motorcycle weight vs. stopping distance
- Thread starter kml
- Start date
The problem in this thread is that most people are having trouble understanding the difference between work as it relates to stopping and the physics of how the work is able to be completed.
Everyone wants to skip the "work" required because they assume it is a static variable versus weight instead of a dynamic variable. They want to skip right to "It takes more distance to stop a greater mass from the same speed" because it fits our perceptions. Our perceptions, I suppose, are more governed by what we see when things slide.
A true statement is "it takes more work to stop a greater mass at the same speed." The question then becomes can we increase the ability to provide that work with a greater mass?
Everyone wants to skip the "work" required because they assume it is a static variable versus weight instead of a dynamic variable. They want to skip right to "It takes more distance to stop a greater mass from the same speed" because it fits our perceptions. Our perceptions, I suppose, are more governed by what we see when things slide.
A true statement is "it takes more work to stop a greater mass at the same speed." The question then becomes can we increase the ability to provide that work with a greater mass?
I have been trying to come up with a real world experiment but I just cannot put my finger on it. For those of you that have a kids small bike in the garage go put it on the driveway and lock up the front brake. Without sitting on the bike try to get the tire to roll with the brake fully depressed. You probably cannot make it happen. Or alternatively, without sitting on the bike, roll it along and intuitively feel the small amount of brake required to lock the wheel.
Now sit your overweight rear on the bike without breaking it or you and try to roll the wheel with the brake fully depressed. You probably can make it turn. If you cannot make it turn you can certainly feel that the pressure required to lock the brake is much greater with you sitting on it.
Voila! you have just seen that with increased mass there is increased ability by the brakes to do work.
Now sit your overweight rear on the bike without breaking it or you and try to roll the wheel with the brake fully depressed. You probably can make it turn. If you cannot make it turn you can certainly feel that the pressure required to lock the brake is much greater with you sitting on it.
Voila! you have just seen that with increased mass there is increased ability by the brakes to do work.
DevilDawg1
Registered
Just my .02 worth -
On the average motorcycle braking system
Lesser weight = less heat on the braking system, this should equal to better braking
Greater weight = more heat on the braking system, this should equal to greater brake fade, which equals to more pressure, which equal to greater heat, which starts this cycle all over again.
Speaking specifically on the motorcycle, I do agree that it is more rider than anything.
On the average motorcycle braking system
Lesser weight = less heat on the braking system, this should equal to better braking
Greater weight = more heat on the braking system, this should equal to greater brake fade, which equals to more pressure, which equal to greater heat, which starts this cycle all over again.
Speaking specifically on the motorcycle, I do agree that it is more rider than anything.
jellyrug
Donating Member
I really enjoyed this thread, not for the technical information, but for the people experience.
Those who have limited education would have a certain perception and believe others are stupid.
Those who are educated but not in the sciences, will debate based on various but more intelegent perceptions. Generally they shoot from the hip.
Those with technical education will attempt to apply physics and mechanics to keep their arguments as factual as possible.
In my job I work with all these types every day, the fun never stops.
Is that gut feel, guessing, or can you substantiate with a few facts? That is about stopping quicker, not the rest.
You don't see the factory race teams addiing weight to their GP bikes so they brake better, do you?
What makes you think braking performance is any different from acceleration when it comes to adding weight?
More mass/kinetic energy takes more to accelerate/decelerate, period; all the egghead math and "theories" don't mean ****.
Less weight = more performance in all areas.
Blue1
KokomoBusa
Banned
you're fighting a losing battle, these clowns are too busy trying to invent their own laws of physics that the basics are just slipping right by them. let the arguement go. these guys have a made a nice home here anyway.
Robot
Donating Member
Looks like a great approach Jellyrug
A company actually asked me to do these calculations when I was a Senior in Solid State Physics. I scratched my head...It appeared that I was missing something in my calculations.
What I needed was the time OR distance the box took to go from freefall to dead stop. Without either of these, an accurate decelleration figure was not possible.
My friend with a doctorate in physics said "One experiment is worth a hundred calculations"
I ended up buying a few of these little shock indicators, If I remember correctly I thought the 3G or 5G shock indicator seemed about right.
Off the top of your head you might think to stick something close to zero in for the time or distance for decelleration, but if you do, the result is a near infinite "g" decelleration. We know this isnt true, the box isnt flat as a pancake. Another good example of calculations providing a starting point, not always an end all answer.
Back to your answer, it is a good approach, if we wanted to be real picky. We could say the "pound" units do not meet the definition of force, (from a Newtonian definition anyway(F=MxA). We would need to multiply by acceleration of gravity at that point.
Robot
Donating Member
Robot,
Glad to see a true physics "nerd" join the fray. I dig physics concepts, but I don't care for the tedium of formulas and calculations. Thanks for your contribution!
Thanks
your use of the term "physics concepts" rather than "physics laws" is 100% correct. I dont think Nature knows anything about all these formulas, Nature will do what it will.
All these calculations are man's attempt to understand and quantify things in nature. Some calculations are close, some need alot of tuning to fit the problem.
Unfortunately these "calculations" and "probabilities" are the best we have to work with at this time.
jellyrug
Donating Member
Thanks
I dont think Nature knows anything about all these formulas, Nature will do what it will.
All these calculations are man's attempt to understand and quantify things in nature. Some calculations are close, some need alot of tuning to fit the problem.
Unfortunately these "calculations" and "probabilities" are the best we have to work with at this time.
These calculations, together with some quantum physics have put a man on the moon and a live robot on Mars. You think that would have been possible with probabilities? Just an innocent question here.???
"Some calculations are close, some need alot of tuning to fit the problem."
With some emperical work, EVERYTHING can be calculated, but sometimes the effort that has to go into calculation cannot be justified.
take your toy dumptruck and lock up the tires
put it on a piece of plywood and start making an incline
note point truck skids off plywood
Put same said truck with a couple bricks in back and repeat..
result will be? ____________________
(sorry skipped right over the math part) that experiment thing works for me
put it on a piece of plywood and start making an incline
note point truck skids off plywood
Put same said truck with a couple bricks in back and repeat..
result will be? ____________________
(sorry skipped right over the math part) that experiment thing works for me
Robot
Donating Member
Great Question
Unfortunately much of quantum physics is Probablilities, worse yet, these probabilities appear not to be due to our ignorance,(or lack of knowledge), of these events but, the nature of these quantum events. The current(for decades now) reasoning is the "Heisenberg Uncertainty Principle" This theory is very deep and profound. The simplist explanation is that on a quantum level things act as waves. Some inherent wave properties are only a probability.
This theory troubled Einstein deeply, he replied "God does not play dice with the universe!"
I believe it was Bohr who told him "Don't tell God what to do with his dice"
Uncertainty theory seems to get constantly reinforced in physics.
On another note, Calculus is a math of approximations. I once had a Professor tell me "Calculus doesnt give you the answer to anything, but sometimes it might get you infinitely close to the answer"
Often probabilities are the best we get from science, a bitter pill to swallow! The good news is often these approximations are good enough to get a man on the moon, etc. Great Question!
jellyrug
Donating Member
take your toy dumptruck and lock up the tires
put it on a piece of plywood and start making an incline
note point truck skids off plywood
Put same said truck with a couple bricks in back and repeat..
result will be? ____________________
(sorry skipped right over the math part) that experiment thing works for me
Sorry I had to do the math, because I stopped playing with toy dump trucks way back and don't have any left.
lease:
Robot
Donating Member
take your toy dumptruck and lock up the tires
put it on a piece of plywood and start making an incline
note point truck skids off plywood
Put same said truck with a couple bricks in back and repeat..
result will be? ____________________
(sorry skipped right over the math part) that experiment thing works for me
Excellent Experiment
jellyrug
Donating Member
Great Question
Unfortunately much of quantum physics is Probablilities,
Uncertainty theory seems to get constantly reinforced in physics.
On another note, Calculus is a math of approximations. I once had a Professor tell me "Calculus doesnt give you the answer to anything, but sometimes it might get you infinitely close to the answer"
Often probabilities are the best we get from science, a bitter pill to swallow! The good news is often these approximations are good enough to get a man on the moon, etc. Great Question!
You are correct. Some of this work started in 1927.
We are going way beyond simple calculations of stopping distance now. The art of a good Physicist is to marry theory with practice successfully. A good Design Engineer needs an intimate understanding of both.
In the example of trying to calculate stopping distance, one can predict a trend, but in practice even with exactly the same weight stopping distance will not be exactly the same for each test, if the test is repeated. In the example of the package falling to the ground, each test will also yield a different result when the package is dropped, as there are variables. This is where we use statistics with standard deviations and a whole lot of theories.
If calculus is applied correctly, it is extremely accurate. If the Engineers at Yamaha used finite element analysis to analyze the frame of the FZ1, it would not have cracked after I had 3,900 miles on the clock and I would probably still have one in my garage.
Good Engineers have to understand a broad range of theories, including laws and regulations to calculate design and build much of what you see around you today. The young generation is spoilt with computer models and have lost an understanding of all the basic fundamentals, because today we have specialists, each only understanding the world in his own little box.
And then some of us are still trying to experiment with toy dump trucks, because we are unaware of discoveries and theory developed in the 16th century.
aww so sorry.... I will always be a kid and keep some toys on the side...Sorry I had to do the math, because I stopped playing with toy dump trucks way back and don't have any left.
I think I may have the needed toy at home even... 
You know, I was just listening to a traffic safety siminar spokesman who stated a typical 6000 ton loaded train going 60 miles an hour takes one and one half miles to stop. Do you suppose it takes a mile and a half to stop an empty train?
All your theories and equasions known to mankind won't make that loaded train stop within the same distance as the empty train.
Toot-Toot! Train's Leaving!
All your theories and equasions known to mankind won't make that loaded train stop within the same distance as the empty train.
Toot-Toot! Train's Leaving!
Commuta_Busa
Donating Member
if the g-meter was calibrated to the correct calulation that would cause the box to trip the stick would it happen every single time? why not?
jellyrug
Donating Member
You know, I was just listening to a traffic safety siminar spokesman who stated a typical 6000 ton loaded train going 60 miles an hour takes one and one half miles to stop. Do you suppose it takes a mile and a half to stop an empty train?
All your theories and equasions known to mankind won't make that loaded train stop within the same distance as the empty train.
Toot-Toot! Train's Leaving!
Depends on whether we have brakes on each single car, and whether all those brakes are 100% effective.
So, tell me, do you think Newton was a nut case and everyone who does not understand his principles are normal????
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