Aero data from 19 wheels by Hambini

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Beaver
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by Beaver

aeroisnteverything wrote:
Tue Sep 11, 2018 12:37 pm
Beaver wrote:
Mon Sep 10, 2018 8:59 pm

In the end a round shape and fulfilling the 105% rule seems to help after all: the Bontrager are 27mm wide outside, 19.5mm inside, with a 23mm tire that's quite a good match.

And Hambini added the new Light Bicycle rim with 30mm outside, 23mm inside - this is also quite good, especially at high speed:
Does it though? Bora 50s perform virtually identical to the 56mm deep LightBicycle and also same as the Bontys. Mavics at 45mm are only marginally worse, and still within the margin of error. How do we explain this? Is this is a fluke?
Don't forget that the differences are not huge, we are talking about nuances between wheels of (nearly) the same height - nothing you would be able to notice on the road. And Campy rims are not that "square", but the 50mm Bontrager has a wider 27mm rim (105% rule) and more inner width (19mm, if it's the D3 model), so the tire shoulders stand straighter and assure a better transition from tire to rim. So the LightBicycle wheels should excel here with 23mm inside, but the 30mm outside also increase the frontal area... Mavics are lower, narrower but only have 36 spokes, that also helps and they are quite close to the others.

So frontal area, 105% rule, inner width, and the numer of spokes are relevant, for the last 0,x watts also inner spoke nipples, spoke shape and width, hub size and shape and so on.
hambini wrote:
Sat Sep 15, 2018 4:59 pm
More wheels are being tested. I will update the original post with results.
:thumbup: Roval CLX 50 would also be interesting for comparison.

ichobi
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by ichobi

On that note Hed jet would be an interesting comparison as well because specialized (and Bontrager back then) bought He'd design patent for their Roval design. Spe added a so called aerodynamic hour Glass shape hub. Rovals got 21mm internal width and designed to matched their s works turbo cotton 26mm tire. Sounds pretty much perfect.

I have been using the Roval clx 32 for 9 months now and they have been flawless except 'one generation behind' braking performance. Would love to see the data. Would have lend you the wheel myself if I live in the UK.

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Jhomewood
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by Jhomewood

Can we have a note of what wheels have been added? it's hard to keep up.

mattr
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by mattr

hambini wrote:
Sat Sep 15, 2018 9:07 pm
Monkeyfudger wrote:
Sat Sep 15, 2018 8:16 pm
Can I just come testing in your wind tunnel...I’ll bring biscuits!
Have you got security clearance?
Yes. (Well, i still have my pass somewhere, i would guess all the "stuff" attached to it has long since expired!)

Or i could try and sneak into one of our low speed tunnels after the current bow wave of work has finished.......

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by Calnago

Monkeyfudger wrote:Biscuits, I’ve got biscuits!!
Warm biscuits, with raisins maybe?.... that should trump any security clearance nonsense.
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tanhalt
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by tanhalt

hambini wrote:
Sun Sep 09, 2018 4:56 pm
RyanH wrote:
Sun Sep 09, 2018 2:22 pm
hambini wrote:At very low yaw angles the rim depth has absolutely the biggest effect on the drag, I guesstimate 46W in a completely straight line. I would need to manipulate the data some mroe but that gives you a ball park number. You would be better off with a deeper Yoeleo wheel.

Just bare in mind, almost any rider will create turbulence because they correct the front wheel without noticing it. Also at 50km/h the effect of traffic and external influences reduce because the forward velocity to crosswind velocity ratio increases.

The best way to think of this is like the front wheel is like a flipper on a dolphin, you can see the wake the dolphin causes because it ripples the water. Same thing is happening on your front wheel - you just can't see it.

Hambini
Hi Hambini,

That's interesting. So in low wind conditions (let's use the track as an extreme) the difference between any two rims is going to be greater than what one would encounter in the tested parameters? What about blustery, windy conditions? I thought that would favor wheels that can handle turbulence well so a deeper wheel would have a lower wattage number over a measured period. Or, is it because blustery windy conditions are going to cause flow separation regardless and both will be like sails.

Using the below graph, it looks like the Reynolds have a slight advantage at low yaw angles that increase as the yaw goes up until flow separation happens. Right? So, on the track, for example, wouldn't the difference between the Flo and Reynolds be roughly 3uN FSR which is lower than what they would be as yaw increases?

Thanks!

Image
I can understand where you are coming from and you've highlighted a reason why I hate putting data up sometimes as the devil is in the detail.

The oscillation on that graph is 2.5deg/s. If you have a different oscillation dtheta/dt (which you indicated you would have) and a lower max amplitude which is what I gauged for then the graph would look different.

With the flipper analogy, it's like bigger flipper moving much slower so the wake is reduced. Less wake means it heads towards the steady state value. Ie instead of 10-15 actual, you might be around 5 deg. Every ride set that was looked at the time at zero degrees was very small unless you dropped the resolution down and made it look like a wind pointer instead of a bernoulli type device.

With anything like this, it's always the average and becomes a PITA when trying to factor in everyone's individual requirements.

Hambini
Perhaps I've missed it, but did you ever answer the question about whether these drag values are in the wind-axis reference frame or body-axis?

hambini
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by hambini

tanhalt wrote:
Thu Sep 20, 2018 4:58 pm


Perhaps I've missed it, but did you ever answer the question about whether these drag values are in the wind-axis reference frame or body-axis?
I can't remember. I have slept since then.
Hambini Aeronautical Engineer, Polluting YouTube since 2016 - views expressed are my own...

tanhalt
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by tanhalt

hambini wrote:
Fri Sep 21, 2018 12:56 pm
tanhalt wrote:
Thu Sep 20, 2018 4:58 pm


Perhaps I've missed it, but did you ever answer the question about whether these drag values are in the wind-axis reference frame or body-axis?
I can't remember. I have slept since then.
Glad to hear you got some sleep. Are they wind-axis drag values or body-axis?

hambini
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by hambini

tanhalt wrote:
Fri Sep 21, 2018 3:12 pm
hambini wrote:
Fri Sep 21, 2018 12:56 pm
tanhalt wrote:
Thu Sep 20, 2018 4:58 pm


Perhaps I've missed it, but did you ever answer the question about whether these drag values are in the wind-axis reference frame or body-axis?
I can't remember. I have slept since then.
Glad to hear you got some sleep. Are they wind-axis drag values or body-axis?
They are FSR values.
Hambini Aeronautical Engineer, Polluting YouTube since 2016 - views expressed are my own...

tanhalt
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by tanhalt

hambini wrote:
Fri Sep 21, 2018 3:14 pm
tanhalt wrote:
Fri Sep 21, 2018 3:12 pm
hambini wrote:
Fri Sep 21, 2018 12:56 pm
tanhalt wrote:
Thu Sep 20, 2018 4:58 pm


Perhaps I've missed it, but did you ever answer the question about whether these drag values are in the wind-axis reference frame or body-axis?
I can't remember. I have slept since then.
Glad to hear you got some sleep. Are they wind-axis drag values or body-axis?
They are FSR values.
I'm unfamiar with that acronym in this context. What does it stand for? A brief explanation would help. Thanks.

hambini
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by hambini

tanhalt wrote:
Sat Sep 22, 2018 12:07 am

I'm unfamiar with that acronym in this context. What does it stand for? A brief explanation would help. Thanks.
If you look hard enough the answer has been given. If you can't decipher it, I'd suggest you ask your chums from the win tunnel.
Hambini Aeronautical Engineer, Polluting YouTube since 2016 - views expressed are my own...

TurboKoo
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by TurboKoo

This thread has so much good information thanks to @Hambini

Question regarding measurements. How much does bike lean to the wind when riding crosswind? Do you have any data on this or does it even happen? I feel that strong crosswind and can see from L/R balance that I also compensate it pedaling. I think this is a something that is not measured in wind tunnel but bike is static hence difference results in real world testing.
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tanhalt
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by tanhalt

hambini wrote:
Sun Sep 23, 2018 2:21 pm
tanhalt wrote:
Sat Sep 22, 2018 12:07 am

I'm unfamiar with that acronym in this context. What does it stand for? A brief explanation would help. Thanks.
If you look hard enough the answer has been given. If you can't decipher it, I'd suggest you ask your chums from the win tunnel.
I have looked, and I don't see an answer from you that's decipherable...so, to save any confusion that may result from a misinterpretation (a common problem on the internent, no?) how about just telling us what that vertical scale on that plot actually means? Again, you are leaving context out of your plots.

Anyway, I don't get this agressive pettiness towards me that you've displayed throughout this entire thread. I've merely calmly asked questions about the protocol and measurements in an attempt to put them in context. All it's been met with from you is appeals to authority ("I'm the EXPERT here, TRUST what I say!"), ad hominem attacks, and obfuscation. You throw up plots with undefined axes and then expect people not to question it...and if they do, you accuse them (falsely) of being "shills", or worse...WTH?

Why are you afraid of questions? If this protocol you've developed IS better than what has been previously done, you should WELCOME questions as opportunities to explain and demonstrate why that is so. Shouting down legitimate questions with nothing but insults and appeals to authority isn't a good way to make your case or win people over...

hambini
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by hambini

TurboKoo wrote:
Sun Sep 23, 2018 4:04 pm
This thread has so much good information thanks to @Hambini

Question regarding measurements. How much does bike lean to the wind when riding crosswind? Do you have any data on this or does it even happen? I feel that strong crosswind and can see from L/R balance that I also compensate it pedaling. I think this is a something that is not measured in wind tunnel but bike is static hence difference results in real world testing.
This depends on a few factors, the main bit being how high up you are in relation to the depth of the wheels. Basically, deeper wheels and more wind means more lean.

If you are riding along in a constant crosswind, then it's possible to ride in very strong crosswinds (40km/h+) but if the wind speed fluctuates, this becomes more problematic.

Hambini
Hambini Aeronautical Engineer, Polluting YouTube since 2016 - views expressed are my own...

hambini
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by hambini

tanhalt wrote:
Sun Sep 23, 2018 9:04 pm
I have looked, and I don't see an answer from you that's decipherable...so, to save any confusion that may result from a misinterpretation (a common problem on the internent, no?) how about just telling us what that vertical scale on that plot actually means? Again, you are leaving context out of your plots.

Anyway, I don't get this agressive pettiness towards me that you've displayed throughout this entire thread. I've merely calmly asked questions about the protocol and measurements in an attempt to put them in context. All it's been met with from you is appeals to authority ("I'm the EXPERT here, TRUST what I say!"), ad hominem attacks, and obfuscation. You throw up plots with undefined axes and then expect people not to question it...and if they do, you accuse them (falsely) of being "shills", or worse...WTH?

Why are you afraid of questions? If this protocol you've developed IS better than what has been previously done, you should WELCOME questions as opportunities to explain and demonstrate why that is so. Shouting down legitimate questions with nothing but insults and appeals to authority isn't a good way to make your case or win people over...
As mentioned previously. Umpteen times. My primary job is not in the bike industry and therefore the resources that myself and my colleagues spend to answer questions is limited. I/We have tried to be accommodating where possible.

I can't be expected to give engineering principles lectures on weightweenies posts because you don't understand something. I have suggested you speak to your friends at Specialized to see if they can assist you with your questions, or speak to mr Coggan, he seems to know everything.

Thanks

Hambini
Hambini Aeronautical Engineer, Polluting YouTube since 2016 - views expressed are my own...

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