| Author | Message | ||
     Jima4media |
Dave, Yes, I've got a copy of that Mamola video around here somewhere. Also the tank-slapper video from the Isle of Man. Here is a good explanation of a highside that goes along with what Blake said... http://www.msgroup.org/TIP001.html http://www.msgroup.org/TIP100.html http://www.msgroup.org/TIP101.html Jim | ||
| José_Quiñones |
Blake, Who wrote the foreword to Mr. Foale's book? | ||
| Blake |
JQ, Funny ain't it. I sure would like to see what Mr. Foale's other countersteering simulations look like. Maybe Amazon has it on sale. Forty five degrees of steering input. I can't believe he had the nerve to actually publish that, let alone include it in his online excerpt. | ||
| Blake |
Jim, The links you posted say... "Naturally, the driver will be thrown in the same direction as the bike is twisted. and "Balance is affected primarily by the gyroscopic stabilization provided by your spinning rear wheel, not speed..." and "While the rear wheel continues to spin there is essentially no danger that your bike is going to fall down - gyroscopic forces are tremendously strong." That does not go along with what I said.  Another faithful believer in the myth of the magic gyro motorcycle.  | ||
| Blake |
Some interesting quotes from Tony's new book... "A steering action to the right, will cause the machine to start turning right, and just as in a car, centrifugal force will cause a lean to the left. This is the major banking influence. This steering action as we have seen, will also produce a small precessional tendency to lean the machine to the left. This is a small effect when the wheels are on the ground." Not quite sure why he says "when the wheels are on the ground." I mean, we are talking about street motorcycles not spacecraft. Maybe just a hint of lingering denial there. and "This gyroscopic torque is in opposition to the rider applied steering torque, and in fact balances most of his input and hence works against rapid steering." So it seems Mr. Foale has revised his stance on the subject. Good for him. Where's Greg anyway?  | ||
| Jima4media |
Blake, You said "Most of us have probably experienced or witnessed a panicky rear wheel lockup where the rear of the bike proceeds to get out of shape or as we say "come around." When the once sliding rear tire suddenly regains traction, it throws the rear of the bike violently back onto its natural track, following the path of the front wheel. This is not a gyroscopic effect." That is right - With the wheel locked up you don't have a gyroscopic effect. Then you quote James Davis as saying "Balance is affected primarily by the gyroscopic stabilization provided by your spinning rear wheel, not speed..." - so he is in agreement with you. When the rear wheel is locked up, you don't have a gyro in the rear wheel. And you keep throwing out this "magic myth of gyroscopic motorcycle thing" which I haven't a clue what you mean. It's not magic and not a myth. You are confusing me and perhaps others. We definately need some drawings and animation on this subject. | ||
| Jima4media |
As far as quoting what Tony Foale has to say in his current book compared to what he has said in the past, I think you need both books, and apparently you don't have either. 45 degree handlebar movement - What part of the statement of "computer simulation" with NO tyre force, on theoretical ice didn't you understand? Tony sent his book out for peer review to hundreds of people. You would think he got it pretty well right at this point.... | ||
| Blake |
Jim, It is a myth that through countersteering the forces of gyroscopic precession cause a motorcycle to lean into a turn. It is a myth that the forces of gyroscopic precession are required and primary in giving a motorcycle its stability. It is a myth that gyroscopic precession aids the maneuverability of a motorcycle. Mr. Davis contends that "Balance is affected primarily by the gyroscopic stabilization provided by your spinning rear wheel, not speed..." That statement is highly inaccurate. Balance on a motorcycle is primarily affected NOT by gyroscopic effects but rather by steering inputs and the heading changes instigated by turning the front wheel. It is a myth that gyroscopic effects are the primary stabilization mechanism for a motorcycle. Those who believe in the myths outlined above are putting their faith in some sort of magical gyro effects that defy the laws of physics. Gyrocopic action does affect the handling and stability of a motorcycle. Gyroscopic effects enhance the stability but hinder the handling of a motorcycle. Like I've said before, motorcycles do not render moot the laws of physics. When I slalom water ski, I don't need a gyro. An ice skater can maneuver on a single blade without a gyro. The small wheels of scooters have negligible gyro action; they are easily controlled. Are you with me? | ||
| Blake |
Why do I need both of Mr. Foale's books in order to quote excerpts posted on the internet?  | ||
| Peter |
Why can I take my hands off the bars and remain vertical while the bike is moving, but go horizontal (if nothing else changes) when the bike stops? What is keeping me upright when it's moving if it's not the "magical gyro effect?" | ||
| Blake |
"45 degree handlebar movement - What part of the statement of "computer simulation" with NO tyre force, on theoretical ice didn't you understand?" Well Jim, I understand perfectly that the results were generated by computer simulation and that the lateral constraints on the tires were removed. My point, and what is laughable, relates perfectly to the old saying in reference to any computer based simulation. You know the one, "garbage in - garbage out." My point, and I think it is quite clear, is that the steering input should have been constrained/limited to a reasonable magnitude. By not doing so, and by publishing the disingenuous results, it gives laymen the impression that gyro effects are indeed significant in helping to lean a motorcycle. They are not. "Tony sent his book out for peer review to hundreds of people. You would think he got it pretty well right at this point." I guess he did that the with the first book too? The entirety remaining of Tony's book may be dead on accurate and forthright. I don't know. I'd love to have a copy to read. I'm curious, how do you know he sent it to "hundreds of people" for peer review?. Did any of th reviewers actually read it? How many submitted comments? Did Kevin Cameron review it? | ||
| Dynarider |
Quote from Blake.....The small wheels of scooters have negligible gyro action; they are easily controlled. Are you with me? ================================================== I wonder then why is it that I can take my hands off the handlebars of either my Dyna or the X1 at say 30 mph & the bike is stable & will continue to go straight unless I either lean or otherwise add an input. However on my daughters 50cc suzuki moped if I take my hands off the handlebars the thing is very unstable & does not track nearly as straight & true as the bikes with the much larger tire & wheel combo's do. I have tried this on both a 50 cc suzuki with wire rims, couldnt have been more than 8-10" rims & on a 1991 Honda spree with the cast mag rims, same effect on both bikes. Why? | ||
| Blake |
"Why can I take my hands off the bars and remain vertical while the bike is moving, but go horizontal (if nothing else changes) when the bike stops? What is keeping me upright when it's moving if it's not the "magical gyro effect?" " The inherent stability of the steering geometry, balance, and gyro effects. Again... Gyroscopic effects enhance the stability but hinder the handling of a motorcycle. How can I loose one ski and still continue down the mountain without falling? How can an ice skater remain upright on one skate? How can we keep beating this poor dead horse?  I'm not saying gyros are magical, just that some misguided pontificators like to assign them magical attributes with respect to their influence on the control of a motorcycle. | ||
| Blake |
Dyna, When I said the scooters are easily controlled, I meant with your hands on the !@#% handlbars. Geesh! Greater mass and inertia significantly enhance stability. Mopeds have little of either. Wider more solid footpegs and a more stable seat enhance stability. And yes, bigger, more effective gyro-like wheels of the big bikes enhance stability. I'll say it again, in case you missed it the last twelve times... | ||
| Dynarider |
Greater mass & inertia you say. Then how come I can do the same experiment on my old 10 speed bike & it will track straight a hell of a lot better than the moped? The moped has more mass & more intertia yet the 10 speed is more stable? Could it possibly have something to do with the gyroscopic effect of the 27" wheels on my bike vs the 8" wheels on the moped? | ||
| Dynarider |
Gyroscopic effects enhance the stability but hinder the handling of a motorcycle ================================================== I dont know about that statement either. My X1 with its magic gyroscopic propulsion wheels handles just fine. I sure as hell wouldnt want to attempt some of the manuevers on a moped that I have on the X1 & supposedly since it has less gyroscopic ability than the X1 it should handle much better, yet it doesnt. So basically what you are saying is the perfect setup is impossible. You need larger tires for stability, yet they screw up handling, get small tires for handling & you have no stability. And another thing, I have forgotten half of what has been posted here but wouldnt the gyroscopic effects of the bikes motor itself affect the handling? I know in the tractor pulling circuit where they allow 5-6 or more motors they will run half the motors in reverse to negate the twist & gyro action that is inherent in them. Now obviously I have never held a running engine directly in my bare hands & felt the gyro action like you can with a bicycle wheel assembly, but I do know with some of my hand held power tools that its pretty damn strong. I have one hand held angle grinder that will damn near rip your arms out when you switch it on. And if you dont hold it tight it will dance all around your ass. And of course some bike motors would have more gyro action than others simply based on their design. | ||
| Rick_A |
I've tried that experiment...hitting the brakes hard and gearing down vs. stopping hard with the clutch pulled in. I found the bike is noticeably "goosier" with the motor idling vs. keeping the motor RPM matched to the approximate road speed. That's my non-scientific assessment  | ||
| Lornce |
Some interesting quotes from Tony's new book... "A steering action to the right, will cause the machine to start turning right, and just as in a car, centrifugal force will cause a lean to the left. This is the major banking influence. This steering action as we have seen, will also produce a small precessional tendency to lean the machine to the left. This is a small effect when the wheels are on the ground." Not quite sure why he says "when the wheels are on the ground." I mean, we are talking about street motorcycles not spacecraft. Maybe just a hint of lingering denial there. Blake, notice front wheel orientation as a bike changes direction while it's front end is unloaded. Believe that may be what's eluded to here.  Really though Blake, I should think you'd take your issues with Tony to where Tony may actually refute them. Head on over to the Motorcycle Chassis and Design site and voice some of your stronger opinions. regards, Lornce | ||
| Jima4media |
Blake, You said "Why do I need both of Mr. Foale's books in order to quote excerpts posted on the internet?" Because only a small portion of the most recent book is on the internet, not the complete book. You can't compare what he may or may not have said in the past with a fraction of what he is saying now. I guess you didn't read the Forward, Acknowledgements and Preface that was posted on his site.... "The new book introduces a wealth of additional material. It has more than five times the text content of the original and more than triple the number of illustrations and photographs. 510 information packed pages." "I've had considerable feedback from readers of that first book and I've done by best to incorporate the many suggestions. Although greatly enlarged, most of the original subject matter remains. Many topics have under gone revision to improve the clarity or remove ambiguity. Material has been added which explores in more depth those subjects which were only briefly mentioned in the original book, most due to publishing space constraints. An example of this is the description of initiating a turn. This topic is central to an understanding of motorcycle behavior. However, it was then covered only briefly, the content on this subject is considerably enhanced in the current book. Completely new chapters hae been added on various topics that just weren't in the original." "Prior to publication in book form, preview versions of the manuscript were made available on CD-ROM, in different stages of completion. In total 250 CDs were distributed, and the feedback and notification of errors from a sizeable proportion of those readers has been an invaluable aid." "A new book was obviously well overdue, although much of the original material is as current today as it always has been. After all, the laws of Newtonian Physics tend to be stable over time" "A multitude of diagrams and graphs from both data logging and computer simulation have been used to demonstrate various phenomenon without a greater number of formulae." - Tony Foale, Spain March 2002 | ||
| Blake |
Dyna, "Then how come I can do the same experiment on my old 10 speed bike & it will track straight a hell of a lot better than the moped? The moped has more mass & more intertia yet the 10 speed is more stable? Could it possibly have something to do with the gyroscopic effect of the 27" wheels on my bike vs the 8" wheels on the moped?" Firstly, you are throwing out anecdotal observations that may not bear the scrutiny of objective formal evaluation. For example, are you sure that you are not using your balancing skills, through leaning and weight shifting, to maintain a stable no-hands track on your motorcycles and bicycle? Maybe you could do the same on the moped if you had a little more practice? Secondly, you *may* have answered your own question. This brings up other more dire issues. I think you may be arguing with yourself. Careful. The moniker "unibomber" comes to mind heheheh. Seriously though, there are other variables such as steering geometry and even tire construction that can affect the free steering stability of a two wheeled vehicle. Thirdly, you were going 30 mph, no-hands, on a bicycle? Fourthly, the roll axis' moment of inertia for a ten speed bike with you sitting on it may be greater than that of a moped with you sitting on it. Can you see why that might be? Remember, inertia is the resistance to a change in motion. In this case we are talking about a change in lean or roll attitude. Fifthly, you are missing my point entirely. I am in no way saying that gyroscopic effects do not exist in a motorcycle. I am saying and have said repeatedly that gyroscopic effects can indeed enhance the stability of a motorcycle; my point is that they hinder the handling of a motorcycle. "I dont know about that statement either. My X1 with its magic gyroscopic propulsion wheels handles just fine. I sure as hell wouldnt want to attempt some of the manuevers on a moped that I have on the X1 & supposedly since it has less gyroscopic ability than the X1 it should handle much better, yet it doesnt." No. That is a gross over-generalization leading to a flawed conclusion. In evaluating the effects of one parameter, gyroscopic effect in our case, we must as best as possible vary only that particular parameter in order to draw any valid conclusion as to its effect(s) on the discreet system, a motorcycle, being examined. In comparing the handling of a motorcycle to a moped or a bicycle, you have altered a myriad of variable parameters, yet you are attempting to draw conclusions with respect to the effects of a single variable parameter. Do you see what I mean? Gyroscopic effect is neither the primary nor the only stabilizing mechanism/parameter present in two wheeled vehicles. "So basically what you are saying is the perfect setup is impossible. You need larger tires for stability, yet they screw up handling, get small tires for handling & you have no stability." Yes and no. You don't necessarily *need* larger wheels/tires for stability. Yes larger diameter wheels/tires can enhance stability, but within reason, you do not *need* large wheels to achieve a stable manually controlled two wheeled vehicle. Doesn't Honda build a 100 mph capable scooter? Adequate stability does not mandate that a vehicle be perfectly stable with no rider input or no other stabilization augmenting mechanisms. Steering dampers are one example of a stabilization augmenting mechanism. "I have forgotten half of what has been posted here but wouldnt the gyroscopic effects of the bikes motor itself affect the handling?" Yes it definitely can. "I know in the tractor pulling circuit where they allow 5-6 or more motors they will run half the motors in reverse to negate the twist & gyro action that is inherent in them." I think you *may* be confusing the torque reaction of a sharply accelerating engine with gyroscopic effects. Quickly revving a large engine produces a significant torque that must be reacted by the motor mounts and ultimately the suspension and tires, like when you rev the engine in your car and it rocks noticeably on its engine mounts. Riders of the big Boss Hoss V-8 powered bikes understand this torque reaction very well. When they blip the throttle, the bike in reaciton has a tendency to roll to one side. This makes a example to demonstrate the law of conservation of momentum. I'll try to explain... Consider the tractor as the discreet *system* wherein the law of conservation of momentum states that... Without external influence, the total momentum of a discreet system will not change. What that means in English is basically that... Lacking the presence of any external forces, an object in motion tends to stay in motion maintaining its same heading/direction and an object at rest tends to stay at rest. This is true whether the motion is linear, like for a bullet flying through space, or rotational, like for a flywheel. A bullet in space does not want to change speed or heading. A flywheel does not want to change speed or the orientation of its axis of rotation. Swallow that and try to digest it for a second. Hopefully you won't get heartburn. Initially consider that the tractor sits at idle in equilibrium; it is not moving, pitching or rolling. It's total angular momentum is described by the total momentum of the idling engines' rotating parts, primarily crankshafts and flywheels. The rest of the vehicle, since it is not rotating, contributes nothing to the total angular momentum of the tractor. Now quickly rev the tractor's engines from idle to racing/pulling speed. The angular momentum of the engines' crankshafts and flywheels increase a LOT, and they do it very quickly even violently. Per the law of conservation of momentum, without any external influences (external to the tractor) the total angular momentum of the vehicle (our discreet system) cannot change. So while the engines are wrapping up clockwise, the huge tractor chassis tries to rotate counter clockwise to offset the change and thus maintain the same overall angular momentum of the system. If floating in space the tractor would indeed rotate counter to the engines. Luckily the tractor does have the benefit of some external influences, namely gravity and the ground supporting the tractor's tires. Where does the additional momentum go? You may laugh at this but it is true, the additional angular momentum gets transfered to a much larger discreet system, the earth. Of course after the tractor's engines' return to idle, the momentum shift is in the opposite sense. You may be right though, when turning or wheelying the gyro effects could be very troublesome as well. In both cases, it definitely sounds like a good idea to run half of the engines counter to the others. "Now obviously I have never held a running engine directly in my bare hands & felt the gyro action like you can with a bicycle wheel assembly, but I do know with some of my hand held power tools that its pretty damn strong. I have one hand held angle grinder that will damn near rip your arms out when you switch it on. And if you dont hold it tight it will dance all around your ass." Again, I think you are confusing the reactive torque resulting from a change angular momentum with gyroscopic effects. Now, once the grinder is running at speed, you should be able to pick it up and hold it staionary just fine. Try to "steer" it however and you can then feel the gyroscopic effects. I definitely notice gyro effects when using my skill saw. Even a Dremel tool running at 10,000+ rpm exhibits some noticeable gyroscopic behavior. There went an hour of my day. I hope you find it interesting and useful. | ||
| Blake |
Lornce, "Blake, notice front wheel orientation as a bike changes direction while it's front end is unloaded. Believe that may be what's eluded to here." I'm not sure what you are getting at. Once again, I am not saying that gyroscopic effects are not present within a motorcycle and its wheels. They most definitely are. My point, again, is that gyro effects hinder, rather than enhance, the ease with which a motorcycle at speed can be turned. That is it. Pretty simple. Funny how people react and get all off course in debating the issue. "Really though Blake, I should think you'd take your issues with Tony to where Tony may actually refute them. Head on over to the Motorcycle Chassis and Design site and voice some of your stronger opinions." Lornce, You aren't suggesting that we should not comment or refute quoted material that is offered as fact when it instead is simply wrong or misleading, are you? I only refuted Mr. Foale's statements with regards to gyroscopic effects on motorcycle steering when they were set forth by others here as expert testimony. It is interesting how my remarks are interpreted. I think I clearly stated that Mr. Foale in his new book, now seems to have changed his stance in agreement with what I have been saying. He is now a reference that I can use in support of the truth concerning gyro effects in motorcycles. I did feel obliged however to point out the misleading nature of his "gyro only" simulation. I would very much like to read his new, revised book. Amazon does not have it. I may go ahead and pay retail. Then I might consider contributing to his discussion site. That might me fun. | ||
| Blake |
Jim, "Blake, You said "Why do I need both of Mr. Foale's books in order to quote excerpts posted on the internet?" Because only a small portion of the most recent book is on the internet, not the complete book. You can't compare what he may or may not have said in the past with a fraction of what he is saying now. I guess you didn't read the Forward, Acknowledgements and Preface that was posted on his site...." <sigh> Please see my comments above to Lornce. Who posted the excerpts or links thereto? I cannot respond to that? Come on Jim. You are being silly. | ||
| Hans |
My conclusions: Steering is initiated by a short counter steering mouvement to lean the bike. Precession helps a little bit to lean the bike but the weight is most important factor by far. Steering back into the wanted direction the precession tries to set the bike upright again, but, as said: The force is not important. I will try to make it likely: At 150 MPH the bike does 220 foot/minute. With a counter steering angle of only 3 degrees it would be 11.5 foot from its straight course in one second. It means that in a split second (1/10 second) the tires are more than a foot beside the straight line at which the CG tries to follow its course. This causes the great momentum to let the bike fall into the turn against the great stabilizing gyroscoping forces of the wheels. That precession is of very limited influence can also made clear: Spitfires have a tail wheel and the huge propellor, driven by an 1700 HP Merlin engine kept the blade tips at 3000 RPM just under the sound speed. Nice gyroscoop. At the start the position of the plane had to become from pointing into the air more horizontal. The big needed momentum was delivered by the resistance of the wheels and the pulling propellor and adjusted by the big horizontal stabilizer. As soon as the tail was of the ground the precession was counteracted only by the small vertical stabilizer, the rudder, at the tail. At the low take off speed that force was small and effectuated by just putting some pressure on the right foot and the rudder. (To lift off was far more complicated because of the asymmetrical pressure on the main wheels cause the torque of the engine and the differences in the structure of the starting/landing area, sometimes just green meadows, and sidewind: A ground loop was not uncommon.) Just putting more confusion in the conversation ? Skip it then. Hans. | ||
| Blake |
Hans may well be the wisest man on BadWeB. Jim, I'm utterly confused by your comments. What do the forward, aknowledgements, or preface have to do with me criticizing a blatantly misleading presentation of test/simulation results? | ||
| Jprovo |
Blake, you at least have one “believer” "It is a myth that the forces of gyroscopic precession are required and primary in giving a motorcycle its stability." I agree, gyroscopic precession assists motorcycle stability, even if it is not required. As to gyroscopic precession being a primary force in motorcycle stability or not, It would definitely depend on speed, but without generating a FBD or running the calculations I wouldn't know. "It is a myth that gyroscopic precession aids the maneuverability of a motorcycle." Of course this statement is true... Gyroscopic precession can not both aid stability and maneuverability, and gyroscopic precession definitely aids stability. "It is a myth that through countersteering the forces of gyroscopic precession cause a motorcycle to lean into a turn." Other than the slight modification added by Hans… (“Precession helps a little bit to lean the bike but the weight is most important factor by far…”), I would agree. “Hans may well be the wisest man on BadWeB.” I couldn’t agree more, Hey Hans, Thanks for stating that better than I ever could. James | ||
| Jima4media |
Blake, You said to Lornce "You aren't suggesting that we should not comment or refute quoted material that is offered as fact when it instead is simply wrong or misleading, are you? I only refuted Mr. Foale's statements with regards to gyroscopic effects on motorcycle steering when they were set forth by others here as expert testimony." Then you said... "I think I clearly stated that Mr. Foale in his new book, now seems to have changed his stance in agreement with what I have been saying. He is now a reference that I can use in support of the truth concerning gyro effects in motorcycles." So I guess Tony rewrote his book to be in agreement with what you say, and he is now as right as you are. Glad we got that cleared up. | ||
| Jima4media |
You can join the MC Chassis Design mail list at http://www.micapeak.com/mailinglists/featured.html Tony Foale is a member of that list. and another good mail list is ... http://autos.groups.yahoo.com/group/mc-engine/ Ian Drysdale is a regular contributor to that list. | ||
| Jima4media |
Here is a good explanation of the physics of a "high side" http://www.mecc.unipd.it/%7Ecos/DINAMOTO/H1_High_side_braking/high_side_braking.html Oh and again, There is no such thing as centrifugal force. http://scienceworld.wolfram.com/physics/CentripetalAcceleration.html http://scienceworld.wolfram.com/physics/CentrifugalForce.html | ||
| S320002 |
"Where's Greg anyway?" Still here. Sometimes laughing so hard I couldn't type if I wanted to. "... gross over-generalization leading to a flawed conclusion." Blake my friend, that applies to a great deal of what you have said in regard to this thread. Greg;-) | ||
| S320002 |
Speaking of tankslappers. How is a high-speed tankslapper possible if steering is sooo hard at high speed? Greg |
