Cycling UK Forum

This is an interesting video about how steering works.

Brilliant - thanks for the link

Interesting video.

The riders of the "zero gravity" bike were just like me when I first got a motorcycle and sidecar.
Until I could convince my sub-conscious that it was not a two wheeler it wouldnt let me turn the steering wheel and put my weight on the outside wheel and the bike wouldnt bank and turn the "normal" way, so I drifted along just like in that video.

The analogy of a bike and an "inverted" pendulum is a good one. .....but I think we knew that you balance a bike by putting the wheels under your centre of gravity.
They have taken gravity out of the system and demonstrated that if you "break" the system (putting the wheels under the centre of gravity to hold the bike upright) then the system doesn't work......so I think its a demonstration of something we knew, rather than a discovery of something new.
I suppose as an academic interest, its OK, but I don't find it terribly relevant to real life. A bit like the academics who torture themselves trying to explain why a riderless, pushed bike can go along on its own for a bit.
I'm more interested in the assertion that you start a turn by counter-steering..........is that always the case?.....is it still the case riding no-hands?.....how would that go....to turn left, I need to counter-steer to the right to start the lean....but to steer to the right, I need to counter-steer to the left to start the lean.......but to steer left.....

Hi,
I once saw a documentry of land speed record on a motorbike, apparenently the driver had to remember to steer / countersteer diffferently six times up to 200 MPH.
So its not straight forward.
If I ride my bike around my garden going around trees turning sharply I am very conscious of balance (tight rope walking with no aid) but on the road counter steering is very evident even with no hands.
Motorcycling trials is like that too.
The test is to cycle with one hand on bars (but no weight pressing down) in all situations and see which way you turn the bars Could be dangerous
Instinctivly we ride by balance and feel which blends so smoothly that we never notice the change between steering and counter steering.
We counter steer to move the COG in the oposite direction, which makes the bike lean round the corner.
The initial counter steer is very momentry but I think that there is a constant swapping of steer and countersteer in a corner if you have then to change the shape of the arc the bike follows

I havent watched the Vid yet but even without gravity there would still be inertia when changing direction which would need countering.

Hi,
The Video.......you can drive a freight train through the holes in using a spring to simulate what
I have not listened to the speech with video yet, would that change my mind

I really liked that - the title is a bit off & you do have to listen to the words to suss what they're trying to say.
My mate at work said "you'd learn to ride that" but the whole point is that you wouldn't 'cos it's impossible!

Hi,
Well I watched and listened bto the vid and I understand what they are saying.
I am not happy with the spring, this is holding the bike up against gravity Clever but crude...........
Aso inertia which still exists in space is ignored
The balancing broom trick also relys on inertia

Open your mind Grasshopper

http://divinecosmos.com/start-here/book ... nd-inertia

"4.2 NEWTON: PIONEER OF GRAVITY AND INERTIA

The answer to this question as well as our understanding of gravity came about from the work of Isaac Newton. Perhaps the ultimate cliché in all of science is the image of Newton sitting under a tree and discovering gravity when an apple fell down and hit him on the head.

From this initial inspiration, Newton composed a series of laws including gravitation and the “law of inertia,” which everyone remembers from their science classes as, “An object at rest tends to stay at rest, and an object in motion tends to stay in motion.” And that means that even in an airless vacuum without gravity, you will encounter a force that will cause you to have difficulty moving something through space!

So what exactly is that object moving through? In the conventional models it is simply a “force” and nothing more is discussed. Here, we will suggest that this force is caused by the energy of the universe. Therefore, if we consider the spiritual perspective of our living in One Ultimate Being, then we can see how this shows us that no matter where we go in the Universe, we are always moving through the energy “body” of that Being, drawing the energy of space along with us."


"4.11.1 DEPALMA’S SPINNING BALL DROP EXPERIMENT

Again, to use a metaphor that involves flowing water, this principle of defying gravity is just as simple as taking a water hose that is pointing downwards and bending it so that the water flows out to the side instead.

"Sideways" is not normally considered to be a gravitational motion, but it clearly does have a force, like when you are riding on a rollercoaster and feel pressure against your chest. This “sideways” force is inertia! Dr. Bruce DePalma, a non-conforming MIT graduate, demonstrated this principle with an extremely simple experiment.

First, he would release two balls from two catapults side-by-side at an equal angle, and have the catapults put an equal amount of force on each ball. The only difference would be that one ball would be spinning at the terrific speed of 27,000 RPM, and the other ball wouldn’t be spinning at all.

In a complete vacuum, he would observe the trajectories of the two balls and see whether anything changed; their height, their angle, their speed of travel. And in so doing, DePalma discovered the impossible:

In defiance of all known physical laws, the spinning ball actually traveled higher, fell faster and moved farther than its non-spinning counterpart.

dpballdrop.jpg (21.26 KiB) Viewed 1831 times

And as a side note, since skeptics are quick to ascribe all this to a principle caused by the atmosphere, we are reminded that it works just as well in a vacuum. The only choice that would remain is to attack the experiment itself, but as we go along we shall see that others have replicated this effect in many ways."

I would say that an experienced tricyclist could ride this along that course.

When rigid the rider steers; when in bicycle mode the rider rides as if on 2 wheels. Now look what happens when it is in sprung mode. The rider attempts to steer right (tricycle mode), the machine reacts by falling to the left (bicycle reaction to countersteering), the rider then reacts by steering into the fall (rider's brain in bicycle mode). Riding a tricycle on anything other than a flat surface has the trike falling down the camber, but an experienced tricyclist resist this with changes in C of G and steering up the slope. So I'd say that an experienced tricyclist would simply dump more weight into the turn, and along with steering input complete the course.

Of course I realise that the video is about how to ride a bike, but I'd say it is not impossible to ride that machine - impractical yes.

"I would say that an experienced tricyclist could ride this along that course."
yep - just what everyone says until they get what they're trying to say.
While we're looking at the impossible - here's a land yacht that accelerates through the wind when going exactly downwind, ending up going ~3 times as fast.
[youtube]5CcgmpBGSCI[/youtube]
Not impossible when you get your head round it

531colin wrote:I'm more interested in the assertion that you start a turn by counter-steering..........is that always the case?.....is it still the case riding no-hands?.....how would that go....to turn left, I need to counter-steer to the right to start the lean....but to steer to the right, I need to counter-steer to the left to start the lean.......but to steer left.....

Hi,

Riding no handed when you lean the the steering automatically countersteers
and then straightens up as you settle into the curve you are taking. When
you come back up no handed the steering automatically turns into the turn
and then straightens up as you straighten up out of the turn, so yes is ...

If your bike won't do this you cannot ride it no handed.

My opinion is most people just lean and go with the flow of the steering.
Not many instigate a turn with the steering and then sort out their balance *.
Racing cyclists and motorcyclists are of course a breed apart to most people.

rgds, sreten.

* most people can't get round tight corners fast because they won't
commit to the lean angle required, which is much more important
than steering input, which is generally very minimal on a turn.

It is odd that most cyclists are blissfully unaware of the way they steer.
One way of looking at is simply weight transfer when you lean, say
right. Naturally that implies more weight on the right bar than
the left which will countersteer with decent bar geometry.

531colin wrote: ....I'm more interested in the assertion that you start a turn by counter-steering..........is that always the case?.....is it still the case riding no-hands?.....how would that go....to turn left, I need to counter-steer to the right to start the lean....but to steer to the right, I need to counter-steer to the left to start the lean.......but to steer left.....

If you start a turn (hands on) by countersteering you can transition from upright to full lean much quicker than otherwise. This isn't normally a big deal on a bicycle but on a motorbike it is a very big deal indeed.

When riding no hands you can countersteer a little, flop into the turn, then rebalance, exactly as you describe.

But this isn't necessary. The bike never goes in a perfectly straight line; in reality it is normally weaving imperceptibly from one side to another as you pedal (you can see this if you look at the tyre tracks running out of puddles). If you choose your moment to just hold the steering perfectly straight (instead of letting it move normally), you will generate the same effect (but more slowly) as a countersteer.

cheers