racer Posted February 12, 2008 Report Share Posted February 12, 2008 Scientifically speaking: As for the idea of "getting weight over the bike to put more weight on the tires" ... first, scientifically speaking, we need to separate the concepts of mass and weight. Mass is a measure of matter, weight is an effect due to a force like gravity. On Earth, 1 kg of mass weighs 2.2 lbs due to gravity. Being that gravity on Earth is constant (at 1g), this relationship is consistent all over the planet, hence, one may express weight in kilograms without confusion ... here on Earth. However, if we travel to the Moon, 1 kg weighs ~ 0.36 lbs as the force of gravity is only 1/6 what it is on Earth (or about 0.166g). So, mass remains consistent regardless of forces applied. Weight does not. uhmmm.. kg and lbs measure the same thing...mass. It's just that the kg is ISO and lbs is imperial system. 1kg is approximately 2.2 lbs everywhere Now, the gravitational force (the weight, or the force pulling a corp towards the center of the Earth) is G=m*g where m is the mass and g is the gravitational acceleration and it is considered a constant (it's almost the same everywhere on Earth) and is about 9.8 meters/square second. So one kg of mass will be pulled down with a force equals with 9.8m/s^2, or 9.8 N, where N (Newton) is the ISO unit for force. A given body will have the same mass on the earth and on the moon, but its weight on the moon will be only about 16% of the weight as measured on the earth, because the gravitational acceleration (g) on the moon is lower than on Earth. Yes, 0.166 ~ 16%. That is exactly what I said, abeit without specifically defining Earth's gravitational constant with a formula in terms of Newtons or acceleration as I didn't feel it was really necessary to understanding the basic concept of separating mass and weight and might only serve to complicate what may already be a somewhat complex matter for the layman without a scientific background. And would be redundant for those who already know that, such as yourself. In any case, the salient point is the separation of mass and weight and your explanation perfectly reiterates the principle. Good stuff! You are obviously a smart person and I prefer not to engage in a pedantic discussion of semantics or terminology to split hairs. That said, as you know, the kilogram is commonly used to express weight as well as mass in many parts of the world (like Canada); and, although technically you are correct that lbs are a metric for mass, it is not common usage and I don't know anyone who does so outside of the lab here in the USA. We commonly reserve kg for mass and lbs for weight. I suppose it might be a unique convention that people who live in countries that use the metric system wouldn't use. Ironically, the separation of weight and mass being a relatively recent historical development, even scientists haphazardly still use weight to describe mass in some instances (atomic weight?). So, just out of curiosity, what metric would you use to express the weight of 1 kg of mass on the Moon up there in TO? Would you tell a grade school student that weighs 100 lbs on Earth that they would feel like they only weighed 16 lbs on the Moon? Or would you only express weight on the Moon in terms of a force/acceleration formula for the child? Cheers, mate. Quote Link to comment Share on other sites More sharing options...
CHAOS Posted February 12, 2008 Author Report Share Posted February 12, 2008 harnois, thanks for the response and that makes perfect sense. I made some notes on a piece of paper while reading your post and i will definitely practice those things. I will be taking my R1 to my next track day because my 750 track bike hasnt arrived yet. It will be my first time running a 1k on the track so i will take it slow and gradually work my way up to speed. Thanks again... Quote Link to comment Share on other sites More sharing options...
Ulysses Posted February 12, 2008 Report Share Posted February 12, 2008 first, scientifically speaking, we need to separate the concepts of mass and weight. Mass is a measure of matter, weight is an effect due to a force like gravity. On Earth, 1 kg of mass weighs 2.2 lbs due to gravity. Being that gravity on Earth is constant (at 1g), this relationship is consistent all over the planet, hence, one may express weight in kilograms without confusion ... here on Earth. However, if we travel to the Moon, 1 kg weighs ~ 0.36 lbs as the force of gravity is only 1/6 what it is on Earth (or about 0.166g). So, mass remains consistent regardless of forces applied. Weight does not. Would you tell a grade school student that weighs 100 lbs on Earth that they would feel like they only weighed 16 lbs on the Moon? Or would you only express weight on the Moon in terms of a force/acceleration formula for the child? Cheers, mate. I don't have a problem with someone telling a 100lbs student that he weighs 16lbs on the moon. But while reading your post I noticed that you stated 'scientifically speaking' that you need to separate mass from force and then you used lbs and kg as they were measuring different things (one mass and another one force), which 'scientifically' is incorrect. I thought I'd clarify that. Sorry if it bothered you. Cheers, Quote Link to comment Share on other sites More sharing options...
racer Posted February 12, 2008 Report Share Posted February 12, 2008 first, scientifically speaking, we need to separate the concepts of mass and weight. Mass is a measure of matter, weight is an effect due to a force like gravity. On Earth, 1 kg of mass weighs 2.2 lbs due to gravity. Being that gravity on Earth is constant (at 1g), this relationship is consistent all over the planet, hence, one may express weight in kilograms without confusion ... here on Earth. However, if we travel to the Moon, 1 kg weighs ~ 0.36 lbs as the force of gravity is only 1/6 what it is on Earth (or about 0.166g). So, mass remains consistent regardless of forces applied. Weight does not. Would you tell a grade school student that weighs 100 lbs on Earth that they would feel like they only weighed 16 lbs on the Moon? Or would you only express weight on the Moon in terms of a force/acceleration formula for the child? Cheers, mate. I don't have a problem with someone telling a 100lbs student that he weighs 16lbs on the moon. But while reading your post I noticed that you stated 'scientifically speaking' that you need to separate mass from force and then you used lbs and kg as they were measuring different things (one mass and another one force), which 'scientifically' is incorrect. I thought I'd clarify that. Sorry if it bothered you. Cheers, No bother! Thanks! I'm sure it really helped all the riders without a scientific education to better understand why getting on top of the bike is not the thing to do in a corner. And we wouldn't want them running off and using a common convention like 300 million other people around here. Good call! In any case, imputing an emotional state for me will not help you to avoid the question. How much does 1 kg of mass weigh on the Moon for someone who lives north of the border? Seriously... I'm sure it will come up again for me and I don't want to scientifically stick my foot in my mouth or cause any cross-cultural misunderstandings. Quote Link to comment Share on other sites More sharing options...
racer Posted February 12, 2008 Report Share Posted February 12, 2008 Ok, in all seriousness... My initial perception/reaction was that you were in full pedant mode looking to pick nits and split hairs on my head without acknowledging that the principle as I explained it was precisely correct and quite clear. However, in the midst of my reply, I noticed you were in Toronto and I had a wee bit of a mini-epiphany that maybe you didn't understand the somewhat colloquial usage and were sincerely trying to be helpful... and that maybe you were only in half-pedant mode. Children of my generation who were in grade school during the adoption of the metric system as a standard in the rest of the world, and the partial adoption of it here in the US before those in charge changed their minds, were taught that kg were for mass and lbs were for weight and it wasn't really until high school physics that we learned anything different. So, I don't how it is taught to kids today; but, like so many other idiosyncratic habits, I still commonly separate mass and weight with kg and lbs. And, frankly, for the sake of a clear and simple single paragraph pre-amble for why "getting weight on top of the bike" is not only a misnomer, but, not really a good thing, it still seems like a good idea to me. For the record, I do understand what Newton-metres and foot-pounds are. Do you? In hindsight, considering that many here on this website will be using a torque wrench, there is every reason for the distinction to be made quite clearly. Good call! That said, my mini-epiphany led to a larger semi-epiphany that, in addition to the domestic economic reasons (ie GM, Ford and Chrysler having to re-tool their factories in the middle of bankruptcy and govmt bail outs) and the pseudo-protectionist/isolationist economic philosophical reasons (ie forcing the rest of the world to buy SAE tools for US exports and forcing US mechanics to buy a new set of tools to work on Japanese cars, effectively doubling the product line of US tool co's) that I believed in my cynical youth, perhaps there was a very real practical/scientific reason to not "go metric" in the middle of the US Apollo space program landing men on the Moon several times a year during that timeframe. I mean, look at the mess we have now working international missions that crash spaceships into Mars while some NASA scientist is saying, "Oooh, that was centimetres, not inches. D'oh! My bad!" Um... yah. Sure glad that wasn't a manned mission or anything. At least, that is what went through my head at 4am this morning. So, anyway... in light of all of that... I really want to know... for the sake of my international communication skills and general enlightenment... How much does 1 kg of mass weigh on the Moon for the common Canadian? I mean, how would you answer that question in simple terms? Quote Link to comment Share on other sites More sharing options...
Ulysses Posted February 13, 2008 Report Share Posted February 13, 2008 Ok, in all seriousness... My initial perception/reaction was that you were in full pedant mode looking to pick nits and split hairs on my head without acknowledging that the principle as I explained it was precisely correct and quite clear. However, in the midst of my reply, I noticed you were in Toronto and I had a wee bit of a mini-epiphany that maybe you didn't understand the somewhat colloquial usage and were sincerely trying to be helpful... and that maybe you were only in half-pedant mode. Children of my generation who were in grade school during the adoption of the metric system as a standard in the rest of the world, and the partial adoption of it here in the US before those in charge changed their minds, were taught that kg were for mass and lbs were for weight and it wasn't really until high school physics in 12th grade that we learned any different. So, I don't how it is taught to kids today; but, like so many other idiosyncratic habits, I still commonly separate mass and weight with kg and lbs. And, frankly, for the sake of a clear and simple single paragraph pre-amble for why "getting weight on top of the bike" is not only a misnomer, but, not really a good thing, it still seems like a good idea to me. While I did understand exactly what you were trying to say, the idea that one can use kg and lbs to measure different things seemed totally wrong to me. Never before I've seen them used the way you did and I had no idea why you wrote that way. Here, in Canada, in the grocery store for instance they use both lbs and kg, because not everybody is yet comfortable with the metric system. So for me there was no doubt that everybody used them for measuring the same thing... until now at least. Far from me the idea of picking on you. At least, that is what went through my head at 4am this morning. Man.. you've got no sleep??? :-) So, in light of all of that... I really want to know... for the sake of my international communication skills and general enlightenment... How much does 1 kg of mass weigh on the Moon for the common Canadian? I mean, how do you answer that question in simple terms? Sorry to disappoint, but I can't answer your question. I'm not a common Canadian (meaning born and raised in Canada). I've done all my studying in Europe, including the university, so I have no clue what they teach in schools here. He, he... 10 years ago I wasn't even speaking good English. In fact I was barely speaking any English. Quote Link to comment Share on other sites More sharing options...
racer Posted February 13, 2008 Report Share Posted February 13, 2008 Mathematics and science are a universal language of which you seem to have a grasp. And your English is quite good. I haven't noticed any of the syntax errors that usually occur with non-native speakers. I would never have guessed that it wasn't your first language. However, now that you mention it, I suppose that is another dimension to consider in our communications. In any case, whether in Canada or Europe, the point that you continue to not so skillfully avoid addressing is the inherent paradox presented by using the same term to express both mass and weight. THAT is what is illogical. It is understandable that, having grown up (somewhere) in Europe and living in Canada (or whatever country that uses the metric standard), you would not have learned to separate mass and weight by assigning a unique metric from different systems to each. So, how much does 1 kg of mass weigh on the Moon? Quote Link to comment Share on other sites More sharing options...
racer Posted February 13, 2008 Report Share Posted February 13, 2008 Welll... there is increased cornering force compressing the suspension at higher speed/lean angles and vice versa. Soo... then the rake would change between being leaned over more and less. Hence, the steering geometry would be altered, ie. the front wheel would be turned in more or less, no? Aand... it would then seem to follow that the more weight biased toward the front, the more effect there will be... Let's just look at one piece of this--rake: if their is more weight on the front, will that compress the front and in effect, steepen the steering angle? Will that then make it easier to steer the bike (let's say rider has not yet come back on the gas)? C Yes, if the front forks are compressed, the rake will be steeper, hence, the steering geometry will be "quicker". I am assuming by context that the rider in your hypothetical scenario is causing more weight to be on the front by body position and merely decelerating off the gas but not on the brakes? PS: Your original question was posted in reply to a question of mine about whether or not a bike maintains turning radius when hanging off to reduce lean angle at a given speed, in other words if you ride the same corner at the same speed hanging off, will the bike turn the same radius as not hanging off at the steeper lean angle. I didn't see the connection of your question to my question, hence, why I talked through the other conditions of more suspension compression at higher cornering speeds to see if I could make the connection. OK, so I suppose that as one is off and on the gas, the front is compressing and extending and the turn tadius is changing at each point. So, once the rider has cracked the throttle, the front comes up a bit ... at that level of acceleration (40/60), let's call that 40/60 a baseline between the two extremes of compressed fork prior to getting back on the gas and full extension of going WFO at the end. So at 40/60 weight bias for a given lean angle, there will be a radius where we spend some significant fraction of the corner (1/3?). More than 1/3? And that lean angle will or should be max lean for that corner. That radius will be determined essentially by how much the front wheel is turned into the corner which will be determined by a combination of lean angle, overall speed (which affects suspension compression and rake) and level of acceleration or weight distribution (which also affects rake). So, basically, the major function of hanging off is to alter the CoM/moment arm to balance more lateral cornering force (speed) for a given lean angle and acceleration, ie. when you hang off, the bike will balance at less lean angle for a given speed, but, assuming a consistent level of acceleration, will track a wider radius circle. Hence, one can go faster for a given lean angle (like max lean, for instance) and radius. Does that make sense to anyone else??? Quote Link to comment Share on other sites More sharing options...
racer Posted February 13, 2008 Report Share Posted February 13, 2008 And the conservation of angular momentum/centripetal formula will only apply for a specific combination of lean angle AND acceleration level/weight bias /fork angle together, ie if you change lean angle, you alter a basic implicit parameter that is not specifically stated in the condensed formula I posted above. I suppose I can attempt a derivation for that if I get bored. But not today thank you. Quote Link to comment Share on other sites More sharing options...
Cobie Fair Posted February 13, 2008 Report Share Posted February 13, 2008 Racer, your post did make sense. Here is what I was trying to do: get this onto more of a single subject at a time, as I think we are covering a lot of ground. Radius has been brought up, and I was going more in the direction of how the body effects what happens on the bike. What do you guys want to do here? Cobie Quote Link to comment Share on other sites More sharing options...
racer Posted February 13, 2008 Report Share Posted February 13, 2008 I understand. I needed to work that out for some closure (for myself) of my "scientifically speaking" deally deal there. I can see how it might be a tad much to swallow all at once. The floor is all yours, sir. Body position. (Notice I didn't mention that in my closure. I was saving it for you) Quote Link to comment Share on other sites More sharing options...
Cobie Fair Posted February 13, 2008 Report Share Posted February 13, 2008 I understand. I needed to work that out for some closure (for myself) of my "scientifically speaking" deally deal there. I can see how it might be a tad much to swallow all at once. The floor is all yours, sir. Actually, I wanted to see what you guys wanted to cover. This thread had started originally on body position, what's better, etc. C Quote Link to comment Share on other sites More sharing options...
CHAOS Posted February 13, 2008 Author Report Share Posted February 13, 2008 I agree...lets get back to that.... Quote Link to comment Share on other sites More sharing options...
Cobie Fair Posted February 13, 2008 Report Share Posted February 13, 2008 I agree...lets get back to that.... OK, here is a thought for you guys---where is the mass of a rider's body, above or below the waist? With that in mind, what's more beneficial to have hung off? What different styles have you guys seen on this? C Quote Link to comment Share on other sites More sharing options...
racer Posted February 13, 2008 Report Share Posted February 13, 2008 Being that a rider must leave nearly 50% of their lower body mass in the form of a leg over the bike, the Center of Mass of the rest of the body hung off (parallel) will move significantly toward the head. Although one arm is also left over the bike, the arm accounts for a much smaller percentage of upper body mass and will only slightly offset that movement. What will that do to the CoM of the bike/rider combo? What about overall weight distribution f/r? Is it still 40/60? What does it mean for the rake/trail and turn radius? What happens if the head is left over the tank? What about if the rider remains more upright than low/level? Quote Link to comment Share on other sites More sharing options...
Ulysses Posted February 14, 2008 Report Share Posted February 14, 2008 In any case, whether in Canada or Europe, the point that you continue to not so skillfully avoid addressing is the inherent paradox presented by using the same term to express both mass and weight. THAT is what is illogical. It is understandable that, having grown up (somewhere) in Europe and living in Canada (or whatever country that uses the metric standard), you would not have learned to separate mass and weight by the very logical technique of assigning a unique metric to each. Perhaps then you could answer the simple question for any country on the metric standard: How much does 1 kg of mass weigh on the Moon? Ok, I'm not trying to avoid it anymore. :-) I think one would say that a corp that weighs one kilogram (1000 grams) on Earth will weigh only 166 grams on the Moon. Scientifically it's incorrect because the mass it's the same everywhere, but as you mentioned, the units of mass are commonly used to express gravitational force too. The metric system does separate the mass and weight, One is measured in kg and the other in N (newtons), being a force. The same way in the imperial system. You measure the mass in pounds and the force in pound-force, the latter meaning, of course, the force exerted by the gravity on a corp with one pound of mass. It still doesn't seem logical to me to use metrics for mass, but from two different systems, to separate mass from weight, but at least now I know where it comes from. Cheers, Quote Link to comment Share on other sites More sharing options...
racer Posted February 14, 2008 Report Share Posted February 14, 2008 "lb" is also a measure of force. http://en.wikipedia.org/wiki/Pound-force everything I said in my "scientifically speaking" post was 100% accurate and correct... scientifically speaking have a nice day Quote Link to comment Share on other sites More sharing options...
Ulysses Posted February 14, 2008 Report Share Posted February 14, 2008 I agree...lets get back to that.... OK, here is a thought for you guys---where is the mass of a rider's body, above or below the waist? With that in mind, what's more beneficial to have hung off? What different styles have you guys seen on this? C I think that regardless of how the mass of a rider's body is distributed (big legs and small body, or big torso and skinny legs) the more body parts he can put closer to the track the lower the combined CoM will be and this is the intended result. Being parallel with the bike, makes it possible to put more of the upper body lower, as opposed to being crossed on the bike, when the upper body is left high. But it takes some practice to get used to being parallel with the bike. Sometimes, if my butt is off the bike too much, it's hard to lock my knee against the tank and the result it's disastrous. I end up using my arms to hang on to the bike and at that moment the ability to be smooth with the controls is lost. It happens to me especially in combinations of turns when I have to shift my body quickly from one side to the other. Also, one needs to consider how he affects the weight distribution between front and rear when the body is parallel with the bike. If the rider is too close to the tank, I think the upper body tends to remain higher, especially for taller people. But going away from the tank loads more the rear and unloads the front. Intuitively, I feel that being too far back is bad. And if I think about it, the more the rear is loaded, the more the rake is changed for the worse. The forks are loaded less and extend a bit more and the rear is also lowered by the added weight. Quote Link to comment Share on other sites More sharing options...
Ulysses Posted February 14, 2008 Report Share Posted February 14, 2008 And you were being a full blown pedant by looking to pick nits have a nice day IC... I'm a bad person and you're good... I guess I can live with that. and split hairs where, in fact, none existed. So... you're bald? That's ok... the helmet fits better. I know first hand. You have a good day too. And a good night before that... Quote Link to comment Share on other sites More sharing options...
racer Posted February 14, 2008 Report Share Posted February 14, 2008 And you were being a full blown pedant by looking to pick nits have a nice day IC... I'm a bad person and you're good... I guess I can live with that. Again with the evasion and weak attempt at a strawman guilt trip. I believe the words you are searching for are something like, "Oops, I was wrong." Quote Link to comment Share on other sites More sharing options...
racer Posted February 14, 2008 Report Share Posted February 14, 2008 . Quote Link to comment Share on other sites More sharing options...
racer Posted February 14, 2008 Report Share Posted February 14, 2008 Also, one needs to consider how he affects the weight distribution between front and rear when the body is parallel with the bike. If the rider is too close to the tank, I think the upper body tends to remain higher, especially for taller people. But going away from the tank loads more the rear and unloads the front. The more parallel/level the body is, the more forward and low the combined CoM moves. The more hunched or upright the body is the more CoM moves rearward and upward. Intuitively, I feel that being too far back is bad. Why? And if I think about it, the more the rear is loaded, the more the rake is changed for the worse. The forks are loaded less and extend a bit more and the rear is also lowered by the added weight. The rear raises under acceleration. Quote Link to comment Share on other sites More sharing options...
Ulysses Posted February 14, 2008 Report Share Posted February 14, 2008 Again with the evasion and weak attempt at a strawman guilt trip. It was a joke meant to put an end to a discussion that had little to do with the topic. By no means it was a guilt trip. What I wrote in my first post is correct and I stand by it. It was a reply to your post, where your idea of separating the mass from weight and their effect on the bike was good, but the way it was explained was ...well ..wrong. What I was evading was asking you if you need to be always right. I believe the words you are searching for are something like, "Oops, I was wrong." Are you talking to your inner self here? Because otherwise your belief is lapping the track in the wrong direction. Quote Link to comment Share on other sites More sharing options...
Ulysses Posted February 14, 2008 Report Share Posted February 14, 2008 The more parallel/level the body is, the more forward and low the combined CoM moves. The more hunched or upright the body is the more CoM moves rearward and upward. I agree. But now take that rider, parallel with the bike and move it to the rear. Will that move the combined CoM to the rear too? What I was saying was that it's easier to be parallel if you're not pushed against the tank, but that offsets a bit the moving forward of the CoM. Intuitively, I feel that being too far back is bad. Why? I don't know. That's why I call it intuition. I need to think about it. The rear raises under acceleration. Right, but it raises more if it's less load on it. That's one reason for assuming it's better to be as far forward as possible while getting parallel with the bike. Quote Link to comment Share on other sites More sharing options...
racer Posted February 14, 2008 Report Share Posted February 14, 2008 That's one reason for assuming it's better to be as far forward as possible while getting parallel with the bike. The more forward you are the less parallel you can be. The less parallel you are, the higher your CoM will be. Quote Link to comment Share on other sites More sharing options...
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