Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

Wheels - lighter weight vs aero

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

Wheels - lighter weight vs aero

Old 02-18-23, 02:11 PM
  #301  
Trakhak
Senior Member
 
Trakhak's Avatar
 
Join Date: Jan 2005
Location: Baltimore, MD
Posts: 4,395
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1877 Post(s)
Liked 2,123 Times in 1,196 Posts
Originally Posted by elcruxio
Isn't weight inconsequential in that? You spend the same energy with a heavy and light bike but you just go slower with the lighter bike.

Also since the heavier wheel maintains speed better it'd likely be less fatiguing.
As demonstrated at the bottom of the post quoted in post 288.

If this thread or one like it is still active, I'll try to remember to provide a link the next time a bass player's forum I look at has a similar "I don't care about the science!" thread going.

My favorite: the guys who claim that older, heavier solid-state amplifiers (a.k.a. "lead sleds") have "heft" and "slam" and that the newer class D amps don't.

Since "heft" and "slam" are (conveniently) not quantifiable because they're undefinable touchy-feely terms, the arguments can go on for hundreds of posts.

When it is pointed out to a heft/slam guy that one of the people they're arguing with has been a professional in the industry for 40 years and that he designed both their favored lead sled and the class D amp they're spitting on, does he back down?

He does not.
Trakhak is offline  
Old 02-18-23, 02:12 PM
  #302  
venturi95
Firm but gentle
 
venturi95's Avatar
 
Join Date: Feb 2007
Location: Oregon
Posts: 581

Bikes: 2005 Litespeed Tuscany, Soma Pescadero, Pure Cycles disc road, Jamis hybrid

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 156 Post(s)
Liked 102 Times in 58 Posts
Originally Posted by tomato coupe
No offense, but one year of physics means you've barely scratched the surface.



Good story (fable?), but physics indicates that situation isn't realistic.
Thank you for the kind words. Out of 38 people who started the course, two of us finished with "A"s, I was one of them. I did struggle with calculus, but I am able to utilize my modest understanding of what goes on around me very well. I devised an experiment to quantify the errors in our steam sampling method while working in geothermal. This was not insignificant; it was something that the genius (one of two I have known) who ran the show, and the 100 or so guys who worked the job before me never realized.
Less of a fable than the pointy nipple perfection of the model I am countering. In fact, not a fable at all, because if your reading comprehension wasn't challenged you would know I've lived it. No offense, but I'd be willing to bet you engineers have never ridden a seriously light sew-up wheel set in a hill climb competition. There are reasons why we race and don't just sit around a plug numbers into an equation. Show me the math where i'm wrong at time = thrice f'd. PLEASE, GO ON.

Last edited by venturi95; 02-18-23 at 02:18 PM.
venturi95 is offline  
Old 02-18-23, 02:16 PM
  #303  
tomato coupe
Senior Member
 
Join Date: Jul 2009
Posts: 5,195

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 3435 Post(s)
Liked 6,226 Times in 2,517 Posts
Originally Posted by venturi95
Thank you for the kind words. Out of 38 people who started the course, two of us finished with "A"s, I was one of them. I did struggle with calculus, but I am able to utilize my modest understanding of what goes on around me very well. I devised an experiment to quantify the errors in our steam sampling method while working in geothermal. This was not insignificant; it was something that the genius (one of two I have known) who ran the show, and the 100 or so guys who worked the job before me never realized.Less of a fable than the pointy nipple perfection of the model I am countering. In fact, not a fable at all, because if your reading comprehension wasn't challenged you would know I've lived it. No offense, but I'd be willing to bet you engineers have never ridden a seriously light sew-up wheel set in a hill climb competition. There are reasons why we race and don't just sit around a plug numbers into an equation. Show me the math where i'm wrong at time = thrice f'd. PLEASE, GO ON.
You seem to think you're the only one that has racing experience. You're as wrong about that as you are about the physics of the scenario you painted.
tomato coupe is offline  
Old 02-18-23, 02:28 PM
  #304  
venturi95
Firm but gentle
 
venturi95's Avatar
 
Join Date: Feb 2007
Location: Oregon
Posts: 581

Bikes: 2005 Litespeed Tuscany, Soma Pescadero, Pure Cycles disc road, Jamis hybrid

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 156 Post(s)
Liked 102 Times in 58 Posts
Originally Posted by tomato coupe
Good story (fable?), but physics indicates that situation isn't realistic.
Wow, just wow. You got me there, we all know how bicycle racers proceed shoulder to shoulder at a steady pace during a hill climb [Sarcasm alert].
Now you have me wondering if you have ever even seen a bike race? [Not being sarcastic].
venturi95 is offline  
Old 02-18-23, 02:34 PM
  #305  
venturi95
Firm but gentle
 
venturi95's Avatar
 
Join Date: Feb 2007
Location: Oregon
Posts: 581

Bikes: 2005 Litespeed Tuscany, Soma Pescadero, Pure Cycles disc road, Jamis hybrid

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 156 Post(s)
Liked 102 Times in 58 Posts
Originally Posted by tomato coupe
You seem to think you're the only one that has racing experience. You're as wrong about that as you are about the physics of the scenario you painted.
My scenario in way goes counter to the laws of physics, what the hell are you refering to exactly?
venturi95 is offline  
Old 02-18-23, 02:38 PM
  #306  
elcruxio
Senior Member
 
elcruxio's Avatar
 
Join Date: Jul 2011
Location: Turku, Finland, Europe
Posts: 2,362

Bikes: 2011 Specialized crux comp, 2013 Specialized Rockhopper Pro

Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 740 Post(s)
Liked 255 Times in 173 Posts
Originally Posted by Trakhak
As demonstrated at the bottom of the post quoted in post 288.

If this thread or one like it is still active, I'll try to remember to provide a link the next time a bass player's forum I look at has a similar "I don't care about the science!" thread going.

My favorite: the guys who claim that older, heavier solid-state amplifiers (a.k.a. "lead sleds") have "heft" and "slam" and that the newer class D amps don't.

Since "heft" and "slam" are (conveniently) not quantifiable because they're undefinable touchy-feely terms, the arguments can go on for hundreds of posts.

When it is pointed out to a heft/slam guy that one of the people they're arguing with has been a professional in the industry for 40 years and that he designed both their favored lead sled and the class D amp they're spitting on, does he back down?

He does not.
I had an unfortunate typo there that I fixed. All other things being equal the heavier wheel will be slower. But they aren't equal.

Originally Posted by venturi95
Wow, just wow. You got me there, we all know how bicycle racers proceed shoulder to shoulder at a steady pace during a hill climb [Sarcasm alert].
Now you have me wondering if you have ever even seen a bike race? [Not being sarcastic].
Your example left out aerodynamics. Bit of an unfair omission that, because some would say it's a pretty big deal.
elcruxio is offline  
Old 02-18-23, 03:20 PM
  #307  
tomato coupe
Senior Member
 
Join Date: Jul 2009
Posts: 5,195

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 3435 Post(s)
Liked 6,226 Times in 2,517 Posts
Originally Posted by venturi95
Wow, just wow. You got me there, we all know how bicycle racers proceed shoulder to shoulder at a steady pace during a hill climb [Sarcasm alert].
Now you have me wondering if you have ever even seen a bike race? [Not being sarcastic].
Originally Posted by venturi95
My scenario in way goes counter to the laws of physics, what the hell are you refering to exactly?
You're arguing that the reduced moment of inertia of his wheels is a factor when the cyclist in your racing scenario attacks on an uphill section and opens a gap. Physics indicates it's an insignificant factor.
tomato coupe is offline  
Old 02-18-23, 03:39 PM
  #308  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 6,332
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 3223 Post(s)
Liked 3,532 Times in 2,228 Posts
Originally Posted by terrymorse
Then there's the not well understood muscle fatigue effect of acceleration-deceleration on every pedal stroke. It's the "throwing a heavy ball a short distance vs. throwing a light ball a long distance" problem. It's certainly a small effect, given the wheel mass differences in question. But I'm not convinced (yet) it's ridiculously small.
Well you've seen from the physics that the magnitude of the cyclical accel-decel is actually reduced with more rotational inertia. So however small that acceleration is, it is going to be even smaller with heavier wheels. The extra wheel mass would of course slow your average climbing speed down ever so slightly (if no aero effect), but there would be less speed variation over each pedal stroke. Or are you suggesting that more speed variation through the pedal stroke might be easier on your muscles? That does sound counter-intuitive to me.
PeteHski is offline  
Old 02-18-23, 03:49 PM
  #309  
venturi95
Firm but gentle
 
venturi95's Avatar
 
Join Date: Feb 2007
Location: Oregon
Posts: 581

Bikes: 2005 Litespeed Tuscany, Soma Pescadero, Pure Cycles disc road, Jamis hybrid

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 156 Post(s)
Liked 102 Times in 58 Posts
Originally Posted by elcruxio
I had an unfortunate typo there that I fixed. All other things being equal the heavier wheel will be slower. But they aren't equal.



Your example left out aerodynamics. Bit of an unfair omission that, because some would say it's a pretty big deal.
Yes, I would say aerodynamics are big deal too, and they still matter, especially for the pros who are of course moving faster. And add to that, many miles of not climbing, but descending or flat (or very close to it) in the Grand Tours in the mountainous stages... I can see the aero wheels being chosen. I just don't see the 7% grade being the trade-off point for this argument, and some accuse me of being a flat earther.
venturi95 is offline  
Old 02-18-23, 03:52 PM
  #310  
Trakhak
Senior Member
 
Trakhak's Avatar
 
Join Date: Jan 2005
Location: Baltimore, MD
Posts: 4,395
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1877 Post(s)
Liked 2,123 Times in 1,196 Posts
Originally Posted by venturi95
No offense, but I'd be willing to bet you engineers have never ridden a seriously light sew-up wheel set in a hill climb competition. There are reasons why we race and don't just sit around a plug numbers into an equation. Show me the math where i'm wrong at time = thrice f'd. PLEASE, GO ON.
Not an engineer, but I raced hill climbs and time trials in the 1980s on a Columbus SL/SP Bianchi Specialissima Super Corsa, sometimes on Campy wheels with Mavic MA4 wheels with light Barum tubulars and sometimes on Hi-E wheels (their lightest model and the lightest production tubular wheels on the market at the time).

Allowing for wind conditions, etc., my times didn't vary much between the two wheel sets. I did set a course record for a 10-mile time trial using the Campy/MA4 wheels, so there's that.

I finally got rid of the Hi-E wheels because I didn't like the subtle but annoying stop-go feel of having to reaccelerate those wheels with every pedal stroke. (See the larger zig-zag lines corresponding to the lighter wheels at the bottom of the aforementioned post.)

Yes, it was a princess-and-the-pea thing to be annoyed by, but once I started noticing it, it was hard to concentrate on maintaining maximum effort.

Last edited by Trakhak; 02-18-23 at 03:56 PM.
Trakhak is offline  
Old 02-18-23, 04:09 PM
  #311  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 6,332
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 3223 Post(s)
Liked 3,532 Times in 2,228 Posts
Originally Posted by venturi95
I'm no dimwit stuck in the past, I agree with everything you are saying except for the real-world example crudely illustrated in the following scenario:
The Old Dullard and the Talented Engineer are equally strong and fit racers, and now their race takes an upward course. The Old Dullard is on his climbing wheels, with crappy old 28 spoke sew-up rims like these
Pity poor Old Dullard, I'm surprised he can even get from point A to point B on such equipment. Now look at the Talented Engineer, he has a modern deep section carbon aero rim (460 grams vs 290 gram sew-up rim). Let's assume all the tires in this scenario are in the 230 gram range, or whatever. The average grade is only 7%, but there are some steeper and shallower sections, as you encounter in the real world.
The Old Dullard attacks on the climb and puts some distance between himself and the Talented Engineer. Now the Talented Engineer is thrice ****ed because:
-He is behind
-He is moving slower
-His bicycle doesn't accelerate on a climb as efficiently.
The only thing your real world example proves is that you can still win on old equipment if you are a bit stronger than the guy on new equipment. If the average gradient was 7% then lighter wheels are likely to be marginally faster for a non-pro rider. Nobody is arguing about that. It's the part where you were arguing that wheel mass is worth significantly more than static mass due to all these "micro-accelerations". Unfortunately the physics doesn't support that view, regardless of what race experience we all have.
PeteHski is offline  
Old 02-18-23, 04:14 PM
  #312  
venturi95
Firm but gentle
 
venturi95's Avatar
 
Join Date: Feb 2007
Location: Oregon
Posts: 581

Bikes: 2005 Litespeed Tuscany, Soma Pescadero, Pure Cycles disc road, Jamis hybrid

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 156 Post(s)
Liked 102 Times in 58 Posts
Originally Posted by tomato coupe
You're arguing that the reduced moment of inertia of his wheels is a factor when the cyclist in your racing scenario attacks on an uphill section and opens a gap. Physics indicates it's an insignificant factor.
How many watts is insignificant?. I would have to educate myself again [Hint: not going to happen] and go over the raw data to believe the Willits numbers posted way back, like I said, hundredths of a Watt? Okay, gradient goes from a low of 6% to a high of 10%, but average is 7%, only difference is the 150 grams per rim. 70 kilos per rider. I have no idea what a pedaling force would be, where the accelerations would be coming at, how to model so I can optimize my argument, minimize my argument, or even an accurate approximation of speeds. I am sure I could not do the math in a timely manner.
Many times I have seen riders who had 2 or 3 pound heavier bikes with heavier wheels ride away from big fields of hard climbing riders. The lightest equipment doesn't guarantee a victory, but you may have 10 or even 20 riders who are physically capable of winning.
venturi95 is offline  
Old 02-18-23, 04:33 PM
  #313  
venturi95
Firm but gentle
 
venturi95's Avatar
 
Join Date: Feb 2007
Location: Oregon
Posts: 581

Bikes: 2005 Litespeed Tuscany, Soma Pescadero, Pure Cycles disc road, Jamis hybrid

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 156 Post(s)
Liked 102 Times in 58 Posts
We need engineers, they make geologists look well-dressed.
In the distant future, a balding, overtly intellectual, skinny old college instructor is giving a physics lecture at a prestigious east coast school:
And here we have venturi's "Thrice F**ked Conundrum" regarding uphill accelerations during cycling competitions.
venturi95 is offline  
Likes For venturi95:
Old 02-18-23, 06:54 PM
  #314  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 6,332
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 3223 Post(s)
Liked 3,532 Times in 2,228 Posts
Originally Posted by venturi95
We need engineers, they make geologists look well-dressed.
In the distant future, a balding, overtly intellectual, skinny old college instructor is giving a physics lecture at a prestigious east coast school:
And here we have venturi's "Thrice F**ked Conundrum" regarding uphill accelerations during cycling competitions.
Uphill accelerations? You mean like accelerating from 9 mph to maybe 11 mph over a couple of seconds? Really you should just give up on this line of thought.
PeteHski is offline  
Likes For PeteHski:
Old 02-18-23, 06:56 PM
  #315  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 6,332
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 3223 Post(s)
Liked 3,532 Times in 2,228 Posts
Originally Posted by venturi95
How many watts is insignificant?. I would have to educate myself again [Hint: not going to happen] and go over the raw data to believe the Willits numbers posted way back, like I said, hundredths of a Watt? Okay, gradient goes from a low of 6% to a high of 10%, but average is 7%, only difference is the 150 grams per rim. 70 kilos per rider. I have no idea what a pedaling force would be, where the accelerations would be coming at, how to model so I can optimize my argument, minimize my argument, or even an accurate approximation of speeds. I am sure I could not do the math in a timely manner.
Many times I have seen riders who had 2 or 3 pound heavier bikes with heavier wheels ride away from big fields of hard climbing riders. The lightest equipment doesn't guarantee a victory, but you may have 10 or even 20 riders who are physically capable of winning.
The maths has been done:-

PeteHski is offline  
Old 02-18-23, 06:58 PM
  #316  
terrymorse 
climber has-been
 
terrymorse's Avatar
 
Join Date: Dec 2004
Location: Palo Alto, CA
Posts: 5,970

Bikes: Scott Addict R1

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 2414 Post(s)
Liked 2,430 Times in 1,228 Posts
Originally Posted by elcruxio
Also since the heavier wheel maintains speed better it'd likely be less fatiguing.
Yes, the higher inertia wheel decelerates more slowly than a low inertia wheel. But it also accelerates more slowly, which is where the muscle fatigue question arises.

Expanding what I wrote above, pedaling the high inertia wheel is like throwing a heavy ball a short distance, pedaling the low inertia wheel is like throwing a light ball a longer distance, and while the work done is identical, it's not at all clear which one is more fatiguing (or if they're equally fatiguing).
__________________
Ride, Rest, Repeat

terrymorse is offline  
Old 02-18-23, 07:10 PM
  #317  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 6,332
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 3223 Post(s)
Liked 3,532 Times in 2,228 Posts
Originally Posted by terrymorse
Yes, the higher inertia wheel decelerates more slowly than a low inertia wheel. But it also accelerates more slowly, which is where the muscle fatigue question arises.

Expanding what I wrote above, pedaling the high inertia wheel is like throwing a heavy ball a short distance, pedaling the low inertia wheel is like throwing a light ball a longer distance, and while the work done is identical, it's not at all clear which one is more fatiguing (or if they're equally fatiguing).
I don't think the difference in this case is significant enough for it to matter either way. At least with the physics it's easy enough to calculate some numbers - even if people are still in denial of the results. In your analogy the differences in both ball weight and distance thrown would be very small. Maybe not even measurable.
PeteHski is offline  
Old 02-18-23, 07:15 PM
  #318  
HTupolev
Senior Member
 
Join Date: Apr 2015
Location: Seattle
Posts: 4,235
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 1955 Post(s)
Liked 1,266 Times in 616 Posts
Originally Posted by venturi95
[Hint: not going to happen]
Why not? If you did fine through a year of collegiate physics, the relevant material is well within your level of understanding.

What you're questioning are conclusions that are literally derived from just basic high-school-level Newtonian kinematics, a quadratic force formula typically represented with no linear element, and coefficients to that force formula that have been getting measured and published since the 19th century (with respect to tire rolling resistance and aerodynamics) or a couple hundred years earlier (gravity).

Over the past few pages of this thread, you've basically taken a position of "I have a moderate background in exactly the subject matter that's relevant to this discussion, but I refuse to leverage that understanding in assembling my argument."
HTupolev is offline  
Likes For HTupolev:
Old 02-18-23, 07:19 PM
  #319  
HTupolev
Senior Member
 
Join Date: Apr 2015
Location: Seattle
Posts: 4,235
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 1955 Post(s)
Liked 1,266 Times in 616 Posts
Originally Posted by PeteHski
I don't think the difference in this case is significant enough for it to matter either way.
What terrymorse is getting at is the issue of crank inertial load, or perhaps more generally, "what are the physiological consequences to changing how the pedals respond to pedaling force." Personally I think it's an underexplored realm of cycling performance, but, I'm inclined to agree that rotational inertia from wheel changes is an extremely marginal part of the discussion. It's an incredibly tiny difference compared with, say, the differences between inertial loads while cruising on the flats versus grinding up a steep hill.
HTupolev is offline  
Likes For HTupolev:
Old 02-18-23, 07:24 PM
  #320  
PeteHski
Senior Member
 
PeteHski's Avatar
 
Join Date: May 2021
Posts: 6,332
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 3223 Post(s)
Liked 3,532 Times in 2,228 Posts
Originally Posted by HTupolev
What terrymorse is getting at is the issue of crank inertial load, or perhaps more generally, "what are the physiological consequences to changing how the pedals respond to pedaling force." Personally I think it's an underexplored realm of cycling performance, but, I'm inclined to agree that rotational inertia from wheel changes is an extremely marginal part of the discussion. It's an incredibly tiny difference compared with, say, the differences between inertial loads while cruising on the flats versus grinding up a steep hill.
Agreed, that's a whole different discussion.
PeteHski is offline  
Old 02-18-23, 08:51 PM
  #321  
Maelochs
Senior Member
 
Maelochs's Avatar
 
Join Date: Oct 2015
Posts: 15,026

Bikes: 2015 Workswell 066, 2017 Workswell 093, 2014 Dawes Sheila, 1983 Cannondale 500, 1984 Raleigh Olympian, 2007 Cannondale Rize 4, 2017 Fuji Sportif 1 LE

Mentioned: 143 Post(s)
Tagged: 0 Thread(s)
Quoted: 7383 Post(s)
Liked 3,017 Times in 1,611 Posts
Here is what I see. One poster keeps saying that the difference is force on the pedals as the cranks rotate is a significant source of fatigue---not spinning them, but the uneven resistance through teh rotation---and that heavier wheels produce significantly less fatigue because they damp out variations in the pressure pulses.

Did I get that right?

And at 8- rpm, there would be 160 pulses per minute? and 150 grams or weight on the rim would reduce load, even though obviously it increases load (it Is load) ?

Okay ... show Any test results. Any data. Anything but "I think it must be this."

Nobody really believed Einstein until some photos showing the Sun bending light were published, many years after his paper was published. Why should we believe you when you say that pedal-pulses are a significant source of fatigue?

Test it, explain the test, and show the results

It seems to me the variations are so minor and so frequent that it would be impossible to feel the difference and possibly impossible to quantify the difference. And if ti is not a Significant difference---if you cannot show a whole-number Watts Lost figure--then we are back to arguing that removing even one molecule Makes a Difference,

Show us the money.
Maelochs is offline  
Old 02-18-23, 09:00 PM
  #322  
tomato coupe
Senior Member
 
Join Date: Jul 2009
Posts: 5,195

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 3435 Post(s)
Liked 6,226 Times in 2,517 Posts
Originally Posted by venturi95
How many watts is insignificant?. I would have to educate myself again [Hint: not going to happen] and go over the raw data to believe the Willits numbers posted way back, like I said, hundredths of a Watt? Okay, gradient goes from a low of 6% to a high of 10%, but average is 7%, only difference is the 150 grams per rim. 70 kilos per rider. I have no idea what a pedaling force would be, where the accelerations would be coming at, how to model so I can optimize my argument, minimize my argument, or even an accurate approximation of speeds. I am sure I could not do the math in a timely manner.
From a physics perspective, estimating the magnitude of these effects is trivial.
tomato coupe is offline  
Old 02-18-23, 10:27 PM
  #323  
RChung
Perceptual Dullard
 
Join Date: Sep 2009
Posts: 2,199
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
Liked 917 Times in 380 Posts
Originally Posted by Maelochs
Here is what I see. One poster keeps saying that the difference is force on the pedals as the cranks rotate is a significant source of fatigue---not spinning them, but the uneven resistance through teh rotation---and that heavier wheels produce significantly less fatigue because they damp out variations in the pressure pulses.

Did I get that right?

And at 8- rpm, there would be 160 pulses per minute? and 150 grams or weight on the rim would reduce load, even though obviously it increases load (it Is load) ?

Okay ... show Any test results. Any data. Anything but "I think it must be this."

Nobody really believed Einstein until some photos showing the Sun bending light were published, many years after his paper was published. Why should we believe you when you say that pedal-pulses are a significant source of fatigue?

Test it, explain the test, and show the results

It seems to me the variations are so minor and so frequent that it would be impossible to feel the difference and possibly impossible to quantify the difference. And if ti is not a Significant difference---if you cannot show a whole-number Watts Lost figure--then we are back to arguing that removing even one molecule Makes a Difference,

Show us the money.
Back in 2011 I worked a little bit on modeling the team pursuit in prep for the 2012 Olympics. (For oddball reasons we worked with the American and Canadian women's pursuit teams). One of the tricky things is that in team pursuit there are pretty wild swings in power (and thus acceleration) as you rotate both through the team and also around the velodrome. Wheel speed actually rises and falls more than center of mass speed since in the turns the bikes lean over so the wheels take a longer path than the rider, and the center of mass drops and then rises as you come out of the turn and onto the straights.

So we knew the geometry of the track and how much each rider would lean at what speed in each turn--and, we knew the wheel weight, and had figured out "where" in the wheel the "mass centroid" was so we could calculate the moment of inertia. We did this because this was one of the first times we were trying to get good high quality high precision estimates of CdA and Crr from field-based tests using power meters. Our model was very good, so once we had proper estimates of CdA and Crr, and using the carefully calibrated power meters, we could absolutely *nail* the speed for power for a rider both on the straight and on the turns. I was agog that my calculations worked so well--I hadn't actually expected that.

Here's the thing: although we had the moment of inertia for the wheels, it quickly became evident that the MOI was a small enough contribution that we could simplify the model and ignore it. Even though the speeds and accelerations were high, our predictions of speed for power didn't significantly depend on it at all.
RChung is offline  
Old 02-18-23, 11:10 PM
  #324  
tomato coupe
Senior Member
 
Join Date: Jul 2009
Posts: 5,195

Bikes: Colnago, Van Dessel, Factor, Cervelo, Ritchey

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 3435 Post(s)
Liked 6,226 Times in 2,517 Posts
Originally Posted by RChung
Back in 2011 I worked a little bit on modeling the team pursuit in prep for the 2012 Olympics. (For oddball reasons we worked with the American and Canadian women's pursuit teams). One of the tricky things is that in team pursuit there are pretty wild swings in power (and thus acceleration) as you rotate both through the team and also around the velodrome. Wheel speed actually rises and falls more than center of mass speed since in the turns the bikes lean over so the wheels take a longer path than the rider, and the center of mass drops and then rises as you come out of the turn and onto the straights.

So we knew the geometry of the track and how much each rider would lean at what speed in each turn--and, we knew the wheel weight, and had figured out "where" in the wheel the "mass centroid" was so we could calculate the moment of inertia. We did this because this was one of the first times we were trying to get good high quality high precision estimates of CdA and Crr from field-based tests using power meters. Our model was very good, so once we had proper estimates of CdA and Crr, and using the carefully calibrated power meters, we could absolutely *nail* the speed for power for a rider both on the straight and on the turns. I was agog that my calculations worked so well--I hadn't actually expected that.

Here's the thing: although we had the moment of inertia for the wheels, it quickly became evident that the MOI was a small enough contribution that we could simplify the model and ignore it. Even though the speeds and accelerations were high, our predictions of speed for power didn't significantly depend on it at all.
Worth emphasizing ...
tomato coupe is offline  
Likes For tomato coupe:
Old 02-19-23, 03:24 AM
  #325  
tFUnK
Senior Member
 
Join Date: Jun 2002
Location: San Jose, CA
Posts: 3,551

Bikes: Too many bikes, too little time to ride

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 389 Post(s)
Liked 382 Times in 269 Posts
Originally Posted by RChung
Even though the speeds and accelerations were high, our predictions of speed for power didn't significantly depend on it at all.
When you say "...didn't significantly depend on (wheel mass)" do you mean statistically significant or functionally significant?
tFUnK is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information -

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.