User talk:AndrewDressel/Archive 6

SI metrics (too) please, if possible.

Your graphics titled ~'bike lean and speed' is a wonderful input except the SAE measurements you gave may baffle some non-proficient americanese tolerant readers. %) 69.126.138.71 (talk) 19:12, 18 February 2011 (UTC)WikiCi

Done. Thanks for the suggestion. -AndrewDressel (talk) 14:45, 19 February 2011 (UTC)

Link Spam, Fender Article

I have posted some material to Talk:Fender_(vehicle) concerning recent removals of links stated to be spam. Please review. Thank you. Bradkay (talk) 18:51, 19 February 2011 (UTC)

effectiveness index

Hello,

I've never edited anything on wiki so I thought I get some feedback , you seem to be busy here. o:) 1st issue: http://en.wikipedia.org/wiki/Bicycle

Body of comments moved to Talk:Bicycle_performance#Force_effectiveness_index

Thanks for your time, and If you could guide me in some way or refer me to someone that may be able to help. I have the pdf's of the studies if you are interested

Thanks Coreyjbryant Coreyjbryant (talk) 03:13, 4 April 2011 (UTC)

You've raised an interesting point, so I've moved your comments to engage a larger audience. -AndrewDressel (talk) 20:03, 4 April 2011 (UTC)

DYK nomination of Two-mass-skate bicycle

Hello! Your submission of Two-mass-skate bicycle at the Did You Know nominations page has been reviewed, and there still are some issues that may need to be clarified. Please review the comment(s) underneath your nomination's entry and respond there as soon as possible. Thank you for contributing to Did You Know! Allen3 ^talk 20:52, 16 April 2011 (UTC)

Motorized bicycle

Hi Andrew. This edit to Motorized bicycle seems to have botched ref 27. It appeared to be a dead link anyway, so at the moment I've removed it. Thought I'd let you know in case you want to take a look at it again. --jjron (talk) 11:20, 17 April 2011 (UTC)

At first, it appeared that the entire Alberta, Canada site was down, but now it works and I found an updated link. Maybe they were undergoing a major update this morning. Thanks for bringing the problem to my attention. -AndrewDressel (talk) 13:55, 17 April 2011 (UTC)

In case it goes down again, it may be jelpful to use http://www.webcitation.org/ to create and use an archive of the page in question. Schmidt, ^{MICHAEL Q.} 06:05, 18 April 2011 (UTC)

Article in Science

You may have seen this already, but in case you haven't I thought I'd give you a heads up that Science published an article on Bicycle Stability. The abstract is avalable free here, but you have to pay to read the full thing. I think I'll have to pick up a copy, dead tree style. --Keithonearth (talk) 05:22, 28 April 2011 (UTC)

Hey Keith! Great to hear from you. It's been a while. Congrats on getting your pictures on Sheldon Brown's site. Sorry if that happened long ago and I just didn't notice.

Anyway, yes, I did see the Science piece. It got some great press coverage. Very exciting. I've tried to update bicycle and motorcycle dynamics, and I created a new article on the two-mass-skate bicycle. There are links at the bottom to the authors' own sites that have PDF copies of their preprints that they are allowed to post for free. There is also a ton of additional material there as well, if you're into that sort of thing. -AndrewDressel (talk) 12:36, 28 April 2011 (UTC)

I'm glad to see you're still here working on the bike articles. I've not been editing much on Wikipedia for a while. I was excited to see my images on SheldonBrown.com! What more could a bike geek ask for? Keep up the good work. --Keithonearth (talk) 06:11, 2 May 2011 (UTC)

counter-steering

Forgive me if I just describe what I understand of counter-steering, rather than answering your questions directly. If a single-tracker is in an auto-stable configuration and the rider does nothing, it will continue in its stable state. If the rider needs to swerve, he/she will have to do something. If his/her hands are on the handlebars, the effective option is to apply steer torque to the bars but, if they are not, leaning the upper body will supply a much reduced form of control, limited in terms of bandwidth and difficult to manage if large amplitudes are used in an attempt to swerve vigorously. Let us imagine that the hands are on the handlebars and steer torque control is to be employed. If the rider has lots of preview of the need to swerve, then optimal rider control theory suggests that the most reward for least effort is obtained by steering well ahead of any obvious path change by very gently exciting the machine in a lightly damped eigenmode, using resonance effectively to build up a response with marginal effort. If the preview is not available (a dog runs into the road right in front of the bike, say) the bike must be steered the "wrong" way to set up the lean angle (bank to turn, like an aircraft) to enable it to swerve quickly enough to avoid the obstacle, or whatever. The steer torque to initiate the action must be in the "wrong" direction, but the self-steering mechanisms of the bike will act, so that the steer angle will change with time.

On the other hand, if the bike is not in an auto-stable state, all the rider has to do to initiate a turn is to stop stabilizing the machine, which will start to capsize in one direction or the other. Again, if the turning is not fast enough, some more vigorous steer-torque action will be needed. Robinssharp (talk) 20:44, 13 May 2011 (UTC)

Betrayal (1929 film)

• ...and about your edits to Betrayal (1929 film)... You got me thinking. The information you questioned was within the sources, but I simply had a citation in the wrong place. Read Hal Erickson's first sentence here where he addresses both your concerns when he writes that the film is "a part-talkie which represented the only screen teaming of Hollywood's Gary Cooper and Germany's Emil Jannings." Schmidt, ^{MICHAEL Q.} 06:43, 18 April 2011 (UTC)

DYK for Two-mass-skate bicycle

The DYK project (nominate) 06:03, 26 April 2011 (UTC)

Bicycle gearing

Thanks for tidying up the terminology. I'm planning further changes to this article, but I'll try and keep to the 'standard'. Murray Langton (talk) 12:43, 22 June 2011 (UTC)

Not at all. You're doing all the heavy lifting. I just cleaned up a couple of simple things I spotted from the sidelines. -AndrewDressel (talk) 09:24, 23 June 2011 (UTC)

Shimano innovations

You reverted an edit from a few days ago in the Shimano article. I agree that it was not my best edit, but there is still something wrong with that section. See my comments on the talk page: Talk:Shimano#Shimano innovations

Regards Nico (talk) 12:21, 7 July 2011 (UTC)

Bicycle page I noticed

Hi there. I noticed you created the page, Bicycle bell. I was surprised that this page was never on here before. I was wondering if you could consider making an article about the bicycle mirror. I mean, there are pages for practically all parts of a bike on here. Thanks! – Tinton5 (talk) 14:32, 7 July 2011 (UTC)

EL in Rigid body dynamics

This may be unnecessary, but good faith is sort of mutually synergistic so I thought I'd confirm with you that I'm still having a cool, detached discussion in the Rigid body dynamics talk page. I did get a little worked up inside at one point. If you sensed an aggressive tone, I'm sorry. I've been reading the WP guidelines and its a whole new world to me. Impressive user page. Keep up the good work.--Tennenrishin (talk) 21:08, 12 July 2011 (UTC)

If your tone did become aggressive, I didn't notice, so we're good. I did notice your addition to the text of the article and was going to say something positive about it, but now I see you've removed it. Why? After this brief personal exchange, let us keep the discussion on the article talk page. -AndrewDressel (talk) 06:40, 13 July 2011 (UTC)

Flat bar road bike Description in List of bicycle types

Hi Andrew,

Do you mind if I change your recently-inserted description of a flat bar road bike to, "a road bike fitted with MTB-style shifters, brake levers and a flat handlebar," which comes straight out of the main FBRB article? That seems more definitive than calling it an "in between" bike. Cheers, Ebikeguy (talk) 19:57, 14 July 2011 (UTC)

Not at all. That does sound better. -AndrewDressel (talk) 20:09, 14 July 2011 (UTC)

DYK for World Bicycle Relief

The DYK project (nominate) 08:03, 19 July 2011 (UTC)

Hi Andy...

Hi Andy. You're the first person I've bumped into on WP that I actually know. I made edits as 108.7.244.101 to Force that you refined. Neato! --Dave Rajczewski (brother of Karen Mackin from MapInfo, and also RPI '85) 108.7.160.63 (talk) 19:41, 27 July 2011 (UTC) (IP address changed since last night)

Great to hear from you. Great edits. Where are you these days? -AndrewDressel (talk) 06:00, 28 July 2011 (UTC)

Your comments etc in NuVinci CVT page

No need to apologize Andrew, I'm (virtually) new to Wikipedia editing, don't know much about it (my interest is in mechanical engineering and mechanisms - CVTs in particular), and your comments etc are helpful. Thanks. — Preceding unsigned comment added by 109.145.82.160 (talk) 11:33, 28 July 2011 (UTC)

Malvern Star

Hi Andrew,

I am new to Wiki, but my mother (Lauris) and I were looking up things about my Father's (John Lee) history. Malvern Star was a big part of his career. I have personally met Bruce Small and spent time with my father and Small's son Kelly at the football. The details of the Malvern Star Factory were missing from the Wiki Page and I thought my personal knowledge might be of interest as part of the Malvern Star Story.

I worked with my Father in these stores when I was a youngster and visited the Malvern Star Factory with him on a number of occasions.

I have, in my possession, several original Letters of Reference for job applications that my Father had applied for. These documents are singed by Sir Hubert Opperman himself. John Lee was well known to Bruce Small and Opperman.

The 'interview' is in the context of private information that my mother confirmed from her personal experience. These details have not been published anywhere else.

If you can tell me how to construct this wiki entry correctly I would be happy to oblige.

Chris Lee leefam@optushome.com.au

By the way. My fathers cycle blood runs deep as I am a 57 yo avid cyclist and complete about 5000 km annually. Completing the 250km Around The Bay recreational ride each year in my home town of Melbourne Australia. — Preceding unsigned comment added by 114.77.114.140 (talk) 10:46, 31 July 2011 (UTC)

Gyroscopic mechanism

Regarding the square gyroscope, I need to know if you could see my point or not. I understand that a contradiction is not popular, but it is a fact that the explanation of "why" a gyroscope does what it does was derived from a mathematical technique that was borrowed for the purpose of describing this effect. Angular Momentum WAS NOT discovered and then described mathematically. It's wrong in a perfectly orthogonal way, so it works, but not from causality.

This says so much about physics and its ability to let math dictate the reality. No one wants to hear that! Then I'm not sure how this message works, so I hope you get this. -Jnhrtmn (talk) 03:13, 7 September 2011 (UTC)

I think I see your point that the current article does not explain why a gyroscope acts as it does. Instead the article outlines the math that correctly calculates how it acts. If your point is that the math is incorrect, then I believe you are mistaken. I believe it is used to calculate too many things accurately to be mistaken. The point that I think you are not seeing is that Wikipedia does not allow original research. If you want to insert details about why a gyroscope acts as it does without the math, that would be great, but you need to find a reliable source to use as a reference. This one comes pretty close: http://www.newton.dep.anl.gov/askasci/phy99/phy99191.htm If you can find the book mentioned at the end of the first response, that would be a good start. -AndrewDressel (talk) 03:38, 7 September 2011 (UTC)

Lightfoot Cycles

Andrew, We do not understand why our additions to the Recumbent Bicycle page are being removed. Perhaps you could help us understand; your credentials certainly suggest that you have your finger on the pulse of this subject and Wikipedia itself. We have tried to follow Wikipedia protocol. We have not attempted to add links. The information we have put forward is credible and relevant. Lightfoot Cycles is an innovator, with a definite place in recumbent cycle history. My assistant Erica has followed protocol, as far as I can tell. Please clarify what might be the problem. Thank you. Rod Miner — Preceding unsigned comment added by Rod miner (talk • contribs) 16:45, 8 September 2011 (UTC)

I appreciate your difficulty, and here are some points, in no particular order, I've noticed that you should be aware of:

• When writing about your own product, you automatically have the real potential of conflict of interest, which is a big taboo here. Your inside knowledge can be a big help, but you have to be extra careful to supply independent references to back up your details. If "Lightfoot Cycles [truly] is an innovator, with a definite place in recumbent cycle history," then there should be plenty of independent sources that can attest to those claims.
• When editing, especially when changing a lot of text, it is very helpful to include an edit summary so that other editors can better understand what you have done. Without your guiding comments, they may simply glance at the changes you've made and make a snap judgement.
• In your most recent edit, you completely deleted the section on Hand-and-foot recumbent tricycles. I can't tell if that was just a mistake or not, and it was far easier to undo everything than deal with that one issue. A promoter of Sky Wheel attempts to insert their url directly into the article, but has been content with a single, though not especially unbiased, reference for a while.
• In your first pair of edits, you inserted the name of your company or product 3 separate times. Cruzbike, Flevo Bike, and RANS, are each mentioned once (though RANS also appears in an image caption, and Cruzbike is pushing things with two image captions). Subsequent edits, attributed to the same user account, did not appear to be substantially different, and so were treated the same way.
• Statements such as "Lightfoot Cycles pioneered", "first demonstrated commercially on the Lightfoot Ranger", and "four wheels can offer greater side-hill stability for off-road recumbents" all need references from reliable sources such as an article in a magazine.
• Finally, the fact that other flaws exist in an article is not a license to duplicate those flaws or add new ones.

If your goal is merely to level the playing field, thinking not-unreasonably that if other brands get a shout-out, why can't yours, I suggest you carefully work instead to remove other unnecessary brand mentions. For example, I don't see how "such as the RANS Dynamik" really helps make the point that "crank-forward designs that facilitate climbing out of the saddle also can be used off-road." Another approach, though no-less fraught with potential problems, is to write a new, separate article about your company. A link to it would certainly be appropriate in the recumbent bicycle see also section. Bicycle tire and others even has a section listing notable manufactures, meaning manufacturers that have their own articles. I have written several articles about companies and can't think of the last time I heard a complaint. Examples include: Wippermann, Hutchinson SA, SRAM Double Tap, and Santana Cycles. Note especially the use of non-corporate sources: nationally or internationally known news sources. Melon Bicycles is one that I helped clean up. Be forewarned, though that if it only contains links to the corporate web site, copies existing text from another web site, or reads like marketing copy, it is likely to be quickly deleted. If your company simply does not have the necessary notability, then that is where you should focus your efforts, and Wikipedia could have an article about it when it does.

I hope some of this helps. -AndrewDressel (talk) 18:28, 8 September 2011 (UTC)

Hello My name is Erica and I am trying to add some information that we feel is important to the recumbent cycle page. Would you help me? You seem to know how to site the information correctly. Thank you, -EricA — Preceding unsigned comment added by Rod miner (talk • contribs) 20:23, 15 September 2011 (UTC)

Sure. Which of the options I outlined above would you like to pursue? -AndrewDressel (talk) 20:35, 15 September 2011 (UTC)

Bicycle wheelbuilding

Comments requested on technical errors in Jobst Brandt's book:

Comments by page #

11. Concrete analogy is flawed. Concrete has no tensile strength. Post-tension tensile strength is "created" by "borrowing" from compressive strength at the cost of lower net compressive. Aluminum rims have both tensile and compressive strength, so there is no net benefit from pre-load other than stiffness.

30. That is stress/strain for plain steel, not stainless steel, actual spoke wire. Stainless is correctly shown on p125. To not understand the "bump" in the shown curve is to not understand the nature of strain aging and/or fatigue, and this misunderstanding leads to incorrect conclusions about "stress relief" later in the book.

35. Wheels do not collapse if spokes go loose. http://www.flickr.com/photos/38636024@N00/417157612 They become less stiff, but collapse is a function of rim strength, not spoke tension. As above, since rim alloys have compressive strength as well as tensile, superimposed compressive pre-load merely reduces capacity for applied load.

39. The left-most ellipse shows "negative tension" - impossible in wire.

46. Only some spokes are swaged (hammered). Others are drawn or ground to shape. Brandt uses the term "swaged" where he should be using the term "butted" - the generic.

57.1. Anodizing is not observed to cause rim cracking. Metallurgical analysis shows it to be a function of excess spoke tension and rim extrusion anisotropy.

57.2. Ceramic does not cause rims to overheat. See thermal conductivity of alumina/titania vs. thermal conductivity of aluminum alloy.

71. See 35.

72. "Correcting the spoke line" is a misnomer - bending a spoke before the hub hole has deformed is by definition going to create a non-alignment with the final form.

74. "Stress relieving" is a misnomer and incorrect supposition. Spokes are observed to initiate fatigue only in regions of high bending stress, not high residual stress. Since they do not coincide, there is no correlation, thus it is fundamentally incorrect and misleading to suggest that metallurgical stress relief is either effective or even being achieved. The practice of over-tension is beneficial in that it serves to embed the spokes in the hub and rim, thus helping to ensure tension evenness and consistency, but this does not and cannot metallurgically address fatigue directly as postulated.

105. The method described causes excess spoke tension. See 57.1.

119. The "formula" fails to account for spoke stiffness. Spokes of the same dimensions but different materials will deflect differently. Observe the Park Tools tensiometer calibration chart for 2.0mm titanium and 2.0mm stainless steel spokes. http://www.parktool.com/documents/ee5fb98f0f91e4f6be32f7b1e0b9f12b10a74bf0.pdf

123. In the "scientific method", the format is Objective, Method, Results, Conclusion. Brandt does not give results, only his conclusion. To credibly contest an industry practice, he needs to publish a table of measurements to allow others to compare and do their own statistical analysis.

131. This is a load calculation, not a strength calculation. It is incorrect and impossible to use load to postulate conclusions about strength. Industry shill (talk) 06:04, 30 September 2011 (UTC)

These details are fascinating, but by now I hope you realize the difficulty with using them on Wikipedia. Without some recognized reliable source stating that there are "several serious technical and math errors" in the book, any attempt to say so will be considered original research. Has this been published anywhere else? -AndrewDressel (talk) 13:27, 30 September 2011 (UTC)

Understand, but at the same time, why would self-evident mistake (eg 11, 30, 39, 46, 57.2, 119, 131) require citation? I can "cite" sources for flat earth theory, but that doesn't make it correct. But this said, each point (this is merely a compilation) has been on rec.bicycles.tech and thus searchable on Google Groups for many years, Re-posting hundreds of pages of r.b.t. is a daunting task, but if this is something you feel strongly about, since you're clearly interested in this field, you could start a (collaborative?) examination that would be citable.Industry shill (talk) 16:31, 30 September 2011 (UTC)

I am interested. Let's talk off-line. You can find an email address here. -AndrewDressel (talk) 16:51, 30 September 2011 (UTC)

Alternate versions of images

I noticed you are the creator of several good diagrams and charts. There are a few in JPEG format, and I was wondering do you have PNG or SVG versions of any of these, or any format without compression artifacts?

• File:Tilting_ball_variator.jpg
• File:Friction_in_a_banked_curve.jpg
• File:Hands_off_steer_angle.jpg
• File:Steer_angle_and_lean_angle_vs_speed.jpg
• File:Bike_lean_angle_vs_speed.jpg
• File:Countersteer_response.JPG
• File:Bike_external_forces.jpg

Thanks! —danhash (talk) 20:29, 12 October 2011 (UTC)

Re:Image:Free Body Diagram.png

Do you have the source to your diagram Image:Free Body Diagram.png? It needs to be modified, since it shows the frictional force going through its true line of action but the normal reaction going through the block's centroid, which is not, which is somewhat misleading. Thanks, BigBlueFish (talk) 16:08, 9 June 2008 (UTC)

Not handy. I just drew it in MS Word, then pasted it into Paint to save it in PNG format. To where do you propose to move the normal force arrow? Its exact location is not known without additional information and further analysis. -AndrewDressel (talk) 16:26, 9 June 2008 (UTC)

I may stand to be corrected, but since the weight acts through the surface of contact, the normal reaction must act through the point on that surface vertically below the centre of mass, or there would be a net rotational acceleration. BigBlueFish (talk) 16:39, 9 June 2008 (UTC)

That would eliminate any moment due to the gravitational and the normal forces if they were in opposite directions, which they are not, and would not address the moment generated by the friction force. All of this only applies to the static case, which is not given. In fact, if the coefficient of friction is zero, then the normal force is correct as drawn. Otherwise, the acceleration must be known in order to correctly place the single, resultant normal force arrow. -AndrewDressel (talk) 16:50, 9 June 2008 (UTC)

If their lines of action intersect then there is no moment regardless of direction. BigBlueFish (talk) 17:06, 9 June 2008 (UTC)

This contradicts your statement above. Since the normal force is not parallel to the gravitational force, their lines of action will always intersect somewhere, no mater where the normal force is applied. That would mean that the normal force and the gravitational force could never create a moment, which is not true. -AndrewDressel (talk) 19:44, 9 June 2008 (UTC)

The normal and gravitational forces only produce a moment if the weight acts outside the surface of contact. Within this boundary the forces must cross on the surface or the frictional force exerts a moment with the other two. BigBlueFish (talk) 20:57, 9 June 2008 (UTC)

Yes, for a three-force member in static equilibrium. However, there is nothing about the diagram or the article that states that the block is not moving. -AndrewDressel (talk) 01:02, 10 June 2008 (UTC)

Even in a dynamic case the block has no angular acceleration, and all acceleration occurs in a plane perpendicular to the normal reaction, so it is not affected. BigBlueFish (talk) 17:06, 9 June 2008 (UTC)

No angular acceleration is necessary for angular momentum to be a factor. A braking car will experience "weight shift" to the front wheels even if the suspension and the wheels are rigid. No rotation is necessary for this to occur. -AndrewDressel (talk) 19:44, 9 June 2008 (UTC)

Forgive me if I find this a little hand-wavey. I'm not aware of any case in which the vertical force on the wheels of a braking car is imbalanced, or indeed there would be a net moment on the car. A truly rigid car has no angular momentum because its path has an infinite radius of curvature. BigBlueFish (talk) 20:57, 9 June 2008 (UTC)

No hand-waving necessary. It follows directly from the definition of angular momentum about a point, H_p = r_/p x mv, and the correct application of angular momentum balance. You may read about it in the Bicycle and motorcycle dynamics article. The citation includes a link to a PDF copy of a statics and dynamics textbook published by Oxford University Press. -AndrewDressel (talk) 01:02, 10 June 2008 (UTC)

Besides whatever effect or phenomenon you're trying to describe, the simple case that the diagram is trying to describe either shows a block in mechanical equilibrium on a plane or a block sliding down it, both of which are cases in which the free body illustrated experiences no net moment. BigBlueFish (talk) 20:57, 9 June 2008 (UTC)

There is no net moment only in the static (or constant velocity) case. If there is acceleration, then the net moment about any point must equal the cross product of the position vector from that point to the center of mass with the product of mass and acceleration vector of the center of mass:M_p = r_cm/p x ma_cm. Using a point that coincides with the center of mass provides no information, of course, because the position vector has zero length: the net moment about the center of mass is zero.

As for what I am showing in that diagram, it happens to coincide with option c of the three "sensible" ways to represent contact force distributions shown on page 95 of the same textbook mentioned above. One more option I've seen in a different text that is slightly more complicated is to indicate an unknown distance "d" from one edge to the point of application. -AndrewDressel (talk) 01:02, 10 June 2008 (UTC)

I come back to this rather old discussion. I agree with Bigbluefish. If we compute the net momentum at the center of mass, then we find that the object has a rotational acceleration due to ${\vec {F}}_{f}$. If we calculate it at the point of application of ${\vec {N}}$, then we find that the object has a rotational acceleration due to ${\vec {P}}$. Etc. This is not possible because the plane prevents the object from turning. This is far different from the bicycle where the link allows an inclination; a planar link between objects does not allow inclination. (Sorry if the technical vocabulary is not accurate, I'm not a native french speaker.) -cdang|write me 07:51, 4 October 2011 (UTC)

Your analysis is only true if the block is stationary. If the block is accelerating along the ramp in either direction, then the sum of moments about a point will not be zero. I do not understand what you are saying about a bicycle and a link. -AndrewDressel (talk) 21:12, 4 October 2011 (UTC)

I partly agree, what I claim is only true if the frame of reference is inertial, and if the inclined plane is not rotating in this frame of reference; we talk about torque, so this is not a matter of acceleration but of angular acceleration: the m⋅a vector applies at G. Forget about the bicycle, it's not so important. Anyway, nothing in the picture or in the caption tells that the ramp could be rotating, or that the frame of reference is not inertial; thus, your picture is misleading, as most people would consider this. -cdang|write me 08:16, 17 October 2011 (UTC)

I have not assumed an accelerating reference frame or that the ramp is rotating. I have also not assumed that the block is stationary. I should have stated above "If the block is accelerating along the ramp in either direction, then the sum of moments about a point other than the center of mass will not be zero. No rotation, only non-zero acceleration, is necessary for angular momentum of the center of mass about some point that is not the center of mass to be non-zero. Again, I refer you to page 95 of this textbook. I have chosen the simplest of the three options for modeling the unknown distribution of contact forces between a block and a ramp, when the acceleration of the block remains, as yet, unknown. -AndrewDressel (talk) 13:39, 17 October 2011 (UTC)

• The sum of the moments of the forces about any point is always the same: if you change the point, you change the moment arms, but you do not change the sum.
• In point particle mechanics, the Newton's second law of motion states ∑F = ma. In rigid bodies mechanics, you add ∑M_A(F) = Iα, where A is any point, center of mass or not, the result is always the same.
• The sum of the moments of the forces about any point is not zero on your picture, therefore an angular acceleration α.
• The p. 95 of the textbook mentions the existence of a couple; there is no couple drawn on your figure. What we, BigBlueFish and I, suggest, is that you represent the "Equivalent force with no couple" (to refere to the textbook). Or that you represent the couple (turning arrow) that set α to 0. -cdang|write me 15:14, 17 October 2011 (UTC)

• The sum of the moments of the forces about any point is always the rate of change of the angular momentum about that point. For a body translating without rotation, the rate of change of angular momentum about the center of mass is zero, and the rate of change of angular momentum about any other point is only zero if there is no acceleration. Thus the sum of the moments about the center of mass will differ from the sum of the moments about some other point for an accelerating body even in pure translation.
• In rigid body mechanics, Euler's second law of motion states ∑M_A = ^d/_dtH, which in 2D can be expressed as r_cm/A x a_cmm + I α
• That the sum of the moments about a point other than the center of mass is non-zero does not mean that angular acceleration is non-zero, but only that the center of mass is accelerating either translationally or rotationally.
• Page 95 of the textbook states "In 3D ... A couple may be required." Since the block on a ramp can reasonably be modeled in 2D, I see no reason for the existence of a couple.
• You may argue that a different free body diagram example might be more appropriate for pedagogical reasons, but I do not believe that you have yet shown any technical errors with the current version. -AndrewDressel (talk) 17:04, 17 October 2011 (UTC)

Yes I argue that a different free body diagram example is more appropriate for pedagogical reasons, no I did not shown any technical errors with the current version.

Concerning the calculation, the english notation is a bit unsusual for me, and I don't have the time to write some math yet (maybe later). Here is thus a graphical consideration: mind that the N and F_f vectors are just the model of a mechanical action; there is just one mechanical action, the action of the ramp on the object, which can be represented by a single vector R, and this vector can be decomposed in N and F_f, see File:Reaction support avec et sans frottement alt.svg.

Now draw your diagram with just mg and R; if mg and R are not on the same line, then you have a couple, therfore an angular acceleration.

cdang|write me 15:30, 18 October 2011 (UTC)

Andrew's free body diagram represents a classic one that could have come straight out of any number of textbooks. Breaking the force vectors into normal force and frictional force is exactly what I was taught when learning to draw such diagrams. Of course there will be a couple present when N and mg are not parallel, but the fact of its existence does not require that it be shown on this diagram. If you can come up with a better diagram, by all means do so, but understand that this diagram is exactly the form that engineering students in the USA are taught to draw. Ebikeguy (talk) 19:31, 18 October 2011 (UTC)

I'll bite anyway. The current free body diagram shows the general case: the dimensions of the block, the angle of the ramp, the coefficient of friction, and the acceleration of the block are all unspecified. The forces generated by the ramp on the black may be modeled in a variety of ways. If we choose to model them with orthogonal frictional and normal components and then model the normal component as a single resultant force, the actual location where it may be considered to act can only be found in three particular situations without calculation: zero angle, zero friction, or zero acceleration. The current diagram happens to be correct for the middle case, zero friction, but that is not its goal, and it only implies angular acceleration if the translational acceleration is known to be not equal to $g(sin(\theta )-\mu cos(\theta ))$. Instead, this general case shows the use of the free body diagram as an analysis tool, not merely a graphical depiction of some precalculated result. The exact location of a single normal force is not known and so is merely placed in the middle.

Which free body diagram would you wish to show instead, and why? -AndrewDressel (talk) 02:02, 19 October 2011 (UTC)

OK, I uploaded a picture: graphics can show what calculations hide. Watch File:Pfd plan incline avec frottement.svg (please magnify to see the application point of R), esp. the right figure : non-inertial frame of reference link to the object, there is an inertial force F_ie = -ma. In this frame of reference, the object is at the equilibrium which means:

• equilibrium in translation, ∑F = 0, the forces form a triangle;
• equilibrium in rotation, the line of forces all go through the same point G:
  • the weight P applies at the center of gravity G, so its moment about G is 0,
  • the inertial force F_ie applies at the center of inertia which is also G, so its moment about G is 0,
  • the object is not turning so the moment of the action of the plane R about G must also be 0, thus G is on the line of the force R.

This means that R does not apply at the center of the downward face of the object (except for a specific valule of the coefficient of friction μ, which is definetly not the general case):

• in statics, it applies vertically below the centre of mass;
• in dynamics, it applies slightly besides the vertical to the center of mass.

If you decompose R into N and F_f, then you can place F_f anywhere on the plane, but N must be on an action line going through G (and having an angle φ = arctan μ with the perpendicular to the plane, i.e. on the cone of friction). Right?

So I recommend that N applies either at the vertical below G (statics) or slightly besides, but not at the center of the downward face of the object

cdang|write me 09:28, 19 October 2011 (UTC)

I uploaded another picture with a bigger inclination, so things are clearer: File:Pfd plan incline plus avec frottement.svg.

OK, in this case, R is quite far away from the vertical to G, it is closer to the center of the downward face, but it is not right at the center of this face. And this is quite caricatural: I have never seen such a slope in the real life.

cdang|write me 09:54, 19 October 2011 (UTC)

I do not understand what you have drawn at all. I asked "which free body diagram would you wish to show instead, and why?"

• They mistakenly show the ramp, which is supposed to be replaced by the forces it applies to the block in a free body diagram of just the block.
• What equations would you write from these diagrams? R + P + ma = 0? Then what? No coordinate system is provided in the diagram so it is not clear how to decompose any of these vectors.
• How would you find the magnitude of the friction force, the normal force, or the location of where a single normal force may be considered to act from this diagram?
• Do you really propose to introduce free body diagrams with a non-inertial frame of reference?
• The "cone of friction" it includes has not a single hit on Wikipedia, so that will take some further explaining and probably deserves its own article.

Instead, if you are still trying to prove that the normal force may not be considered to act in the middle of the face, why? I do not claim it is. I merely claim that its location cannot be known until further analysis is done, and the middle of the bottom edge is good enough to start. The free body diagram is a tool used to analyze a problem with unknowns, not merely a diagram to depict the results all neat and tidy. -AndrewDressel (talk) 14:57, 19 October 2011 (UTC)

Free-body diagram for a block on a ramp

I did not draw what you should draw (i.e. I did not draw free body diagrams), I just draw a picture that explains what I mean. This type of drawing is usual for low level students (e.g. vocational education) in France, they need to see things and have problems with abstraction (replacing an object by an arrow puzzle them). I don't suggest you to draw the cone (see below on that topic) nor to use a non inertial frame of reference; this non inertial frame of reference makes it easier to understand the problem of rotation (you don't need to introduce the angular momentum), and why R must be where it is.

To be clear, here is what I do not like in your picture:

• the F_f arrow is longer than N, which would mean that μ > 1; if ever this situation exist, it should be rather rare and thus not the general case; please draw F_f smaller than N (half would be quite enough);
• N acts in the middle of the face, which is not the general case.

I don't use equations here, I use graphic statics (statics = the reason why I need to replace ma by F_ie), which is more useful to draw correct diagrams. Here are some basics about graphic statics:

• cone of friction: if F_f = μ×N, then the angle between R = F_f + N (vectors) and the normal to the plane is φ = arctan (F_f/N) = arctan μ; this defines a cone, see File:Adherence traction horizontale.gif;
• R + P - ma = 0 or R + P + F_ie = 0; graphically, the sum of vectors is placing vectors one after each other, 0 means that the distance between the extremities is 0, thus a closed triangle; so if you know P, the direction of a (the ramp) and the direction of R (φ/normal), you can graphically determine the length of R and ma (you know 1 side of the triangle, and the direction of the 2 other sides) without calculation and thus draw a correct diagram even without any value;
• the line of forces must be concurrent in case of 3 forces that are not parallel; see File:Equilibre des forces 3 cables.svg, and search "graphic statics concurrent" (the case of 3 forces is very restrictive, it however allows the solving of numerous problems).

Finally, here is how the diagram should look. You can ask for deletion if you want, I will not use it because I mainly write for French wiki.

cdang|write me 15:54, 19 October 2011 (UTC)

This is all very nice, but it appears that you are confusing the free body diagram, a tool used to set up the equations of equilibrium or motion so that they can be solved for the unknown forces, with some kind of "graphic statics" diagram, a tool apparently used to solve directly for the directions and magnitudes of the unknown forces. I have checked several textbooks, and none mentions using the length of the force arrow to indicate the magnitude of the force, though I am familiar with the concept from graphical methods of vector analysis. Probably in the age of slide rules, such direct graphical techniques were probably better than converting to numbers only to manipulate them by other graphical techniques. In the age of digital calculators and computers, however, I believe the preferred technique is to manipulate the numbers directly, and it is probably far more scalable as well. -AndrewDressel (talk) 01:06, 20 October 2011 (UTC)

(I come back to the left because the indentation starts to be a little bit too big.)

OK, the free body diagram is just used to set up things and not to directly find the solution. However, it should not provide false informations, amongst which:

• F_f cannot be greater than N; the typical coefficient of friction range 0.1 (steel/bronze+lubrication)-0.8 (tyre/dry road), I don't know any μ higher than 1 (although I don't pretend it is impossible);
• the application point of N has no reason to be at the center of the face, this is important to figure out the couple that can be transmitted in a planar joint.

For the latter point, I have another explanation: the action of the ramp on the block is spread all over the surface, and has no reason to be uniform (no symetry). The bottom carries more weight than the top, so the contact pressure is more important at the bottom. N is the integration of this pressure, and is placed at its barycenter; this barycenter is on the down side, not at the center. When a vehicle accelerates, the weight is transfered backwards; this is the same here, so the application point moves towards the top when the block slides, but there is no reason why it should come to the center. It is not impossible, it is just exceptional, and is not likely to occur (unless the slope is very steep).

Placing N at the center is just like drawing an equilateral triangle to explain a general property (like ∑angle = 180°); it is not false, it is just misleading as one could think this is always the case. Got my point?

Concerning graphi statics: yes, it was invented before the calculators and computers. However, it is a powerful tool that allows teaching mechanics to students who have a poor level in math, which is my case. Additionally, it helps thinking, esp. in design: when designing in mechanical engineering, it is more useful to think "moment arm" than "cross product", because the calculations come only once you decided the general architecture.

Yes, calculations are universal and allow a big accuracy, and graphic statics only applies for planar problems and have a limited accuracy. But graphic statics is useful to make illustrations that provide correct information.

cdang|write me 07:20, 20 October 2011 (UTC)

No answer, I considere this discussion as "stable", which does not mean I considere I am right just because I was the last to talk. I copy the discussion on commons:File talk:Free body diagram.svg, so anybody can make his own opinion on the topic.

cdang|write me 14:20, 2 November 2011 (UTC)

Bottecchia article

Thank you, for the "useful" advice... — Preceding unsigned comment added by Vrgsmm01 (talk • contribs) 11:40, 4 November 2011 (UTC)

Humber bicycle

Hi,this message is for Andrew Dressel which has a bike similar to the Humber, one of my friends that has it would like to get rid of it if you're interested in buying it or someone you know thats willing to pay a good amount of money for it. My name is Fernando Colon and I'm from South Windsor, CT. If you are interested please e-mail me back at fernandocolon@live.com or call me at (860)-680-6797, thank you. — Preceding unsigned comment added by Fernandoshideaway (talk • contribs) 15:48, 12 November 2011 (UTC)

Fallbrook

I don't want to get into a long discusssion with you or others in the wiki community but the ability to use CVT technology (NuVinci CVP technology is a new class of CVT) in a varaible speed accessory drive is a sea change in CVT technology. It deserves to be identified as such. It not that different from the fact that others have tried to use a CVT in a bicycle without ever producing something that was commercially viable. NuVinci techology is affect other applications as well including primary transmissions. Incidentally, the Fallbrook Advisory Board consists of retired senior executives from Ford, General Motors, and Peugeot in addition to David Cole who is a respected elder statesman in the automotive industry. If they didn't believe that NuVinci technology was a radical development, they wouldn't be on the advisory board as their reputations are too valuable to them to be "hyping" something for personal gain. You list an impressive and knowledgeable background and yes, I have an association with Fallbrook which includes being a stockholder and a consultant. As such, I would be glad to put you in touch with one the senior technical people if you'd like to discuss how the technology is revolutionary and its application to accessory drives ties in directly.

For reasons that have nothing to do with my association with Fallbrook, I do not have a Wikipedia account that is associated with my name but you can reach me either via talk to GearfreeZone or bberkov@earthlink.net. — Preceding unsigned comment added by 64.73.224.162 (talk) 21:59, 6 December 2011 (UTC)

The NuVinci CVP appears to be an exciting new technology, and I would like to see it successfully applied wherever it can offer an improvement over existing technology, but that doesn't have much to do with an encyclopedia entry. First and foremost, Wikipedia is an encyclopedia that should only contain facts that can be independently verified and that should remain free of conflict of interest. Thus, when and if the sea actually changes and reliabale, third-party, non-affiliated parties report that fact, I would be happy to add that detail to the NuVinci Continuously Variable Transmission article myself. While I can certainly understand the desire for anyone associated with the technology to shout its praises to the rafters or even calmly state how transformative it will be, Wikipedia simply is not the appropriate venue. -AndrewDressel (talk) 02:35, 7 December 2011 (UTC)

I'm sure Fallbrook would be delighted if you or others who are knowledgeable would edit the article in fashion that the Wikipedia community finds more acceptable. The dilemma, however, is that Fallbrook has something truly new and unique with over 400 patents and 14,000 patent claims worldwide. For a variety of reasons, Fallbrook's press releases are carefully reviewed to make sure they don't make claims that cannot be substantiated and the Fallbrook website has various press releases describing validation testing and quotes from noted and reliable sources. The SAE doesn't publish articles that are marketing hype and David Cole is a noted authority. Fallbrook doesn't try to hide affiliations and just because there is a relationship doesn't mean that there is conflict of interest. Some firms apparently hire people who use pseudonyms to post copy and they can use references that may or may not check out. And there are a number of "pay for play" references cited all over Wikipedia as the basis for various statements. Fallbrook's purpose in putting material into Wikipedia is not to generate sales but to explain something about which there is still considerable skepticism. Skeptics who actually meet with Fallbrook under non-disclsure agrements typically come away amazed and believers. And anyone who rides a bicycle equipped with a NuVinci transmission has an experience unlike any prior riding experience. Even if it isn't appropriate for how and what they ride but the idea that someone could actually make a continuously variable transmission for a bicycle that works is a surprise to many. Similarly, the ability to improve both economy and performance at the same time has been thought to be difficult if not impossible. NuVinci's DeltaSeries(tm) prototypes show that it can be done. People like you who understand what's going on can help Fallbrook IF they are Wikipedia contributors and so motivated but at this stage there is a need and task to make people aware and Fallbrook pretty much has to do it. if Wikipedia had existed at the time Jonas Salk invented his vaccine, there probably would have been "editors" who would have rejected an article about it prior to its widespread adoption. I'm not arguing that NuVinci is a cure for the fossil fuel crisis but the point isn't completely far fetched.24.152.182.171 (talk) 07:12, 7 December 2011 (UTC)

It is completely understandable that a magazine article about a potential new technology will be full of statements such as

• There is potential to resolve this seemingly inflexible conflict...
• this may permit use of smaller accessory components...
• The total accessory package potentially can be made smaller...
• A new type of CVT developed by Fallbrook Technologies offers the potential...
• the products in its development pipeline provide...
• this should provide attractive economic and fuel efficiency benefits.

In an encyclopedia, however, these are considered weasel words, and they simply have no place. If and when these innovations come to market and are reported on as established facts, then I will be happy to add them to the article. Until then they simply must be omitted. -AndrewDressel (talk) 15:26, 7 December 2011 (UTC)

Wolfram and hot air balloons

hello. i see that you removed the external links pointing to the wolfram scientific formuli for hot air baloon lift, fair enough that you may deem them unfit to be appended to the 20 line formula explanation text, but they certainly belong in the external links addendum, i spend 45 minutes researching them.

worlfram is a non profit informational scientific website which happens to be able to provide interactive hot air and helium baloon formulas.

seeing as the external links tab in hot air baloon is empty, i hope you havent removed all the links that were ever posted there.

i will post the wolfram hot air baloon formulas again in external links, if you wish to remove them perhaps we can see laterally in wiki what others think.

regards ant stewart — Preceding unsigned comment added by 92.145.143.37 (talk) 09:48, 13 December 2011 (UTC)

Turns out, I didn't have to remove them. Some other editor also found them to be link spam before I could take a look. Although Wolfram Research offers the capabilities of their scientific calculator free to the public, they are far from being a nonprofit organization. -AndrewDressel (talk) 01:43, 14 December 2011 (UTC)

please help me

i study mechanical engineering and i have to design a Center Pull Brakes for machine design lesson so i want if u can help me in this subject at first i want to know how can i do stress analysis with computer(which software?) & how can i find the best material for it? thanks — Preceding unsigned comment added by Ahmad353 (talk • contribs) 06:41, 28 December 2011 (UTC)

please help me

∇∂∆ i study mechanical engineering and i have to design a Center Pull Brakes for machine design lesson so i want if u can help me in this subject at first i want to know how can i do stress analysis with computer(which software?) thanks — Preceding unsigned comment added by Ahmad353 (talk • contribs) 06:44, 28 December 2011 (UTC)

Schwinn Doctoring Bicycle History

I posted the page I listed because the Wiki Schwinn Page says Al Fritz went to Cali in 1962 and found out about the High Rise Movement. This is untrue because Al Fritz has many Interviews where he tells he went in 1963 to Cali. I posted the page that is an interview with Al Fritz about going in 1963. Somebody has changed the Schwinn page to say 1962 so they can further their Myths and lies to be the first High Rise Bicycle. The other page I posted which is an article from a 1963 Newspaper shows Peter Mole and Huffy having a press release about the new Huffy Penguin High Rise bicycle. The article dates itself to March 3rd 1963. Which is exactly a month and a half before Schwinn even put together a proto type of the Stingray. This is why people no longer trust Wikipedia it has been hijacked by people who want to see history through clouded eyes! I will not stop until you people stop posting biased info to further their agenda! I just want the truth posted!

http://en.wikipedia.org/wiki/File:March_3rd_1963.jpg — Preceding unsigned comment added by HuffyHistory (talk • contribs) 21:54, 15 January 2012 (UTC)

That is all fine, and I want to get these article correct as well, but the images you have posted do not prove your point. There is no year visible anywhere in the image that you have titled "File:March 3rd 1963.jpg". For any of these images to be useful, they need the same information any other decent reference requires: author, publisher, and date. -AndrewDressel (talk) 22:52, 15 January 2012 (UTC)

13:54, 25 November 2011‎ AndrewDressel (talk | contribs)‎ (9,582 bytes) (Undid revision 462399811 by Treesme still commercial according to the "about" tab.

Hi Andrew,

I have undone the change you made (see above reference). Just to explain about the 'none commercial site' part. We did sell bike trailers about 2-3 years ago, but no longer do so. We left the site active, as some pages contain information about buying trailers. Also we gained knowledge selling trailers, so we thought we may as well pass this on to buyers - Hence the link to 'buying a bicycle trailer'. We occasionally get people e-mailing general queries about trailers and it seems a waste letting the knowledge gained, (having sold them in the past) go to waste. The link is only there to help others who might be buying a trailer.

P.s. The advertising on the site is to cover the hosting costs (which helps, but still doesn't cover all the costs).

Kind regards,

Mark & Marie Treesme (talk) 11:44, 22 January 2012 (UTC)