Stationary or not....

Micky

Never knowingly understood
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Never mind what sort of a GS you ride... 650 through to 1200.

If you are travelling at, lets say 60mph, I have to believe that the bottom of the tyre, in contact with the road, is stationary at the very moment it contacts the road surface... it must surely be so! Mustn't it? Or the tyre would be slipping/skidding... but it's not.

If this is the case then the top of the tyre must surely be doing 120mph to overtake, get in front of, go round, back to the bottom to travel backwards, and then be stationary when/where it touches the road surface. Must this be not so also.

How can one part, the contact patch, be stationary, when the rest of the tyre is picking up speed, accelerating, then slowing down to a standstill for a fraction of a second as it touches the ground again!

Gosh... I need a bier :beer:
 
I think you're confusing linear motion with rotational motion.
 
Ah but, isn't it the rotational motion which results in the linear motion.

OK, no more JD for me...........where the fecks me coat.............. :tosser
 
Aidan1150 said:
Ah but, isn't it the rotational motion which results in the linear motion.
If you really want to know, you could plumb the depths of this thread...... :eek: It starts out being a thread about suspension but..... :eek:
 
How can one part, the contact patch, be stationary, when the rest of the tyre is picking up speed, accelerating, then slowing down to a standstill for a fraction of a second as it touches the ground again!

You are right; the tyre, relative to the road, is stationary at the point of contact. Of course the wheel is rotating at a constant speed (at constant speed).

Compare it with walking. One foot is stationary on the ground, the other is moving forward twice as fast as your walking pace.

Paul
 
A few years ago, this very question went on for months in the magazine "motorcycle sport" .

All very interesting , but even if you fully understand the pyschics of it all, it makes no difference to how you ride your bicycle. :D

So i tend not to dwell to much on these things.
 
If you think about it, the axle of the wheel has the same VELOCITY as the bike (i.e. speed in a certain direction) e.g. 60mph. If you now consider the wheel stationary with you looking at it along the axis of the axle - the bottom of the wheel would appear to be going 60mph to the rear of the bike and the top 60mph to the front of the bike.

Now add these two together i.e. the wheel going 60mph forward, the bottom of the wheel going 60mph backwards and the top of the wheel going 60mph forward and you will see that to an observer at the side of the road it would appear that the bottom of the wheel is stationary and the top going at 120mph.

This occurs because the wheel is rotating and as such the outer surface of the tyre is subject to constantly changing velocity i.e. the speed is the same BUT the direction is changing. The acceleration to make this change in velocity is called centripetal acceleration.

Hope this explains things:)
 
Micky

What you say is true of tracked vehicles, the track is laid down and is stationary, the vehicle moves over it, not sure its true of wheels though, Christ i need a beer now.

Jimbo
 
Anyone want to discuss the slip in the ballbearing? Ball is rolling on two different dia's and must be slipping on one or t'other?
 
Jimb said:
What you say is true of tracked vehicles,
..no it just true full stop - basic laws of motion. It was sorted a few hundred years ago, so lets not drag it all up again. Have a beer :beer: :thumb
 


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