I am not going to respond to your questions anymore but I did want to say the above has to be on my all time list of how people can take a little bit of information and knowledge, make a couple of wrong assumptions, and put it together completely wrong. Such statements are why I have given up. If nothing else though, it is entertaining.vadiver said:
...and Force is roughly equal to aerodynamic drag (ie, kV^2) in the case of a rider on a flat, smooth road, where rolling resistance and elevation change are negligible.vadiver said:
Rolling resistance and elevation change produce a constant frictional force on the rider, which means that power is proportional only to velocity for those terms. Aero drag varies with velocity^2, which means that the power requirement for that term varies with velocity^3. The KK has both a linear term and a cubic term, which is why it simulates a rider traveling up a slight incline.vadiver said:
Question: You don't mean to say it is the presence of the linear term that simulates a rider traveling up a slight incline do you. Isn't the linear term always there and it is the magnitude of that term that simulates flat or any particular incline?frenchyge said:
This is fine as a rough estimate assuming the rider is 'at speed'. Which is fine, I do not have a problem with that all though the units do not match. This is back to the previous post that if speed is high, and the change is small it is a better approximation. When speed is low and the change is high the approximation is much less accurate.frenchyge said:
Reading the KK website on this they use DifEQ/numerical analysis to derive the formula. It has been a long time since I took/applied DifEQ but I understand what they are saying. Since they are saying that they are only estimating Watts, I think they are not concerned about units.frenchyge said:
Fday said:
Yes, your rephrasing is more correct. On the road there are several components which are all linear, including drivetrain frictional/mechanical losses, rolling resistance, elevation changes, etc. which may be combined or neglected depending on the accuracy one desired in a model. In the KK unit, the linear term would be associated with internal friction and rolling resistance between the tire and roller. My guess is that the KK engineers used a best fit to determine the magnitude of their linear term and then determined the corresponding slope and rolling resistance of a virtual rider.Fday said:
It's not equal, but it is proportional. The constant k combines parameters of frontal area (m^2), drag coefficient based on shape (dimensionless), and air density (kgm^-3) which matches things up when multiplied by velocity^2.vadiver said:
Correct, just understand that the default Cd and FA values in analyticcyling.com are pretty much world-class aero. A typical rider, even in an aero position, will not get near those values, and on a typical ride the values are higher still. You and Frank can argue about how accurate is accurate enough for the basis of the discussion, I was just trying to help illustrate the conditions under which power is proportional to velocity^3.vadiver said:
The winner in the sprint will be the one with the most power. The maximum downward pedal force for a small portion of the circle is a small part of that output so the person with biggest maximum force does not necessarily have the most power. He may, but it is not guaranteed.n crowley said:
Correct, they state that in one of their discussions. I think the one on their computer.frenchyge said:
That will work. There is the KG and the extra meter,Thanks.frenchyge said:
That explains it. The accuracy comes from the constant k. If I wanted the KK formula to work the DifEQ/NA would be done on my mass and frontal area. It would be great for me, not so good for others. Their site does a good job at explaining the "rider" the used.frenchyge said:
Again, doesn't matter, the one with the most net force (and perhaps the lightest net weight if there is a difference. By net force I mean the combination of the two crank forces together. Once the pedals are moving it is the one with the highest power, before they are moving it is the one with the highest net force. Watch track riders on the pursuit where acceleration is important. Watch how hard they pull up on the back.n crowley said:
Just FWIW, only this past week I experimented with sprinting, cadence, and technique. I confirmed that I do better in a sprint by using a light gear, very high cadence, and concentrate on spinning circles while sprinting.n crowley said:
. At 40 I'm still better off concentrating on climbing.
I haven't a clue. I can tell you how much negative torque they apply there or anywhere around the circle including the top, bottom, and anywhere on the upward portion: ZERO. Other than that I don't EXPECT them to do anything. I suspect all riders are different and it would depend a lot on the kind of racing they do.n crowley said:
