<div class='quotetop'>QUOTE (mylexicon @ Jun 21 2008, 02:18 AM) <{POST_SNAPBACK}><div class='quotemain'>I know you learned about leverage/torque at some point in your life. When I bike is leaned on it's side, the tires are the fulcrum of the lever. If you take an object of set mass (an engine) and move it farther from the fulcrum, greater leverage is generated. The extra leverage makes easy work when balancing a speeding bike at full lean. Unfortunately, all additional leverage obtained from moving the mass outward must be overcome when moving the bike from full lean back to vertical.
Ok, now I get it, and I think you are right about the physics. I see the advantage, and disadvantage.
Allthough the issue is to move the bike inward to full lean without upsetting the bike to much, not to raise the bike up again. Higher forces means higher forces no matter how well the suspension are sorted. it can only help so much.
<div class='quotetop'>QUOTE <div class='quotemain'>In other words, you need spirited steering (good for Nicky, not good for Dani) and a rider with enough mass to chuck the bike around (good for Nicky, not good for Dani).
I agree with that.
<div class='quotetop'>QUOTE <div class='quotemain'>Sorry if I was unclear. I was trying to say that moving the engine up towards the tank lets the bike do some of its own "hanging off". The rider can stay in farther in the saddle and get better feedback from both tires.
I agree,
but there is another thing, you said the Yamaha had high COG? but the first of all, the fight for years has been to lower the cog. The tank you talk about is just a carbon cover for the airfilter, the tank is mainly under the seat. The IL has inherntly a lower COG than the V4. That's one of the few drawbacks witht the V4, it got lots of heavy rotating parts due to it's four cam shafts, and two setts of cam drive train, compared to the IL's 2 shafts and one dive train. Of course the COG might have raised a bit with the pnumatics but I'm not sure it changes it much at all. Heavy springs are just that, heavy. So my bet is that the Yamaha have a lower COG than the old spring valve Honda
<div class='quotetop'>QUOTE <div class='quotemain'>The contact patch size is important but what is most important is the work it is required to perform. The less a bike leans, the less torsional stress the tires undergo. Even when the contact patch is huge, if all the tire's grip is being used to manage torsional forces there is no grip left to handle acceleration.
Now I'm lost again. No matter how COG influence the lean angle the tire has to cope with the same amount of forces. The bikes lean angle does not alone change that. As you said you increase leverage with higher COG, in that case it's proprtional with the coresponding increased lean angle from a lower COG, the tire has the exact same amount of forces to handle, only thing different is where on the tire the forces attac. Do we agree on that?
There is not any added or substracted forces involved for the tire no matter where the COG is.
The only thing the rider/design can influence is where on the tire these forces work.
<div class='quotetop'>QUOTE <div class='quotemain'>When you have extra torque generated by a high center of gravity you can countersteer less and steer more. In other words you are keeping the bike vertical and limiting the tortional forces on the contact patch. When torsional forces are limited you have more grip to handle acceleration and braking.
Again, keeping the bike vertical does nothing for torsional forces (as long as we are talking about the same thing here, the sentripital force) The sentripetal force does not change, it's a function of speed, radius and mass and has nothing to do with COG of lean angle.
<div class='quotetop'>QUOTE <div class='quotemain'>Obviously, the above is way oversimplified and I wouldn't even know how such phenomenon's actually manifest themselves with today's tire technology. Nonetheless, such a phenomenon still exists.
I think you fell for the myth that raising the bike up wihle leaning in will make it act as if it's going straight forward, avoiding the bike from sliding off.
In the wet it has some advantages as it reduce contact patch and thereby increse the force/area and that again increase the penetrating ability avoiding aqua planing, and I guess that similar holds true in a lot of dirt track conditions but for dry asphalt riding you really want to find the angle of maximum contact patch when you want maximum acceleration out of a turn and the tire has the exact same force to cope with no matter cog.
<div class='quotetop'>QUOTE <div class='quotemain'>High CG is not absolutely better, but, if you have a rider large enough to overcome it's shortcomings, moving the engine upward can only help the handling characteristics.
So the fight for lower COG the last 20 years has been a complete waste?
<div class='quotetop'>QUOTE <div class='quotemain'>P.S. I have made one mistake when talking about high CG machines. I said corner entry is the difficult bit. That is incorrect, corner exit is the difficult bit. Getting the bike to full lean is easy picking it back up again is the hard part. Obviously, I was confronted with my mistake when Nicky talked about how hard difficult the RC212V is to get out of corners when equipped with the pneumatic engine.
I screwed up?!
I think you should stop transfering what Hayden says as being all about COG. The power delivery is much rougher on the air valve engine, of course tha bike is harder to handle out of the corners, but it's not about COG.
Ok, now I get it, and I think you are right about the physics. I see the advantage, and disadvantage.
Allthough the issue is to move the bike inward to full lean without upsetting the bike to much, not to raise the bike up again. Higher forces means higher forces no matter how well the suspension are sorted. it can only help so much.
<div class='quotetop'>QUOTE <div class='quotemain'>In other words, you need spirited steering (good for Nicky, not good for Dani) and a rider with enough mass to chuck the bike around (good for Nicky, not good for Dani).
I agree with that.
<div class='quotetop'>QUOTE <div class='quotemain'>Sorry if I was unclear. I was trying to say that moving the engine up towards the tank lets the bike do some of its own "hanging off". The rider can stay in farther in the saddle and get better feedback from both tires.
I agree,
but there is another thing, you said the Yamaha had high COG? but the first of all, the fight for years has been to lower the cog. The tank you talk about is just a carbon cover for the airfilter, the tank is mainly under the seat. The IL has inherntly a lower COG than the V4. That's one of the few drawbacks witht the V4, it got lots of heavy rotating parts due to it's four cam shafts, and two setts of cam drive train, compared to the IL's 2 shafts and one dive train. Of course the COG might have raised a bit with the pnumatics but I'm not sure it changes it much at all. Heavy springs are just that, heavy. So my bet is that the Yamaha have a lower COG than the old spring valve Honda
<div class='quotetop'>QUOTE <div class='quotemain'>The contact patch size is important but what is most important is the work it is required to perform. The less a bike leans, the less torsional stress the tires undergo. Even when the contact patch is huge, if all the tire's grip is being used to manage torsional forces there is no grip left to handle acceleration.
Now I'm lost again. No matter how COG influence the lean angle the tire has to cope with the same amount of forces. The bikes lean angle does not alone change that. As you said you increase leverage with higher COG, in that case it's proprtional with the coresponding increased lean angle from a lower COG, the tire has the exact same amount of forces to handle, only thing different is where on the tire the forces attac. Do we agree on that?
There is not any added or substracted forces involved for the tire no matter where the COG is.
The only thing the rider/design can influence is where on the tire these forces work.
<div class='quotetop'>QUOTE <div class='quotemain'>When you have extra torque generated by a high center of gravity you can countersteer less and steer more. In other words you are keeping the bike vertical and limiting the tortional forces on the contact patch. When torsional forces are limited you have more grip to handle acceleration and braking.
Again, keeping the bike vertical does nothing for torsional forces (as long as we are talking about the same thing here, the sentripital force) The sentripetal force does not change, it's a function of speed, radius and mass and has nothing to do with COG of lean angle.
<div class='quotetop'>QUOTE <div class='quotemain'>Obviously, the above is way oversimplified and I wouldn't even know how such phenomenon's actually manifest themselves with today's tire technology. Nonetheless, such a phenomenon still exists.
I think you fell for the myth that raising the bike up wihle leaning in will make it act as if it's going straight forward, avoiding the bike from sliding off.
In the wet it has some advantages as it reduce contact patch and thereby increse the force/area and that again increase the penetrating ability avoiding aqua planing, and I guess that similar holds true in a lot of dirt track conditions but for dry asphalt riding you really want to find the angle of maximum contact patch when you want maximum acceleration out of a turn and the tire has the exact same force to cope with no matter cog.
<div class='quotetop'>QUOTE <div class='quotemain'>High CG is not absolutely better, but, if you have a rider large enough to overcome it's shortcomings, moving the engine upward can only help the handling characteristics.
So the fight for lower COG the last 20 years has been a complete waste?
<div class='quotetop'>QUOTE <div class='quotemain'>P.S. I have made one mistake when talking about high CG machines. I said corner entry is the difficult bit. That is incorrect, corner exit is the difficult bit. Getting the bike to full lean is easy picking it back up again is the hard part. Obviously, I was confronted with my mistake when Nicky talked about how hard difficult the RC212V is to get out of corners when equipped with the pneumatic engine.
I think you should stop transfering what Hayden says as being all about COG. The power delivery is much rougher on the air valve engine, of course tha bike is harder to handle out of the corners, but it's not about COG.
