GPTECHMAN
12-22-2003, 01:16 PM
I know that this is a debateable topic to no end...there are views of preference and simple physics, but as long as we keep the rubber side down, I feel that as long as you have fun thats all that matters...please lets make this thread constructive, cause I think that this will benefit most of us, as a learning tool, or as a reminder...
Oh yeah you gotta look good will doing it any ways right?:headbang:
Two good books to read are written by Gary Jaehne
"Sportbiking the Real World" & "Sportbiking the Real World 2"
The mechanics are as such.
HANGING OFF
The force that keeps the tires from slipping is due to the bikes (and rider) mass being pulled downward by gravity and the rubber to pavement friction coefficient. That force does not change with lean angle.
The gravitational force on the rider & bike component cg remains normal to the earth. As lean angle changes this component role in the force on the tires decreases. The portion that is removed from the tire's normal force is offset by gyroscopic and tire force effects so that all forces balance and the bike remains upright.
A second force (horizontal) is generated by the fact we are turning. The higher the total weight, the higher the traveling speed and the tighter the radius, the greater this force gets. It does not depend on the motorcycle's lean angle.
Lean angle does affect the force. The reason that a motorcycle can corner is because camber thrust produces a force to counteract the centrifugal forces described above and is dependent on the tires "camber" or angle with respect to a line perpendicular to the road surface. The first force provides the traction. The second one, combined with braking or accelerating will eventually overcome traction if high enough.
How does hanging off the bike help us to turn faster?
A) It allows the bike to be more upright which increases ground clearance, first because obviously the bike has more clearance the more upright it is and also because by being more upright the suspension is not as much compressed as it would otherwise be (by the horizontal centrifugal force) which also contributes to better ground clearance.
B) It might also have a benefit effect on the contact patch area. If we consider the tire to be a very soft balloon with a certain pressure inside, the contact patch area would then simply be Total weight / tire pressure. In reality the tire has certain stiffness and does not have to squish that much to support the bike. What that means is that a stiff tire will create a smaller contact patch for a given motorcycle weight and tire pressure. Now when the bike is leaned over pretty far, the sidewall rigidity of the tire comes more into play and I suspect an increase in tire rigidity under those circumstances thus a reduction in contact patch area, which is not what we need for better traction. I think it would be reasonable to conclude that by keeping the bike more upright, we get a bigger contact patch and better traction.
C) A bike's suspension does a much better job at absorbing bumps in the direction of wheel travel than sideways. The more upright the bike, the better the suspension can absorb bumps. This is true, and the reason that very stiff frames can have stability problems when traveling over bumps at high lean angles. Another advantage to leaning is that the rider’s cg moves forward increasing the weight on the front tire.
Here is a good article to help out to.
http://www.ducatimeccanica.com/articles/hanging_off_1.jpg
:)
http://www.ducatimeccanica.com/articles/hanging_off_2.jpg
:)
http://www.ducatimeccanica.com/articles/hanging_off_3.jpg
:)
http://www.ducatimeccanica.com/articles/Hanging_off_4.html
Oh yeah you gotta look good will doing it any ways right?:headbang:
Two good books to read are written by Gary Jaehne
"Sportbiking the Real World" & "Sportbiking the Real World 2"
The mechanics are as such.
HANGING OFF
The force that keeps the tires from slipping is due to the bikes (and rider) mass being pulled downward by gravity and the rubber to pavement friction coefficient. That force does not change with lean angle.
The gravitational force on the rider & bike component cg remains normal to the earth. As lean angle changes this component role in the force on the tires decreases. The portion that is removed from the tire's normal force is offset by gyroscopic and tire force effects so that all forces balance and the bike remains upright.
A second force (horizontal) is generated by the fact we are turning. The higher the total weight, the higher the traveling speed and the tighter the radius, the greater this force gets. It does not depend on the motorcycle's lean angle.
Lean angle does affect the force. The reason that a motorcycle can corner is because camber thrust produces a force to counteract the centrifugal forces described above and is dependent on the tires "camber" or angle with respect to a line perpendicular to the road surface. The first force provides the traction. The second one, combined with braking or accelerating will eventually overcome traction if high enough.
How does hanging off the bike help us to turn faster?
A) It allows the bike to be more upright which increases ground clearance, first because obviously the bike has more clearance the more upright it is and also because by being more upright the suspension is not as much compressed as it would otherwise be (by the horizontal centrifugal force) which also contributes to better ground clearance.
B) It might also have a benefit effect on the contact patch area. If we consider the tire to be a very soft balloon with a certain pressure inside, the contact patch area would then simply be Total weight / tire pressure. In reality the tire has certain stiffness and does not have to squish that much to support the bike. What that means is that a stiff tire will create a smaller contact patch for a given motorcycle weight and tire pressure. Now when the bike is leaned over pretty far, the sidewall rigidity of the tire comes more into play and I suspect an increase in tire rigidity under those circumstances thus a reduction in contact patch area, which is not what we need for better traction. I think it would be reasonable to conclude that by keeping the bike more upright, we get a bigger contact patch and better traction.
C) A bike's suspension does a much better job at absorbing bumps in the direction of wheel travel than sideways. The more upright the bike, the better the suspension can absorb bumps. This is true, and the reason that very stiff frames can have stability problems when traveling over bumps at high lean angles. Another advantage to leaning is that the rider’s cg moves forward increasing the weight on the front tire.
Here is a good article to help out to.
http://www.ducatimeccanica.com/articles/hanging_off_1.jpg
:)
http://www.ducatimeccanica.com/articles/hanging_off_2.jpg
:)
http://www.ducatimeccanica.com/articles/hanging_off_3.jpg
:)
http://www.ducatimeccanica.com/articles/Hanging_off_4.html