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James R. Davis
 Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
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 Posted - 08/21/2009 : 8:47 PM
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Thanks for the clarification.
quote:
Off topic but something that may be beneficial. I was trying to explain counter steering to by beloved and doing a lousy job of it. She saw a picture of us on a ride and it became clear to her. She noticed the front tire was turning left but we were turning right.
Just so that all readers are really on the same page ... the fact that your bike was leaned over to the right shows that you were turning to the right. Since that can only happen as a result of your steering angle being to the RIGHT of center, it must be that the interpretation of the picture showing your front wheel 'pointing to the left' is at best an optical illusion. The only time your front wheel would actually point to the left of center is at the moment you start a right turn (while the bike is still vertical.) |
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rtbain
Ex-Member
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Posted - 08/22/2009 : 8:59 AM
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quote:
Originally posted by James R. Davis
Thanks for the clarification.
quote:
Off topic but something that may be beneficial. I was trying to explain counter steering to by beloved and doing a lousy job of it. She saw a picture of us on a ride and it became clear to her. She noticed the front tire was turning left but we were turning right.
Just so that all readers are really on the same page ... the fact that your bike was leaned over to the right shows that you were turning to the right. Since that can only happen as a result of your steering angle being to the RIGHT of center, it must be that the interpretation of the picture showing your front wheel 'pointing to the left' is at best an optical illusion. The only time your front wheel would actually point to the left of center is at the moment you start a right turn (while the bike is still vertical.)
Pardon the thread hijack, it was unintentional. Please feel free to move this discussion to the appropriate area if so desired. Please forgive the following, I could not resist. And what would the picture depict at worst?
I'll slightly disagree. I would agree that one only turns right to go left at the initiation of the turn. To me initiation lasts until one reaches a steady state rotation phase.
Turning a motorcycle has three basic stages:
1. Turn in turning right to go left
2. Rotation keeping the bars in a neutral position
3. Stand up or exit usually assisted by applying throttle after the apex of the turn.
We seem to be in agreement on the first two steps. The assertion that turn in only occurs while the bike is still vertical is in question.
The turn(s) in question are either a series of decreasing radius curves or one giant decreasing radius u-turn. Pardon the use of bandwidth as I use photos. All photos are shown in sequence.
Photo 1
This photo, in my opinion shows the motorbike in rotational phase after the initial turn in at the beginning of the first part of the turn. It may also give the viewer a sense of the type of turn. Note the scooter is positioned towards the corners outside edge. This is preparation for turn in as the radius decreases.
Photo 2
This photo shows the drive to apex. Lean angle has significantly increased as the turn tightens. Since the turn radius has changed the rate of rotation must change or the bike will run wide, hence the use of counter steering. Counter steering is not the only method to accomplish this, but it is the fastest method.
Photo 3
This photo shows another riders method of negotiating the same turn. Less speed and lean angle (the two are not necessarily directly related). This bike is in rotation mode, and to his credit severely slowing down the vehicles piling up behind him. But hey, everyone should stick to their personal limits.
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James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
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Posted - 08/22/2009 : 9:12 AM
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quote:
And what would the picture depict at worst?
LOL
I meant that the picture may look, to some, like the front wheel is pointing to the left (optical illusion) while to others there is no such interpretation.
quote:
3. Stand up or exit usually assisted by applying throttle after the apex of the turn.
I have been astonished, really, at the number of riders who obviously know what they are doing out there who nonetheless insist that applying throttle while in a turn stands the bike taller (or even 'assists' in doing so).
There are at least two other threads on the site which currently has that as a contentious assertion by some posters.
At counter-steering speeds accelerating increases the lean angle. If you simultaneously widen your turn, then use of the throttle tends to inhibit rather than assist the bike standing taller.
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rtbain
Ex-Member
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Posted - 08/22/2009 : 9:43 AM
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quote:
Originally posted by James R. Davis
quote:
And what would the picture depict at worst?
LOL
I meant that the picture may look, to some, like the front wheel is pointing to the left (optical illusion) while to others there is no such interpretation.
quote:
3. Stand up or exit usually assisted by applying throttle after the apex of the turn.
I have been astonished, really, at the number of riders who obviously know what they are doing out there who nonetheless insist that applying throttle while in a turn stands the bike taller (or even 'assists' in doing so).
There are at least two other threads on the site which currently has that as a contentious assertion by some posters.
At counter-steering speeds accelerating increases the lean angle. If you simultaneously widen your turn, then use of the throttle tends to inhibit rather than assist the bike standing taller.
And if you do not simultaneously widen your turn? |
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James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
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Posted - 08/22/2009 : 9:45 AM
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As I said, it will increase your lean angle, not decrease it.
Your lean angle is the result of centrifugal force. That increases as your speed increases or your turn radius decreases. |
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rayg50
Advanced Member
851 Posts
[Mentor]
NYC, NY
USA
Honda
Shadow Spirit 750DC
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Posted - 08/22/2009 : 10:43 AM
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Equilibrium - a state of rest or balance due to the equal action of opposing forces.
Centrifugal - moving or directed outward from the center (opposed to centripetal ).
Gravity - the force of attraction by which terrestrial bodies tend to fall toward the center of the earth.
Let me restate what I have gotten from this thread. The points below are based on an ideal road surface, ideal weather, ideal bike, ideal rider, where no rider adjustments are needed and loss of traction is not an issue (your contact patch is welded to the ground as the tire turns).
1- If you maintain a constant radius in a turn and increase speed the long term effect is greater lean (gravity and centrifugal force reaching an equilibrium, you do not fly out of the circle nor fall towards the center of the earth).
2- If you maintain constant radius in a turn and constant speed in a turn your lean angle will remain constant (once that equilibrium is reached).
3- If you maintain a constant speed in a turn but increase the radius of a turn your lean angle will decrease (less centrifugal force therefore less gravity needed to maintain the equilibrium).
I don't think the above points are at issue but would like to know if they are.
4- If you both increase speed and radius, as most riders do when exiting a turn, points 1 and 3 would both kick in. If the increase in speed is modest in comparison to the increase in radius point 3 (less lean angle) wins out but at a slower rate because point 1 (increased lean angle) is still offsetting some, not all, of it.
5- If your increase in radius is modest in comparison to your increase in speed then point 1 wins out (more lean angle) but again at a slower rate because point 3 (less lean angle) is offsetting some, not all, of it.
Assuming what I have typed is what I meant to, and based upon riders having experienced the first 3 points, would you disagree that 4 and 5 must follow?
I am trying to solidify my understanding of what happens in a non physics way.
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James R. Davis
Administrator
14909 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
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Posted - 08/22/2009 : 11:36 AM
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| You've got it, sir. |
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Tburd
Senior Member
406 Posts
Waukesha, WI
USA
Suzuki
Boulevard S50
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Posted - 08/22/2009 : 9:24 PM
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rtbain,
You've made a few statements and I'm curious about how you came to those conclusions.
quote:
This photo shows the drive to apex. Lean angle has significantly increased as the turn tightens. Since the turn radius has changed the rate of rotation must change or the bike will run wide, hence the use of counter steering. Counter steering is not the only method to accomplish this, but it is the fastest method.
At speeds above say about 10 mph isn't counter-steering the only way to turn?
quote:
This photo shows another riders method of negotiating the same turn. Less speed and lean angle (the two are not necessarily directly related).
Given speed and radius there is only one lean angle that satisfies equilibrium. How then is speed and lean angle not related? |
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rtbain
Ex-Member
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Posted - 08/22/2009 : 10:07 PM
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quote:
Originally posted by Tburd
rtbain,
You've made a few statements and I'm curious about how you came to those conclusions.
quote:
This photo shows the drive to apex. Lean angle has significantly increased as the turn tightens. Since the turn radius has changed the rate of rotation must change or the bike will run wide, hence the use of counter steering. Counter steering is not the only method to accomplish this, but it is the fastest method.
At speeds above say about 10 mph isn't counter-steering the only way to turn?
quote:
This photo shows another riders method of negotiating the same turn. Less speed and lean angle (the two are not necessarily directly related).
Given speed and radius there is only one lean angle that satisfies equilibrium. How then is speed and lean angle not related?
To me its a matter of perspective. In another thread someone posted a video of a bike being piloted hands free doing a pylon maneuver at what appeared to be above the speed at which counter steering takes over. To the poster the video proved that leaning would turn a motorcycle.
My thinking is that counter steering was initiated by lean angle. If you look closely at the video the front end can be seen to be reacting to lean inputs.
Your comment about only one lean angle satisfying equilibrium discounts rider position. When properly executed, a rider who shifts their weight to the inside of the turn can carry the same speed with less lean angle than a rider who sits upright in the saddle.
One important distinction I have noticed in this discussion is the relationship between cause and effect. I offer the following.
A remotely controlled motorcycle is maneuvered into a constant turning radius at a certain speed and lean angle above the speed at which counter steering occurs. In short its riding in a circle. Handle bar inputs are locked. There is no rider to shift their weight. The only change made is to increase or decrease throttle.
This is where I am having trouble following along.
If I understand correctly this thread seems to propose that if the throttle is opened to increase speed the motorbikes angle of lean will increase. The corollary is that if the throttle is closed, reducing speed the motorbikes angle of lean will decrease. Am I stating the theory correctly?
If I am stating the premise correctly what mechanism causes the motorbike to increase or decrease lean angle?
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Tburd
Senior Member
406 Posts
Waukesha, WI
USA
Suzuki
Boulevard S50
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Posted - 08/22/2009 : 11:10 PM
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quote:
To me its a matter of perspective. In another thread someone posted a video of a bike being piloted hands free doing a pylon maneuver at what appeared to be above the speed at which counter steering takes over. To the poster the video proved that leaning would turn a motorcycle.
I agree that a small amount of directional change can be accomplished by leaning as illustrated by the video you mention, but it doesn't meet my definition of steering. It's a small course change that in this case weaved through some pylons, or was it street lights.
quote:
Your comment about only one lean angle satisfying equilibrium discounts rider position. When properly executed, a rider who shifts their weight to the inside of the turn can carry the same speed with less lean angle than a rider who sits upright in the saddle.
When we discuss lean angle relating to centrifugal forces and a radius of a curve we mean the combined cg of both the rider and bike. A rider can lean off and can shift his cg to the inside for example, but the bike will move the other way or to the outside. The result is that the combined cg stays in the same place and nothing has changed concerning the dynamics of the turn.
Several of the topics you bring up have been discussed in detail during the last week so I think a quick review of these will give you a good explanation of where we are right now. |
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whittlebeast
Junior Member
30 Posts
St Louis, MO
USA
Yamaha
FZ1
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Posted - 09/21/2009 : 8:25 PM
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Does a bike squat when power is applied peaked my intrest so I looked into it.
A little overview:
The bike is a 2008 FZ1 weighing about 700 lbs with rider and is chain drive. The 3 axis accelerometer is mount in the area of the passenger seat and sampling at 20 samples per sec. The bike in is capable of 130 MPH 1/4 trap speeds so if there is any real up and down motion of the seat, a quick pass thru a well executed first to second shift should expose any motion.
The dark blue trace is linier acceleration peaking at .811 geez as the motor approaches 10000 RPM. At 493.2 sec I lift and snap second gear and roll the power back on. Total shift time is about 3/4 sec. second ger had power applied for about .25 sec and I lifted and then applied the brakes at about .25 geez.
At the top is the blue/green trace that is unfiltered vertical geez. The lavender trace is filtered vertical geez. The conclusion that I come to is if anything the rear rises (as indicated by geez greater than 1) as lots power is applied but to say the least, the effect is only for about .3 sec or a very short period of time.
My conclusion is that with a modern chain drive bike, the application of any reasonable amount of power to raise the bike will only result in an increase in speed and the need to worry even more about whatever is scraping.
Hope this helps
WB
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Andrew Dressel
Standard Member
153 Posts
Milwaukee, WI
USA
Moto Guzzi
California Special
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Posted - 09/22/2009 : 9:57 AM
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quote:
Originally posted by whittlebeast
The lavender trace is filtered vertical geez. The conclusion that I come to is if anything the rear rises (as indicated by geez greater than 1) as lots power is applied but to say the least, the effect is only for about .3 sec or a very short period of time.
Perhaps I misunderstand your text or your graph or both, but I come to the opposite conclusion. It appears that the filtered vertical geez are below 1.0 when forward acceleration is greatest: ~0.75. If 1.0 represents the acceleration due to gravity when stationary, then below 1.0 should indicate sinking/squatting, right? Free fall would be represented by 0.0 geez. In the right 1/4 or 1/5, the filtered vertical geez appear to be above 1.0, suggesting the squat is reversing when you are hitting the brakes. |
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whittlebeast
Junior Member
30 Posts
St Louis, MO
USA
Yamaha
FZ1
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Posted - 09/22/2009 : 1:06 PM
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I thought about taking the filtered geez trace off of the trace for this screen shot as the filter is not really tuned for the frequency of the movement that we are looking at. I was mostly looking at the unfiltered part of that trace (light blue/green). As the torque is climbing after the shift the vertical geez go positive (above 1) implying that the seat is rising as the power is coming back on.
I would have to do quite a few of those tests to be really sure that the results are repeatable.
That program was developed to do G-G friction circles and not really optimized to do this. I guess that it is possible that we are looking at tire shake or some other phenomenon but I doubt it as the acceleration numbers look as I would expect and there is very little filtering on that part of the trace.
The slow rise in the accel rate is due to the factory wheelie control over-riding the hand throttle. Way cool stuff.
WB |
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Andrew Dressel
Standard Member
153 Posts
Milwaukee, WI
USA
Moto Guzzi
California Special
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Posted - 09/22/2009 : 1:41 PM
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quote:
Originally posted by whittlebeast
I was mostly looking at the unfiltered part of that trace (light blue/green). As the torque is climbing after the shift the vertical geez go positive (above 1) implying that the seat is rising as the power is coming back on.
I guess that it is possible that we are looking at tire shake or some other phenomenon but I doubt it as the acceleration numbers look as I would expect and there is very little filtering on that part of the trace.
I agree with your guess then: perhaps just bumps in the pavement. The oscillations at 492.5 seconds, with no obviously associated large change in forward acceleration, appear about as big as the spike just before 494 seconds, and so do not indicate to me any strong correlation with forward acceleration. If anything, the unfiltered trace still suggests a slight squat as forward acceleration peaks, and then a slight rise as you brake.
However, you obviously know you equipment better than I possibly can. I can only comment on how the graph looks.
In any case, it is fun to see some real data.
(edited to fix typos) |
Edited by - Andrew Dressel on 09/22/2009 4:39 PM |
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