Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Xjazz on October 04, 2002, 03:46:59 AM
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Its really look.... eehh.... somehing (http://www.allamericanracers.com/alligator/alligator_photo43.html)
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Looks like some fatso jumped on it.
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how could you slice and dice the canyons on that thing? the center of gravity is aaaalllll fluffied up.
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wow, they finaly blended the worst of both worlds.
ugly like a cafe racer and sloppy handling like a chopper.
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I knew a guy who did that with a Triumph Bonneville. He wound up running it into a car. The center post tore some of his very important parts off. Ouch!
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hmmm there might no be that type of problem easymo. the triumph bonnyville wasnt made to be like that this thing was so they might have done different things so it works better.
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Originally posted by hawk220
how could you slice and dice the canyons on that thing? the center of gravity is aaaalllll fluffied up.
Doesn't it lower the CG? Wouldn't that be a good thing?
(http://www.allamericanracers.com/alligator/images/gator_ws4l.jpg)
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no, lowering yourself in the bike makes it less responsive.
think about how much you'd have to shift your weight to have the same amount of effect in corners.
closest analogy I can get is a plane. fighterplanes are made with the wings low for faster turning. but someting like a cesna with the lower center of gravity stays up right better but takes alot more force to tip out of plumb. at speed you don't use the stearing so much as just shifting weight
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Originally posted by capt. apathy
no, lowering yourself in the bike makes it less responsive.
think about how much you'd have to shift your weight to have the same amount of effect in corners.
You're shifting your weight because you're higher and above the bike's CG. If you're in the middle of it, there's no reason to shift at all.
Don't take my word for it... I'm sure Gurney (http://www.allamericanracers.com/alligator/alligator_history.html) knows much more about racing than either of us.
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With its low center of gravity, it looks unique and most importantly, it feels like nothing else on the road. It produces a high degree of riding confidence and security with a fabulous fun factor to match!
I read the page and nowhere does it say this design improves handling or makes it more responsive. and you shift your weight to tip the bike, thats how bikes corner. the lower you sit the more effort it takes to tip the bike. thats why you won't see a chopper type frame design keeping up with the Buell on the road even if you had the horsepower the same. long and low for comfort & style. but if you want handling the rider sits on top.
take any bike into a corner flat(vertical) at speed and check it for yourself. make sure to take some video so you can sell it to pay for your med bills.
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Your back would kill you long before the motorbike did.
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You're shifting your weight because you're higher and above the bike's CG. If you're in the middle of it, there's no reason to shift at all.
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Have you ever riden a motorcycle? You have to shift your weight if you want to turn. You can only turn the front wheel at very low speed.
If you cant assert your weight at higher speed, the bike will just want to keep going straight. You could run right off the road if you are not able to shift the cg of the bike fast enough.
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With all do respect to Mr. Gurnys knowledge of autos. Based on that pic, He doesn't know squat about bikes.
To corner you have to overcome the gyroscopic effect of the motorcycle. Being higher gives you more leverage to do this. All you have to do is lean. your body weight does the work. The only way that thing is going to turn properly is to get very familiar with the feel of the front brake. An old motocross trick we used, was to throw our leg out as far forward as possible, while grabbing the binders. This collapsed the front fork and thereby changed the steering geometry of the front end. That maneuver would be too radical for a street bike. But a degree of it might be employed with this thing.
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Originally posted by NUKE
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Have you ever riden a motorcycle?
Yes. Probably not as much as you, Nuke. I haven't ridden anything in years. But... don't you think that some of the instability of motorcycles is a direct result of the added weight of the rider perched on top of it?
This must be a fake:
(http://www.allamericanracers.com/alligator/images/gator27l.jpg)
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check your own pic. the wheels are parallel the rider is not just leaning he's moved himself clear off the seat to the inside of the corner. the bike is leaning and thats why it's turning
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Yes. Probably not as much as you, Nuke. I haven't ridden anything in years. But... don't you think that some of the instability of motorcycles is a direct result of the added weight of the rider perched on top
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Cool Pic Sandman!
I agree that stability is sacrificed by the weight of the rider perched on it. However, stability and maneuverability are two different things.
A stable aircraft will fly straight and level, yet will not turn as well as a less "stable" aircraft.
If you want a stable bike, plan on going straight most of the time.
To turn a bike, you need to counter the centrifical force of the wheels ( like you are doing in that pic)
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"A stable aircraft will fly straight and level, yet will not turn as well as a less "stable" aircraft. "
How this could relate to airplanes, even remotely, is beyond me. With bikes its all a matter of rake, and trail.
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Leaning one's body to go fast in a turn (say one is racing on an on road track) is for traction, not for the turn. By leaning over (hanging off the bike as one can see roadracers do), one allows the bike to be a bit more upright (to maintain the tire's footprint, read increased traction) than one that does not hang off the bike.
Shifting your weight over to turn is actually counter-productive as the bike counters that motion (Newton's Third Law of Motion, Action and Reaction) as the rider is a counter weight to the bike in those circumstances. Racers turn fast by a snap counter steering into a turn that forces the center of gravity to shift and snap the bike into a lean. The racers are hanging off the bike for the traction they need in a turn to maintain traction of the tires, not for the turning.
For cruising, the bike with the lower center of gravity should be more stable as one doesn't have to hang off the bike in turns at non-race speeds.
BTW, one needs to counter the gyro-scopic effect of the wheels/tires, not the motor.
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Originally posted by NUKE
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Have you ever riden a motorcycle? You have to shift your weight if you want to turn. You can only turn the front wheel at very low speed.
If you cant assert your weight at higher speed, the bike will just want to keep going straight. You could run right off the road if you are not able to shift the cg of the bike fast enough.
Shifting you and the bike at speed is far more efficient to snap counter-steer into a turn rather than leaning over (you'll be fighting the bike to lean over rather than letting the bike lean you over.) By acting as one unit and allowing the bike to do the 'leaning' work, you'll cut faster turns.
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LOL. That works real good, right up to the point you hit that patch of loose sand.
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Originally posted by easymo
LOL. That works real good, right up to the point you hit that patch of loose sand.
....or oil, or anti-freeze, etc.
Not healthy for the motorcyclist no matter how you lean it over in a turn... or are you saying that one that tries to force the lean by shifting body weight alone magically has more traction?
LOL! You ARE funny. ;)
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please someone post a video of a bike hitting a corner at speed without leaning into the turn. even this low C of G bike. if you look at the pic sandman posted you can see that the rider has shifted his bellybutton clear off the seat. there's no info on how fast he is going but I've seen conventional frame designs race at very high speed and have took quite a few corners at high speed myself and I've never had to actually climb out of the saddle to take a corner. I've leaned way out there so the peds are almost touching the ground but never had to drop my bellybutton over the side to get the thing to lean far enough. this bike doesn't apear to hit the corner any different than any other bike. the rider just looks like he's working harder to make it perform.
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Subaru has it right. The lean has nothing to do with getting the bike to turn. Getting the bike to turn is done with the handle bars. In a right hand turn, you turn the front wheel ever so slightly to the left, causing the bike to fall to the right, you turn the wheel back to the right to keep it from going all the way over and more to the right to bring it up straight again.
Have you not ever on a long trip hung off of one side or the other while going straight down the road just to relieve some butt pain?
You guys are funny.
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Driver turns front-wheel to left if he wants to turn the bike right. When bike leans to the right after that the frontwheels right side has smaller spinning radius than the center of the wheel, making bike turn.
Easy isn't it :)
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hmm I'm wondering if it would be too cold weather to borrow my friend's Moto-Guzzi for a small ride...
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lizard, read your own post. you just explained how you can use stearing to help get the bike to lean so you can turn. your own post states how the leaning is nescasary to turn. if it was the stearing that causes the bike to turn why do you stear left (while leaning right) to go right at high speed, but stear right to go right at low speed?
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Subaru has it right. The lean has nothing to do with getting the bike to turn. Getting the bike to turn is done with the handle bars. In a right hand turn, you turn the front wheel ever so slightly to the left, causing the bike to fall to the right, you turn the wheel back to the right to keep it from going all the way over and more to the right to bring it up straight again.
Ever take a passenger who refuses to lean into the turns? You can hardly turn the bike! In fact , the passenger can turn the bike and they arent touching the bars.
Shifting your weight has everything to do with turning.
Every see someone ride without hands, yet turn?
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http://www.montreal4ever.com/performance_riding.htm
Its not mentioned here, but the gyro phenomenon will also create "weight". When you are in mid air, if you are going to land nose down, you can rev the motor, and the spinning rear tire will cause the butt end to lower.
BTW. The lack of knowledge, in this thread, of something as basic as cornering, is what is funny.
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Originally posted by capt. apathy
lizard, read your own post. you just explained how you can use stearing to help get the bike to lean so you can turn. your own post states how the leaning is nescasary to turn. if it was the stearing that causes the bike to turn why do you stear left (while leaning right) to go right at high speed, but stear right to go right at low speed?
Leaning the bike, not you. You can put on a seatbelt, a back brace and a cervical collar and still ride and turn a bike.
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Originally posted by NUKE
Ever take a passenger who refuses to lean into the turns? You can hardly turn the bike! In fact , the passenger can turn the bike and they arent touching the bars.
Shifting your weight has everything to do with turning.
Every see someone ride without hands, yet turn?
Yes, those passengers were the good ones. The ones that tried to lean into or out of every corner got told to stop. All the leaning screwed up the balance of the bike. It made for much wobbley turns. Leaning may increase or decrease your rate of turn, but isn't necessary.
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What part of this did you not understand?
Now, why does this make a difference in corner negotiation. We must understand that the wheels of a motorcycle act as a gyroscope, and that this gyroscopic effect is increases in proportion to speed. One property of a gyroscope that applies here is the reaction called precession. When a gyroscope is acted upon by an outside force (in this case, gravity, when the bike is leaned over) it will react, or precess by causing an opposing force acting at 90 degrees to the applied force. Since gravity acts downward through the center of mass of the bike, the opposing force from the gyroscopic effect of the wheels will act at 90 degrees to this, which in a flat corner will be parallel to the ground, opposite to the lean of the motorcycle.
This reaction has its pros and cons. The gyroscopic effect is what keeps the bike from falling over in a turn ( in spite of gravity). It is not momentum that causes this! However, this effect also means that as you try to lean your bike in a fast sweeper, or try to accelerate through a curve, there is a force acting to straighten the bike up, which may cause you to drift wide, and then perhaps cause the worst!
When you shift your weight into a corner, you effectively move the center of mass of the entire rider / bike package further from the tire (contact patch). The effect is that resultant force pulling the bike down into the turn is greater. (This is the same principle as using the length a lever to increase resultant force)
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Originally posted by easymo
BTW. The lack of knowledge, in this thread, of something as basic as cornering, is what is funny.
easymo, from your vast motorcycling knowledge, please comment to the attached. So you're saying that those riders attained their lean angle on their bikes by shifting their body weight over their bike and not by steering input? Please give us a running description of what they did to enter the turn to get that angle?
BTW I don't believe anyone here that rides bikes disputes that the bike has to lean for the turn, just how to get the bike to lean. Re-read my posts above.
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Originally posted by easymo
What part of this did you not understand?
Now, why does this make a difference in corner negotiation. We must understand that the wheels of a motorcycle act as a gyroscope, and that this gyroscopic effect is increases in proportion to speed. One property of a gyroscope that applies here is the reaction called precession. When a gyroscope is acted upon by an outside force (in this case, gravity, when the bike is leaned over) it will react, or precess by causing an opposing force acting at 90 degrees to the applied force. Since gravity acts downward through the center of mass of the bike, the opposing force from the gyroscopic effect of the wheels will act at 90 degrees to this, which in a flat corner will be parallel to the ground, opposite to the lean of the motorcycle.
This reaction has its pros and cons. The gyroscopic effect is what keeps the bike from falling over in a turn ( in spite of gravity). It is not momentum that causes this! However, this effect also means that as you try to lean your bike in a fast sweeper, or try to accelerate through a curve, there is a force acting to straighten the bike up, which may cause you to drift wide, and then perhaps cause the worst!
When you shift your weight into a corner, you effectively move the center of mass of the entire rider / bike package further from the tire (contact patch). The effect is that resultant force pulling the bike down into the turn is greater. (This is the same principle as using the length a lever to increase resultant force)
LOL! Try riding in a straight line with your bike leaned over. You'll fall over.
It is the fight between the forces of gravity and centrifugal force that keeps the bike in check in a turn. Too much centrifugal force in a turn and you'll highside it (provided the tires keep their grip) and go flying off your bike. Lowslide it if your tires lose their traction. As long as the net vector force (gravity + Centrifugal) drives the bike through its tire's contact patch with the road's surface, you'll keep traction and the turn rate.
(I sure wish waaay back in school I paid more attention in my English class. Seems some are having trouble understanding what I'm trying to type. :( )
BTW, how do you make emergency avoidance maneuvers? Shifting your weight on your bike only? Can we say accident?
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I don't see any point. You have decided you have it all figured out.
I will tell you this. I once won a hundred bucks from a guy by doing what you see in the pic. Holding on to nothing but the gas tank with both hands. He has his weight shifted forward, collapsing the forks ever so slightly and changing the steering geometry. His knee sticking out is causing a lot of wind resistance. this allows him to cause additional opposing force by "pulling'' the bike into the turn. You can do the same thing pulling on the tank. I could go on, but I think i am wasting my time.
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Originally posted by senna
Easymo is right about the rake stuff. The steeper the rake, allows for faster lean and angle stuff. Countersteering is a phenomena (SP) of "thrust camber" and the gyroscope effect is what pulls the bike or leans it the opposite of the direction of force of the object to the direction of the turn (bike and riders head should lean to outside of turn if not for counterstearing). Gyro causes wheel and road angle close from 90 degrees like what was said above. IMHO, counterstearing is required because a motorcycles tires behave differently than a cars tires. Cars generate slip angles with higher performance tires having steeper slope slip angles drastically droping off. Motorcycle tires instantly generate negative slip angles sort of reverse of an automobiles tire. On a motorcycle, after 15-20 miles per hour, you turn the bike (of course) by countersteering. Reason is is that at that speed, the tire actually goes into an instant loss of traction (bst way to describe it in relation to how car tires work). In a car, if you loose traction at rear, you would countersteer. On a bike this sort of happens automatically (not noticable) thus you must preemptively countersteer to turn in the opposite direction. This concept is better understood if you look at it from a tires slip angle graph (which is how I figured it out).
Hmm my front tire doesn't normally lose traction in my countersteer input for a change of direction (nor would I want it to lose traction). What I see happening is that the front tire steers out a bit before turning it back. The bike's center of gravity has now shifted from its base of support (tire's contact patch) forcing the lean of rider and bike in opposite direction of the countersteer (via lever action pivoting around the center of gravity.). The accelleration (change in direction, read turn), helps create centrifugal force keeping the lean in check. Too much lean in a turn and you'll slide it out from under you. Too little and you'll highside it.
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Interesting discussion. Last year I took the MSF advanced rider course. I was able to find some of the reference material they gave us. I think it might clarify this issue a bit. I'll try to attach it...hope I sized it right. Here goes nothin.
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Last one. Sorry in advance if I killed anyones load times. I made em as small as I could while still keeping em readable. S!
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One of Newtons laws of motion has to do with the observations of effects of Inertia:
Things at rest tend to stay at rest unless acted upon by an outside force.
Things at a constant motion, (non - accelerating) tend to stay at that constant motion unless acted upon by an outside force.
The only place a motorcycle or bicycle has that acts with the outside world is the tire contact patch. In order to upset the balance of the cycle, the only choice is to steer out from underneath your center of gravity. (unless you push against a car pacing beside you)
When you lean into a corner without countersteer, the geometry of the front forks causes the front wheel to turn, and that in effect causes the countersteer you don't think you are doing. This is how you can ride "hands off".
As for a low center of gravity, this is good in a car, because it keeps the car from rolling or tumbling before the tires lose traction. It is not necessarily an advantage in a vehicle that needs to be balanced. Ever try to balance an ax with the head down? It is a lot more difficult than with the head up...
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Originally posted by DblTrubl
Last one. Sorry in advance if I killed anyones load times. I made em as small as I could while still keeping em readable. S!
Thanks! Had I had access to those materials, my arguement might have been more concise. S!
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and you shift your weight to tip the bike, thats how bikes corner
You have to shift your weight if you want to turn. You can only turn the front wheel at very low speed.
To corner you have to overcome the gyroscopic effect of the motorcycle. Being higher gives you more leverage to do this. All you have to do is lean. your body weight does the work.
Shifting your weight has everything to do with turning.
You know what easymo? About the only statement of yours that I agree with is:
BTW. The lack of knowledge, in this thread, of something as basic as cornering, is what is funny.
The sad part is that you and some others didn't understand it. I hope you do now.
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:rolleyes: Man, not that I doubted you for a moment, Saburo, but to think I was about to go out and try to turn my bike without steering it, lol.
-Nitro
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Originally posted by NITRO
:rolleyes: Man, not that I doubted you for a moment, Saburo, but to think I was about to go out and try to turn my bike without steering it, lol.
-Nitro
LOL ;)
I can take disagreements on religion, politics, etc. We all have an outlook on things and see things in a different light.
I do draw the line however when some post 'tips' that can get a novice rider killed or injured.
Obviously they are:
1) novice riders themselves (or have actually never ridden a motorcycle)....
and/or
2) ignorant of the physics to get a bike to turn/handle.....
and if they still believe what they've been posting,
3) plain stupid.
What was really rich was when one ignorant (stupid?) person posts a link to another ignorant person's ideas.
Edited to remove double quote.