"Negative Steering" Please explain. 1

[Tryan]

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?

 

[Tryan]

Obssv, I hope that in the couple of days since your last post that you've had time to think a bit more about your theories! If not, lets work thru the first one. Steering head welded,cable attached to bike and a fixed point, bike perfectly vertical,now roll on the throttle and bike tries to move in a staight direction, however cable wants it to go in a circle! The cable will try to pull the bike over and providing the forward speed of the bike is sufficient, it will lean and go round the circle! The speed of the bike would determine the angle of lean!
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!!

 

[evelrod]

obssy, re read the second sentence of my July 21 post.
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

 

[kcj]

my two cents worth at attmepting to clarify:
-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

 

[Metalguy]

My experience with a flatter profile rear tire was just the opposite-the bike didn't want to lay over and turn. Also, when you countersteer, the effect seems linear-slightly more pressure, bike leans and THEREFORE turns more.

At least for countersteering, gyro forces mean nothing.

 

[kcj]

I should clarify. I agree with your comments. In my analogy of a 10 inch wide roller shape, leaning left would put the contact patch 5 inches left, (more than the front moved left) which would tend to drive right and resist the lean.
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.