Talk:Bicycle and motorcycle dynamics
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[edit] Bicycle physics in German
If anyone speaks German, de:Fahrradfahren seems to be about bicycle physics. --Christopherlin 03:25, 3 April 2006 (UTC)
- I don't speak German, but the existing links cover the topic quite well. Perhaps you would be interested in modifying the section with thinks such as these:
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- Effect of steering-column angle on trail and stability
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- - Finally covered, but out of Whitt and Wilson. -AndrewDressel 16:32, 8 August 2006 (UTC)
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- Give typical values of trail and explain the pros/cons of different values
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- - Partially covered, but out of Whitt and Wilson. -AndrewDressel 16:32, 8 August 2006 (UTC)
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- Flense the speculation about shimmy
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- - Don't know if there is any left. -AndrewDressel 16:32, 8 August 2006 (UTC)
- JethroElfman 22:02, 3 April 2006 (UTC)
- Which 'existing links' do you mean? The steering and trail discussion could use some expansion. Another one of those things I'll do when I get a round tuit... :-> --Christopherlin 00:50, 4 April 2006 (UTC)
[edit] Bicycle physics
Copied from the article:
"A rider stays upright on a bicycle by steering the bicycle so that the point where the wheels touch the ground stays underneath the center of gravity. Once underway, this effort is largely replaced by physical forces generated by the rotation of the wheels which produce a remarkable "self-steering" effect. The angular momentum of the wheels and the torque applied to them by the ground generates a phenomenon called precession, by which the wheel turns, or trails, toward whichever side the bicycle tilts. Like the rider's steering adjustments, this motion automatically returns the contact point of the wheel directly under the center of gravity. These forces, perhaps aided at very high speeds by the gyroscopic effect of the spinning wheels,4 are sufficiently strong that a riderless bicycle going down a slope will stay upright by itself."
The effect described in sentences 2, 3, and 4 above IS the gyroscopic effect, so to say in sentence 5 that it is perhaps aided by the gyroscopic effect is confusing. The more important effect, according to Jones and others, is that of trail, described in the third paragraph of the 'Bicycle physics' section. Rracecarr 18:54, 11 May 2006 (UTC)
- I agree. In fact, 2, 3, and 4 are far too vague. They are only valid for a particular range of forward speeds and only for bikes that have the necessary geometry and mass distribution. "The wheel" should be identified as "the front wheel". Using "trail" to describe this phenomenon begs confusion with "trail" described below.
- Also, Andy Townsend's article (note #4) gives a poor analysis of the mechanics involved. There is no 'gyroscopic "resistance" to change in lean angle' no mater how fast the wheels are turning.
- Again, "are sufficiently strong that a riderless bicycle going down a slope will stay upright by itself" is only true within a certain speed range and for bikes with the necessary geometry and mass distribution.
- Finally, in the second paragraph, the last sentence shows that the gyroscopic effects are "unnecessary to ride a bicycle", not necessarily "unimportant". AndrewDressel 21:34, 14 May 2006 (UTC)
All of these issues were corrected by me back in February. On May 5 someone reverted the entire article back a few months. Even the first sentence here is poor. The goal isn't just to keep the centre of gravity over the line between the wheels -- the rider also wishes to drive the bike where he wants it to go. While turning, the centre of gravity must lean into the turn (not stay over the wheels) or the bike will tip over. - JethroElfman 16:26, 15 May 2006 (UTC) Okay, I restored the section. Perhaps someone would like to restore the entire article. The physics section could be tinkered with further. For instance, the "geometry of the front forks" has two components. One is how the contact of the tire to the road trails where the steering axis intersects the road. The second is the angle of attack of the steering axis. The exaggerated angle of a chopper is less stable, yet it is presumably advantageous to have the slight angle of a regular bike. I don't understand why it isn't perpendicular like a furniture caster. The length of trail is 1.5" for standard use, and up to 2.5" for racing duty. Increased distance adds stability for hands-free or aero bar operation, but makes cornering stiff. The speed-wobble section could be reworded. I don't think the comparison to a shopping-cart wheel is entirely accurate in this case. JethroElfman 16:43, 15 May 2006 (UTC)
- It's definitely better than it was. I don't know enough to add anything myself, but I would like to see a discussion of rake angle included in this section. Rracecarr 17:56, 15 May 2006 (UTC)
- Much better. I'll look for a better reference than Townsend AndrewDressel 18:00, 15 May 2006 (UTC)
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- I've gone ahead and made some major changes. I clarified self-stability vs rider control and what role gyroscopic effects play. I added a diagram to clarify head angle, rake, and trail. I added a paragraph about the effect of the steering assembly center of mass. I added a link to a video demonstration of self-stability. I probably violated some protocols, but I'll happily fix them when pointed out. AndrewDressel 04:28, 16 May 2006 (UTC)
I think you are putting too much emphasis on precession. I thought that the Jones article settled that precession isn't such a big deal for bicycles.
- My reading is that he established that is isn't necessary. I don't mean to emphasize it. I could put it last. It is still significant because it varies with speed and so contributes to the low and high speed instabilities that usually bracket the self-stable range. AndrewDressel 18:18, 16 May 2006 (UTC)
For motorcycles it is, so it's good to explain the principles involved.
- Its role there is arguable. AndrewDressel 18:18, 16 May 2006 (UTC)
In that regard, the rear wheel is restrained from precessing because it is rigidly attached to the frame, whereas the front wheel can turn the head axis.
- And the frame is constrained because it is attached to two wheels that touch the ground. I just mention the friction of the wheels with the ground, but could add text to include the frame necessary to transmit the force to the rear wheel. AndrewDressel 18:18, 16 May 2006 (UTC)
Even so, as the bike turns through the corner, the rear wheel is thereby allowed to precess and thus aid in turning the mass of the bike.
- Nope. Still constrained by the frame, wheels, and friction with the ground, as above. AndrewDressel 18:18, 16 May 2006 (UTC)
The first paragraph offends my memories of grade 10 physics class. Inertia is not a force. Its effects are applied to the bike through the tire contact to the road.
- Depends on the reference frame used, as I mention. See Centrifugal force. AndrewDressel 18:18, 16 May 2006 (UTC)
I think your descriptions of trail and head angle are still too intertwined. Trail turns the wheel by gravity when the bike is leaning. Head angle generates a gravitational force to turn the wheel when the wheel is turned off centre, even if the bike is perfectly vertical.
- Sorry, but I don't follow you here at all. I specifically do not understand what you mean by "Trail turns the wheel by gravity" and "Head angle generates a gravitational force". Could you clarify? AndrewDressel 02:15, 17 May 2006 (UTC)
If trail is kept to zero, a leaning bike's wheel won't turn regardless of the head angle (you have to extend the curvature of the forks forward to do this).
- Not true. With zero trail, it won't turn due to the ground reaction force, but if the CG of the entire steering mechanism, including front wheel, fork, stem, handlebars, brake levers, shifters, basket, rack, etc., is forward of the steering axis, as is common, then it will turn into the lean. If it is behind, then it will turn away from the lean. Either case effects self-stability, of course. AndrewDressel 02:15, 17 May 2006 (UTC)
Oh, and Jones claims that negative trail makes a bike entirely unrideable, so what's your reference that says it's rideable but difficult?
- I'll have to reread. It may be a matter of degree. Rear steering with negative trail is very unstable, but people do learn to ride fixed-gear bikes backwards as a trick. AndrewDressel 18:18, 16 May 2006 (UTC)
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- The exact quote, from the second to last paragraph of the article, is "I made URB IV by moving the front wheel of my bicycle just four inches ahead of its normal position [giving it negative trial, as seen in FIG. 1 of the article], setting the system well into the unstable region. It was indeed very dodgy to ride, though not as impossible as I had hoped" AndrewDressel 01:27, 17 May 2006 (UTC)
What's your reference for the note about long-wheel-based recumbents. It sounds interesting and I'd like to read that one.
- I just performed the physical experiment described by Zinn on such a bike. I'll see if I can find someone else who has and wrote about it. AndrewDressel 18:18, 16 May 2006 (UTC)
I still don't understand why head angle isn't just 90 degrees. Is it to keep the rider from going over the handlebars when braking perhaps?
- It negligibly reduces that tipping tendency. I think is mostly for trail. I remember reading that the historical origin is lost, but it works well and so is continued. I'll look for that reference. AndrewDressel 18:18, 16 May 2006 (UTC)
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- It increases the steering effect of the steering mechanism's forward CG. AndrewDressel 01:27, 17 May 2006 (UTC)
Your internal links are done with html references rather than the simple square-bracket approach. Why is that? - JethroElfman 16:40, 16 May 2006 (UTC)
- User error. Will fix. AndrewDressel 18:18, 16 May 2006 (UTC)
In the new diagram, things are labeled differently from how I learned them. I thought rake was the angle of the steering axis from vertical, which in the diagram is labeled "head angle" (well, 90 degrees minus what I thought was rake is so labeled). Someone on wikipediea appears to agree with me: rake and trail. Here is another random example: www.performanceoiltechnology.com/rake_and_trail.htm However, I also found a reference agreeing with AndrewDressel: www.sheldonbrown.com/gloss_ra-e.html ???? Rracecarr 19:10, 16 May 2006 (UTC)
- Perhaps things are different in the motor cycle world, but go to any bicycle manufacterer's web site (LeMond, for example), head angle is given in degrees from the horizontal (73°, for example), and rake is give as the offset in milimeters of the front hub from the steering axis (45mm, for example). These two parameters, along with wheel radius, define trail. That's how Zinn defines them, too. AndrewDressel 21:39, 16 May 2006 (UTC)
- Sure enough, all the motorcycle manufactures specs I found use 'rake' for head angle. At the same time, bicycle fork manufacturers seem to use either offset or rake. Meanwhile, the Wikipedia rake and trail article was actually "nominated for deletion on 2 April 2006" and the WIkipedia [Bicycle fork] article mentions neither rake nor offset.AndrewDressel 02:01, 17 May 2006 (UTC)
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- Okay, I did some sketches and see what you mean about the recumbent. If the wheel rather than projecting forward of the forks, is mounted rearwards, the centre-of-mass makes it steer the opposite way.
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- Actually, the one I used has a normal fork, but a long boom to bring the handlebars back to the rider. I've actually flipped the fork around to increase trail, and it goes a long way toward counteracting the adverse effects of the CG being so far behind the steering axis. Still need to find a reference, though. AndrewDressel 23:44, 16 May 2006 (UTC)
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- The rake and trail article is terrific. I didn't know it existed. It needs linked, and perhaps the caster-angle article as well.
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- I thought it was, if I can't find it, I'll add it. AndrewDressel 23:44, 16 May 2006 (UTC)
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- What I meant about precession is that you put an awful lot of verbage covering it, when everything I've read, including the rake-and-trail and caster-angle articles says that it's trail that makes the bike stable. Angle provides damping in respect to trail. The one motorcycle reference though, says that precession makes a motorcycle corner. How about moving precession farther down and abbreviating it a whole bunch? - JethroElfman 22:22, 16 May 2006 (UTC)
I've changed the links I can from html references to the simple square-bracket approach. I've found and moved the Zinn reference to come at the end of the trail paragraph. I've moved gyroscopic effects to last, but left it verbose because it is the one effect that varies with speed. I've added a reference for the low and high speed instabilities I mention. I've added information about making turns. AndrewDressel 01:27, 17 May 2006 (UTC)
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- Fixed some typos AndrewDressel 03:56, 18 May 2006 (UTC)
- I think the paragraphs on countersteering are too absolute concerning it. The very fact that you can ride and negotiate a corner with no hands makes it look to me like you don't necessarily have to employ the technique.
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- Just because you don't have your hands on the handlebars, doesn't mean you don't countersteer. You do steer in the direction of a turn as necessary, right? If the bike starts to lean, you do steer the wheels back under the center of gravity, right? I get that one can have quite a lot of control over the steering of a bike without the use of hands. The issue is lean angle, however. AndrewDressel 03:56, 18 May 2006 (UTC)
- On a motorcycle sure, since the bike outweighs the rider. On a bicycle, since the rider is so much heavier (and manoevreable compared to being on a motorcycle seat) the rider can shift his weight to produce lean.
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- Ah, but leaning the bicycle does not move the combined center of gravity of the bicycle and rider to the side. It just lowers it in most cases. If the combined center of gravity is not leaned into the turn, the bicycle and rider will fall over as soon as the turn is initiated due to centrifigul force, or, if you prefer, because they continue straight as the wheels begin to accelerate around the center of the turn. There simply is no other way to initiate a lean, short of some external influence. AndrewDressel 03:56, 18 May 2006 (UTC)
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- Here is a fascinating page about steering motorcycles: No B.S. Machine. Perhaps the Countersteering article should reference it. I'll reference it here for now. AndrewDressel 03:56, 18 May 2006 (UTC)
- It won't be as efficient, and might not be the norm, but isn't it at least possible?
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- Nope. No more so than accelerating in space without expelling mass. AndrewDressel 03:56, 18 May 2006 (UTC)
- If the rider tightly grips the handlebars to rigidly keep the wheel straight, the bike will lean just by gravity.
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- Well, yes, you could continue riding in a straight line until an inevitable purturbation tips you in the desired direction. Then, override the natural righting tendency inherent in the bicycle design until the necessary lean angle is achieved. However, if you want to turn when you want to turn, your only alternative is countersteering. AndrewDressel 03:56, 18 May 2006 (UTC)
- To feel the effect of shifting weight, try riding by standing with your left foot on the right pedal. The bike leans greatly left, and you must torque the handlebars right to go in a straight line.
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- True, due mostly to trail, and not related to the issue except as an extreme example of moving the combined center of gravity far from the vertical axis of the bike. If you let the bike steer to the left, you'd better have leaned the combined center of mass appropriately. AndrewDressel 03:56, 18 May 2006 (UTC)
- Likewise, I still dispute the precession contribution of the rear wheel. If the frame is constraining the wheel to not precess, the wheel is conversely applying the same rotational moment back onto the frame in the direction of the turn. Hence the spinning rear wheel is applying a yaw torque to aid the yaw torque coming from the friction of the road on the front wheel. Will you say naw to that?
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- The problem is that unless the precession induced in the rear wheel by leaning the bike has enough torque to skid the front wheel (say 100ft-lbs or more for an adult rider on an average bike with rubber tires on pavement), then it has no effect on the yaw of the bike. The front wheel of a bicycle does not skid in the direction of the turn, and so applies a torque through the frame on the rear wheel about the vertical axis. If you follow the right-hand rule, you find that this torque induces a precession in the rear wheel about the longitudinal axis of the bike causing it to lean in the same direction as the bike is leaning. You can verify this with much more rigor by applying Euler's Equations for 3D rigid body motion. You can also demonstrate it with a toy gyroscope. AndrewDressel 03:56, 18 May 2006 (UTC)
- With my link to the Rake and trail article it is unfortunate that they define rake as equivalent to caster angle.
- - JethroElfman 02:24, 18 May 2006 (UTC)
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- Yeah, that one needs attention, too. AndrewDressel 03:56, 18 May 2006 (UTC)
[edit] Bicycle braking
Added quick analysis of braking forces, but forgot to login first AndrewDressel 12:42, 7 June 2006 (UTC)
[edit] Generalization needed
All of the topics mentioned in the article apply equally to motorcycles as well. Moreso in fact due to their larger mass. --Hooperbloob 13:56, 7 June 2006 (UTC)
- I'd agree, but I dread the controversy. Many of the references are different. Much of the motorcycle research includes front and rear suspension which does effect the dynamics. I don't know of any single source that explicitely covers both vehicles. AndrewDressel 19:43, 7 June 2006 (UTC)
Kudos on the bicycle->bike revision, it does the job perfectly. --Hooperbloob 15:17, 20 June 2006 (UTC)
- I guess all I have to do then is incorporate the main section on stability from the motorcycle article (different due to full suspension, tires size, mass, etc.) and then we can have just one article, not two. AndrewDressel 01:32, 21 June 2006 (UTC)
Then the last step would involve renaming the article itself to "Bicycle & motorcycle physics" ? --Hooperbloob 02:11, 21 June 2006 (UTC)
- Done, without too many errors, I hope. AndrewDressel 12:40, 22 June 2006 (UTC)
[edit] Racing physics
I notice on my bicycle that I shift my body away from the direction of a turn. That is, on left-hand turn lean the bike left, but keep a body position almost vertical. This is to counteract the way the front-wheel trail wants to straighten the bike back up. In motorcycle racing however, they lean way into the turn (with a knee stuck out). Is this because the gyroscopic effect of the wheels is trying to stand the bike up, and needs counterbalanced? JethroElfman 16:02, 30 May 2006 (UTC)
- I cannot say for sure why you lean away from the direction of a turn on your bicycle. It is not commonly practiced in racing. Check out pictures on http://www.freewheel.com/mvw/pooleyphotos.htm
- In motorcycle racing, I just read recently, but can't yet find the link, that riders lean into the turn in order to lean the combined bike/rider center of gravity farther than would otherwise be possible due to interference between the bike and the ground. The lean of the combined CG is exactly dictated by the radius of the turn and the forward speed.AndrewDressel 01:27, 31 May 2006 (UTC)
- Here are more details from http://www.superbikeschool.com
- "Hanging off certainly moves YOUR CG to the inside of the corner (but moves the bikes out a little...) and the COMBINED CG stays at the same height."
- "One would want to pick the bike up off the edge of the tire while coming out for a couple reasons... One, you want to save the edge to maximise mid-corner speed through the race. Two, you can put more power down when the tire isn't right on the edge. Three... (this ones a little tough to follow for some) the tire is smaller the closer you get to the edge... This means that when you roll over to the edge, if you keep the same speed, your RPM's will rise... You can use that extra HP WHILE picking the bike up to help add drive out of the turn... If you're in an endurance race you MAY be able to save a bit of fuel by hanging way off and using the larger portion of the tire. That is... if the extra wind resistance isn't offsetting the fuel savings..."
- "Each tire will have a lean angle where it will generate the most grip. You want to use THAT lean angle mid-turn"
- AndrewDressel 03:23, 31 May 2006 (UTC)
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- From my recollection of a brief involvement in seventies production motorcycle racing, "hanging off" was a tactic used to offset poor ground clearance. Seasalt 01:42, 15 October 2006 (UTC)
[edit] Steering section
Having read through the steering section, I've noticed that the description of a number of items (particularly in the 'counter-steering' portions) don't square with my own experience riding. In particular, there are two items I feel might warrant changes: 1. The process of counter-steering a motorcycle through a turn does not, at least in my riding experience, involve a discernable deflection in the actual path of the motorcycle. It's possible that there is some small path change, but in my experience (at street speeds) it's not a significant (or even noticable) effect.
- Even if you don't discern it, there isn't another way to lean the combined center of gravity of a bike and rider, short of waiting for it to tip in the desired direction due to random perturbations, and then letting it continue to lean without correction. At street speeds, it doesn't take much countersteering to create the necessary lean. At 15mph a 1° deflection of the front wheel will move the wheels nearly 5 inches in that direction in just 1 second, 5° will get you nearly 2 feet. AndrewDressel 04:25, 14 June 2006 (UTC)
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- Perhaps I'm not steering very aggressively, but at speeds over around 15 mph I don't notice the wheel deflecting much at all when I'm steering - perhaps that's why I don't see a path change when I steer? Saturn V 16:39, 14 June 2006 (UTC)
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- Right. It doesn't take much. -AndrewDressel 12:14, 8 August 2006 (UTC)
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2. There is a statement to the effect that 'all turning on a motorcycle uses counter-steering' which is not strictly true, I don't believe. While it is probably the case that basically all steering on a motorcycle involves deflection of the front wheel, the cause of that deflection is not necessarily counter-steering. The shifting of body weight on the motorcycle (without input to the handlebars) can cause the motorcycle to steer (although it is markedly less efficient than the use of the bars), and any wheel deflection involved is due to frame geometry effects as opposed to active counter-steering.
- Well, the first sentence defines countersteering as the turning of the front wheel and does concede "usually via the handlebars". You as a rider are welcome to use whatever technique you prefer, but the handlebars are certainly the most direct and efficient. AndrewDressel 04:25, 14 June 2006 (UTC)
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- I certainly agree that using the handlebars is indeed the most efficient way of controlling the bike - I think it is important, however, to at least mention that it's not the only way in which you can affect the path of the bike. Saturn V 16:39, 14 June 2006 (UTC)
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- Done. No-hands riding has its own section immediately following countersteering.-AndrewDressel 12:14, 8 August 2006 (UTC)
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I think perhaps a wording change is in order there (and the citation of the 'no-bs' bike isn't without the potential for controversy).
- The No B.S. Bike meerly provides a vehicle for riders to discover this for themselves. By all means, cite other examples of physical experiment. I submit, however, that an individual rider's own perception of what they do during a turn is not exactly objective. AndrewDressel 04:25, 14 June 2006 (UTC)
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- Another neat experiment was performed by Dr. Richard Klein at University of Illinois. "The Rocket Bike" had a small rocket attached to the handlebars and fired momentarily while the bike was rolling without a rider (demonstrating self-stability). When the rocket fired, it applied a torque to the steering. Counter-intuitively, the bike turned in the opposite direction. -AndrewDressel 12:14, 8 August 2006 (UTC)
Would anyone else like to chime in here before I go and edit this section? [The above entry is by user Saturn_V timestamped 15:39 13 June 2006]
- Have at it. There is still too much of a "rider school lecture" flavor to it for my taste. AndrewDressel 04:25, 14 June 2006 (UTC)
- I thought that the no-bs article was wonderful and I don't know in what way it can be considered controversial. Any other literature I have seen agrees that you must countersteer. I can see there being an argument if you are talking about a bicycle, because the rider's mass is so much greater than the bike's. Even in that case, if you ride with no hands, the bike will countersteer for you. When you shift body weight to the right, the bike responds by leaning to the left. Front-wheel trail will make the forks turn into the direction of the lean. Hence, when you lean right, the bike naturally countersteers left, and you end up going right. - JethroElfman 04:21, 14 June 2006 (UTC)
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- The primary issue I've seen come up in the discussions of the no-bs bike is that it is sometimes used to argue that weight transfers (without active pressure on the handlebars) on the bike have no effect on the path of the bike. That's the only issue I take with it... Saturn V 16:39, 14 June 2006 (UTC)
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- Code concedes "The best result was one of my riding coaches. He got into a full hang-off position and was able to persuade the bike, by jerking on it, to start on a wide, wide arc in the paddock at Laguna Seca" so the assertion of 'no effect' is perhaps a misread. AndrewDressel 20:25, 14 June 2006 (UTC)
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[edit] New topics
Unicycle physics and Physics of a rolling coin Wow! Anyone know who is 80.168.225.36? The "fmt hdrs as per manual of sty" looks good. AndrewDressel 13:56, 23 June 2006 (UTC)
[edit] Misconceptions
The_Anome "rm unnecessary cite: all this can be confirmed from the other cites given below" at 22:49 on 23 June 2006, but I think he misunderstood why I included the link. Instead of just restoring it, I made a new section and listed a handfull of other examples. It may not be appropriate for this article, but it gives me a chuckle. AndrewDressel 01:23, 24 June 2006 (UTC)
[edit] Name Change?
After reading the FA requirements, especially for lead section, I'm thinking of changing the title to "Bicycle and motorcycle dynamics". Dynamics is a much better fit than physics. Otherwise, in order to be complete, the article would need to be expanded to include performance, efficiency, etc. Given the very different power plants and speed ranges of bicycle and motorcycles, I believe this would be impractical. Comments? AndrewDressel 14:32, 26 June 2006 (UTC)
- Done AndrewDressel 14:28, 27 June 2006 (UTC)
[edit] Peer Review
I probably won't be able to go through this article in the detail I'd like until this weekend, but I'll try and put the things I find that I haven't had the time to correct yet and maybe some other folks can help? Some of these are more questions of style than actual problems...
- Do we really want a 'Examples of misconception' section? It seems odd to point to information that is known to be incorrect. In my mind, it is sufficient to have correct and verified information in this article.
- -My concern is that the misconception is so prevalent that if the article doesn't address it, it becomes a glaring omission. The Coriolis effect article addresses the "popular misconception...that the Coriolis effect determines the direction in which bathtubs or toilets drain". Perhaps that is not the gold standard. AndrewDressel 01:44, 30 June 2006 (UTC)
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- I wonder if it'd be better to address common misconceptions in the main portion of the article (perhaps with references to sites which have an incorrect explanation), rather than a section which has only links to external sites that are 'incorrect,' but without reference to what at those sites is incorrect? Saturn V 17:36, 30 June 2006 (UTC)
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- Took a step in that direction. AndrewDressel 01:21, 2 July 2006 (UTC)
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- The braking section is almost entirely bicycle-centric (if that's a valid term). For example, flipping the rider over with the front brake is less of a concern (to my mind) for motorcycling than locking the front wheel. I don't know whether the dynamics of high-side crashes on motorcycles are appropriate for this article, but to my (purely annocdotal) knowledge, a front tire locking is the most common cause of such events...
- -It may be more prevalent with bicycles, but just do a quick Google image search on "stoppy" to see how 'popular' it is with motorcycles. Perhaps I can list cruiser style motorcycles as another example along with recumbents. AndrewDressel 01:44, 30 June 2006 (UTC)
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- Stoppies are often discussed in reference to motorcycle stunting, and most modern sportbikes and standards have powerful enough front brakes to allow for such behavior (although it's not really recommended as a panic stopping technique), but I think that in everyday motorcycle usage, locking the front wheel is a much larger concern. That's not to say that the physics presented on the amount of brake force required shouldn't be included - it should. My wish is that I'll be able to find something with reasonable physics content on high-side dynamics to accompany this portion of the article. Saturn V 17:36, 30 June 2006 (UTC)
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- High-side physics will be tricky. It all depends on an increase in friction: either from hitting a solid object such as a curb or sliding through a low friction patch such as oil or sand. AndrewDressel 01:21, 2 July 2006 (UTC)
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- 'Mass distribution' contains no mention of rider positioning, which again may be primarily a motorcycling concern.
- -Actually, given the ratios of rider mass to machine mass, it is a bigger factor in bicycling. What mention do you suggest? AndrewDressel 01:44, 30 June 2006 (UTC)
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- I was thinking of including it in the last sentence - I'll try and wordsmith it this weekend...Saturn V 17:36, 30 June 2006 (UTC)
- Question for the physics savvy out there: Does tire profile play any role in the dynamics of motorcycles (or bicycles) beyond providing a surface for traction? Are there differences in the amount of deflection of tire required to initiate the lean based on tire profile, or even width?
- -Yes, tire profile does play a role. Tires are mentioned in the second paragraph of the "Balance" section and again in the "Stability with full suspension" section. Perhaps there should be more. AndrewDressel 01:44, 30 June 2006 (UTC)
- Another question for the physicists: The article states that '(vehicles) with more trail feel harder to steer.' I assume that this is because they are harder to steer (in other words, it takes greater force to deflect the tire while moving) - which means that we probably ought to include something on why that is.
- -If we can find someone who "published" an explanation, right? AndrewDressel 01:44, 30 June 2006 (UTC)
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- Yes - I'll go looking for an explanation that I remember reading about in an article in one of the online motorcycle magazines on motorcycle dynamics, since I think that's where I remember reading something about why trail has this effect. I'll try and vet the actual physics of the article when I find it. Saturn V 17:36, 30 June 2006 (UTC)
- Should there perhaps be at least a mention of wheelbase and the effects of that variable, since it's in the figure for this document?
- -Same as above. I believe that the effects are secondary or tertiary. I'll see what I can find. AndrewDressel 01:44, 30 June 2006 (UTC)
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- Although wheelbase is generally a secondary variable, for things like turning, the wheelbase has a significant determinative value (imagine, in a completely silly example, a motorcycle with a 100m wheelbase - the turning radius is unlikely to be that of a motorcycle with a 1m wheelbase, regardless of lean angles involved) in some aspects of the dynamics of the bike. Saturn V 17:36, 30 June 2006 (UTC)
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- All true, but not necessarily a 'dynamics' issue. AndrewDressel 01:21, 2 July 2006 (UTC)
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- I disagree with the statement (in 'Stability with a full suspension') that high frequency front wheel oscillations are "relatively harmless" - in the case of motorcycles, the oscillation (also referred to as a 'tank-slapper' when it gets bad) can occur with enough force to injure the riders arms and hands, and uncorrected can cause loss of control of the bike. I've also read that slowing down (well, actually, more specifically braking) may not be the best way to correct the issue - braking will transfer weight to the front wheel, which if I'm understanding it correctly, can lead to more forceful oscillations.
I'll update this list as I find more (or fix things). Saturn V 16:58, 29 June 2006 (UTC)
[edit] Automated peer review suggestions
- See if possible if there is a free use image that can go on the top right corner of this article.
- - is it possible to have lead image next to table of contents for better use of space? AndrewDressel 02:03, 28 June 2006 (UTC)
- - added caption to last image AndrewDressel 02:03, 28 June 2006 (UTC)
- There may be an applicable infobox for this article. For example, see Template:Infobox Biography, Template:Infobox School, or Template:Infobox City. (Note that there might not be an applicable infobox; remember that these suggestions are not generated manually)
- -Don't know of one that would apply. AndrewDressel 02:03, 28 June 2006 (UTC)
- Per WP:MOSNUM, there should be a non-breaking space -
between a number and the unit of measurement. For example, instead of 18mm, use 18 mm, which when you are editing the page, should look like: 18 mm.
- -Done. AndrewDressel 13:47, 28 June 2006 (UTC)
- Per WP:MOSNUM, when doing conversions, please use standard abbreviations: for example, miles -> mi, kilometers squared -> km2, and pounds -> lb.
- -Done. AndrewDressel 13:47, 28 June 2006 (UTC)
- Per WP:MOS#Headings, headings generally do not start with the word "The". For example, ==The Biography== would be changed to ==Biography==.
- - None do. AndrewDressel 02:03, 28 June 2006 (UTC)
- Please alphabetize the categories and/or interlanguage links.
- - Done. AndrewDressel 02:03, 28 June 2006 (UTC)
- There are a few occurrences of weasel words in this article- please observe WP:AWT. Certain phrases should specify exactly who supports, considers, believes, etc., such a view. For example,
- correctly - not in this case AndrewDressel 02:03, 28 June 2006 (UTC)
- Watch for redundancies that make the article too wordy instead of being crisp and concise. (You may wish to try Tony1's redundancy exercises.)
- While additive terms like “also”, “in addition”, “additionally”, “moreover”, and “furthermore” may sometimes be useful, overusing them when they aren't necessary can instead detract from the brilliancy of the article. This article has 10 additive terms, a bit too much.
- Vague terms of size often are unnecessary and redundant - “some”, “a variety/number/majority of”, “several”, “a few”, “many”, “any”, and “all”. For example, “
Allpigs are pink, so we thought ofa number ofways to turn them green.”
- This article needs footnotes, preferably in the cite.php format recommended by WP:WIAFA. Simply, enclose inline citations, with WP:CITE or WP:CITE/ES information, with <ref>THE FOOTNOTE</ref>. At the bottom of the article, in a section named “References” or “Footnotes”, add
<div class="references-small"><references/></div>.
- - It now has a references section. I prefer the Embedded HTML links option over footnotes. AndrewDressel 02:03, 28 June 2006 (UTC)
-
- To assist you with this, add
{{subst:js|User:AndyZ/monobook.js/footnotehelper.js}}to your monobook.js file (mine is located at User:AndyZ/monobook.js) and then bypass your browser's cache by pressing: Mozilla/Safari/Konqueror: hold down Shift while clicking Reload (or press Ctrl-Shift-R), Internet Explorer: press Ctrl-F5, Opera: press F5. In editing mode, click on the "Footnote creater" tab that appears.
- To assist you with this, add
- The article will need references. See WP:CITE and WP:V for more information.
- - It now has a references section.
- Please ensure that the article has gone through a thorough copyediting so that the it exemplifies some of Wikipedia's best work. See also User:Tony1/How to satisfy Criterion 2a.
[edit] Featured Article Candiated (Failed)
[edit] What still needs to be done?
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- Clean up notes and references. There seems to be a few different styles in use.
- -Worked on, perhaps done.
- Does the section on braking belong? It is certainly a part of bike physics, but it is not mentioned in the intro, and I can't think of a good way to add it.
- -Now mentioned in lead section
- Is the section on misconceptions appropriate?
- -See discussion below...
- A picture showing the relevant forces (gravitational, inertial if in a turn, aerodynamic, and ground reaction) would be nice.
- -Added in turning section
- Turning and braking could also use an illustration, but I can't think of what they would be, yet.
- Should 'Turning' and 'Braking' come before 'Wobble and Shimmy' and 'Stability with full suspension'? They seem to be more basic.
- -Well, wobble, shimmy, and stability all relate to balance, so leave them there.
AndrewDressel 01:33, 24 June 2006 (UTC)
[edit] Suggestions
1. This article is awfully light on non-science explanations - it would be nice if instead of "Bicycle and motorcycle dynamics is the science of the motions and forces of bicycles and motorcycles. It includes how they balance, steer, and brake." and so on that it was a bit simplified for the casual reader. For example, something like "Bicycle and motorcycle dynamics is the science of the steering, balancing, and breaking of bicycles and motorcycles." or something (I imagine that is incorrect but hopefully helps someone).
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- -Thanks for the suggestion on the lead paragraph. I tried to model it after other science articles, and it was a mess. AndrewDressel 01:24, 30 June 2006 (UTC)
2. "Examples of misconception" scares me - if it were me I'd nuke it - it seems pointless and something the reader should decide. Ditto for the mention of "incorrect" online examples (which, BTW, in these articles one really needs to be more specific then just "online").
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- -The problem is that with the prevalence of these misconceptions, it could seem that the article is incomplete without at least addressing them. AndrewDressel 01:24, 30 June 2006 (UTC)
3. "careful" in the lead is really redundant and speculative without attribution - "in fact", again, makes me think that the article is trying to prove some sort of point.
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- -Again, there are sites that refer to holding a spinning bicycle wheel to see how the gyroscopic effect keeps a bike upright. However, this is not correct. AndrewDressel 01:24, 30 June 2006 (UTC)
4. The lead should really have less stubby "paragraphs" 5. Referencing is a bit odd, I'd recommend some sort of script to convert those links to some other more accessable reference style.
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- -Isn't this "Embedded HTML links" as desicribed in Wikipedia:Citing sources?AndrewDressel 01:24, 30 June 2006 (UTC)
6. "The design charactersics of a bike can affect the stability in the following ways"
- a. "caractersics" is misspelled :) -Ouch AndrewDressel 01:24, 30 June 2006 (UTC)
- b. This list should really be turned into prose
7. "A bike is a nonholonomic system because its outcome is path-dependent" and now the writer has lost me :(. This makes it difficult to evaluate the article... RN 08:03, 29 June 2006 (UTC)
- Good job on improving the article!! I'm still uncomfortable with the misconception section, but even that is quite a bit better. Hopefully you'll get some comments from someone else! RN 06:54, 3 July 2006 (UTC)
[edit] Removed uncited claim
Would love to find a reference for:
- "Nonstandard bike configurations, such as long-wheel-base recumbents that have a long steering boom, may have the steering mechanism center of gravity so far behind the steering axis, that in a lean, this factor over-powers all others, the front wheel actually steers away from the lean, and they do not exhibit self-stability at any forward speed."
Until one is found, it can stay here. -AndrewDressel 00:50, 4 August 2006 (UTC)
[edit] References
I’ve tried to change the citations a bit, away from the style of the articles named in the todo list. The problem with it is that it’s difficult to follow while reading the article—it’s hard to tell whether a given citation refers to a newspaper article or a published paper. Also, with the other style, there is no need to maintain a second list of the same sources in the references section.
- - However, now the individual page numbers are lost. The reader has to hunt for 7 references in 35 pages of Whitt and Wilson. -AndrewDressel 14:52, 5 August 2006 (UTC)
In the process, I omitted some sources because I did not think they are really usable. Since the article is about physics, it’s probably a good idea to stick to published scientific works for all important points. On this topic, could you please check whether Hand’s thesis has been published anywhere?
- - No, I don't belive Hand's these has been published anywhere, though it is prominently referenced by Schwab, Meijaard, and Papadopoulos. For that matter, Klein, Zinn, Foale, Evangelou, and Wannee are just web pages or magazine articles. Also, Keith Code's no B.S. bike is a rare example of physical experimentation with motorcycles and has been published in Popular Mechanics. -AndrewDressel 14:52, 5 August 2006 (UTC)
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- Well, we should stick to peer-reviewed scientific works as much as possible, but I’m not proposing to throw out the rest. Can you find the precise citation for Code (in {{cite journal}} format)? Here is the web version with the date of publication, but as far as I can tell, no library in my area has the hardcopy. —xyzzyn 15:49, 5 August 2006 (UTC)
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- Would Popular Mechanics qualify as a journal anyway? The web page is certainly more accessible. -AndrewDressel 01:59, 7 August 2006 (UTC)
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As for the misconceptions, I don’t think the section should remain in that form at all. If there is a different point of view on the issue, it should be explained properly in the article—even if it’s technically wrong. —xyzzyn 17:49, 4 August 2006 (UTC)
- - That completely misses the point. For example, the Coriolis effect article, arguably a physics article, tackles head on the issue of common missconception about draining bathtubs. The Centrifugal force article does the same thing. -AndrewDressel 14:52, 5 August 2006 (UTC)
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- That doesn’t mean doing this is right. We cannot just say that view 1 is right and view 2 is wrong. What we can do, however, is to cite people who do so, preferably in the form of published studies (meta-studies reporting on recent research in the area and saying so are best for this purpose). We still have to present the other point of view appropriately, though. See also WP:V and WP:NPOV for more on this. Since you’re the expert, I hope you know some stuff to cite. —xyzzyn 15:49, 5 August 2006 (UTC)
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- Perhaps right is not the best word either. Anyway the only survey of the liturature that I know of is in Hand's thesis, but it is aimed only at published derivations of the equations of motion. I've tried again using the language about fact and hypothesis from the evolution feature article. -AndrewDressel 01:59, 7 August 2006 (UTC)
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[edit] Lean angle calculations
I cannot believe that stayed incorrect as long as it did. Maybe someone tweaked it and I didn't notice. More likely, I just goofed. The equation that was there was for lean away from vertical, but the drawing of course shows lean up from horizontal. Anyway, great thanks to 128.227.67.147 (in their first and only edit so far) for noticing it and fixing it. -AndrewDressel 03:14, 8 February 2007 (UTC)
[edit] Physics article assessment
While I may be biased, because of the work I have done on this article, I gave it an "A" because I believe it meets these criteria:
- Provides a well-written, reasonably clear and complete description of the topic
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- -Check
- It should be of a length suitable for the subject, with
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- a well-written introduction and
- -Check
- an appropriate series of headings to break up the content.
- -Check
- It should have sufficient external literature references, preferably from "hard" (peer-reviewed where appropriate) literature rather than websites.
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- -Check
- Should be well illustrated, with no copyright problems.
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- -Check
- Very useful to readers.
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- A non-expert in the subject matter would typically find nothing wanting.
- -Check
- May miss a few relevant points.
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- -Probably true
- Minor edits and adjustments would improve the article, particularly if brought to bear by a subject-matter expert. In particular, issues of breadth, completeness, and balance may need work.
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- -Probably true
- Peer-review would be helpful at this stage.
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- -Done, but only 2 editors participated, and one was automated.
- At the stage where it could at least be considered for featured article status, corresponds to the "Wikipedia 1.0" standard.
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- -Nominated by The Anome 22:47, 23 June 2006 (UTC), but failed.
If anyone disagrees, I'd love to hear about it. -AndrewDressel 18:40, 1 March 2007 (UTC)
