Cornering...

"Summer"

hth

 

from memory, or little black PDA?

 

heh. Memory.

 

Ah - my hobby-horse. As I've said many times before, from everything
I've read and experienced on countersteering, gyroscopic effects have
very little or nothing to do with it. If anything, gyroscopes make it
_harder_ to turn (seeing as a gyroscope wants to maintain its
direction of travel).

The most conclusive proof of this to me, is that vehicles without
wheels (e.g. jetskis) can be countersteered. There can't possibly be
any gyroscopes involved there.

In addition, if gyroscopes were the main enabler of countersteering,
then a bike with lightweight racing wheels would be harder to turn
than bikes with heavy steel wheels, which obviously isn't the case.

Gyroscopes might add stability, but they don't aid cornering.

Countersteering simply makes the bike 'fall' into the turn due to
'centrifugal' forces e.g. turning the bars left will 'throw' the bike
and rider to the right, setting up for a right-hand turn.
Countersteering simply enables you to get the bike leant over quicker
- it doesn't actually make you turn the corner.

 

Once you've got the turn set-up, you _don't_ countersteer. If you did,
the bike would keep leaning further and further until it hit the deck.
A cranked-over bike, at a constant lean angle, will have its bars
turned _into_ the turn slightly.

 

What do you do if you want to tighten the turn?

 

Why would it? The bike wants to stay upright, it's being pushed out by the
centrifugal force like a conker on a string being swung round the head. It's
harder to turn a bike into a corner than to go straight, etc.
Countersteering surely just makes the bike drop down to compensate for this
and make the turn possible at all.

 

No it doesn't.

WHich is countered by the camber thrust generated from the tyres. At
a steady speed, and a constant radius, the forces are in equilibrium

 

You countersteer some more.

 

This way madeness lies.

 

Exactly. And I'd ask you to imagine being cranked over, knee-down, at
high speed on a racetrack, and ask yourself what you might feel if,
when countersteering like this, the wheel first moved _away_ from you
before dropping into the turn. I find it impossible to believe that
you wouldn't notice this, whereas in fact all you feel is that you
push the bar and the bike drops further into the turn.

What I'd ask all the gyro-doubters to do is this: Take a bicycle
wheel, held in both hands on the axle, and spin it. Then imagine the
axle is a handlebar and push one side away from you gently. Instead of
moving in that direction it will move up (or down, depending on spin
direction) with exactly the same amount of force you're applying.

 

I've no idea what you're trying to say here. If you countersteer, the
wheel "moves away" from the direction of travel. We already agree
that countersteering is what makes bikes steer, so what's the
argument?

So what? If you read the pages of John Robinson's stuff I typed in,
the maths shows that there's no need to resort to gyros to explain it,
so why do you feel the need?

 

eh? why? In a corner the bike is *not* upright, so how can it "want
to stay upright"?

 

No, I mean for me

 

A number of people have said that the gyroscopic effect is
insignificant and that what happens is that there's a movement of the
wheel in the opposite direction before the bike's geometry settles it
into the corner. I'm saying I don't believe that, as you'd notice it
in the circumstances described..

Because he doesn't tackle the issue I'm trying to deal with. All his
explanations about camber thrust are trying to show how, when the
bike's C of G is shifted to one side, it will 'follow' that and lean
that way/turn in that direction.

He still seems to be suggesting that there is first a movement in the
direction you push, followed by a reaction to that movement as the
bike drops into the corner. I'd like to know if you think this is the
case, and whether you can feel it happening in high-speed, knee-down
corners.

 

Ace wrote

Pile on the throttle until the back comes round.

 

Champ wrote

So why do all you track heroes spend so much of your time making sure
the bike does stay as upright as possible by getting off and running
beside it then?

 

Hmm. I need to ask you some questions here:
1. Do you believe that all steering above walking pace is done by
counter steering? (Either from upright to leant over, or from leant
over at one angle to some other angle).
2. When you countersteer, does the contact patch move?
3. Immediately after counter-steering, do you 'correct' the steering
to maintain a steady attitude at the new lean angle?

I don't know that I can feel it happening, but this is what I think
happens.

 

Ace says...

Alot harder to manage on something as light as the CB250RS. The throttle
sticks at about 35 in top gear, so I can play with hands off the bars.
It takes quite a bit of leaning over to make the bike go round the very
slight bends down our road at that speed. FWIW I now weight about 11
stone and I am leaning right over to make it move off course, but it
will go. Once the turn has started, it is easily centralised again.

The Thunderace won't budge, it just ploughs straight ahead unless I hold
the fuel tank with my hands and shift weight. Donb't ask me why, but
this is the only way it will budge off centre with hands off the bars.

 

No. Body weight shift also plays a part.

Afterwards, yes, but only as a result of the changing angle of the
bike.

[1] It auto-corrects, for reasons as explained by JR in your earlier
quote.

Ah. Doesn't it seem strange that you don't notice it though?

[1] Of course, one possible explanation that occurs to me, and
possibly what JR's getting at, is that the steering angle actually
remains where you put it with your contersteering input, and the
camber thrust etc. turns you ruond the corner _even though the wheel's
pointing slightly the other way_.

This is something I'll have to think about...