John in CR
100 TW
Safe,
Even if I lend you a couple of clues you'd still be clueless, so why bother?
John
Even if I lend you a couple of clues you'd still be clueless, so why bother?
John
Mounting your battery, Center of Gravity.
- Thread starter Patriot
- Start date
Ok, so I was gonna say DoctorBass'es bike with batteries mounted as seen here is the best riding ebike I've tried so far, that backpack batteries are better and to confirm that rack mount lead sucks ass...
However I wanted to read the thread first, and having wasted my time reading it up to page 11 I hereby declare this to be the worst train wreck I've ever had the misfortune to stumble upon within the confines of the Endless-sphere grand Imperial Dynasty. Even worse then safe's gearing vs hub motor monologue.
View attachment 1
In fact I immortalized the moment by making a graph.
Edit: Forgot to add myself in said graph. Oh well.
However I wanted to read the thread first, and having wasted my time reading it up to page 11 I hereby declare this to be the worst train wreck I've ever had the misfortune to stumble upon within the confines of the Endless-sphere grand Imperial Dynasty. Even worse then safe's gearing vs hub motor monologue.
View attachment 1
In fact I immortalized the moment by making a graph.
Edit: Forgot to add myself in said graph. Oh well.
SteveMush
10 mW
"We", of course meaning "Safe"...
Nope - I specifically said consider the bike's lean in relation to the ground reference frame. Bikers are concerned with the ground. Pilots are concerned with the horizon.
Again safe continues to assert what is clearly debatable, as though it were not refutable.
A "safe" would be where one locks things away from anyone else's observations, eh?
Safe - kindly stop boring us with senslessly repetitive references to "countersteer". Yes, that is really fascinating and that is a fully accepted component of the theory of the initiation of turns for bikes or motorcysles. It is a result of masses and motions, not the cause - so LET IT GO.....
The fact that "countersteer" is correct and that it is really cool does not make "countersteer" the answer to every other concept. That is foolish.
FYI, "roll" is the rotation of an obect about an axis of equal mass moments. It is a circular motion about that axis. As such, a circulat moment about that axis on a bicycle would literally lift the tires off the road as the bike "rolls" about that axis and no turn would occur - just an amaxzingly impossible barrel roll in the air. GET IT? No amount of sensless repitition of "countersteer" or pretty pictures will change this picture. It's a fact.
If the predicted or real action of a body (a bicycle) does not match your theory, then it's time to suck it up and change your paradigm.
A lesson for you, Safe: The equations of moments of inertia and rotation of a body are equally valid if written from the frame of reference of a rotational axis or from the surface upon which the body initially rests. Describing "roll" about an axis only does not fully describe the actions of a bike as it initiates or completes a turn, nor does "countersteer" as a be all and end all. Describing the movements about the points of contact with the ground and their changing locations can more fully describe a bike leaning and turning and resulting path - including your indisputed and most beloved countersteer.
Now that we have the tire contact points in constant contact with the ground (rather than "rolling" upward away from the ground), we can start to take other important factors into account besides countersteer. The geometry and measurements of the front of a bike have major effects on the bike's behavious, as does the amount of mass at the front of the main frame section.
Why don't you pry your clenched fingers off your beloved "countersteer", which is a description of a resulting movement rather than a governing force, and take a look at the mass and weight of the forward main frame mass in relation to the front fork's rake angle (stability at minimal speeds), it's "trail" (stability at operating speeds) and the dynamic levering action of "trail" as the bike leans or as the handlebars are turned.
Move your frame of reference to the ground and you'll see that a bike with very effective "trail" can start a turn with handlebar movement as the initiator: As the handlebars are turned in the direction of a turn, the "trail" span will lever the mass at the main frame's front to the outside of the turn. This effectively "kicks its feet out from under it" and the bike begins to fall (lean) into the turn. On a bike with little or no "trail" in the front fork assembly, simply turning the handlebar will result in the bike begining to fall (lean) to the outside of the turn. There are no forces to counter this unless the rider manipulates his weight toward the inside of the turn. As people do not react instantaneously and because the mass of the bike will react outward to the rider's leaning into the turn, there is a momentary lean of the bike to the outside and resulting turn of the fork to the outside, producing countersteer until the rider's shift of his own mass overcomes it and the bike proceeds to fall (lean) toward the inside of the turn. As it does, the geometries of the fork rake and trail will act toward keeping the bike balanced in it's leaning (with relation to the ground frame of reference) with the rider's manipulating his weight to trim the bike's action and path. As to which comes first - turning the steering wheel or the rider shifting his mass (and kicking the bike toward the outside momentarily), one could argue forever. It doesn't matter. One's body learns and "knows" what to do automatically.
Note that this is all in relation to the ground frame of reference. At no time does the bike simply "roll" about its axis of equal moments of inertia (the definition of roll). The tires stay in contact with the ground - as we know they do - as the bike falls (leans) into its countersteer and steer.
If you want to talk about roll only to desribe rotational motion, go to an airplane forum. If you want to describe a bike's actions and path along the ground that it is in contact with, then you most assuredly have to take the ground into consideration, along with all the complications and actions of the bike front's geometry.
Wordy? Yes, but I'm sure you can read the above as many times as you need to to get your blinders off, Safe. Change your point of reference , widen your view, and the real world comes into focus.
safe
1 GW
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I've said in various postings that to truly describe steering geometry is a rather complex thing to do.
That being said...
"Roll" as in an airplane would be along a simple axis through the centerline of the bike. Obviously that doesn't happen and the bike has to actually lower itself closer to the ground in order to roll. At high enough speed you can get so low as to be able to stick your knee out and drag it on the ground. So "roll" is something that also combines with all the complexities of the wheelbase, the steeering head angle, the steering offset (defining the trail) and where all the weight is located to produce some behavior. This would be looking at the bike from the front or back, the blue color being the tire.
My point was more of criticism of the idea of contact patches as being an axis of rotation. That's clearly wrong and the countersteer argument is the "easiest" way to make it clear that such an idea is in fact wrong.
I mean all you have to do is imagine a 10 ton weight somehow attached at a place exactly at the rear contact patch. Now make the thought experiment:
"How can I make this 10 ton weight change direction so as to produce that rear wheel divergence in countersteer?"
...at this point one can only go "ah ha, now I get it". The rear wheel needs to diverge from it's straight line "contact patch" path and this means that the axis is NOT on the ground. (by definition) Otherwise you are going to get one nasty handling bike.
While the "roll" is complicated by the lowering of the bike it's still a "roll". The "lean" doesn't occur until the secondary step... and by that point the issue of weight distribution is of less importance because you've already done the "work" of setting up for the turn with the "roll" part.
See where I'm going with this?
The turning in part of the turn (second part) is not as critical as the initial rotation... and it's the initial rotation that is effected by the distribution of mass.
The rear mounted weight location is not all that bad... compared to some other ideas it's far less flawed than others. But the ideal location for weight is (as has been repeated often) in the tightest concentration in the middle of the bike.
The "conventional wisdom" is still correct... it's the best choice... are we there yet?
That being said...
"Roll" as in an airplane would be along a simple axis through the centerline of the bike. Obviously that doesn't happen and the bike has to actually lower itself closer to the ground in order to roll. At high enough speed you can get so low as to be able to stick your knee out and drag it on the ground. So "roll" is something that also combines with all the complexities of the wheelbase, the steeering head angle, the steering offset (defining the trail) and where all the weight is located to produce some behavior. This would be looking at the bike from the front or back, the blue color being the tire.
My point was more of criticism of the idea of contact patches as being an axis of rotation. That's clearly wrong and the countersteer argument is the "easiest" way to make it clear that such an idea is in fact wrong.
I mean all you have to do is imagine a 10 ton weight somehow attached at a place exactly at the rear contact patch. Now make the thought experiment:
"How can I make this 10 ton weight change direction so as to produce that rear wheel divergence in countersteer?"
...at this point one can only go "ah ha, now I get it". The rear wheel needs to diverge from it's straight line "contact patch" path and this means that the axis is NOT on the ground. (by definition) Otherwise you are going to get one nasty handling bike.
While the "roll" is complicated by the lowering of the bike it's still a "roll". The "lean" doesn't occur until the secondary step... and by that point the issue of weight distribution is of less importance because you've already done the "work" of setting up for the turn with the "roll" part.
See where I'm going with this?The turning in part of the turn (second part) is not as critical as the initial rotation... and it's the initial rotation that is effected by the distribution of mass.
The rear mounted weight location is not all that bad... compared to some other ideas it's far less flawed than others. But the ideal location for weight is (as has been repeated often) in the tightest concentration in the middle of the bike.
The "conventional wisdom" is still correct... it's the best choice... are we there yet?
lostcoyote
10 W
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- Aug 26, 2008
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- 72
SteveMush
10 mW
Ah....I see now.... Let's change the definition of "ground" so that Safe can remain THE AUTHORITY.......
Paradigm shift - The ground does not move up - the bike leans down.
I know its hard, Safe......
(If you write "countersteer real often and add large pictures, do you get excited?)
Paradigm shift - The ground does not move up - the bike leans down.
I know its hard, Safe......
(If you write "countersteer real often and add large pictures, do you get excited?)
SteveMush
10 mW
Why is it that the blind and the desperate inevitably resort to obnoxiously large, bolded, italicized fonts when flailing about like you? Oh, yes - Let's not forget annoyingly large, colored illustrations, too.
Perhaps you should post at a mortorcycle forum, as it's obvious that's what you are fixated on.
If you can still think (rather than just spew), consider that the rotational mass and inertia of a motorcycle are huge compared to a light bicycle with the much larger mass of its rider on it.
The rotational behavior of a massive motorcycle might be expected to be rather different than that of a motorcycle, where the forces exerted by the rider and the road are much larger than the rotational mass of the lightweight frame between. It's only when we start lumping on massive sla's that approach the weight of the frame itself that we start seeing considerable inertial moment effects. To answer that situational question with treatises on the roll behavior of heavy motorcycles just might be a wee bit off the mark.
Do you acknowledge that the ground and the rider exert the major forces on a bicycle?
Do you understand the term "frame of reference"? A shift of reference frame does not invalidate rotational movement at all. It may, though, allow one to see dynamic movements in a different way. BTW - "rotational movement" is not the same thing as "roll", and you have not got the definition of roll right - objects do not simply roll along an axis through the middle, as you say.
What's your educational background, Safe?
Read the excellent articles at:
http://en.wikipedia.org/wiki/Bicycle_an ... e_dynamics
http://www.dclxvi.org/chunk/tech/trail/
EXCELLENT explanations of factors affecting bike stability and control.
Surprisingly, their learned authors don't seem to share your need for large, obnoxious fonts and repettitive large, annoying illustrations to bolster their points.
Why is that, I wonder? Is it that your "street cred" on this topic is so lacking that you must fill the screen with excessivly large drivel to bolster yourself?
Perhaps you should post at a mortorcycle forum, as it's obvious that's what you are fixated on.
If you can still think (rather than just spew), consider that the rotational mass and inertia of a motorcycle are huge compared to a light bicycle with the much larger mass of its rider on it.
The rotational behavior of a massive motorcycle might be expected to be rather different than that of a motorcycle, where the forces exerted by the rider and the road are much larger than the rotational mass of the lightweight frame between. It's only when we start lumping on massive sla's that approach the weight of the frame itself that we start seeing considerable inertial moment effects. To answer that situational question with treatises on the roll behavior of heavy motorcycles just might be a wee bit off the mark.
Do you acknowledge that the ground and the rider exert the major forces on a bicycle?
Do you understand the term "frame of reference"? A shift of reference frame does not invalidate rotational movement at all. It may, though, allow one to see dynamic movements in a different way. BTW - "rotational movement" is not the same thing as "roll", and you have not got the definition of roll right - objects do not simply roll along an axis through the middle, as you say.
What's your educational background, Safe?
Read the excellent articles at:
http://en.wikipedia.org/wiki/Bicycle_an ... e_dynamics
http://www.dclxvi.org/chunk/tech/trail/
EXCELLENT explanations of factors affecting bike stability and control.
Surprisingly, their learned authors don't seem to share your need for large, obnoxious fonts and repettitive large, annoying illustrations to bolster their points.
Why is that, I wonder? Is it that your "street cred" on this topic is so lacking that you must fill the screen with excessivly large drivel to bolster yourself?
Tiberius
10 kW
SteveMush said:
Steve,
That is good advice, but I have to wonder if you yourself have read these articles properly. They contradict each other on at least one important point, so I wonder why you describe them as "EXCELLENT". Where they do agree, they generally support safe and undermine you and John.
Nick
SteveMush
10 mW
That bike dynamics and behavior are continuing topics of discussion is pretty good proof that there are many theories and ways to look at the topic; not just Safe's and certainly not just mine.
I have no illusions of exclusivity. Safe does.
I have no illusions of exclusivity. Safe does.
Tiberius
10 kW
SteveMush said:
There is a well established scientific method for testing and improving theories. Why are you so insistent on hurling abuse instead of following that?
Nick
TylerDurden
100 GW
Safe has a well-established history of trying to rewrite nomenclature (particularly in areas he has little experience in... i.e. "current warping").
"Roll" and "lean" describe relationships: "roll" referring to motion (or position) in relation to CoM/CoG, "lean" referring to motion/position in relation to the ground.
Countersteer makes the bike lean, by moving the front contact-patch to the side (the rider's momentum continues to pull the bike to the opposite side). The bike will continue to lean that direction (catastrophically), unless the rider turns the fork to direct the front contact patch to counteract the lean.
Similarly, the action does also result in "roll" motion/position change, but the mass of a bicycle is so small that the roll-momentum is inconsequential.
"Roll" and "lean" describe relationships: "roll" referring to motion (or position) in relation to CoM/CoG, "lean" referring to motion/position in relation to the ground.
Countersteer makes the bike lean, by moving the front contact-patch to the side (the rider's momentum continues to pull the bike to the opposite side). The bike will continue to lean that direction (catastrophically), unless the rider turns the fork to direct the front contact patch to counteract the lean.
Similarly, the action does also result in "roll" motion/position change, but the mass of a bicycle is so small that the roll-momentum is inconsequential.
safe
1 GW
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- Dec 22, 2006
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- 5,681
We can all agree that this topic is complex.But we also need to be faithful to what truths have come to have been known over the years. (if wikipedia has one definition of things you should be wary of latching onto something else)
http://en.wikipedia.org/wiki/Countersteering
All I've been doing is being persistent in asserting the basics (again and again) in order to steer things towards the right answer. I think what happens (and this has happened to me) is that once you get a particular idea into your head even if others point out that the idea is flawed you cannot shake it until you really understand the topic deeply enough.
When I first got here I was having the hardest time with the inductance of electric motors and how that inductance combined with a PWM actually allowed MORE currrent to pass than what the current limiter in the controller was programmed to permit. (this has been called "current multiplication" here) I just couldn't believe it!
Well, now I realize that I was wrong and it's absolutely true that motor inductance causes large current to flow at low rpms. (which causes rapid motor heating)All I'm saying is that there is a single idea that has been presented here that is clearly wrong and it's the idea of pivoting on the rear wheel contact patch as the roll axis. I'm not trying to answer all things to all people, but just to correct that one mistake.
TylerDurden
100 GW
safe said:
safe said:
safe said:
safe said:
Ypedal
100 TW
Hey.. i offered to purge safe from this thread on page 4 or so... you all got what you wished for lol.... :wink:
safe
1 GW
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- Dec 22, 2006
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- 5,681
There is no difference from what I've been saying and wikipedia or any other reputable online source.
The "conventional wisdom" simply says that the ideal location for all weight on the bike is in the center. Knowing where the center really is can be an issue (that's where it gets complex) but conceptually I really am the one on the side of truth here.
(I can understand "safe bashing" but when we talk about truth I am coming down on the correct side of it)
Maybe what's needed is some OTHER website that has something posted that SUPPORTS the "pivot at the rear contact patch" theory.
I challenge the people who support this "revolutionary vision" to do something to support their position. Let's see some supporting documentation!!!
Let the revolutionaries prove themselves!!!
The "conventional wisdom" simply says that the ideal location for all weight on the bike is in the center. Knowing where the center really is can be an issue (that's where it gets complex) but conceptually I really am the one on the side of truth here.
(I can understand "safe bashing" but when we talk about truth I am coming down on the correct side of it)
Maybe what's needed is some OTHER website that has something posted that SUPPORTS the "pivot at the rear contact patch" theory.I challenge the people who support this "revolutionary vision" to do something to support their position. Let's see some supporting documentation!!!
Let the revolutionaries prove themselves!!!
John in CR
100 TW
Safe,
You can't even get "conventional wisdom" right. Look at where the Chineses put their batteries, which are typically lead acid. They make and use e-bikes by the tens of millions, not by the tens like the designs you use as support, and with few exceptions the batteries are placed as close to the rear wheel and as low as practical. Even their sit down electric scooters have their battery weight located there, and because of this they will be more agile and bike-like in handling than any of the things you are building. Sure you're putting pedals on the latest version, so you can call it a bike, but what kind of idiot would build a bike that can't reasonably or comfortably be pedaled? All I can say is thank goodness I don't have to deal with you in person, *** *** *** edit *** *** ***
Have a nice day,
John
You can't even get "conventional wisdom" right. Look at where the Chineses put their batteries, which are typically lead acid. They make and use e-bikes by the tens of millions, not by the tens like the designs you use as support, and with few exceptions the batteries are placed as close to the rear wheel and as low as practical. Even their sit down electric scooters have their battery weight located there, and because of this they will be more agile and bike-like in handling than any of the things you are building. Sure you're putting pedals on the latest version, so you can call it a bike, but what kind of idiot would build a bike that can't reasonably or comfortably be pedaled? All I can say is thank goodness I don't have to deal with you in person, *** *** *** edit *** *** ***
Have a nice day,
John
TylerDurden
100 GW
"Equilibrium is achieved when the angle of lean is such as to balance the two opposing moments, the one due to centrifugal force acting outward, and the other to gravitational force acting downward (both acting through the C.of G.). The actual angle, which depends on the radius of the turn and the speed of the machine, is that at which the resultant of the two forces passes through a line joining the front and rear tyre contact patches."
http://www.tonyfoale.com/Articles/Balance/BALANCE.htm
http://www.tonyfoale.com/Articles/Balance/BALANCE.htm
Tiberius
10 kW
John in CR said:
Wow, this takes the quality of rational discourse to a new low. I'd be surprised and disappointed if the moderators don't take action against postings of this sort.
There is no justification for this, John. Its irrelevant that, on the point you and safe have discussed the most here, he is right and you are wrong.
Nick
John in CR
100 TW
Tiberius said:
Oh really? Please do explain. While you're thinking about how to do so, think about this. Imagine 2 infinitely small 500lb weights and two identical bikes. Place one weight at the unladen CoG of one bike and one weight at the rear contact patch of the other bike. Neither weight changes the CoG of either bike as long as both wheels remain on the ground. Let's ignore the impact on traction, tire deformations and the fact that during turns the contact surface moves away from the centerline, because these are all irrelevant to the point of disagreement.
I maintain that one will feel heavy and steer like a motorcycle with the difference in handling quite noticeable, and the other will lean, steer, and countersteer exactly as it did before adding the weight (identical angles and feel). There will be a small effect resulting from countersteer moving the contact patch weight a slightly greater lateral distance, however, the angles are so small that even at 500lbs the difference is negligible. Note that I'm not saying you won't feel that you're dragging around an extra 500lbs, just that it won't really change the way the bike turns.
Note that I also never said handling like a motorcycle is necessarily bad. The point I've tried to make is that as you move away from the rear contact patch, the weight of batteries will have more effect on handling. Others have already described the effects depending upon the location, but only a few have agreed which direction minimizes those effects. The rear contact patch is just a starting point, because it's the anchor point of all movement in the frame, and there are other considerations to take into account in determining battery placement including convenience, which I consider to be more important than all other factors. By convenience I mean not getting in the way and not making it cumbersome when off the bike, but Safe would never consider using that to explain why those expensive bikes put their batteries in the center, since no one would disagree.
Edit: Please note that knocking sense into youknowwho was meant only in a joking and figurative way, not literal. For someone to take offense is either misunderstanding or typical oversensitivity toward political correctness that has become problematic in today's society. I don't believe my post warranted modification, though I would have done so myself if asked. Rude and crude, sure, but only in jest, and still far less obnoxious than the repeated posting of irrelevant large pics and graphics.
John
safe
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So we have two weight locations. (I just want to be sure we are in agreement) One is in the center, what I can the "conventional wisdom" location. The second is in the rear contact patch location.John in CR said:
I think I can identify your mistake here. (and others feel free to comment about just list limited issue and don't sidetrack things please)John in CR said:
The problem is in the assumption that a 500 lb weight (a heavy motorcycle) during countersteer would have only a negligible effect. There are two cases:
Slow Speed - At slow speed the rear contact patch diverges only a small amount and you very well might be able to treat the weight as negligible. This is the situation that you are likely focused on.
High Speed - Let's say we are traveling at 50 mph. (something that you might do on a steep downhill) At this speed countersteering 500 lbs would require the bike to be seriously leaned over. In order to get to the desired lean angle you first have to countersteer and that creates a rotational torque on the center of gravity of the bike. The bike wants to continue in a straight line (momentum) so your front and rear contact patches need to drift waaaaay out to get the lean angle you want.
In the first case you are doing fine. (speeds around 5-10 mph would be no problem) But at the high speed you have a serious problem facing you because the closer the weight is to the ground the more it will work to prevent your attempts of getting the bike set up for the turn. You have to think of bike rotation as acting like an "inverted pendulum".
Now before we go on, let's agree that speed matters. What might be perfectly acceptable at slow speeds can be life threatening at higher speeds.
Can we agree so far?Note to Papa:
I've been stubburn and wrong before too. It might be a simple matter of getting John to see why what he thinks does not apply in all cases. He does have a point at extremely slow speeds. Many of these little scooter things are perfectly capable of doing their job at speeds below 10-15 mph.
John in CR
100 TW
Papa,
You have officially entered the "Safe Zone" from which it will be difficult to return, and I'd be pissed off too if I found myself there. You my friend are wrong, and yes adding weight at the rear contact patch has zero effect on the CoG of the bike as long as that wheel remains on the ground. I'll go even further to say that the CoG of the bike itself is of little importance for a bike, because the weight of the rider is so dominant, and because the frame is not only leaning from left to right, but is also turning from left to right.
Safe,
2 bikes and weight in different locations. Yes the one with the weight placed in the original CoG of the bike will be all but impossible to ride, unlike the bike hauling the 500lbs at the ground. WRT to turning at speed, the faster you go the longer the distance covered during countersteer, so the angles remain very small. I'd be more concerned about sharper turns at lower speed, like whipping the bike around a pothole. That's where the increased lateral movement would become more than negligible. The ideal placement for such a maneuver will vary with speed and size of the pothole, but the one with the 500lbs at the CoG isn't whipping around anything because it's momentum will resist the left/right turn of the frame required. ie don't just look at the rear view, look at it from above as well. With the weight at the rear tire patch, the weight just follows where the front leads it.
John
You have officially entered the "Safe Zone" from which it will be difficult to return, and I'd be pissed off too if I found myself there. You my friend are wrong, and yes adding weight at the rear contact patch has zero effect on the CoG of the bike as long as that wheel remains on the ground. I'll go even further to say that the CoG of the bike itself is of little importance for a bike, because the weight of the rider is so dominant, and because the frame is not only leaning from left to right, but is also turning from left to right.
Safe,
2 bikes and weight in different locations. Yes the one with the weight placed in the original CoG of the bike will be all but impossible to ride, unlike the bike hauling the 500lbs at the ground. WRT to turning at speed, the faster you go the longer the distance covered during countersteer, so the angles remain very small. I'd be more concerned about sharper turns at lower speed, like whipping the bike around a pothole. That's where the increased lateral movement would become more than negligible. The ideal placement for such a maneuver will vary with speed and size of the pothole, but the one with the 500lbs at the CoG isn't whipping around anything because it's momentum will resist the left/right turn of the frame required. ie don't just look at the rear view, look at it from above as well. With the weight at the rear tire patch, the weight just follows where the front leads it.
John
lostcoyote
10 W
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- Aug 26, 2008
- Messages
- 72
john,
have you taken any physics courses?
center of gravity has to do with mass distribution and specifically, the balancing point (fulcrum or centroid)) of that volume of mass integrated over 3 dimensions..
furthermore, it is independant of whether the body of mass rests on the ground at 2,3, or 4 points or if it floats above a cloud.
http://en.wikipedia.org/wiki/Center_of_gravity
try this simple exeriment:
support a 12 inch ruler on each end with a glass or aluminum can. put your finger on the 6 inch mark and lift. the ruler is more or less balanced on your finger at this point, which marks the rulers center of gravity.
rest the ruler back on the cans or glasses. add a quarter to the 10 inch mark. place your finger back under the 6 inch mark and lift it up again. guess what? the cnetr of gravity of the ruler has shifted away from the 6 inch mark as the 12 inch side tips down.
the bike is no different. center of gravity is determined by spatial mass distribution.
study the link provided above and understand the simple math equations as well as the concept presented.
to add to the experiemnt outlined above, get a 6 long 2x6 board and 2 bathroom scales. place each end of the wood board on the scales.
next, put a 10 pound bag of sugar at the center of the board (the 3 foot point) and measure the scale. assuming a 5 pound board, each scale would record 7.5 pounds.
next, shift the bag of sugar to about the 5 foot position. note that the scale closer to the bag of sugar increases in weight while the scale further away decreases (but each scale adds up to 15 pounds still)
try it.
this is high school physics.
i don't mean to come across as being arrogant here, but your statement that the center of gravity does not change when you add weight over the rear wheel is simply not correct just because it makes contact with the ground. if that was true, then part 2 of the experiment with the 2x6 would indicate that no matter where you place the sugar bag along the 2x6, each scale would always indicate 7.5 pounds.
have you taken any physics courses?
center of gravity has to do with mass distribution and specifically, the balancing point (fulcrum or centroid)) of that volume of mass integrated over 3 dimensions..
furthermore, it is independant of whether the body of mass rests on the ground at 2,3, or 4 points or if it floats above a cloud.
http://en.wikipedia.org/wiki/Center_of_gravity
try this simple exeriment:
support a 12 inch ruler on each end with a glass or aluminum can. put your finger on the 6 inch mark and lift. the ruler is more or less balanced on your finger at this point, which marks the rulers center of gravity.
rest the ruler back on the cans or glasses. add a quarter to the 10 inch mark. place your finger back under the 6 inch mark and lift it up again. guess what? the cnetr of gravity of the ruler has shifted away from the 6 inch mark as the 12 inch side tips down.
the bike is no different. center of gravity is determined by spatial mass distribution.
study the link provided above and understand the simple math equations as well as the concept presented.
to add to the experiemnt outlined above, get a 6 long 2x6 board and 2 bathroom scales. place each end of the wood board on the scales.
next, put a 10 pound bag of sugar at the center of the board (the 3 foot point) and measure the scale. assuming a 5 pound board, each scale would record 7.5 pounds.
next, shift the bag of sugar to about the 5 foot position. note that the scale closer to the bag of sugar increases in weight while the scale further away decreases (but each scale adds up to 15 pounds still)
try it.
this is high school physics.
i don't mean to come across as being arrogant here, but your statement that the center of gravity does not change when you add weight over the rear wheel is simply not correct just because it makes contact with the ground. if that was true, then part 2 of the experiment with the 2x6 would indicate that no matter where you place the sugar bag along the 2x6, each scale would always indicate 7.5 pounds.
