Paging the R1-isti

Eiron wrote:
in message news:...

I suspect, I'm one of Champ's 'little friends' for
the purposes of this reply.

You are the one making the schoolboy error.

 

Actually, I've not been corrected yet. I'm awaiting your explanation
as to why I'm wrong.

 

"Just because."

 

I couldn't have put it better myself.

 

er, surely there *is* travel in the direction of the force?

 

Not the main force. As Mark says, the only force in the direction of
travel is the (minimal) force needed to keep you moving at a constant
speed - as in a straight line, near enough. The main force in a turn
is at right angles to the direction of travel.

 

<shrug> When I was at school I was taught that a change in velocity
(not speed) was an acceleration. So where's the accelerating force
coming from, then?

 

It's the centripetal force along the radius of the curve.

 

**** sake. If you didn't need extra energy to change direction, you
wouldn't need to lean the bike over either.

 

I'll have to check: can't really visualize what I do or exactly when.
Still doesn't really explain why the R1 is so much more difficult than
other bikes, though.

This is the problem I'm having.

 

Same as a spinning wheel: every point on the wheel is being
accelerated towards the centre of the hub; the accelerating force is
the tension in the material it's constructed from. No energy is being
expended, though.

However, recall an earlier argument I had with Simian <winces>

 

Whilst we're in the R1 thread, I have got an R1 rear wheel spindle,
wheel adjuster blocks and nut going spare if anyone wants it.

If anyone's interested before I lob it on ebay, send me a mail to my
zym address.

Cheers,

Paul.

 

Ace wibbled...

On a slight tangent, there isn't always more sidewall to the tyre if they're
trails tyres.

You'll know when you've found this point when no amount of leaning off /
leaning over makes it turn any sharper :-S

 

Ace wibbled...

If you didn't need power to go round a bend you could turn the engine off
and never stop going round a roundabout.

FFS Eiron, shoolboy howler? Nursery school howler. Put brain into gear
before typing.

 

Mark Olson wibbled...

Which is what Champ was talking about, the real world.

Unless he's started racing bikes in Space?

Plus that little bit of power to overcome friction and other losses is on
top of a neutral throttle to overcome engine braking / gearbox friction.

 

Mark Olson posted:

As I understand it [1]:
Speed is scalar (i.e. has magnitude but no direction).
Velocity is vector (i.e. has magnitude and direction).
Acceleration is a change in velocity (i.e. change in either magnitude
or direction - or both).

Acceleration (in scientific terms, may be positive or negative)
requires force to be applied. This should be fairly obvious; Newton's
Laws of Motion [2] and the Laws of Thermodynamics cover it nicely. You
cannot change direction, even at a constant speed, without some force
being applied other than that required to maintain the speed.

Satellites are a special case - they are constantly falling, but
nobody's told them that so they stay up [3] ...

[1] Poorly-remembered 22-year old O-level Physics (grade B).
[2] http://en.wikipedia.org/wiki/Newton's_laws_of_motion
[3] This may not be true. If you'll trust Wikipedia, why not trust me?

 

Put your own brain into gear, frag. You need power to overcome friction.
It was Champ's lack of understanding of the science of circular motion
that we were discussing.
See the moon in the sky? Where's the power to keep it orbiting at a
constant speed?
It's all explained earlier in the thread.

 

Eiron wibbled...

You are wibbling on about perfect frictionless systems.

Champ is wibbling on about a bike going round a corner.

You can't just ignore half the environment (friction, engine braking, air
resistance), extract whats left and then say its wrong.

 

Gravitational forces.

 

Isn't that just what Champ did here:
"The 'science' behind this is that turning (changing direction) is
"acceleration, and to accelerate you need a force. So, even to corner
"at a steady speed, you need some power."

He seems to have ignored "friction, engine braking and air resistance",
which is the only reason you need some power to corner at a steady speed,
extracted what's left, and wrongly deduced that a centripetal force
requires some power.