfred Ryder said:

Quoted message said:

Head bearings develop dimples from ball bearing fretting while on long
coasting descents that require no steering motions that would to
replenish lubricant as the fork crown articulates fore and aft through
vibration angles. Dimples in cup and cone are galling pull-outs that
leave a matte finish unlike a Brinell dimple that is spherical and
shiny. This type of failure is common on cars shipped by train over
long distances. The differential and wheel bearings fret into galling
and can often be heard on BMW's as they shhhhhhhh past on the road.

Quoted message said:

Quoted message said:

I'm sure there are other examples.

Quoted message said:

Last year I replaced by head bearings which had developed dimples in
the cup and cone. I did not spend any time wondering how they got
there since I felt it was obvious. Like many phenomena, it is more
complex than I realized.

Quoted message said:

But here is, I think, another example of the phenomenon. When I was
in high school, the local fad was to take a quarter (quarters were
soft with a relatively high silver content then) and a spoon and,
holding the quarter between finger and thumb, hit it with the convex
part of the spoon. After hours of tapping the edge of the coin, the
edge would begin to spread out. And after many, many hours, it
would spread out enough so that, when the center was drilled out, it
became a silver ring for the finger. Although a lot of us walked
around school taping our quarters, I never saw anyone actually keep
it up long enough to finish.

Quoted message said:

It was the many little taps that made the metal "flow". There is no
way that a few heavy blows could do the same thing. And I am not
sure this is the same as "fretting".

That is not fretting. Each of these blows was causing plastic
deformation, however small, and I guess the added up as you describe,
although I can't imagine anyone doing that successfully.

Fretting is friction induced micro-welding and breaking of these
welds. It is not causing deformation but rather erosion by tearing
out tiny bits of metal. These are hardened steel bearing races and
harder steel bearing balls of which we speak.

[email hidden]

Quoted message said:

Alfred Ryder said:

Quoted message said:

Head bearings develop dimples from ball bearing fretting while on long
coasting descents that require no steering motions that would to
replenish lubricant as the fork crown articulates fore and aft through
vibration angles. Dimples in cup and cone are galling pull-outs that
leave a matte finish unlike a Brinell dimple that is spherical and
shiny. This type of failure is common on cars shipped by train over
long distances. The differential and wheel bearings fret into galling
and can often be heard on BMW's as they shhhhhhhh past on the road.

Quoted message said:

Quoted message said:

I'm sure there are other examples.

Quoted message said:

Last year I replaced by head bearings which had developed dimples in
the cup and cone. I did not spend any time wondering how they got
there since I felt it was obvious. Like many phenomena, it is more
complex than I realized.

Quoted message said:

But here is, I think, another example of the phenomenon. When I was
in high school, the local fad was to take a quarter (quarters were
soft with a relatively high silver content then) and a spoon and,
holding the quarter between finger and thumb, hit it with the convex
part of the spoon. After hours of tapping the edge of the coin, the
edge would begin to spread out. And after many, many hours, it
would spread out enough so that, when the center was drilled out, it
became a silver ring for the finger. Although a lot of us walked
around school taping our quarters, I never saw anyone actually keep
it up long enough to finish.

Quoted message said:

It was the many little taps that made the metal "flow". There is no
way that a few heavy blows could do the same thing. And I am not
sure this is the same as "fretting".

That is not fretting. Each of these blows was causing plastic
deformation, however small, and I guess the added up as you describe,
although I can't imagine anyone doing that successfully.

you're such a joke jobst. deformation occurs in one metal system, but
not another??? utterly ridiculous.

Quoted message said:

Fretting is friction induced micro-welding and breaking of these
welds. It is not causing deformation but rather erosion by tearing
out tiny bits of metal.

that /is/ a description of fretting, but it's pure guesswork on your
part that it's occuring if you can't grasp the fact that even hardened
metals plastically deform.

Quoted message said:

These are hardened steel bearing races and
harder steel bearing balls of which we speak.

that plastically deform when overloaded.

Quoted message said:

[email hidden]

Quoted message said:

Alfred Ryder said:

After hours of tapping the edge of the coin, the
edge would begin to spread out. And after many, many hours, it
would spread out enough so that, when the center was drilled out,
it became a silver ring for the finger.

That is not fretting. Each of these blows was causing plastic
deformation, however small, and I guess the added up as you describe,
although I can't imagine anyone doing that successfully.

It has been done. I have not only seen rings made from 90% silver
half-dollars, I have seen laminated quarters turned into little
barrel-shaped webbed rings by having been trapped inside a tumble dryer
for years.

The spoon method is probably most appropriate for OCD sufferers-- it
takes a *long* time to finish.

Chalo Colina

Alfred Ryder said:

jobst.brandt wrote
(snip)

Quoted message said:

Head bearings develop dimples from ball bearing fretting while on long
coasting descents that require no steering motions that would to
replenish lubricant as the fork crown articulates fore and aft through
vibration angles. Dimples in cup and cone are galling pull-outs that
leave a matte finish unlike a Brinell dimple that is spherical and
shiny. This type of failure is common on cars shipped by train over
long distances. The differential and wheel bearings fret into galling
and can often be heard on BMW's as they shhhhhhhh past on the road.

I'm sure there are other examples.

Last year I replaced by head bearings which had developed dimples in the cup
and cone. I did not spend any time wondering how they got there since I felt
it was obvious. Like many phenomena, it is more complex than I realized.

But here is, I think, another example of the phenomenon. When I was in high
school, the local fad was to take a quarter (quarters were soft with a
relatively high silver content then) and a spoon and, holding the quarter
between finger and thumb, hit it with the convex part of the spoon. After
hours of tapping the edge of the coin, the edge would begin to spread out.
And after many, many hours, it would spread out enough so that, when the
center was drilled out, it became a silver ring for the finger. Although a
lot of us walked around school taping our quarters, I never saw anyone
actually keep it up long enough to finish.

It was the many little taps that made the metal "flow". There is no way that
a few heavy blows could do the same thing. And I am not sure this is the
same as "fretting".

Dear Alfred,

I promptly decided that you were a nutcase with a coin
fetish and even said so to several other people.

Then I decided to look up your ridiculous idea:

D'oh!

http://forgedunderthemountain.com/FUTMPG3.html

Nice pictures that show the result that you have in mind.
They cheat and use a hammer, but the gentle repeated tapping
is emphasized

Thanks for the odd information and the lesson in the dangers
of dismissing odd ideas out of hand.

Carl Fogel

Chalo said:

My thinking is that true brinelling in an installed headset may be
possible, because manufacturers push the limits of cheapness in their
parts. If a properly hardened bearing race made of conventional
bearing materials can never exhibit brinelling as used, then why not
cut costs by using lesser materials or simpler manufacturing processes?
The limit of how much this reasoning can be extended is determined by
the magnitudes of the forces most bikes are exposed to, most of the
time.

Not to mention that things that never break are bad for business.

Jasper

Quoted message said:

Nice pictures that show the result that you have in mind.
They cheat and use a hammer, but the gentle repeated tapping
is emphasized

It's the same sort of process as Middle-Eastern coppermiths use: they
start with a block of copper, and beat it out until it's a serving dish or
a teapot, usually sumptuously decorated using the patterns left by the
hammers.

Jasper