"Negative Steering" Please explain.
"Negative Steering" Please explain.
(OP)
Could somebody please explain to me the phenomenen called negative steering on a motorcycle? While it has been something I have been aware of and used for about 35 years riding, I haven't found anybody who could explain it!Simply put, when you pull on the righthand side of your handlebars you go left and vice versa! Some people think you are quite strange when you tell them, others are aware of it but can't explain it! Anybody?
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
Check out "Proficient Motorcycling" by David Hough. He explains it in the first book, and expands on it in the second, "More Proficient Motorcycling". He's good at simple explanations.
The second book (which I am currently reading) also describes the gyroscopic effect necessary to right the bike after it leans.
If you hypothetical bike turns by leaning, it would probably work. Watch a flat-track motorcycle race sometime on TV. You'll see the bikes take a left turn while leaning left, but with the front wheel turned to the right. Countersteering in the extreme.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
At what speed does countersteering begin?
If you're walking the bike, you turn the front wheel toward the direction you want to go. At some low speed (riding, hopefully), countersteering takes effect. I'm sure it has to do with the friction between front tire and surface, speed of the wheel, and angle of the turn.
Has anyone developed an equation for this? Is it even possible to calculate? Does the rear tire, CoG, bike weight, etc. affect the calculation?
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
The quickest way to initiate lean is to twitch the bars the wrong way. This makes the bike lean, which makes it turn.
What the dirt-trackers do is not countersteering. My opinion is that once you start dealing with lots of wheelspin and big slip angles, there is hardly anything in the pavement world that applies.
Yes, I know that road racers now use big slip angles and slide a lot. When they do that, all the stuff they learned in the years of not doing it has to go out the window and they have become dirt trackers with a higher coefficient of friction.
Jess Davis
Davis Precision Design
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
You're certainly right about the terminology. I was just referring to countersteering as it applies to street bikes. What you do when you slide is a different thing but the term countersteering is certainly descriptive. It needs a name.
If anyone has metalguy's explanation saved, I'd like to read it.
RE: "Negative Steering" Please explain.
Bike going along perpendicular with a fork angle say, 10 deg , pull on h/bar, wheel turns slightly taking the bike in that direction, momentarily .If it was a car it would simply follow the direction of the front wheel.By turning the wheel, it moves the centerline of the front wheel slightly to the right, because of the fork angle.The inertia of the perpendicular bike going straight ahead basically makes the bike fall over or lean in the opposite direction! Out of interest, would counter steering work on a bike with zero steering head angle, and axle and forks all in line with the steering head ? I'm thinking no!
RE: "Negative Steering" Please explain.
I think it would work even with zero angle if you were moving. The centrifugal force would make the bike lean even if the fork geometry didn't. Actually, I think the centrifugal force is what does it anyway, or at least it seems to dominate at high speeds. It doesn't take much of a pull to start the turn. On the other hand, a harley takes a lot more pull than a cbr900, so rake may have something to do with it. Soft, mushy tires, wimply forks, and flexy frames may have something to do with it, too.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
Yes, I think you did a great job re-writing my orig. comments.
All I can add is that the effect is VERY strong-new riders should know that it's more a pressue/force that you apply to the bars rather than actually moving them much at all. The DO move, but very little.
Tonight on my way home I'll attempt to see just how much they actually move in order to use this method to get around a "fast sweeper"--around 80 MPH on my ZX10 Ninja. Good thing I'm in Italy.<g>
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
You have to remember that *I* didn't invent/discover this phenonena about countersteering, so no "thunder" is involved.
"Live to ride-ride to live"!
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
Here's something else to ponder. It has been demonstrated via very high speed measurements that a gyro, when enclosed in a sphere (IIRC), falls thru air at different speeds when it is spinning fast vs. not. Don't know why, but I found something about it on the net a while ago. I'll look for it if I get time.
I'm in Italy not too far from pisa. Anyone know Galileo's phone number? <g>
RE: "Negative Steering" Please explain.
What about the guys who ride supercross and motocross, the guys who are good at jumping can throw the bike sideways in mid-air and then straighten the bike up again by revving the bike and spinning the back wheel. How does that work?
I will try it the next time I do a 40 foot double. Well now that I think about it maybe not.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
I'm a motorcycle instructor but when teaching the "push steering" we simply tell them to try it and then demo that it works. Last thing you want them to be doing is physics of mechanics as they cross a parking lot with 34 other novices around.
It is a gyroscopic effect, only taking effect at around 20-25kph. It becomes more pronounced as the velocity increases. I forget the exact law, but it goes something like ".. for each input there will be an opposite and equal reaction 90° out of phase."
This is best demonstrated by holding the front of the front wheel while stationary, and pushing on one of the handlebars (eg the right). The bike will lean to the right as the front of the wheel wants to stay where it is. Once the lean is initiated, the wheel will fall in (ie lean) and the same pressure will be required to hold it there. As a result more handlebar pressure will tend to make the bike lean in further and pressure on the opposite bar will tend to make the bike right itself.
We have some great slow motion video's of a bike heading at the camera, and the push steering is really evident. When I first heard of this, I sat in the parking lot while a (trusted) friend headed towards me with his bike at 30mph. He would swerve when he got close and watching the front of the bike it became obvious.
RE: "Negative Steering" Please explain.
Jess Davis
RE: "Negative Steering" Please explain.
You may be a fine MC instructor, but you're incorrect about the gyro effect. At the speeds you mention, any gyro effects would be a few ounces/grams at the most, given the very slow wheel RPM, while the leaning of the bike requires far more-eg, you can easily counter the weight effect of a timid passenger who leans the wrong way.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
Anybody mention that you can "pick" the bike up out of a bend by applying a turning force into the bend? If it was a gyroscopic force then wouldn't that just lift the front wheel in the air?
RE: "Negative Steering" Please explain.
So if this is the basis of counter steering then it would only work if you jerk hard on the h/bars, and what about the other gyro on the back that has no forces acting on it! Wouldn't they cancel each other out?
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
Tryan, good ideas except for the spinning wheel example. The fact that the wheel leans when you try to turn it in your hands has a lot more to do with the fact that your hands are hardly "fixed" in the horizontal plain. The very reason a bike is more stable at speed is the difficulty in getting the spinning wheels to deviate from the verticle. Some relation to the shifting of the CG in the horizontal plain and the change in circumferance of the tire from center to side would be interesting.
Thanks guys. Like I said, interesting discussion. "Counter steering" is just something I have always done mechanically without concious thought, until now.
Rod
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
This is the most activity in this forum I have seen in three years. Thanks all. Let's start another post on the tire profile and coumpound deal. I had a Metzler on a 441 Victor and did not like it then , either.
Rod
RE: "Negative Steering" Please explain.
Counter steering dynamics is my project for the quarter since I ride a crotch-rocket and counter-steer constantly.
I've read all of your posts and I'm starting to get a bit of a picture. I have an idea I'd like you to consider. Suppose you take a bike and fix the front wheel in line with the rear wheel, stand it up perfectly vertical, attach a cable (of fixed length) to its CoG (CoM?) and then fix the other end of the cable to a fixed point away from the bike. Now, roll on the throttle and watch out. In my mind, the bike can't go in a perfect circle with the front wheel fixed. This seems more obvious if you imagine the wheel base of the bike as high compared with the radius of the circle; the wheels can't be on the circle. So, Countersteering must, somehow, bring the front wheel into "alignment" on that circle. Another thought, is it possible that the front tire being opposed to the actual turning direction produce some opposing force that counteracts the motion of bike?
RE: "Negative Steering" Please explain.
Rod
RE: "Negative Steering" Please explain.
RE: "Negative Steering" Please explain.
Out of interest if we released the cable what would happen?
Countersteering is only one way of making a bike change direction and once in the new direction it ceases to exist! It simply inniates the change!!
RE: "Negative Steering" Please explain.
Counter steer is just the action that establishes the lean angle, turning the wheel back through neutral and into the direction of turn "HOWEVER SLIGHTLY", completes the action.
As to you cable senario---even if the wheel is turned opposite to the turn and scrubs like crazy, the bike, car, whatever that is tethered will turn in a circle around the point of attachment as long as sufficient power is applied and traction is good.
Get on a bicycle and ride hands off. Make a few turnes and watch what the front wheel/bars do. You can do the same on a motorcycle but, the action is a lot more 'observable' on a bicycle. Your inniating the turn by altering the CG horizontally and the front wheel 'counter steers' briefly before establishing it's turn angle.
This line of thought is giving me a headache so I'll stop now.
In fact, I am going to fire up the Norton and go up to the Tool Co. in Temecula.
Rod
RE: "Negative Steering" Please explain.
-all the gyroscopic forces etc are all there, but basically when you countersteer right, for an instant the front wheel runs right, just like a car. However, then the tire contact patch is out from under the cg. Since the driving force is outside of the cg, the bike will now turn left. If you have ever driven a skid steer loader, driving the outside wheel turns the machine around its cg. The bar pressure initiates the turn, then the corrections keep it in balance.
-dirt track bikes and cars initiate a turn in, but use throttle steering of the rear wheels, which is a whole different topic.
-in the air, the rear wheel is a great flywheel. throttle reacts against it, essentially doing a wheelie up. Rear brake couples the bike to the rear wheel momentum and tries to rotate the bike in the direction of the wheel, i.e. down.
-tire profile: I had a wider shoulder rear tire on a bmw that did not match the rounded front profile. As the bike leaned over, the front contact patch moves a certain distance, fairly small distance. However, the back contact patch moved way inside because of the flat sholder. imagine leaning over on a 10 inch wide roller. the contact patch would now be the inside edge, 5 inches inside of c/l of bike. In my case, it usually tended to drive the rear outward at a more unpredictable, faster rate. Sort of an oversteer effect. Unpredictable, I didn't like it. My own fault, as the profiles were not a matched set, so I changed it.
kcj
observed trials rider, (barely)
mc rider for 35 years
engineer
RE: "Negative Steering" Please explain.
At least for countersteering, gyro forces mean nothing.
RE: "Negative Steering" Please explain.
Its been many years since that, but as I recall, it tended to resist the initial lean in, but once started it fairly abruptly oversteered. It also seemed to resist more on slight turns, but oversteer more in tight turns. It never spit me on the ground, but the unpredictability was not good.
'leans and therefore turns'. agree. that's what I was trying to describe, the front contact patch runs out from under the cg and the bike turns.
A fairly abrupt turn can be initiated with strong counter pressure, then an opposite correction to stabilize it. Its awesome for me to watch the world level people snapping their beast left right left right so easily.