# The Naked Scientists Forum

### Author Topic: why doesnt the axis of a wheel disintegrate via friction?  (Read 4408 times)

#### CZARCAR

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##### why doesnt the axis of a wheel disintegrate via friction?
« on: 23/11/2009 19:59:01 »
spinning wheel ,1 side moves in 1 direction [N] & the opposite side moves in the opposite direction . as the circumference of the same wheel gets smaller,the rotational speed slows. the wheel's circumference can get infinitesmally smaller as can the speed but at the axis how can the rotation stop?if not, the opposite forces would disintegrate the axis via friction?
THE WHEEL IS HORIZONTAL & SPINNING ATOP A BALANCED POINT LOCATED UNDER THE AXIS
« Last Edit: 23/11/2009 21:12:22 by CZARCAR »

#### Geezer

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##### Re: why doesnt the axis of a wheel disintegrate via friction?
« Reply #1 on: 23/11/2009 20:45:30 »
Not sure I understand. Can you sketch a diagram?

#### CZARCAR

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #2 on: 23/11/2009 21:19:17 »
i edited the op but now it has lines thru the script! still readable but sorry 4 the hassle. im trying to describe a horizontal wheel spinning  on a frictionless axially located point below its axis/center.

#### Geezer

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #3 on: 24/11/2009 04:13:18 »

"Why does the axle that supports a rapidly spinning wheel not wear out due to friction?"

Well, it would if you don't do something to reduce the friction. Depending on the speed of rotation, the load etc. you could use simple oil, grease, ball bearings, roller bearings or air bearings. High speed turbines use something called a foil bearing. I believe there are even magnetic suspension bearings.

If there is a lot of force acting along the axis of rotation, you will need something called a thrust bearing to support that force. It can also use most of the techniques above.

You should be able to find references for all of these on Wikipedia.

#### CZARCAR

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #4 on: 24/11/2009 10:54:49 »
no, the center of the wheel itself. the frictionless point supporting the horizontal wheel is only for description of the situation. the wheel has its opposite circumferences moving in opposite directions & if brought together by the shrinking of the diameter would result in friction or the exact center would have no rotation

#### Geezer

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #5 on: 24/11/2009 19:15:36 »
I thought it might be too easy

I'm still don't understand the "experiment". Maybe you could start again from the beginning.

#### Bored chemist

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #6 on: 24/11/2009 19:20:30 »
The edges of a spinning wheel are moving fastest. Nearer the middle the speed of the motion is smaller.
Right at the middle the speed is zero- so there's no motion and therefore no friction.

#### Geezer

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #7 on: 24/11/2009 19:57:03 »
Oh! Is that what it was?

Then all we need is an axle with a diameter of zero, and we're good to go.

#### CZARCAR

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #8 on: 24/11/2009 20:02:10 »
The edges of a spinning wheel are moving fastest. Nearer the middle the speed of the motion is smaller.
Right at the middle the speed is zero- so there's no motion and therefore no friction.
between the center & the proximal "smallest" wheel there is no friction?

#### Geezer

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #9 on: 24/11/2009 21:25:00 »
The edges of a spinning wheel are moving fastest. Nearer the middle the speed of the motion is smaller.
Right at the middle the speed is zero- so there's no motion and therefore no friction.
between the center & the proximal "smallest" wheel there is no friction?

You wouldn't be trying to build a perpetual motion machine by any chance?

#### CZARCAR

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #10 on: 24/11/2009 23:36:15 »
The edges of a spinning wheel are moving fastest. Nearer the middle the speed of the motion is smaller.
Right at the middle the speed is zero- so there's no motion and therefore no friction.
between the center & the proximal "smallest" wheel there is no friction?

You wouldn't be trying to build a perpetual motion machine by any chance?
only if i cant not avoid it!

#### wolfekeeper

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##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #11 on: 25/11/2009 01:46:28 »
The axle of a wheel at the bearing *does* gradually disintegrate!

It disintegrates more slowly than simply dragging something across the ground, because when the wheel moves (say) 10 feet at the rim, the relative motion is only a few inches (say) at the axle (depending on the diameter of the wheel, and the diameter of the axle.)

The weight is the same, but the distance is much less. So it still wears away, but more slowly.
« Last Edit: 25/11/2009 01:53:35 by wolfekeeper »

#### The Naked Scientists Forum

##### why doesnt the axis of a wheel disintegrate via friction?
« Reply #11 on: 25/11/2009 01:46:28 »