Paging all 'bladeisti

Eiron · Sep 10, 2005

Ace said:

I was giving this a lot of thought recently, after Champ commented on
the fact that I hardly ever shift my bum off the bike. 'Chicken
strips' seemed to indicate that my max lean angle was slightly less
than his (both had identical new rear tyres allowing a good
comparison) but we'd been riding the same roads at the same speeds,
taking very similar lines through most corners.

The distance of the CoM from the pivot point has a great effect on a
rotating body, as can be seen when looking at ice skaters, who extend
their arms and legs to slow a rotation and vice-versa. So the closer
to the pivot point the faster the turn for a given amount of energy,
or put another way, the less energy required for a given amount of
turn.

On a leaning bike, the higher the mass is kept the closer it is to the
(virtual) pivot point, giving the same effect. To a lesser extent, at
low angles of lean, weight shifting side to side will have this
effect, but once you're leant over by any significant amount the
height thing is much more important.
Click to expand...

What's all this bollocks about energy required to start a bike leaning
and more energy to stop it?

The significant thing about CoG height is that a bike with a higher CoG
leans less than a bike with a lower CoG on the same curve.
The line between CoG and centre of tyre contact patch has the same angle
for both bikes.

Pip · Sep 10, 2005

A direct comparism between the 9R & 10R shows the more modern bike to
be higher with the only thing lower being the bars.
Click to expand...

You mean that the bars are shorter overall on the 10?

Pip Luscher · Sep 10, 2005

It is, I think.

If bikes *are* taller (and I've no idea - my impression is that
they're getting smaller in every dimension), then it'll to be to raise
the CofG - this give quicker steering, and (I think) means a bike has
to be leant over less for a particular cornering radius/speed
Click to expand...

Well, my experience of modern sports bikes is rather limited, but I do
get the impression that they're getting taller.

I'm not sure about the quicker steering: wouldn't that mean a larger
arc for the combined C of G to swing through - though the smaller lean
angles might mitigate that.

The only reason I can see for a smaller lean angle, though, is because
the movement of the contact patches of the tyres becomes less
significant with a higher C of G.

If one does the parallelogram of forces thing then the height has no
effect at all on the lean angle without allowing for the contact
patch, unless there's some other factor that I haven't thought of.
Which is entirely possible.

BGN · Sep 10, 2005

Well, my experience of modern sports bikes is rather limited, but I do
get the impression that they're getting taller.
Click to expand...

Bike did this a couple of months ago. I got the impression from the
graphs that bikes were getting bigger.

JackH · Sep 10, 2005

ogden said:

Heh. I remember watching that happen the day you picked the VFR up, on
the M1 by Scratchwood services. One of us remembered about the fucking
great bump on the motorway, the other didn't.
Click to expand...

Ho ho ho
Click to expand...

LOL... didn't realise you got that good a view of it, given you were on a
much slower bike.

But aye, that's the one... scared the shit out of me, it did.

platypus · Sep 11, 2005

Ace said:

I was giving this a lot of thought recently, after Champ commented on
the fact that I hardly ever shift my bum off the bike. 'Chicken
strips' seemed to indicate that my max lean angle was slightly less
than his (both had identical new rear tyres allowing a good
comparison) but we'd been riding the same roads at the same speeds,
taking very similar lines through most corners.

The distance of the CoM from the pivot point has a great effect on a
rotating body, as can be seen when looking at ice skaters, who extend
their arms and legs to slow a rotation and vice-versa. So the closer
to the pivot point the faster the turn for a given amount of energy,
or put another way, the less energy required for a given amount of
turn.
Yep.

On a leaning bike, the higher the mass is kept the closer it is to the
(virtual) pivot point, giving the same effect. To a lesser extent, at
low angles of lean, weight shifting side to side will have this
effect, but once you're leant over by any significant amount the
height thing is much more important.
Click to expand...

This is where you lose me. The pivot point is the contact patch, yes? Then
the higher the mass is kept, the further away from the pivot point it is.

Of course, this only works for people of normal height and build.
Those vertically challenged, low CoG types like yourself will be much
less inclined [1] to notice this.
Click to expand...

**** off, you lanky ****.

[1] Accidental, honest.
Click to expand...

Ace · Sep 11, 2005

Ace wrote:

This is where you lose me. The pivot point is the contact patch, yes?
Click to expand...

No, it's the centre of the circle of which you're riding on the
circumference.

Then
the higher the mass is kept, the further away from the pivot point it is.
Click to expand...

So it's the opposite of that.

--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ GSX-R1000K3
`\\ | //' BOTAFOT#3, SbS#2, UKRMMA#13, DFV#8, SKA#2
`\|/`
`

Paging all 'bladeisti

Eiron Guest

Advertisements

Pip Guest

Advertisements

Pip Luscher Guest

BGN Guest

JackH Guest

platypus Guest

Ace Guest

Advertisements

Want to reply to this thread or ask your own question?

Paging all BMW R100 owners

Paging Tog et all - GT380 Value

Paging Timo the Kraut et all

Paging all the pagers

Paging All present/past ZZR1100 owners.......

You can't please all the people all the time

You must all be bored - but are you all fools?

Oh, so it wasn't all about oil after all, then...

Paging all 'bladeisti

Eiron Guest

Advertisements

Pip Guest

Advertisements

Pip Luscher Guest

BGN Guest

JackH Guest

platypus Guest

Ace Guest

Advertisements

Want to reply to this thread or ask your own question?

Useful Searches