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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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hambini wrote:
bloodyshogun wrote:
How did you Measure rotational drag? Did you mean 20-30% of total drag (presume-ably of the wheel itself) is the equivalent to spin the wheel up or keep the wheel spinning?


It's the power required to keep the wheel spinning not to accelerate the wheel(s).

This is done by spinning the wheels up and measuring how much power you need to keep them spinning at a given speed.
Did you build a rig to do this in the tunnel? Or can it be done independently and then calculated in?
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [trail] [ In reply to ]
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trail wrote:
hambini wrote:
don't think you understand how things in the Aerospace world work.


Would you describe your public presentation of data and methods as consistent with how such presentation is done in the aerospace industry?

I would say when it was presented with a more aerospace bias, some individuals requested a "yaw vs drag" graph or a "yaw against time graph". I tried to produce them and was criticized because the values did not add to 100% in the second case. And if you watch the video, you will understand the two measures are not one and the same, hence it does not add to 100.

But parking that to one side, I would say it's 65-70% yes.

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [MattyK] [ In reply to ]
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MattyK wrote:
hambini wrote:
bloodyshogun wrote:
How did you Measure rotational drag? Did you mean 20-30% of total drag (presume-ably of the wheel itself) is the equivalent to spin the wheel up or keep the wheel spinning?


It's the power required to keep the wheel spinning not to accelerate the wheel(s).

This is done by spinning the wheels up and measuring how much power you need to keep them spinning at a given speed.

Did you build a rig to do this in the tunnel? Or can it be done independently and then calculated in?

it is in the rig

Most tunnels that are equipped for aircraft have rollers or a belt built in, this is to test for landing / take off scenarios.

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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Here we go again.

Much of what is presented in the video is a knock-down of the validity of current measurement techniques to evaluate aerodynamics of bikes/parts. Egos aside, i think it does raise a valid point... that the real world is not as laminar as we might wish. The optimal design in a lab (or enclosed velodrome) may not be as optimal in the wild. The MIG example is an interesting one. Sacrificing ultimate aero efficiency to better deal with non ideal aero situations. Sounds a lot like the mantra that zipp used to try to make their wheels not just faster, but more stable in cross winds.

BUT... is hambinis protocol more representative of reality? Everything is trying to model reality, the issue is that reality is constantly changing (wind that is), and no two moments are ever the same. So what test best models reality, and which reality are we testing?

So here is what we have for test options:
- eyeball it/armchair logic
- cfd
- wind tunnel (traditional)
- wind tunnel (non laminar airflow)
- outdoor testing (velodrome)
- chung method
- roll-down tests
- i am sure i am missing a few

Which creates “valid” data? Even if hambinis data was more representative of reality, he states a 2.5% error, so i will not use it to compare wheel a to wheel b, because the 2w difference between those wheels are within the margin of error of the test. Compare this to a laminar flow wind tunnel that may be able to theoretically be more precise, but is it as representative of the real world? Pros and cons.

Rider on bs rider off data is the same issue. Rider on is reality, but a rider increases your error. So dummies were created. But i am not shaped like you, and on and on....

The trends this data shows, deeper is more aero, yeah, i buy that. Aero spokes, hide the nippples. Yup. But just as hambini said he could improve a riders aero with a profile picture, i could also improve the aero of a given poor wheel design without an aerospace degree or fancy wind tunnel with louvres (but isn’t that part of how we got here in the first place... people cutting corners in design...). I could probably look at a line of wheels and with a calliper and a few tools to check spoke alignment, could probably align the fastest to slowest wheels with decent accuracy. It is not rocket science.

The trick is not just design, but to make that product to a high quality, at a budget that makes the product/business sustainable. Poor alignment of aero spokes will kill a wheel performance aerodynamically. It is not a design issue, but a manufacturing one. Accountants are always the bane of the engineer. Maybe every wheel maker could make a faster wheel, but at what cost? Most shy from internal nipples due to inconvenience to the buyer. It is a conscious design decision.

In reality, no test protocol is perfect. The trick is to know/accept the limitations. Actually, the chung method is pretty smart imho. Also, i think the aerocoach approach that mixes outdoor velodrome testing with wind tunnel is pretty good to. Why, because both are accessible and reproducible, and involve some element of in vivo real world testing. But in vivo comes with it’s own set of issues (multiple variables you can not control), so there is no one perfect test. The key is knowing the limits of each test.

The ideal test(s)& is one that is accessible (equipment, cost), and easily reproducible. Anything that requires a test protocol that is only accessible to a couple of aerospace companies... is god damn useless to the common bike rider trying to shave a few seconds off their next bike split.

Reduce frontal area
Don’t balloon your tires beyond the rim
Avoid wrinkles in your clothes
Shave your legs
Aero helmet
Deeper rims
Less spokes, and aero spokes.
Hidden spoke nipples
Quality bearings
Optimal tire pressures
Etc

But like most things, aero performance is not a maximize/minimize issue. Wider tires hurt aero but have other benefits. Less spokes reduces rotating drag, but makes for a weaker wheel. Deeper rims suffer more side force. Deeper frames are heavier. Etc. Etc.

It will be interesting to see if future wind tunnels adopt some of what hambini has expressed. But we will be back to... any optimization will be to the test conditions. And is the test condition really your reality? Or their reality? Or her reality? Or the reality of tomorrow (i am talking weather change by the way).

The reality is there will be wheels that do better on calm days, and others that do better in wind, and others that do better in turbulent changing conditions. There will be no best design. Just a best design for a particular situation. Beyond that, aero spokes, as few as you can, as deep a rim as you can get, not too wide a tire, hide the nipples, narrower hubs, etc...
Last edited by: Rocket_racing: Aug 21, 19 9:53
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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hambini wrote:
Tom A. wrote:
hambini wrote:
Tom A. wrote:
Nazgul350r wrote:
HA, I wish I could watch that, I will miss it. I hope the comments are enabled on the live stream.


Speaking of comments...how ironic is it that the first youtube comment is from our buddy Dan Sotelo (the wheel balance evangelist) telling Hambini that his testing doesn't take into account the aero affects of wheel imbalance? The irony is rich! LOL...

I actually endured watching it yesterday. Here's a couple of observations:
- The phrase "lots of hand-waving" kept popping into my head
- He admits his drag plots are in the wind axis, and not the body axis of the vehicle...does that mean his results ignore the contribution of any lift in the direction of travel? That would be a big faux pas...
- He claims they now use a pressure rake behind the rider and "edit" that out...I'm not buying it.
- He also mentions that he can calculate the expected drag just based on rim section measurements...and that he's got "grad students" working on it and can make the "measurements" in ~4 minutes. Is he really doing the tests or just making calculations?
- Still no example of an application to a real world prediction and how his data "helps"

edit: - He seems to focus on tire leading aerodynamics and ignore the rim leading contribution.

Nothing surprising though...


This is a genuine question and not sarcasm but are you really that naive and ignorant that things in Europe get done slightly differently - ie grad schemes etc? use of company resources for further projects? 6 weeks of holiday etc...

I thought you were pulling my leg previously but I sincerely don't think you understand how things in the Aerospace world work.


Yeah...I guess a lot of these types of questions (on both sides) could be avoided if someone did a better job of explanation in the first place :-/

I think I'd just settle for an actual demonstration that the "data" presented allows for a better and more accurate prediction of real world performance than current methods. That shouldn't be so hard, should it?

Lastly...of all the things observed above, that's the ONLY part you're going to comment on? Ummm...OK. I guess the deflections and redirects continue. At least you're consistent.


Most of your post were statements such as I was moving my hands a lot, faux pas with terminology I did not understand or you were not buying something which I was not selling. I don't know what I was supposed to comment on.

In summary Tom,

Whatever I say or do is never going to be up to your standards. Thus I leave you to make your own conclusions and views.

Thanks

Hambini


I guess this went over your head, but "hand waving" is a term for what someone does when they're presenting incomplete information and/or are glossing over important details and dismissing out of hand legitimate questions.

The fact that you were actually gesticulating quite a bit just brought that home.

This classic cartoon came to mind:


http://bikeblather.blogspot.com/
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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hambini wrote:
Tom wrote:
- He admits his drag plots are in the wind axis, and not the body axis of the vehicle...does that mean his results ignore the contribution of any lift in the direction of travel? That would be a big faux pas...


Most of your post were statements such as I was moving my hands a lot, faux pas with terminology I did not understand...

Wait...are you saying you didn't understand the comment about body axis vs wind axis drag components? Interesting...

http://bikeblather.blogspot.com/
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [Tom A.] [ In reply to ]
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Tom A. wrote:
hambini wrote:
Tom wrote:

- He admits his drag plots are in the wind axis, and not the body axis of the vehicle...does that mean his results ignore the contribution of any lift in the direction of travel? That would be a big faux pas...


Most of your post were statements such as I was moving my hands a lot, faux pas with terminology I did not understand...


Wait...are you saying you didn't understand the comment about body axis vs wind axis drag components? Interesting...

I've never heard anyone quote axes. Axes are used for moments, typically Cm.

I think, although not certain you are referring to planes.

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [Rocket_racing] [ In reply to ]
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Rocket_racing wrote:
Here we go again.

Much of what is presented in the video is a knock-down of the validity of current measurement techniques to evaluate aerodynamics of bikes/parts. Egos aside, i think it does raise a valid point... that the real world is not as laminar as we might wish. The optimal design in a lab (or enclosed velodrome) may not be as optimal in the wild. The MIG example is an interesting one. Sacrificing ultimate aero efficiency to better deal with non ideal aero situations. Sounds a lot like the mantra that zipp used to try to make their wheels not just faster, but more stable in cross winds.

BUT... is hambinis protocol more representative of reality? Everything is trying to model reality, the issue is that reality is constantly changing (wind that is), and no two moments are ever the same. So what test best models reality, and which reality are we testing?

So here is what we have for test options:
- eyeball it/armchair logic
- cfd
- wind tunnel (traditional)
- wind tunnel (non laminar airflow)
- outdoor testing (velodrome)
- chung method
- roll-down tests
- i am sure i am missing a few

Which creates “valid” data? Even if hambinis data was more representative of reality, he states a 2.5% error, so i will not use it to compare wheel a to wheel b, because the 2w difference between those wheels are within the margin of error of the test. Compare this to a laminar flow wind tunnel that may be able to theoretically be more precise, but is it as representative of the real world? Pros and cons.

Rider on bs rider off data is the same issue. Rider on is reality, but a rider increases your error. So dummies were created. But i am not shaped like you, and on and on....

The trends this data shows, deeper is more aero, yeah, i buy that. Aero spokes, hide the nippples. Yup. But just as hambini said he could improve a riders aero with a profile picture, i could also improve the aero of a given poor wheel design without an aerospace degree or fancy wind tunnel with louvres (but isn’t that part of how we got here in the first place... people cutting corners in design...). I could probably look at a line of wheels and with a calliper and a few tools to check spoke alignment, could probably align the fastest to slowest wheels with decent accuracy. It is not rocket science.

The trick is not just design, but to make that product to a high quality, at a budget that makes the product/business sustainable. Poor alignment of aero spokes will kill a wheel performance aerodynamically. It is not a design issue, but a manufacturing one. Accountants are always the bane of the engineer. Maybe every wheel maker could make a faster wheel, but at what cost? Most shy from internal nipples due to inconvenience to the buyer. It is a conscious design decision.

In reality, no test protocol is perfect. The trick is to know/accept the limitations. Actually, the chung method is pretty smart imho. Also, i think the aerocoach approach that mixes outdoor velodrome testing with wind tunnel is pretty good to. Why, because both are accessible and reproducible, and involve some element of in vivo real world testing. But in vivo comes with it’s own set of issues (multiple variables you can not control), so there is no one perfect test. The key is knowing the limits of each test.

The ideal test(s)& is one that is accessible (equipment, cost), and easily reproducible. Anything that requires a test protocol that is only accessible to a couple of aerospace companies... is god damn useless to the common bike rider trying to shave a few seconds off their next bike split.

Reduce frontal area
Don’t balloon your tires beyond the rim
Avoid wrinkles in your clothes
Shave your legs
Aero helmet
Deeper rims
Less spokes, and aero spokes.
Hidden spoke nipples
Quality bearings
Optimal tire pressures
Etc

But like most things, aero performance is not a maximize/minimize issue. Wider tires hurt aero but have other benefits. Less spokes reduces rotating drag, but makes for a weaker wheel. Deeper rims suffer more side force. Deeper frames are heavier. Etc. Etc.

It will be interesting to see if future wind tunnels adopt some of what hambini has expressed. But we will be back to... any optimization will be to the test conditions. And is the test condition really your reality? Or their reality? Or her reality? Or the reality of tomorrow (i am talking weather change by the way).

The reality is there will be wheels that do better on calm days, and others that do better in wind, and others that do better in turbulent changing conditions. There will be no best design. Just a best design for a particular situation. Beyond that, aero spokes, as few as you can, as deep a rim as you can get, not too wide a tire, hide the nipples, narrower hubs, etc...

Good post.

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
Quote | Reply
hambini wrote:
Tom A. wrote:
hambini wrote:
Tom wrote:

- He admits his drag plots are in the wind axis, and not the body axis of the vehicle...does that mean his results ignore the contribution of any lift in the direction of travel? That would be a big faux pas...


Most of your post were statements such as I was moving my hands a lot, faux pas with terminology I did not understand...


Wait...are you saying you didn't understand the comment about body axis vs wind axis drag components? Interesting...


I've never heard anyone quote axes. Axes are used for moments, typically Cm.

I think, although not certain you are referring to planes.

Huh...seems to be the terminology more commonly used for ground vehicles. For example, here's a slide from Kim Blair at MIT:




https://ocw.mit.edu/...TES_010S13_lec10.pdf

I also often wonder if it's easier for folks with a sailing background to better understand the physics at play (apparent wind, component of "lift" in the travel direction, etc.) with bicycles than it is for folks with an aircraft background...

http://bikeblather.blogspot.com/
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
Quote | Reply
hambini wrote:

I've never heard anyone quote axes. Axes are used for moments, typically Cm.

I think, although not certain you are referring to planes.

hmmmmm: https://www.google.com/...nd+axis+aerodynamics
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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hambini wrote:
lyrrad wrote:
Still waiting for a link to those patents with your name on them


You won't.

Within EADS Patents are centrally handled by the IP department. It has been this way since China started mass counterfeiting.

LOL - even large corporate IP departments are required to list the name of the actual inventor on patents or risk them being invalidated and the inventor is required to sign off on them.

-------------
Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [Tom A.] [ In reply to ]
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Tom A. wrote:
hambini wrote:
Tom A. wrote:
hambini wrote:
Tom wrote:

- He admits his drag plots are in the wind axis, and not the body axis of the vehicle...does that mean his results ignore the contribution of any lift in the direction of travel? That would be a big faux pas...


Most of your post were statements such as I was moving my hands a lot, faux pas with terminology I did not understand...


Wait...are you saying you didn't understand the comment about body axis vs wind axis drag components? Interesting...


I've never heard anyone quote axes. Axes are used for moments, typically Cm.

I think, although not certain you are referring to planes.


Huh...seems to be the terminology more commonly used for ground vehicles. For example, here's a slide from Kim Blair at MIT:




https://ocw.mit.edu/...TES_010S13_lec10.pdf

I also often wonder if it's easier for folks with a sailing background to better understand the physics at play (apparent wind, component of "lift" in the travel direction, etc.) with bicycles than it is for folks with an aircraft background...

Why spend so much time debating tests that did not even happen? It still seems to me that it is much more likely that this guy did not sneak all this time in to this wind tunnel. It also seems to me that people that DO spend a lot of time in that wind tunnel, like Jean-Paul Ballard, would have heard of Hambini if he was there so much. But during the Q&A section of this Google talk, someone asks him about Hambini and he says he has no idea who that is.

http://www.youtube.com/watch?v=lmqdqcOvrlc

-------------
Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [RowToTri] [ In reply to ]
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RowToTri wrote:
Why spend so much time debating tests that did not even happen? It still seems to me that it is much more likely that this guy did not sneak all this time in to this wind tunnel. It also seems to me that people that DO spend a lot of time in that wind tunnel, like Jean-Paul Ballard, would have heard of Hambini if he was there so much. But during the Q&A section of this Google talk, someone asks him about Hambini and he says he has no idea who that is.

http://www.youtube.com/watch?v=lmqdqcOvrlc

Look, I think Hambini is a arrogant jerk too. He is also very clearly full of bias - as he has made some pretty big enemies and slags them pretty hard (partly for entertainment of his followers, but I think that is just who he is also). He also sells product/services, and has a Youtube channel that pays for views. Sure it is not his day job, but between the money and ego, it is all in his benefit to grow, build his name. Without looking, I can 100% guarantee that his Aero wheels blog post has more views than every other post combined. So there is a lot of reason for him to perpetuate that discussion. THat is why he continues to test more wheels. And the more we say his name, the more recognition we given him. And like certain politicians (and news agencies) have figured out, controversy generates interest, notoriety, and support.

Maybe he made all the data up. It would be an interesting exercise in psycology and personality disorder if he did. The coworker using his account. The flow legal letter. But the reality is that we will never really know. It all comes down to credibility, and our trust. Given there is no true peer review of his data/process, we have to go on what we see.

Even if his data was real, I would not use it to chose wheel A over B because his protocol error of 2.5% overlaps most of the wheels in each test. But even if the data was not real, or fatally flawed, the basic principals of aerodynamics that he brings to the table is worth considering. i.e. be careful of how much weight you place on data generated from a laminar flow situation, because the real outside world is often not laminar. My armchair PHD tells me that the higher the wind velocity on the day you ride, the farther off the data may be. Or is it that far off?

But at the same time, assuming his data is real, I still think it supports that our current methods of designing and aero wheels is on point. The general aerodynamic principles and trends are still there. Deeper rims = faster. Just don;t use it to say rim A is faster than Rim b, because in other situations, the pecking order might change.

IS his data more valid of real world than data from other forms of testing? The only way to know is if his data was more accurate at predicting real world performance gains. The problem is, outside of an indoor velodrome, or minimal wind days, reality has a lot of noise in the data... so the magic 8 ball answer will always be "answer unclear." But from what I understand, current protocols are pretty damn good at predicting real world performance gains. So a ground up rethink of how the industry does things may not be required. Rather, non laminar aero data may just enhance our knowledge.

What I would like to see teased from Hambinis data (or any large volume test data) would be things like spoke count, spoke type, spoke alignment, exposed nipples, rim profile, rim with to mounted tire with. Brake that up by rim depth. Show us how much rim depth vs say spokes really matter in building a fast wheel. same for tire to rim width. Maybe the poor performers just simply had poor spoke alignment... and their rim shapes were pretty good. Maybe it was that 23c tires at 120psi (I estimate could be an easy 26mm on some rims) killed the aero of some rims because they were just too damn wide. Maybe depth is more important than shape, and terroidal vs naca is really just the final 5% of gains for a rim... and the best answer depends on the environmental conditions at the time. Intuitively I think we know what will be faster to maybe 95% of the wheels potential. The last 5% is the trick, but with the rider taking 80% of drag... maybe who cares, because as a system, that 5% is now 0.3% or some similarly small number. And that 0.3% is far less than the error of any test method we have... so we can;t prove it anyway. IT is not easy to detect a pattern among the noise, and the real world has a ton of noise.

What I am taking from this, and everything I have learned of bike aerodynamics from the comfort of my couch, is that there is no one best model. And it is key to understand the limitations, and strengths/advantages of each testing method. And they all have value. But the ones with the most value are easily reproducible, and accessible. And don't take any protocol that says wheel/frame A is faster than frame B too seriously, but don't ignore it either.
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [Rocket_racing] [ In reply to ]
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So here is a question, if it is true that "many aero wheels will perform better in an laminar air flow vs non laminar" (i.e. in reality they may not give as many gains as advertised), and "deeper rims will perform better in non laminar air flow than shallow"... than what about bike frames?

Lets consider a frame designed for low yaw performance like a P5, vs a frame with deeper foil sections like a Shiv or IA, vs say kamm tail designs. In a non laminar environment, would the deeper frames stay closer to their predicted performance (measured in laminar conditions) because they would better be able to keep/recapture the air? Or does the virtual foil of a kamm tail still operate well in such conditions?
Last edited by: Rocket_racing: Aug 21, 19 19:36
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [bloodyshogun] [ In reply to ]
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bloodyshogun wrote:
How did you Measure rotational drag? Did you mean 20-30% of total drag (presume-ably of the wheel itself) is the equivalent to spin the wheel up or keep the wheel spinning?


FWIW this is not out of line with what Swisside found when they investigated rotational drag.

Edit to add: ~20-30% of the total drag of the wheel itself.
https://www.swissside.com/...neglected-resistance
https://www.swissside.com/...tional-drag-insights


Last edited by: GreenPlease: Aug 21, 19 20:16
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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Finally got around to watching the video. Trying to be Switzerland here and not throw fuel on any fire already burning in this thread but I want to point out one line of thought you kind of started down but didn't totally finish (paraphrasing):

Quote:
When you ride you constantly make micro steering corrections and this is especially true when you experience a crosswind...

It's never been entirely clear to me field surveys of yaw properly take into account a rider's normal reaction to a crosswind. Let's take a look at Flo's rig which is attached to the handlebar and fork:



No matter how hard Jon, or Chris, or whoever is riding that bike tries to ride a straight line the reality is that they will constantly be making small steering inputs. If the wind hits the rider from his left, that will cause the rider to counter steer into the wind thus lowering the apparent yaw relative to the direction of the bike's travel. From the wheel's perspective yaw is temporarily lower than from the frame's perspective. I'd be very interested to see data from an encoder in the steerer tube but it wouldn't shock me if these counter-steering inputs were on the order of 2.5-5 degrees during a crosswind.

Also along those lines, when we test in the tunnel our front wheel is perfectly aligned with our bike. I've never seen testing for a tire/wheel/frame system combo for when the wheel is turned 5 degrees to the left or right.

With the foregoing said, I'm not sure that the tunnel/track/VE testing is completely invalid considering that it can make reasonably accurate predictions. My TT times match up very well with my predicted times based on my estimated CdA from the tunnel and VE testing. Call current protocols a heuristic or whatever but, for the vast majority (including really fast people), it's good enough. If I were designing a product from the ground up I might look for a better understanding and a better testing protocol.
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [GreenPlease] [ In reply to ]
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GreenPlease wrote:
bloodyshogun wrote:
How did you Measure rotational drag? Did you mean 20-30% of total drag (presume-ably of the wheel itself) is the equivalent to spin the wheel up or keep the wheel spinning?


FWIW this is not out of line with what Swisside found when they investigated rotational drag.

Edit to add: ~20-30% of the total drag of the wheel itself.
https://www.swissside.com/...neglected-resistance
https://www.swissside.com/...tional-drag-insights


Thanks for those links. I found this quantification by Swiss Side interesting to put things in perspective: “... for example the difference between round spokes and aero spokes is 1.5W, which is 12% of the total wheel drag. Similarly hidden nipples make a difference of 0.5W, another 4% saving.”
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [rik] [ In reply to ]
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rik wrote:
hambini wrote:


I've never heard anyone quote axes. Axes are used for moments, typically Cm.

I think, although not certain you are referring to planes.


hmmmmm: https://www.google.com/...nd+axis+aerodynamics

And that is correct, the first picture shows the moments.

When summing the pressures to give you the net force, nobody knows where you are going to make the cut so we talk planes.

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [RowToTri] [ In reply to ]
Quote | Reply
RowToTri wrote:

Why spend so much time debating tests that did not even happen? It still seems to me that it is much more likely that this guy did not sneak all this time in to this wind tunnel. It also seems to me that people that DO spend a lot of time in that wind tunnel, like Jean-Paul Ballard, would have heard of Hambini if he was there so much. But during the Q&A section of this Google talk, someone asks him about Hambini and he says he has no idea who that is.

http://www.youtube.com/watch?v=lmqdqcOvrlc

I think you may have been confused by geography or you perhaps you just want to find fault.

I get the feeling you might be slightly upset as your shoes that you are designing will be in completely erratic flow thus rendering your wattage claim of 6-10W as "optimistic", I would say it was fabricated :)

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [GreenPlease] [ In reply to ]
Quote | Reply
GreenPlease wrote:
bloodyshogun wrote:
How did you Measure rotational drag? Did you mean 20-30% of total drag (presume-ably of the wheel itself) is the equivalent to spin the wheel up or keep the wheel spinning?


FWIW this is not out of line with what Swisside found when they investigated rotational drag.

Edit to add: ~20-30% of the total drag of the wheel itself.
https://www.swissside.com/...neglected-resistance
https://www.swissside.com/...tional-drag-insights


I would say it's a compound effect, if you improve the trailing edge turbulence, it benefits at the other end of the wheel with improved airflow.

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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It’s been a while since I’ve looked at your original shootout so I don’t recall: did you test a tri-spoke or twin-spoke wheel?
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [GreenPlease] [ In reply to ]
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GreenPlease wrote:
It’s been a while since I’ve looked at your original shootout so I don’t recall: did you test a tri-spoke or twin-spoke wheel?

Nope

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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Thoughts on those wheel types?
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [GreenPlease] [ In reply to ]
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One of the grads is borrowing one next week. I will update the charts after that.

HELLO HAMBINI FANS!!!
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Re: Updated: A Comprehensive (But Controversial) Wind Tunnel Wheel Shootout [hambini] [ In reply to ]
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hambini wrote:
rik wrote:
hambini wrote:


I've never heard anyone quote axes. Axes are used for moments, typically Cm.

I think, although not certain you are referring to planes.


hmmmmm: https://www.google.com/...nd+axis+aerodynamics

And that is correct, the first picture shows the moments.

When summing the pressures to give you the net force, nobody knows where you are going to make the cut so we talk planes.

Let me get this straight: you make the statement that nobody uses the term “axes,” and then confronted with evidence from a cursory Google search that the term is widely used, you double down?
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