User talk:AndrewDressel/Archive 3

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Chicken strips

OK doke. --WoohookittyWoohoo! 17:31, 2 February 2008 (UTC)

Bicycle and Motorcycle Dynamics

Yeah, no worries. I know how hard to swallow a delist can be, and how long articles can sit once nominated. Some editors doing sweeps put articles "on hold" for a week to see if improvements happen—I've found that rare enough that it's easier to delist and relist if necessary. Thanks again for you prompt, hard work after my comments! --jwandersTalk 20:25, 14 February 2008 (UTC)

You're Welcome

I fix typos wherever I can, glad you appreciate it. My time at RPI has been a great few years. Thanks for the note on my links, all better. It's incredible that you helped found MapInfo. The Formula SAE team actually uses the parking lot behind the headquarters for trial runs and tuning. Also of note is the Formula Hybrid team which was recently founded. Next time you're in Troy, stop by either shop. The teams could probably benefit from your experience with bike/motorcycle dynamics. Lombar2 (talk) 07:44, 26 March 2008 (UTC)

Cyclocomputer sensor caption

Hi! This may sound really trivial and petty... scratch "may sound", it is really trivial and petty, but...
The caption for Image:Cyclocomputer_sensor.JPG reads "A wired Hall effect sensor with spoke mounted magnet." Me, I'd much rather have computer which works by interesting Hall effect than by a boring old reed switch. Tesla and Edison pretty much irrelevant to this, but as famous engineers go, who's the more interesting?
Naturally enough, instead of looking for reliable, verifiable and peer-reviewed reference info, I did some good old fashioned Original Research. The sensor in the pic is the sensor unit for a Cateye cyclocomputer. Got similar Cateye sensors on my bikes. Waved a fridge magnet at them (sensors, not the bicycles) and could hear a teeny "pink, pink, pink" of what I guess is a reed switch, as the cadence read-out displayed 199.99 and my maximum trip speed went up from 35kmh to 92kmh.
Admittedly, my sensor kits (like my bikes, and myself) are all pretty ancient. Going by the forks' paintwork, the forks (Reynolds tubing? Columbus?) and their dropout pattern, and the QR skewer's cam lever and retaining nut, the bike in the pic looks like an oldie-but-goodie. The sensor unit looks newer. However, I don't think Cateye would have more latterly changed from reed switch to Hall effect sensors - Hall effect sensors apparently have magnitudes larger current drain on head unit batteries. Do you think the pic caption should be altered?
--Shirt58 (talk) 11:34, 26 March 2008 (UTC)
ps: Is that an old Avocet hub-mounted sensor magnet in the pic? Now, they used Hall effect - and this comment may be even more completely wrong-headed than it is already...

Free body diagram

Hi. I ran into Image:Free_Body_Diagram.png this evening and I was wondering what software you used to generate it. I have occasionally wanted to draw diagrammatic stuff and gotten stuck somewhere between Paint (too little) and Illustrator (often too much). Thanks in advance for whatever tips you can offer. --Dvortygirl (talk) 02:38, 20 May 2008 (UTC)

Re: Bicycle tool kits and French chalk

Specifically this bit At the least this will include a tire patch kit (these contain tube-patching material, an adhesive, a block of French chalk and a metal grater to reduce the chalk to powder

I've seen this around so they're available at least in the UK, no idea what merits the inclusion of "Many" cyclists carrying them however. SeveroTC 14:29, 23 May 2008 (UTC)

I can't verify "to reduce the chalk to powder". I was going to offer to take a picture of a kit I have in the other room with a metal grater and chalk, but the chalk has gone missing! SeveroTC 10:18, 29 May 2008 (UTC)

Your source is wrong, also needs better reference, half true! —Preceding unsigned comment added by Indwisdom (talk • contribs) 20:25, 28 May 2008 (UTC)

Edits to Bicycle

Hi Andrew—That's really strange. Actually, the edit was to remove the piping in the wikilink, which is always done. But I removed the grater --> greater edit, as you pointed out. Why AWB got the two mixed up, I have no idea. Perhaps I should stop allowing AWB to provide the Edit Summary. Do you know if it commonly makes ES mistakes like this? In any case, thanks for bringing this to my attention. --AnnaFrance (talk) 15:29, 26 May 2008 (UTC)

Bicycle and motorcycle dynamics

Looks like a fascinating article, but I see from the talk page that the WP:GA group thinks it needs a copy-edit, that it doesn't follow WP:MOS guidelines. I'd be delighted to see if I can help with this effort. I think I could get started tomorrow. Thanks for letting me join the group. --AnnaFrance (talk) 17:17, 26 May 2008 (UTC)

Bicycle and motorcycle dynamics talk page archive

I left you a message on the talk page today about the Instability section, and that I was going to try my hand at archiving the talk page late tonight. I have just done that, and it appears to have worked just fine. If you didn't see my message earlier, this will give you a chance to check out the archive, which is where that message is now. --AnnaFrance (talk) 04:36, 1 June 2008 (UTC)

Bicycle and motorcycle dynamics images

Wow. That's bizarre. How could text and images get mixed up in a table? IE must be unusual, because we tested with several browsers on Macs and PCs, to make sure everything looked just right. Anyway, so the images are in bad shape as they stand now. I guess you'd better fix them. --AnnaFrance (talk) 02:30, 17 June 2008 (UTC)

Dangerous old books

I recently acquired a reprint of one of the coolest old books and was reading some of it today. I like to read it, it doesn't make me want to change my gender but it helps me to enjoy the other (I am old school, and think that there are only two of these...). One of the chapters might contain information that would be good for a balloon article -- I am not familiar with the structure of those articles here enough to add it though. Here is as beautiful of a citation filled out that I can make for it:

  • Beard, Daniel Carter (1890). "Chapter XV: Fourth of July Balloons with New and Novel Attachments". [[The American Boy's Handy Book]]. Retrieved 2008-06-26. {{cite book}}: External link in |chapterurl= (help); URL–wikilink conflict (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)

If you already knew of this, forgive me for the redundancy. -- carol (talk) 04:40, 26 June 2008 (UTC)

Eigenvalues

Hi Andrew,

I'm unfamiliar with the conventions for contributing to Wikipedia, so forgive me if my note to you is inappropriate. I just put the following comment in the "Talk" section for "Bicycle and motorcycle dynamics". Since you seem to be very active on bicycle related articles, I thought I would ask you directly. I'm very puzzled about the "Eigenvalues" section:

It appears to me that the capsize speed and the weave speed are reversed, both in the text, in the eigenvalue plot and in the PDF reference [17] by Meijaard, et al. My own experience is that at low speed a bicycle will "capsize" (fall over without any weaves), while at high speed on a poorly designed bicycle the weaves can increase in amplitude until "failure". I'm not an expert, nor a prior contributer to Wikipedia, so I hesitate to make any changes. Maybe the text is simply very confusing and in need of editing (if so, I could easily manage that!).

I guess it is not standard practice to give email addresses, but I don't mind giving mine: srwenner@verizon.net. —Preceding unsigned comment added by 70.19.219.159 (talk) 23:09, 13 July 2008 (UTC)

The text currently glosses over a mode that perhaps matches what you describe. Before the two most positive eigenvalues coalesce into a complex conjugate pair, which indicates oscillation, they indicate simply falling instead, as an inverted pendulum. It is only when the complex components show up, at about 1 m/s, that the weave oscillation begins. Perhaps that better matches your experience. You or I should add that detail. -AndrewDressel (talk) 23:38, 13 July 2008 (UTC)

Countersteering

Yes, a fascinating discussion. I feel like I'm always on the edge of totally understanding the topic, but never quite there. I guess it's a bit like balancing a bike... This article and your comments have been very illuminating for me. By the way I just added a Countersteering#Bicycles section which hopefully you agree complements the existing Motorcycles section that now follows it. --Serge (talk) 19:06, 7 August 2008 (UTC)

Cogset article

Hi, I see you've been editing the cogset article, and seem to be active on wikipedia and very knowledgeable about bikes. I think I may have changed a few of your edits, I hope you don't mind.

There seems to be a lot to do on the bicycle articles here, I'm open to any suggestions of where to start (I've only edited wikipedia very occasionally, but would like to put some work in to the bike stuff.)

That's a good point about most single speed (non-bmx) bikes using a coaster brake, I'd not thought of that. That's probably true for N. American, (I'm Canadian), but I was thinking of the Asian Utility bikes when I wrote that... maybe I can make that make sense. --Keithonearth (talk) 00:43, 29 September 2008 (UTC)

Keep up the good work. If you get a chance, perhaps you could take a look at Bicycle and motorcycle dynamics, Bicycle and motorcycle geometry, and Bicycle performance. -AndrewDressel (talk) 12:59, 30 September 2008 (UTC)
Thanks for the encouragement, and Awesome job on the freehub/threaded-hub diagram. I skimed over those articles mention and I gotta say, they intimidate me. I love the bikes, but my knowledge (and collection of reference books) is the nuts and bolts. Don't know 'bout that physics stuff. I'll look them over all the same, maybe there be a few little things I could add. --Keithonearth (talk) 05:13, 1 October 2008 (UTC)
Hey, I was thinking of editing your Freehub_vs_freewheel_hub to do a cut away section of each to show the bearings. (well, at least to try to) What did you use to make it? Would you have a svg (or other format that inkscape can handle) kicking around somewhere?--Keithonearth (talk) 06:23, 5 November 2008 (UTC)
No such luck, sorry. I drew it in MS Word. I can send you that, if it would help. -AndrewDressel (talk) 14:09, 5 November 2008 (UTC)
Thanks for the offer, but I don't think it'll be of use for me in that format. Maybe I'll just do some tracing.--Keithonearth

I seem to be stepping on your toes more than I mean to these days...sorry about that. I just replaced your diagram of a Freehub vs a freewheel hub on the cogset article. I hope you like it, but let me know if you don't. Maybe I/someone can change the diagram I put up. Or maybe both images could go up, but I think the article is a bit to small for that. Let me know what you think.--Keithonearth (talk) 09:13, 4 December 2008 (UTC)

trail and self stability

Either I missed it in the article, or the article left out the key factor in self stability, which is trail. This is easily demonstrated on bicycles where the front wheel can be turned backwards; by turning the front wheel backwards (assuming forward offset forks, the trail is increased a lot and the bicycle will almost come to a complete stop before falling over. Jeffareid (talk) 01:55, 18 October 2008 (UTC)

Perhaps the existing text inadvertantly emphasizes the influence of gyroscopic effects on self-stability, simply due to the order of the sections. While I don't doubt the experiment you cite, first we would need a published source for it not to be OR; and second, it only suggests that increasing trail lowers the lower bound of the stable range. It doesn't indicate that trail is necessary nor sufficient for self-stability. -AndrewDressel (talk) 14:09, 18 October 2008 (UTC)

On a side note, too little trail is one source of speed wobble. This was an issue for the first year production of Honda's 900 RR motorcycle, where speed wobble was an issue when these motorcycles were raced. In the second and later years, the forks were adjusted 3/8" back to increase the trail and eliminate the speed wobble issue. Jeffareid (talk) 01:55, 18 October 2008 (UTC)

All Cossalter says is that "wobble frequency goes up as trial increases and front-frame inertia decreases". He continues with "[it] is determined mainly by the stiffness and damping of the front tire, although the lateral flexibility of the front fork also plays a part." Can anyone verify that the amount of trail was the only change that Honda made? -AndrewDressel (talk) 14:09, 18 October 2008 (UTC)
It wasn't the only change, and Honda made the change much later than I thought. The issue created an aftermarket for triple clamps with more trail (less offset), and is mentioned in this Wiki reference to the 1998 model: 5 mm (0.20 in) less triple clamp offset (an almost universal aftermarket upgrade to previous models). Jeffareid (talk) 01:48, 20 October 2008 (UTC)


You are raising excellent points about the article. Thanks for taking a look at it. -AndrewDressel (talk) 14:09, 18 October 2008 (UTC)

Bicycle and motorcycle dynamics: trail and self stability

Perhaps you could help out here when you get the time?

Regarding bicycles (or motocycles) I've alway's thought that main source of self stability was fork trail. I've read this in numerous articles, that included the results of actual testing of real bicycles where the trail was varied from negative (no stability) to very positive (lots of stability). However, Andrew Dressel appears to be disputing a relationship between trail snd self stability.

In all the excitement, you might have missed that I actually am Andrew Dressel. -AndrewDressel (talk) 19:49, 18 October 2008 (UTC)

I've added the following section to the talk page:

trail and self stability

I'm also confused about the capsize speed, since I've never experienced this. The eigenvalues section includes a diagram showing that some model of a bicycle will go unstable at around 18mph. However this speed seems slow. A winning racing bicyclist often goes hand free at the end of a race, well over 30mph, with no apparent instability. Motorcycle races sometimes fall off their bikes at high speeds, and the bikes continue on with no apparenty instability.

Jeffareid (talk) 19:20, 18 October 2008 (UTC)

  1. The particular eigenvalues plotted are for a utility bicycle, not a race bike nor a motorcycle.
  2. A rider sitting up on his bike with his hands in the air is completely different from a riderless bike. Riding no-hands is not a demonstration of self-stability.
As the article already states: a capsize can happen very slowly if the bike is moving forward rapidly. Because the capsize instability is so slow, on the order of seconds, it is easy for the rider to control, and is actually used by the rider to initiate the lean necessary for a turn. -AndrewDressel (talk) 19:49, 18 October 2008 (UTC)

I've experienced turning a motorcycle at 100mph (not all out, but at about 80% of maximum grip), and the main difference is that the bike tends to hold it's lean angle (lean stability) as opposed to straightening up (vertical stability), when I wasn't applying any torque to the handle bars. I had to use the same amount of inwards counter steering to straighten up as outwards counter steering to lean over. It was similar to flying a plane with no dihedral effects, once banked, it just held the bank angle (the motorcycle at 100mph). At slower speeds, the motorcycle tends to straighten up and requires a constant amount of outwards counter-steering torque in order to hold a lean angle.

It sounds as though you are experiencing the different behaviours on either side of the so-called inversion speed. As the article already states: at speeds below the capsize speed, also called the inversion speed, the self-stability of the bike will cause it to tend to steer into the turn, righting itself and exiting the turn, unless a torque is applied in the opposite direction of the turn. At speeds above the capsize speed, the capsize instability will cause it to tend to steer out of the turn, increasing the lean, unless a torque is applied in the direction of the turn. At the capsize speed no input steering torque is necessary to maintain the steady-state turn. -AndrewDressel (talk) 19:49, 18 October 2008 (UTC)

I've always thought that the tendency to straighten up is due to the inwards yaw torque on the steering due to fork trail effect. Regarding the transition into lean stability at high speeds, I've always though that it was due to gyroscopic effets.

Jeffareid (talk) 19:33, 18 October 2008 (UTC)

  • I've read about the same neutral handling (no steering required to hold a lean angle) effect not having a known upper limit in articles about motocycle racing. It starts at around 100mph, and continues to feel the same up to the 200mph or so speeds that racing motorcycles reach. Most racing tracks don't have turns at this speed. Daytona has a 180+mph turn, but it's steeply banked. The main exception is the Ilse of Mann (it's a timed event verus a true race), where there are several 150mph to 200mph turns. The racers claim that 200mph turns feel no different than 100mph turns, no steering inputs are required to maintain a lean angle, stereing input are only used to change the lean angle. However the faster you go, the more counter steering force it takes to change the lean angle, and the force is quite large at high speeds. At slower speeds, 80mph or less, some amount of constant counter steering and/or hanging off the motorcycle is required to maintain lean angles to prevent the motorcycle from reducing the lean angle (returning to vertical). The reason stated for neutral handling at high speeds was gyroscopic effects, which resist any change in the roll axis. Yaw torque due to trail on the front wheel should result in some outwards roll precession, but the rate is very small and resisted by the rear tire which is larger and has more momentum. The reason usually given for vertical stability at lower speeds is fork trail. Jeffareid (talk) 20:51, 18 October 2008 (UTC)
There is a ton of conventional wisdom and lore out there, perhaps largely because the correct equations have been so hard to pin down and so opaque to conventional dynamic analysis. I have yet to see a convincing treatment that teases out what parameter is responsible for what behavior at what speed. That may not even be possible. Another part of the problem could be that there are so many parameters at play. I'm afraid the best we can do in this article at this point is point out that parameters that do contribute.
It may be true that racing motorcycles do not have a capsize speed, but I have not seen physical test data, and the one eigenvalue plot for motorcycles I have seen, by Cossalter, which does appear to have a finite capsize speed does not indicate how complete the model is. Perhaps it doesn't include tire effects, and they increase the capsize speed on real bikes. -AndrewDressel (talk) 22:15, 18 October 2008 (UTC)
Since that page you link to doesn't state a capsize speed, I'm guessing you are refering to the capsize speed stated in this wikipedia article. That value is merely an example calculated for one particular idealized bicycle. I've added some words that I hope make it clearer that the plot of eigenvalues is for one particular bike. -AndrewDressel (talk) 14:28, 19 October 2008 (UTC)
The capsize speed is shown in a graph on another article from Delft, and it appears to be the same bicycle: Koo06.pdf
The graphs shows capsize speed at below 8m/s, but the tread mill runs shows and states that the bicycle is very stable at 30km/s == 8.64 m /s. I'm waiting for feedback from someone at Delft, but my guess is that tire width is an issue. When leaned over, the contact patch is on the side of the tire, and this offset creates an outwards torque on the roll axis. Tire width and a rear tire much larger than the front tire may explain why the capsize "rate" is imperceptible on motorcycles at high speed. Jeffareid (talk) 23:07, 19 October 2008 (UTC)

slip angle

  • slip angle links (plenty of these at various web sites)

Slip angle

Not much for references. One of the three links appears to be broken. -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)

motorcycle slip angle

I'm leery of these guys. They also claim that the rear wheel and engine provide significant stabilization via gyroscopic forces (The third gyroscope), and they provide no credible source for such claims. -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)
I seem to recall some square 4 cylinder engines in racing bikes that had counter rotating flywheels, and the riders claimed to notice the difference. Jeffareid (talk) 04:13, 21 October 2008 (UTC)
  • camber thrust (again plenty links on this):

Article explaining camber thrust: tyres

While I don't dispute the final results, I don't like the argument used to develop it. They completely ignore the fact that bikes and cars have front and rear tires and the center of curvature is at the intersection of their axes. -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)

Tiny graph in this link: motorcycle tire information

Seems to agree with Cossalter: camber thrust generates more than enough centripetal force for cornering up to about 30 degrees. Below that, there will actually be negative side slip. Above that, side slip increases rapidly. -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)

Experiment disputing camber thrust: wheels that don't turn Scroll down web page for this link. It's currently broke though. A description of the experiment: Terry made a rig that consisted of two paper cups and a frame. The axles of the paper cups were parallel to each other. Even though the "outer" diameters of the paper cups were larger than the "inner" diameters, the rig rolled in a straight line.

Ignores the fact that camber thrust is caused by deforming the tire carcass, not simply by the conical shape. -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)
Which is why I'd like to see the experiment repeated with conical tires that would deform instead of slip. Jeffareid (talk) 04:03, 21 October 2008 (UTC)
  • my thought - camber torque versus camber thrust versus slip angle

A cone segment shaped tire turns in a circle because it's contact patch generates an inwards yaw torque as the tire rolls forwards, which causes the tire to turn (yaw) over time and travel in a circular path. The contact patch deforms in normal slip angle mode. As speed increases, the radius will become larger because the slip angle increases with centripetal force, which increases relative to speed^2. The point here is that the cone aspect of the tire creates a (yawing) torque, not a (centripetal) force.

Tires with non-zero camber angle can generate a yawing torque, a centripetal force, or some combination of the two. -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)

Now expand this to a vehicle with two cone segment shaped tires. The inwards yaw torque from the rear tire produces an inwards force on the front tire. The inwards yaw torque from the front tire is more complicated because the front wheel can yaw (steer). It would produce an outwards force on the rear tire if the steering angle was fixed or resisted by a rider. The net difference in these forces, could be considered camber thrust. These camber related forces would be added to the centripetal related forces on the tires, eventually ending up as conventional slip angle related deformations. Note that the inwards yaw camber torque at the front tire causes it to steer inwards, and this may be factor in capsize speed in the case of a riderless bicycle. Camber torque must be relatively small, because it doesn't prevent a riderless bicycle from being stable within reasonable speed range, and it doesn't exhibit itself as a significant torque felt at the handlebars by a rider.

Wilson and Papadopoulos, citing Cossalter, agree that tire "scrub" torque may be responsible for suppression of the capsize instability at high speed. -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)

If the two cone shaped tire vehicle had parallel axis, then I'm not sure what happens. Terry Colon did an experiment using paper cups, but the friction was low allowing slippage, and it's possible that the straight line was really a circle with a very large radius. Note that the yawing torque from each tire is resisted by a sideways force by the other tire, so I don't know if there is any net torque or force on the overall vehicle. I wonder what would happen if only one of the tires was cone like and the other was flat?

Jeffareid (talk) 21:02, 20 October 2008 (UTC)

I can find several examples of authors that claim that side slip causes centripetal force, instead of merely being a symptom of centripetal force. The best treatment I know of online is at http://www.dinamoto.it/ -AndrewDressel (talk) 01:28, 21 October 2008 (UTC)

In compliance with Newtons 3rd law, and rather than specify cause and effect, I was just trying to state that slip angle deformation coexists with centripetal force. It's my belief that the conical aspect so often referred to as camber thrust is actually a torque and not a linear force. I get the feeling that some of these articles are using the term camber thrust to include factors other than the difference in diameters of the inner and outer sufaces of a contact patch. Then again, perhaps I've generalized the term slip angle too much to include any deformation that results in the effective radius of a turn being larger than the no-load radius of a turn. Jeffareid (talk) 04:03, 21 October 2008 (UTC)
Regarding camber thrust, if a single tire is rolling along a banked track, does it turn uphill? Jeffareid (talk) 04:03, 21 October 2008 (UTC)

Stem (bicycle part)

Nice work on the Stem article! 842U (talk) 22:01, 24 November 2008 (UTC)

Don't mind at all. You made terrific edits, and every bit helps. 842U (talk) 22:14, 24 November 2008 (UTC)
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