| Author |
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Ceejay
| | Posted on Thursday, March 08, 2007 - 11:56 pm: | 
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Man that is a cool pic!!! |
Steve899
| | Posted on Friday, March 09, 2007 - 12:04 am: |
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I think so too! |
Reepicheep
| | Posted on Friday, March 09, 2007 - 08:50 am: |
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To really be able to correctly interpret that picture, You would have to know the mass of each rider and identify their center of gravity (which could be different even if they have the same mass) and then be able to accurately measure where their center of gravity actually is relative to the bike...
They front guy, leaned off the least, is also the "tallest" over the bike, which gives him more leverage for X lean.
I'm not arguing with you though, I expect I could get a PHD on the topic and still not completely understand why a motorcycle turns.
That is a cool picture!
I know (just from going in circles in a parking lot) that I can keep speed constant and keep the radius of my turn constant, and lean my body more or the bike less, or the bike more and my body less, and still carve the identical circle.
Again, keeping speed as a constant, if I lean both my bike and my body more, I carve a tighter circle. If i lean my bike and my body less, I carve a wider circle. There is some sort of offsetting balance thing happening there. |
Steve899
| | Posted on Friday, March 09, 2007 - 10:17 pm: |
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There is one factor you are overlooking, The Random Factor,if the weights and the CG of the riders are different, then why are the bikes at the same angle, the only logical answer to me would be that the hangoff amount is irrelevant to the equation. And yes I know I can't prove there angles are exact, but if hanging off allows you to put the bike more on the center of the tire, then judging by this picture there is not very much too gain.
One wonders if the difference would matter to the stickiness of todays tires.
let me just say it is a pleasure to talk to people on this board, most comments are informative and respectful. |
Ceejay
| | Posted on Saturday, March 10, 2007 - 01:55 am: |
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In theory there shouldn't be any larger tire area per given bike lean, right? I mean unless you're street riding a lot on your race tires there is a reason that they are shaped the way they are. Given that there is more weight displaced directly on the tire when the bike is at 90 to the ground the area may be larger but shouldn't that be taken up the inflation specs/tire design? I would think the biggest benifit to leaning off, which reep stated, would be that it can allow better suspension useage. Going fast around a corner and leaning off is probably more related to how a person learned to ride and what is more comfortable to them, which in turn makes them faster.
Making that above pic a very cool one-each has his own way of making lemonade, and from looking at it they all seem to be pretty good at it...
When a person loses that traction at a lesser lean angle there is more room for recovery. If you lose it at 90 to the ground most of the time there's a squiggle. If you lose it half cranked over, a bit more drastic squiggle, but recoverable-at least at my speeds , if you lose traction at full tilt/lean-well your already at the edge of your tire and there's nowhere to go, but down.
899-I agree!! |
Steve899
| | Posted on Saturday, March 10, 2007 - 11:00 pm: |
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I like this thread, I have thought about how a motorcycle changes direction a great deal and it is interesting how many pts of view there are, Ceejay , you state that a motorcycle tire has the greatest weight on it at 90 degrees to the ground, I believe it is greater as you lean, a centrifuge affect happens as a motorcycle turn, actually anything that follows a circle path experiences a centrifuge affect
In a centrifuge there is some type of mechanical linkage keeping the object on a circular path.
A motorcycle uses the grip of the tires to hold it on the circular path, as the bike makes a turn it experiences G forces on it as well as the tires, the force of gravity is lessoned on the tires when leaned over but the G forces increase with a smaller radius turn or greater speed or both. So your tire patch size maybe larger when lean over and carring speed.
Ceejay I agree with you that hanging off is about how comfortable it makes a person feel than the physics of turing a motorcycle
I have done alot of research on Centrifugal force (Inertia tring to take over) Centipetal force (center seeking), angular acceleration, gyroscopic progression as it applies to a motorcycle turning ( I know I have too much free time in the evening) and it seems to me that a motorcycles ability to turn is amazing.
Anybody up for some physics, I would love to know what you guys think, I have yet to hear a concrete theory on this stuff. |
Steve899
| | Posted on Saturday, March 10, 2007 - 11:11 pm: |
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check out the rear tire deformation and the front, in a turn the tires do squooosh out. |
Jackbequick
| | Posted on Sunday, March 11, 2007 - 09:34 am: |
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Steve,
The Discovery Channel's Speed on Two Wheels special last year gave some attention to the physics of motorcycle racing and how the forces apply themselves and are dealt with by the rider.
They have released that on DVD:
http://www.speedontwowheels.com/
I bought the DVD and have watched it a couple of times, it is interesting. And with the general paucity of motorcycle related technical programs on TV, it may be a high point for information in that area.
Send me an email to "jacker at midmaine dot com", I can send you the DVD to watch if you'll return it.
Jack |
Reepicheep
| | Posted on Sunday, March 11, 2007 - 09:40 am: |
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Modern tires are amazing... |
Ceejay
| | Posted on Sunday, March 11, 2007 - 11:02 am: |
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I've taken a few physics classes. The labs for those were some of the most fun and interesting classes I'd ever taken. put me in the classroom with a bunch of numbers-well I didn't enjoy that as much.
If you play with the gyroscopes and the like(I have kids-there's some great learning tools being made) just by messing with those, I'd agree with you-getting a motorcycle to turn is a feat in of itself. Especially at the speeds that the racers are expecting to turn at. Then if you throw physics and numbers at it, the picture gets even more muddled, given the little amount of input required to make a direction change. I have a bunch of related articles also, as I find it super interesting too. Force transfer, coefficients of friction, geometry-there's a bunch of cool stuff going there. I have one article with a cool pic of Rossi, at full tilt with a vector analysis written over the pic, but I can't find it right now-left it at work. |
Sparky
| | Posted on Monday, March 12, 2007 - 12:25 pm: |
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Related to theories on how motorcycles turn is the relatively new idea of applying counter-rotating brake rotors to help offset the gyroscopic effects of a spinning front wheel. This idea has been tried on a demonstrator bike and has, I believe, proven the concept of radically easier flickability.
I'm wondering if the physics involved in the effectiveness of counter-rotating brake rotors can be proven.
Wow, if this theory could be produced in a dead-reliable mechanism, this could only lead to more exciting racing and safer on-road performance. |
Steve899
| | Posted on Monday, March 12, 2007 - 03:44 pm: |
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http://www.reverserotatingrotors.com/whyitworks2.h tml
they look pretty cool. |
Steve899
| | Posted on Tuesday, March 13, 2007 - 11:11 pm: |
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Hey Jackbequick, I have seen it, it is one of the best shows about sportbikes I have seen, thank you though. |
Jackbequick
| | Posted on Wednesday, March 14, 2007 - 12:40 pm: |
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Okay, they say it has some extra content but it can't be too much as it only runs 58 minutes. So they added about enough to cover the time that was spend on commercials on the broadcast.
Anyone else want to see the Speed on Two Wheels DVD? I'll mail it for free and you can send it on to someone else when your done with it. I'm sure it will get back home eventually and I'm not going to watch it again anytime soon. It is kind of Buell deficient but worth watching.
Yesterday I stumbled onto the Speed Channel about mid-morning and they were running a four hour replay on the Speed Week practice and qualifying sessions and then they showed the SuperStock and SuperSport races again. That had some great interviews, pit area shots, and technical details.
For today (all times EDT):
1:30 PM - AMA Flat Track Championship
2:30 PM - AMA Formula Xtreme
Oh boy! Another chance to hear and see the Buells in action at 2:30!
Jack |
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