max lean, plus fork lock?

[Phil B]

Sooo.. has any of you whacky track racers, ever gotten to such an extreme corner, that you were practically scraping the pegs, and also had the handlebars basically turned to the locking point?


I have not... and I'm scared to try it.


I was going around a corner today   (regular road, flat, but very wide corner, open area) at lets say 30mph.


I got overenthusiastic about my lean setup, and was practically dragging a knee (heck I probably could have if I had my knee out  )


But... I was turning at a relatively wide arc radius.  I think my arms were a bit locked up, and I was still holding the bars relatively straight, rather than letting it settle into the turn properly.

My HEAD told me, "uhh.. youd better turn it in now". But my emotions kept yelling at me "NONONONO something bad will happen!!"


So I guess I have two related questions.

1. Normally, I know that our GS500 really LIKES to have its front turn in to a corner, so much so that some people complain about it 

But have you racers noticed if there's a lean angle past which, it doesnt want to turn in by itself any more?


2. *will* "something bad happen" if I turn it in forcibly?
Will it try to do a leaned-over "stoppie" and do a forward flip or something?
Does it depend on whether i turn it in quickly vs slowly?
(okay that was 3-in-1 questions there. sorry )

[comradeiggy]

Probably high side.

[SAFE-T]

Max lean angle + turning forks to lock = crashing LOL

Lowside, not highside.

Mostly, you are putting two things together that are used at different speeds ~ low speed = turn handlebars in direction you want to go; higher speed = push steer in direction you want to go. What you are describing would be like leaning left but push steering to the right ~ at the very least the bike would feel really unstable. If your speed was under 20mph (30km/h) the gyroscopic procession of the wheels would be miminal, and you would tuck the front tire and low-side.   

[Phil B]

Mostly, you are putting two things together that are used at different speeds ~ low speed = turn handlebars in direction you want to go; higher speed = push steer in direction you want to go.

Not entirely true for the second one.

At higher speeds, yes you push the side that you want to steer to, to set up the lean. But once the lean is established, you normally losen up your push, and let the front wheel settle where the bike wants to point it.
Which, due to the rake of the front wheel, is *into* the turn. 

In the "similar yet different" category: Some people keep pushing on the right side of the bars, throughout the whole time they are completing a right turn.  Most people do, particular since the gs500 "wants to turn in", so you want to counter that. But if you actually *look at the wheel angle* the next time you're doing a turn at speed, you should notice that after you establish the lean, it's still actually pointing in.

"exterting pressure in a leftwards direction", is not the same thing as "the wheels is actually pointing left all the time"

Well, you might not notice, actually. Most people only use a small turn angle at high speed, so it's tough to see.. but it *does* turn in. Otherwise you wouldnt actually turn.
Go look at slow-mo replays of professional races.

Or, take a look at this "in cockpit" video of a CBR1000, and look very carefully which way the bars are tilting on the high speed turns, when it's actually IN the turns.

http://www.youtube.com/watch?v=Z2axvGaDCyY

[SAFE-T]

Correct-a-mundo. Once the bike leans over, the wheel does turn a very slight amount in the direction you are going. But if then try to actually turn the handlebars in that direction you will be unhappy with the results.

[SAFE-T]

In another discussion elsewhere it was noted that authors like Lee Parks and Keith Code teach pushing on the bars to steer in the direction you want to while weighting the outside peg (left for right, right for left) to stabilize the bike. 

[comradeiggy]

In another discussion elsewhere it was noted that authors like Lee Parks and Keith Code teach pushing on the bars to steer in the direction you want to while weighting the outside peg (left for right, right for left) to stabilize the bike.

This is what I was taught to do when I took my MSF class for slow speed maneuvering.

[bombsquad83]

Correct-a-mundo. Once the bike leans over, the wheel does turn a very slight amount in the direction you are going. But if then try to actually turn the handlebars in that direction you will be unhappy with the results.

And by unhappy, I think he means a likely high-side at speed. Yikes!

P.S. 500th post 

[SAFE-T]

At 'max lean' LOL, your front tire will slide out and you will low-side. High-sides are caused by the back end of the bike losing traction and then suddenly regaining it. Not steering. 

[burning1]

Mostly, you are putting two things together that are used at different speeds ~ low speed = turn handlebars in direction you want to go

This isn't really true. Unless you are walking the bike with your feet, you still have to counter steer to control your direction and lean angle.

Counter steer to lean the bike over.
Counter steer to keep the bike from falling over.

[BockinBboy]

So imagine you have begun a max lean left turn with a fluent pull on the right bar (or push on the left bar if you prefer) and you begin to lean to the left of the bike as you accelerate slightly.  You must maintain a pulling pressure on the right bar (or push pressure on the left bar) in order to keep the bike leaned and stable during the turn.  If you were to let up on that pressure during the turn, and allow the front wheel to turn slightly leftward and back to center as it wants, the bike would also want go back upright with you still slightly hung on the left of the bike... which can be an undesirable feeling if you aren't prepared for it. 

If you were to actually turn the bar left and the wheel left during a max lean left, the bike would want to not only go upright, but would want to lean right (opposite your turn!), and you may still be hanging slightly left of the bike... good luck holding on while the bike abruptly changes direction, if it remains stable at all.

-Bboy

[SAFE-T]

"Slow speed" is under 20km/h, or about 12mph

[SAFE-T]

You can countersteer a little bit down to maybe 15km/h, but there is very little gyroscopic precession from the wheels so it's going to be pretty sloppy. I spent 15 yrs. working with the application of this and have a very good understanding of the boundary at which your motorcycle changes the way in which it reacts to steering inputs. 

[SAFE-T]

I have tried to force the bike to turn left by leaning to the left while push-steering on the right handlebar to the point of standing on the left foot peg with all my weight, and the bike still tried to chuck me off and turn right.

[burning1]

You can countersteer a little bit down to maybe 15km/h, but there is very little gyroscopic procession from the wheels so it's going to be pretty sloppy. I spent 15 yrs. working with the application of this and have a very good understanding of the boundary at which your motorcycle changes the way in which it reacts to steering inputs.

I'm pretty sure your model is wrong, but it would take a lot of time and effort to really discuss that claim. I will say that gyroscopic precession has very little to do with counter steering.

Motorcycles steer around their center of gravity, not around the contact patch. In order to turn left, you must first steer the wheel to the right, out from under the CoG - this is true at any speed.

At high speeds, the bike will typically self stabilize to a great degree as soon as you release steering pressure. At low speeds, you must counter steer into the corner to keep the bike from falling over. This second counter steering input is much larger than the first input, and is what leads most people to believe that the bike direct steers at low speeds. In reality, you're accomplishing two things - turning, and counter-steering to keep the bike from falling over.

For a source, I'll cite Vittore Cossalter's book, Motorcycle Dynamics, although I can't say the issue is really spelled out in that book.

[Phil B]

At low speeds, you must counter steer into the corner to keep the bike from falling over.

Err.. I think you meant, "at low speeds, you must steer into the corner to keep the bike from falling over".
which is the opposite of "counter steer".



If you're going slowly right  (@15mph), around a right hand turn, and you "counter steer" to the left.. you and your bike will fall over on the right side.

[SAFE-T]

I will say that gyroscopic precession has very little to do with counter steering.

Actually, it's the very reason countersteering exists on a single-track vehicle...

http://en.wikipedia.org/wiki/Precession

Particularly the part regarding Torque-induced precession

Also, from http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

"Experimentation and mathematical analysis have shown that a bike stays upright when it is steered to keep its center of mass over its wheels. This steering is usually supplied by a rider, or in certain circumstances, by the bike itself. Several factors, including geometry, mass distribution, and gyroscopic effect all contribute in varying degrees to this self-stability, but long-standing hypotheses and claims that any single effect, such as gyroscopic or trail, is solely responsible for the stabilizing force have been discredited.[1][5][6][7]"

[burning1]

At low speeds, you must counter steer into the corner to keep the bike from falling over.

Err.. I think you meant, "at low speeds, you must steer into the corner to keep the bike from falling over".
which is the opposite of "counter steer".



If you're going slowly right  (@15mph), around a right hand turn, and you "counter steer" to the left.. you and your bike will fall over on the right side.

It really depends on your perspective.

When you're leaning left at low speed, the bike wants to fall to the left. I want to create an equal but opposite force trying to pick the bike up. My goal is to induce a force leaning the bike to the right, to counteract the desire of the bike to fall to the left. So, I counter steer - I turn the wheel to the left to make the bike lean right - opposing the force pulling the bike to the left.

[burning1]

I will say that gyroscopic precession has very little to do with counter steering.

Actually, it's the very reason countersteering exists on a single-track vehicle...

http://en.wikipedia.org/wiki/Precession

Particularly the part regarding Torque-induced precession

Also, from http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

"Experimentation and mathematical analysis have shown that a bike stays upright when it is steered to keep its center of mass over its wheels. This steering is usually supplied by a rider, or in certain circumstances, by the bike itself. Several factors, including geometry, mass distribution, and gyroscopic effect all contribute in varying degrees to this self-stability, but long-standing hypotheses and claims that any single effect, such as gyroscopic or trail, is solely responsible for the stabilizing force have been discredited.[1][5][6][7]"

First, ignore the article on gyroscopic procession, because it's completely wrong. If you replaced the wheels with skis, there would be no gyroscopic procession what-so-ever, and the bike would still counter steer. It would also remain stable.

http://www.youtube.com/watch?v=mT6pDvkmtFM

I need to review some of the new data in detail. I can tell you however, that it's pretty obvious that steering head trail isn't necessary for stability - anyone who can ride out a wheelie has shown that a motorcycle is stable without front wheel trail. We do know however, that trail at the front wheel has a huge impact on stability at the front steering axis, and that the wrong values will cause the motorcycle to become very unstable at high speed.

I've observed that when riding out a wheelie, the motorcycle seems to be stable so long as the center of mass is ahead of the rear wheel. This does create a strong degree of trail. The dynamics of hauling a trailer appear to be similar, so a study of trailer loading may be helpful here - generally, the trailer will remain stable so long as you have sufficient tongue weight, and the load is sufficiently biased ahead of the axle.

Here's one theory on how the TMS bike stabilizes. Haven't had a chance to review it, but seems like an interesting review.

http://www.youtube.com/watch?v=84Wczsi4vHg

[burning1]

FWIW... Studied this in depth a couple of years ago. Really good to see that there's new data and new experiments.