formula energy wheel

[ada@prorider.or]

i try to calc the potential energy together with it's aerodymic's data
but all formula's i know there is only talking about mass
but to calc this its also moving in air
so in my opion you must take this calc at the same time as the aerodynamics data is take
becuase in my mind the lighter the air its moves more easily
to if you take data from day that the pressure is
1.20 kg /m3 then the next day its 1.18 kg/m3 its value's is differant
does some has a formula to calc this so you can include the aerodynamics data
this what i have
Ek = mvC2/2 + m.r2.?2/4


who can help
i am just a simple bike mechanic who try to understand where i go wrong
cees :banana:

[Louis]

Cees,

As you know, potential energy is stored energy, e.g. a deflected spring (0.5 k x^2) or a mass at the top of a hill (mgh).

Other than the air in the tire, aerodynamics on the bike is mostly drag and wind forces on the wheel and rider. Aerodynamic effects should have little to do with potential energy, (at least the way I look at the problem).

Maybe I don’t understand the question, but I don’t see the connection between aerodynamics and stored energy.

Louis

See also:

http://en.wikipedia.org/wiki/Potential_energy

[Argos]

Maybe you should contact your local Low Speed Wind Tunnnel. I was down at the corner wind tunnel this morning on my way back during my ride... I picked up a Slurpee and some Fig Newtons and kept going, but they were doing all sorts of higher math and just having a grand old time.

[ada@prorider.or]

Cees,

As you know, potential energy is stored energy, e.g. a deflected spring (0.5 k x^2) or a mass at the top of a hill (mgh).

Other than the air in the tire, aerodynamics on the bike is mostly drag and wind forces on the wheel and rider. Aerodynamic effects should have little to do with potential energy, (at least the way I look at the problem).

Maybe I don’t understand the question, but I don’t see the connection between aerodynamics and stored energy.

Louis

See also:

http://en.wikipedia.org/wiki/Potential_energy

well if i have a wheel and its aerodynamic's coeff
and want also to calc it's energy that's need it to move
you do this by testing its angle speed in time
thats needed but this also implies in my opion that you meassure at the same time its aerodynamics effect
but to isolate this you must eliminate this
so who do i do that? in a formula?

[Louis]

Cees,

I would start here: http://www.analyticcycling.com/WheelsConcept_Disc.html

They also give some references that might be usefull. You could also try a Google search for "bicycle wheel forces" or something like that.

Good luck
Louis

[Argos]

Am I the only one that finds it weird that he comes here for his reasearch information?

[ada@prorider.or]

Am I the only one that finds it weird that he comes here for his reasearch information?

can you then meaby say where otherwise then a bicyle forum can ask bicyle related question's is that not the meaning of bicycle forums?
or do you only want to know how to inflate up your tyre
of your presta valve?

[93legendti]

Am I the only one that finds it weird that he comes here for his reasearch information?

I agree--that is when I understand what his point is. His posts do not increase my faith in his products.

[ada@prorider.or]

I agree--that is when I understand what his point is. His posts do not increase my faith in his products.

yes that right that why i ask questions to become smarter again i am just a plain stupid bike mechanic
but i learned at shool the stupids people are who not ask question about someyhing that they do not understand

and do as they undestand but really do not

[Argos]

can you then meaby say where otherwise then a bicyle forum can ask bicyle related question's is that not the meaning of bicycle forums?
or do you only want to know how to inflate up your tyre
of your presta valve?

Yes, please let me know how to inflate the air into my many pairs of Zipp wheels. That is clearly what I am asking you and what you must confine your line of discussion to.

No, Cees. Similar to what 93LegendTi alluded to, you are a high end wheel builder, so it seems odd for you to be asking us opinions on how to build/test/evaluate/modify your product.

This is an open forum, and you are as free to ask whatever you want as well as I am free to question its appropriateness. And I am only questioning its appropriateness based on the source.

If, for example, FORUM USER X asked the same question, except was not known to build world class cycling components, especially wheels, for a living, and was instead a Postal Worker in our lovely American city of Boise, then the source of the question would have different implications on the intent of the question.

Or, as an analogy, "this question you pose" is to "odd and suspicious" as "Your last question regarding Zipp claims" was to "innapropriate and out of place"

[ada@prorider.or]

[QUOTE=Argos]No, Cees. Similar to what 93LegendTi alluded to, you are a high end wheel builder, so it seems odd for you to be asking us opinions on how to build/test/evaluate/modify your product.
QUOTE]

again this is not to modify any of my products

i am just searching to calc performance of differant setups it's performance
again i am not here for my products
i suggested sveral time's to modify my name so it become's more independent
but i am a person who does not hide and find another name
i aks questions i honest way with no meaning whats ver behind it and certainly not to promote any product
again i am just a simple bike mechanic not more or less despite what other;s say so my questions are from personal interest in something i do not understand .

i do not know everything !!!!!!!!!!!
and i also was a postman years ago so we have that that same

and what zipp regarding is i never say something that about there products only about the 2 graphs that i do not understand and you also not i recon otherwise some could give me the right answer

do you find it strange if you do not undertand that you aks question about it in hope some one does understand and can explain

i am always please when i get a explanation about something that i could not understand before

another thing is how many designers ask questions openly?
i am not afraid of asking things that i do not understand despite what people think of me


cees

[Argos]

Uh, sure, ok, what you said.

You want help? Try this, it's very effective.

www.google.com

I'm pretty sure if the answer you are looking for exists you can find it here.

I was never a Postal Worker, that was an example.

[Ken Lehner]

can you then meaby say where otherwise then a bicyle forum can ask bicyle related question's is that not the meaning of bicycle forums?
or do you only want to know how to inflate up your tyre
of your presta valve?

Try Bike Tech Review (http://biketechreview.com/v-web/bulletin/bb/index.php). Real scientist-types and excellent cyclists hang out there; many do some interesting tests of wheels, tires, etc. I'm sure your questions and input would be quite welcome.

[jerk]

cees-
don't mind these guys. your questions are welcome and hopefully someone here can help you out.
jerk

[Mud]

:bike:

[Chief]

i try to calc the potential energy together with it's aerodymic's data
but all formula's i know there is only talking about mass
but to calc this its also moving in air
so in my opion you must take this calc at the same time as the aerodynamics data is take
becuase in my mind the lighter the air its moves more easily
to if you take data from day that the pressure is
1.20 kg /m3 then the next day its 1.18 kg/m3 its value's is differant
does some has a formula to calc this so you can include the aerodynamics data
this what i have
Ek = mvC2/2 + m.r2.?2/4


who can help
i am just a simple bike mechanic who try to understand where i go wrong
cees :banana:


The aerodynamic drag F for a body of frontal area A and aerodynamic drag coefficient Cd moving at a speed V through a fluid (air) of mass density d is

F=Cd*A*(d*V*V/2)

The quantity within the parenthesis is the stagnation pressure--that is, the pressure exerted on a flat body resuting from a fluid of speed V impacting the body.

The work done by this force or the energy E required to move the body through the air is

E=F*D=Cd*A*(d*V*V/2)*D

where D is the distance that the body is moved.

However, I think you are probably more interested in the power than the energy in which case the power P is

P=F*V=Cd*A*(d*V*V/2)*V

It is clear from these formulae that the energy or power is proportional to the density of the fluid. Therefore, if density of air is 1.20 kg/m3 on one day and 1.18 kg/m3 the next day, then the energy or power for the latter condition at the same speed V, etc., will be 1.18/1.20=0.98 as much; ie, approximately 2% less.

I hope this will be of some benefit to you.

[Climb01742]

The aerodynamic drag F for a body of frontal area A and aerodynamic drag coefficient Cd moving at a speed V through a fluid (air) of mass density d is

F=Cd*A*(d*V*V/2)

The quantity within the parenthesis is the stagnation pressure--that is, the pressure exerted on a flat body resuting from a fluid of speed V impacting the body.

The work done by this force or the energy E required to move the body through the air is

E=F*D=Cd*A*(d*V*V/2)*D

where D is the distance that the body is moved.

However, I think you are probably more interested in the power than the energy in which case the power P is

P=F*V=Cd*A*(d*V*V/2)*V

It is clear from these formulae that the energy or power is proportional to the density of the fluid. Therefore, if density of air is 1.20 kg/m3 on one day and 1.18 kg/m3 the next day, then the energy or power for the latter condition at the same speed V, etc., will be 1.18/1.20=0.98 as much; ie, approximately 2% less.

I hope this will be of some benefit to you.

darn, i was gonna say that, but chief beat me to it!
:banana:

[flydhest]

chief,

Does this formula need to be modified to account for the fact that the wheel is spinning? The top/leading edge is going faster than the hub and the bottom/trailing edge is going slower. Moreover, as the wheel is spinning, there's a continuum of velocities that each point on the wheel goes through.

[Chief]

chief,

Does this formula need to be modified to account for the fact that the wheel is spinning? The top/leading edge is going faster than the hub and the bottom/trailing edge is going slower. Moreover, as the wheel is spinning, there's a continuum of velocities that each point on the wheel goes through.


I agree that there is the complicating factor of the spinning wheel, but as I understand the question it is to relate the influence of changes in the mass density of air on the energy/power in which case the energy/power will be proportional to the mass density regardless of this complicating factor. The continuum velocities of which you speak are proportional to the speed of the wheel/bike. Therefore, this complicating factor can be included in the definition of the drag coeffient for a rolling wheel which I is suspect is done in estimating wheel drag. If such a definition for the drag coeffient is used, then it is not necessary to modify the formulae. The determination of the drag coefficient would probably have to be determined experimentally because of the complexity of solving the fluid dynamic problem for the aerodynamic drag of a rollling wheel. The presentation in my earlier post was an effort to provide a simple engineering solution that one could use to evaluate the relative influence of various paramters (e.g., air density) on the aerodynamic drag.

[flydhest]

Chief,

If I read the formula you wrote correctly (no guarantees and it's your own fault for engaging me in conversation, I make not claims about knowing what I'm talking about here) it looks like force is non-linear (indeed, quadratic) in velocity. If that's the case, then it strikes me that the velocity differentials that the parts of the wheel experience do change the relationship--perhaps (likely?) not dramatically, but non-linearity is one of my favorite characteristics of cycling.

Of course, if you're right about the coefficient including this fact, then I suppose you're right, but I think (based on this exchange) that this coefficient would therefore be a function of density. If these are all calculated experimentally, one might as well answer the OP's question that way.

Am I making sense?

The bottom line, however, appears to be to ride just before a storm.

[Chief]

Chief,

If I read the formula you wrote correctly (no guarantees and it's your own fault for engaging me in conversation, I make not claims about knowing what I'm talking about here) it looks like force is non-linear (indeed, quadratic) in velocity. If that's the case, then it strikes me that the velocity differentials that the parts of the wheel experience do change the relationship--perhaps (likely?) not dramatically, but non-linearity is one of my favorite characteristics of cycling.

Of course, if you're right about the coefficient including this fact, then I suppose you're right, but I think (based on this exchange) that this coefficient would therefore be a function of density. If these are all calculated experimentally, one might as well answer the OP's question that way.

Am I making sense?

The bottom line, however, appears to be to ride just before a storm.

The velocity differentials of which you speak are proportional to the speed. Therefore, one can factor out the speed quantity and the remainder which is independent of the speed while squared can be included in the definition of the drag coefficient so that the formulae remain unchanged. I hope you follow this because this forum and editor does not lend itself for presenting the mathematical details.

A Google search lead to the following sites which provide formulae in agreement with the ones I persented.

http://www.canecreek.com/166.html

http://www.bsn.com/cycling/WheelAerodynamics.html

Unfortunately the latter does not define the symbols, but I think one can deduce what they are based upon my previous post and the first link. I also think the latter contains a typo.

By the way riding before a storm (low pressure) and when it it hot reduces the air density and hence the drag. Maybe that is why I feel sluggish riding in the winter.