Cornering...

In uk.rec.motorcycles, Porl burped loudly and ejected the following:

The amount by which the wind blows up yer petticoat.

 

Rope bored us all completely to death with wittery prose along the
lines of:

I was thinking of the French Run. If I get time to do an EOSM, I will.

--
Cab :^) - almost as fast as Ginge.
GSX 1400 - 'Tarts Handbag' (tm) Bike, dead 550/4 Rat
UKRMMA#10 (KoTL), IbW#015, Bob#4, POTM#3

P.S. Remove your_head from the cab. ICQ: 83023471

 

This should keep you quite :
http://www.tut.fi/plastics/tyreschool/moduulit/moduuli_10/hypertext/3/3_1.html

However, I probably misused the phrase. The following is worth what
you paid for it:

Imagine a cone, on it's side. If you rotate it, it decribes a circle.
This is how a bike corners - a bike tyre can be thought of as two
cones, joined at their bases. of course, these cones don't have
straight sides - the radius changes across the profile of the tyre,
allowing you to "roll into" a corner.

Now, your front and rear tyres have different profiles - i.e. they are
different sized cones. Depending on the relationship between the
profile of front and rear tyres, you may have to steer into, steer
ahead, or steer out of the corner for a particular speed and lean
angle. I *think* I've heard (read, in fact) the amount of steering
input reqd in a steady speed corner referred to as the slip angle.

John Robinson's book "Motorcyle Tuning : Chassis" goes into this in
some mathematical detail.

 

Thought it was that simple, I guess I'm just not opening it fast enough.

If only it were *that* large a bonus. Actually as long as I got a
black/red one Claire probably wouldn't notice that I'd changed.

TBH if I had the money I'd go tomorrow but I'm some way short
unfortunately !

 

Cheers for that. I will avoid pointing at your previous assertation that you
don't think about the mechanics of riding...

 

I hadn't to be honest I'd just assumed that a Fazer might be more in my
price range than a Gixer. A quick scan on MCN disproves that theory.

Again it's a cost thing. But also I don't see why I'd need a thou since
I can't get near the abilities of my current Gixer so why would I need a
bigger one.

Besides Gixer Thou's are chickwheels

 

No problem

I'm indebted. After all, if we can't be inconsistent here, what's the
point?

 

Exactly. You use the get out of jail free card and meanwhile I chalk up
another victory point. It's a good year for me so far.

 

Don't worry, I never managed it more than a couple of inches.

Heh, how about a 2nd hand Thou like mine? Cost to change of maybe 3k.

 

Ooh yes !!!

Depends on how narrow our definition of countersteering is. If
we mean giving steering input to the handlebars in the opposite
direction to where we want to go it is no problem in a corner that
is not to sharp. Just let go of the handlebar and steer by body
weight shift.

Workes quite well. The problem is that the bike is so damn
sensitive to weight shift at those speeds that you have to
concentrate real hard to isolate the effect of countersteering.

The fact that it is there does not mean that it is important at
all. Weight shift is far more important at low speed.

 

You don't need hands on bars to countersteer.

The bars will do it on their own.
--
| ___ Salad Dodger
|/ \
_/_____\_ GL1500SEV/CBR1100XXX/KH500A8/TS250C
|_\_____/_| ..66073../..15556.../..3157./.19406
(>|_|_|<) TPPFATUICG#7 DIAABTCOD#9 YTC#4 PM#5
|__|_|__| BOTAFOT #70 BOTAFOF #09 two#11 WG*
\ |^| / IbW#0 & KotIbW# BotTOS#6 GP#4
\|^|/ ANORAK#17
'^' RBR-Visited:35 Pts: 705 Miles:2429

 

Eh? No, the bars will move as a secondary effect when the bike is
cornering, but in the direction of the turn, not away from it.
Countersteering when cranked over in a turn doesn't actually move the
bars at all[1], it just causes the bike to lean more, _then_ the front
wheel and bars will turn to the natural angle dictated by the steering
geometry. The latter will occur regardless of how the turn was
initiated.

[1] Or a minute amount only.

 

If that was the case then why can't the bike be turned soley by weighting
the footpegs? I think K Code has a bike with locked handlebars to prove that
the bars have to move to countersteer.

 

A bike _can_ be turned, albeit slowly, just by shifting your body
around. Forget the footpegs, that's just a red herring here.

I thought it was California Race School (or is that the same mob?) who
did this, but it was just an extra set of bars - the originals were
free to move. The results showed, IIRC, that with no handlebar input a
bike is very hard to steer and that weighting the footpegs without
moving the body around has no effect unless it's to help with
countersteering handlebar input.

 

Clearly it's possible to alter the bike's direction by shifting weight,
jiggling about a bit, contorting one's body etc etc - but it's hardly a
practical way to turn a motorbike at any speed.

Same mob.

 

I don't understand why the bars turning are a _secondary effect_ in the
turning process.

 

As the bike leans over, the built-in stability of a bike's geometry
coupled with the tyre profile will actually cause the front wheel to
turn towards the direction in which it's being leaned.

So, the primary action is to get the bike to lean over - this may be
initiated by body weight shift, which will work slowly, or by
countersteering, where the gyroscopic effect of pushing one side of
the bars forward causes the bike to lean to that side.

In either case, the secondary effect is the front wheel turning in the
right direction to ensure the bike turns a corner rather than just
falling over.

This help? If not, get your pushbike out and push it along by the
saddle - experiment with leaning it over and watch what happens to the
front wheel.

 

That suggests that countersteering takes place first, whereupon the wheel
turns away from the direction of the bend (as I understand it) , and then
the wheel turns back again as per this paragraph "turn towards the
direction in which it's being leaned", which doesn't make sense to me. Is it
semantics and I've misinterpreted it or is this what happens?

 

That's exactly what happens.
When you countersteer you are in effect pointing the wheel away from where
you want to go - but, gyroscopics being what they are, this causes the bike
to lean over towards the direction you want to go - which is where the
geometry of the bike and the profile of the tyres keep, rather then
continued countersteering, keep the bike leant-over & stable until the rider
does something to change things - e.g. increases (or decreases!) throttle,
effects some more counter-steer (or steer) action throught bars or touches
the brakes.

 

Which happens all the time at the track, right? When you're going into a
corner you're still decelerating a bit and then you're acceleratnig out of
it. Or is that why I crash?