Which is best in wheels- weight or aerodynamics?



alienator

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mpre53 said:
It's an inherent problem in the Huddler platform used to power the site. Almost every Huddler powered site suffers from it. :rolleyes:
I've never been a fan of the software running this site.
 

howardjd

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hmm I see your point about the water not spinning, although it probably does spin to some degree. Some type of gelatin mixture would probably be preferable. If I was rich I have in-visioned making a set of solid steel disk wheels I was going to call "Rampager Heavy Elites" to get a good extremum data point. I'm more of a experimentalist and tend not to trust computational models very much, because after all they are just 'models' and not reality.
 

alienator

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howardjd said:
hmm I see your point about the water not spinning, although it probably does spin to some degree. Some type of gelatin mixture would probably be preferable. If I was rich I have in-visioned making a set of solid steel disk wheels I was going to call "Rampager Heavy Elites" to get a good extremum data point. I'm more of a experimentalist and tend not to trust computational models very much, because after all they are just 'models' and not reality. 
You're a physics student and you don't trust simple Newtonian mechanics? There's nothing revolutionary here. The equations work. Extreme points aren't needed because of the wonder of curve fitting. You're a physics student: prove the equations wrong. How much water do you use?
 

alienator

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howardjd said:
hmm I see your point about the water not spinning, although it probably does spin to some degree. Some type of gelatin mixture would probably be preferable. If I was rich I have in-visioned making a set of solid steel disk wheels I was going to call "Rampager Heavy Elites" to get a good extremum data point. I'm more of a experimentalist and tend not to trust computational models very much, because after all they are just 'models' and not reality. 
You're a physics student and you don't trust simple Newtonian mechanics? There's nothing revolutionary here. The equations work. Extreme points aren't needed because of the wonder of curve fitting. You're a physics student: prove the equations wrong. How much water do you use?
 

howardjd

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The problem I have with the models is they do not account for motions perpendicular to the road surface nor account for the sinusoidal power input of riders or the energy of the riding system(they only account for power required to overcome drag). The models are approximations. No rider rides completely straight. The calculations necessary to predict perpendicular to travel motions would be incredible laborious. The torque applied to the cranks is produced offset from center line therefore will produce some motion about the contact points perpendicular from the direction of travel, the rider also produces side to side forces across the seat that result in these motions as well, these motions are clearly visible in video. For a model to be accurate it has to be verified by experiment, and as far as I know there has been no definitive infield study to verify wheel inertia models. Yes newtonian mechanics works, but all variables have to be accounted for the model to be accurate, the models used now are done in 2space vrs 3space and hence not complete models.

It doesn't matter how smart you are, it doesn't matter how beautiful your theory is if it fails the test of experiment, its wrong.
Feynman

Just for fun, I really want this bike
https://www.youtube.com/watch?v=2xFUMGCHI94
 

alienator

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howardjd said:
The problem I have with the models is they do not account for motions perpendicular to the road surface nor account for the sinusoidal power input of riders or the energy of the riding system(they only account for power required to overcome drag). The models are approximations. No rider rides completely straight. The calculations necessary to predict perpendicular to travel motions  would be incredible laborious. The torque applied to the cranks is produced offset from center line therefore will produce some motion about the contact points perpendicular from the direction of travel, the rider also produces side to side forces across the seat that result in these motions as well, these motions are clearly visible in video. For a model to be accurate it has to be verified by experiment, and as far as I know there has been no definitive infield study to verify wheel inertia models. Yes newtonian mechanics works, but all variables have to be accounted for the model to be accurate, the models used now are done in 2space vrs 3space and hence not complete models.  It doesn't matter how smart you are, it doesn't matter how beautiful your theory is if it fails the test of experiment, its wrong.  Feynman Just for fun, I really want this bike https://www.youtube.com/watch?v=2xFUMGCHI94
You haven't said how any of the things you mentioned--motion normal to road surface, sinusoidal power input--have any affect on the influence of wheel mass and wheel MOI. Further you don't need pedaling to test wheel mass and MOI. Coast-downs are all you need. The influence of motion normal to the road surface is a function of the quality of the road surface and is very likely to show up as noise in any measurement. That will be especially so since it's virtually impossible to follow the exact same path over the pavement for every single test. In fact, that's one reason why I suggest so doing many test runs. Noise goes down with the square of the number of samples, i.e., it goes as 1/n^2. Double the number of samples taken, and the noise will go down by 4. Not steering in a perfectly straight line only adds more noise to the measurement. It doesn't however affect the relationship between power to accelerate to a given velocity and a wheel's mass and MOI. You're adding many non-relevant factors. As an experimentalist, you should know that it's necessary to control many variables to insure that you are measuring what you intend to measure. You'll need quite the sensor set to quantify how not steering perfectly straight affects velocity and acceleration. Feel free to poo-poo the theory all you like, but while doing so you should understand that being an experimentalist requires understanding the current theory. As such, it requires understanding what current theory would lead you to expect in a given experiment. Then, you either confirm what was expected, or you find that results diverge. You'll have to then look at you data and analyze it. That will require, uhm, curve fitting (gosh, this all sounds so familiar). I'm willing to bet a very large sum of money that you will find that your data will confirm that inertial factors--mass and MOI--have a linear effect on velocity and acceleration, just as all the physicists and engineers who've looked at this have found. Your data will, of course, not be perfect, i.e. it will definitely have some measure of variance that will be a function of experimental setup, sensor precision, and etc. I will also bet a large some of money that your 3D analysis of the effects of wheel mass and MOI will reveal nothing that is not already known.
 

alienator

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howardjd said:
The wheels came in at about 5 pounds per wheel. 
That doesn't say anything about how much water was in the wheels. What was the mass of each wheel before water was added and the mass after? Also, you posted the video of Moser and you mentioned also Sosenka. Now why is it do you think they chose to use a wheel with such large mass and/or MOI? What was it about their rides that was different than what the average cyclist encounters? Yeah, it's a simple question, but it's a question that points at exactly why such wheels aren't a benefit to the vast majority of riders and riding situations.
 

howardjd

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Angular momentum resists being moved from its plane of rotation, so the theory is that with more angular momentum you will be able to ride the bike straighter. The other theory is that with more energy in your system the bike will deccelerate less inbetween the pedal strokes and therefor ride with a more stable velocity. The other theory is that on a course with short up and down hills, ones that you roll most of the way back up the next one, a heavier wheel will store energy and aid in lifting you up the next hill. I could notice the effect of the extra lift when riding my twelve pound disk. I think the 12 pounder has enough energy at 30mph to lift 100kilos 2m or something. The major problem I am having with testing wheel inertia is that the equipment that would be required to control all the other variables would be highly specialized and is unavailable.

The reason I think Moser used the wheel is from the reasons given by my theories, riding straighter and the fly wheel effect, and the fact that it is a flat course. And yes it does depend on the circumstances, being rider course and conditions. I actually have a theorem related to this.

Howards theorem of cycling performance

For every rider, course, and conditions there will be an ideal wheel inertia for the front and rear wheel that will allow the rider to perform at and optimal level and this inertia will not always trend towards the smallest possible value.

think about what inertias you might want for the following circumstances.

all up hill
straight shot all down hill
rider the size of an ant
rider the size of a T-rex
riding on the moon(no atmosphere)
riding in very windy conditions
flat course
gently rolling course
technical hilly and flat course.
peloton or timetrialing for all of the above

I'm not sure about the wheel mass before and after, this will have to be measured if I ever recover from this injury and am able to continue testing.

A big part I've found about wheel inertia is not all about its direct effect on linear velocity, but on its effect on the riding qualities of the bike. I had the perception that they make the bike easier to ride straight and therefore allow for more efficient riding. When you don't ride straight your aero dynamics and rolling resistance are affected along with the distance you travel. To me it seems heavy is good for timetrial but would be bad for peleton riding because of the need to move laterally quickly and continually make accelerations.
 

alienator

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howardjd said:
Angular momentum resists being moved from its plane of rotation, so the theory is that with more angular momentum you will be able to ride the bike straighter. The other theory is that with more energy in your system the bike will deccelerate less inbetween the pedal strokes and therefor ride with a more stable velocity. The other theory is that on a course with short up and down hills, ones that you roll most of the way back up the next one, a heavier wheel will store energy and aid in lifting you up the next hill. I could notice the effect of the extra lift when riding my twelve pound disk. I think the 12 pounder has enough energy at 30mph to lift 100kilos 2m or something. The major problem I am having with testing wheel inertia is that the equipment that would be required to control all the other variables  would be highly specialized and is unavailable.  The reason I think Moser used the wheel is from the reasons given by my theories, riding straighter and the fly wheel effect, and the fact that it is a flat course. And yes it does depend on the circumstances, being rider course and conditions. I actually have a theorem related to this.  Howards theorem of cycling performance For every rider, course, and conditions there will be an ideal wheel inertia for the front and rear wheel that will allow the rider to perform at and optimal level and this inertia will not always trend towards the smallest possible value.  think about what inertias you might want for the following circumstances. all up hill straight shot all down hill rider the size of an ant rider the size of a T-rex riding on the moon(no atmosphere) riding in very windy conditions flat course gently rolling course technical hilly and flat course.  peloton or timetrialing for all of the above I'm not sure about the wheel mass before and after, this will have to be measured if I ever recover from this injury and am able to continue testing.  A big part I've found about wheel inertia is not all about its direct effect on linear velocity, but on its effect on the riding qualities of the bike. I had the perception that they make the bike easier to ride straight and therefore allow for more efficient riding. When you don't ride straight your aero dynamics and rolling resistance are affected along with the distance you travel. To me it seems heavy is good for timetrial but would be bad for peleton riding because of the need to move laterally quickly and continually make accelerations.  [/quote Straighter? Do you think that's a real issue in cycling? Rider the size of an ant: irrelevant. Rider the size of T-rex: irrelevant. Riding on the moon: irrelevant The model I linked to will give you the acceleration at any instant. As someone studying physics, you should have no issue with solving the equation for a given set of variables. Note that the model also includes power delivery as a sinusoidal function. You're not saying anything instructive about inertias, and it's not apparent that your experiment will reveal anything that is not already known. Also, trying to analyze all the variables you've mentioned will make for a very complex experiment. If I were you I would sit down and do a very careful error analysis of your experimental setup to see what sort of uncertainty you can expect. It also appears that some of the things you are looking for are opinion, not fact based. Simply put, there are very few things that are optimal for all riders. What is your physics background?
 

An old Guy

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Feb 12, 2011
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Originally Posted by howardjd .

Angular momentum resists being moved from its plane of rotation, so the theory is that with more angular momentum you will be able to ride the bike straighter. The other theory is that with more energy in your system the bike will deccelerate less inbetween the pedal strokes and therefor ride with a more stable velocity. The other theory is that on a course with short up and down hills, ones that you roll most of the way back up the next one, a heavier wheel will store energy and aid in lifting you up the next hill. I could notice the effect of the extra lift when riding my twelve pound disk. I think the 12 pounder has enough energy at 30mph to lift 100kilos 2m or something. The major problem I am having with testing wheel inertia is that the equipment that would be required to control all the other variables would be highly specialized and is unavailable.
I have found that all the variables are controlled, when I sit at a desk and do the math. After I have done the math, I go out and see how well the the math matches the bicycling.

Simple physics formulas say that 1 pound of rotating weight at the rim is equivalent to 2 pounds of non-rotating weight. That solves the acceleration problem completely. It seems easy to verify.

The angular momentum problem is most likely solved by looking at experiments where people have tried to make unstable bicycles by cancelling out the angular momentum. They find the bikes are still stable. The conclusion is that the angular momentum of normal weight wheels is not a significant issue. We know that for motorcycles that angular momentum of the wheels is imporant. That gives us a big range in which to search for the point where angular momentum is important. (I don't even know what to look for in this matter.)
 

maydog

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Feb 5, 2010
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Originally Posted by howardjd .

Angular momentum resists being moved from its plane of rotation, so the theory is that with more angular momentum you will be able to ride the bike straighter. The other theory is that with more energy in your system the bike will decelerate less in between the pedal strokes and therefor ride with a more stable velocity. The other theory is that on a course with short up and down hills, ones that you roll most of the way back up the next one, a heavier wheel will store energy and aid in lifting you up the next hill. I could notice the effect of the extra lift when riding my twelve pound disk. I think the 12 pounder has enough energy at 30mph to lift 100kilos 2m or something. The major problem I am having with testing wheel inertia is that the equipment that would be required to control all the other variables would be highly specialized and is unavailable.
You theories are not well developed. Adding mass will dampen both accelerations and decelerations, since these are very small we can ignore changes in wind resistance - the average speed will remain the same. In addition, more inertia results in a slower initial acceleration.

The extra inertia doesn't help you up the hill, the rider will need to expend incremental energy to maintain speed vs. that rider on a less massive system. Extra mass will also result in a faster decent, which guess what, will result in more overall energy losses in the system vs. a slower lighter decent. Extra energy up + more losses down does not equate to savings.


Unless the increased moment results in a measureable increase in ride efficiency due to a stabilizing effect (doubtful) - there will be no benefit.
 

howardjd

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Apr 16, 2013
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cool thanks for the insight. Do you have controlled infield data about wheel inertia by chance?
 

howardjd

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Even if you cancel out the moment of inertia vectors, the wheels will still each individually resist moving out of their plane of motion although the corresponding torque produced will equate to zero. The self righting effect of a bicycle has been shown not to be due to the gyroscopic effects of wheels but non the less gyroscopic stability is a real thing. Again thanks for all the insight. If your ever near Asheboro NC give me a shout and you can come by to ride the disks if you like for your own independent observations. So far I'm the only one whom has ridden them and would love to have others so I can get some more info on the topic.
 

alienator

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howardjd said:
Even if you cancel out the moment of inertia vectors, the wheels will still each  individually resist moving out of their plane of motion although the corresponding torque produced will equate to zero. The self righting effect of a bicycle has been shown not to be due to the gyroscopic effects of wheels but non the less gyroscopic stability is a real thing. Again thanks for all the insight. If your ever near Asheboro NC give me a shout and you can come by to ride the disks if you like for your own independent observations. So far I'm the only one whom has ridden them and would love to have others so I can get some more info on the topic. 
I've spent a long time doing experiments and testing, and I can tell you that you are looking at far too many things at once. You need to break down whatever model you have,look at the terms influencing that model, and test each term to find how it changes with a given influence, all the while minimizing the number of free variables in each test. So, you're interest in MOI and wheel mass and their effects on steering, acceleration, stability..... Right off the bat you have to test wheels to find the MOI of those wheels. Every time you add water, you'll have to measure the MOI again. For every wheel configuration that you test, you'll need a measured MOI. Looking up an MOI won't cut it as that could introduce great error. You want to understand acceleration. Well, you'll need a specific test for that, and you have to take into consideration all the things that influence acceleration: power output, Crr, bike/rider system mass, wheel MOI, and etc. You want to measure the stability of various wheel configurations (i.e. their susceptibility to crosswinds, bumps, and the like), you'll need a specific test for that, and you have to take into consideration all the things that affect stability: bike geometry, mass distribution on the bike, tires, inflation pressures, and etc. You want to know the effect of wind on a given wheel type? Well, that's another test for which you'll need to know the meteorological conditions and a slew of other things. This happens every time you add something you want to know. There is no single type of test that reveals all of this. Then for every measured quantity and every quantity of influence, you'll need to know the uncertainty in that measurement and how that uncertainty propagates through the system and effects your "model". I can tell you straight off that it is impossible to construct a theory that will tell any given rider what wheel would be optimum for them to use in a given situation. First, there are no sharp boundaries in bicycle performance between the influence of differing parameters. Why is that? Because riders all value different performance parameters, and most importantly humans are subject to bias because of all manner of things, and as such, their perceptions of what they think they're feeling may not actually reflect physical reality. Even if you hand them a bike setup to provide them with the optimal performance according to your "theory", they may not perform optimally on that bike since what they perceive may not feel optimal and may have an untoward influence on their performance. I can tell you that short of doing a time trial or wishing to make a fashion statement on a fixie, no one wants to ride with a disc wheel. I can also tell you that there absolutely no reason whatsoever to test at the very extremes of wheel mass and MOI. The physical laws don't change according to mass and MOI.
 

howardjd

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Apr 16, 2013
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Cool you know your most likely right about everything and I'm just jumping to conclusions. Wish I wasn't injured so I could continue to test though. Thanks for all the insight.
 

Eichers

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Sep 17, 2010
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Originally Posted by mcfc09 .
... I've been looking to get some new wheels in the price range of £750-£1500 but I can't decide which is better lightweight or aerodynamics can anyone help?
Hi mcfc09, actually both are best and best balanced /img/vbsmilies/smilies/smile.gif

A weight of about 1500g or less is good, and the more aero the better but not at the expense of the rim depths being to deep where riding in crosswinds dramatically affects bike balance (between 27mm and 50mm seem to be good rim depths, depending on weight, desired wheel stiffness) /img/vbsmilies/smilies/smile.gif

EDIT: Although, rim depths >50mm appear to be ok when wider 23mm or 24mm rims are used. The consensus is that wider rims give more comfort (lower tyre pressure can be used, ie 105 -> 95/100), better cornering (tire has more round shape - almost tubular), stiffer, better handling in cross winds (wind from side), little higher weight. That is 50Dx23W or 60Dx24W Tubs/CL are much better in wind than 50Dx20W or 60Dx20W Tubs/CL. I can tell that.

So, 50Dx23W or 60Dx24W Tubs/CL might be the best weight (about 1500g or less) and aero wheelset combinations for all cycling conditions, but 27D to 40D is also very good and also exist in alloy rims (especially 27D to 30D) /img/vbsmilies/smilies/smile.gif

thanks KL /img/vbsmilies/smilies/smile.gif