Aerodinamical data for some wheel sets (from the "Tour" magazine)
Emilio Lopes
45 Km/h for some current aerowheel sets. The numbers are from the
German magazine "Tour" (April 2000). The tests were carried by a
professional rider using an SRM-equiped bicycle in a track.
Wheel Set Power in Watts (for v=45 Km/h)
Corima 4-Spoke HM 381.9
Corima Spokewheel 384.5
Lightweight 385.0
Citec 3000 390.0
Mavic Ksyrium 391.8
Zipp 530 394.7
Ritchey OCR 395.7
Shimano Dura Ace 399.7
Rolf Vector Pro Carbon 407.0
Spinergy Spox R2 413.3
I don't know why Campagnolo's Shamal or Bora were not tested.
Jon Isaacs
>45 Km/h for some current aerowheel sets. The numbers are from the
>German magazine "Tour" (April 2000). The tests were carried by a
>professional rider using an SRM-equiped bicycle in a track.
>
Thanks for posting this. Too bad they didn't test some true disks, I would be
interested in that data.
Jon Isaacs
cog...@grecc.umaryland.edu
cycling and John Cobb's wind tunnel data for the Corima wire-spoked
wheel and the Rolf Vector Pro (the only two wheels tested by both),
here's what I get:
Corima wheelset:
Power = 384 W (measured by Tour magazine)
Total aerodynamic drag @ 30 mph (20 deg C, zero wind) = 7.00
lbs.
Rolf Vector Pro wheelset:
Power =
Coefficient of rolling resistance
In article <871z4bk...@nuc04.t30.physik.tu-muenchen.de>,
Emilio Lopes <Emilio.Lo...@Physik.TU-Muenchen.DE> wrote:
> Following table shows the power needed to sustain a velocity of
> 45 Km/h for some current aerowheel sets. The numbers are from the
> German magazine "Tour" (April 2000). The tests were carried by a
> professional rider using an SRM-equiped bicycle in a track.
>
> Wheel Set Power in Watts (for v=45 Km/h)
>
> Corima 4-Spoke HM 381.9
> Corima Spokewheel 384.5
> Lightweight 385.0
> Citec 3000 390.0
> Mavic Ksyrium 391.8
> Zipp 530 394.7
> Ritchey OCR 395.7
> Shimano Dura Ace 399.7
> Rolf Vector Pro Carbon 407.0
> Spinergy Spox R2 413.3
>
> I don't know why Campagnolo's Shamal or Bora were not tested.
>
--
Andrew Coggan
Sent via Deja.com http://www.deja.com/
Before you buy.
cog...@grecc.umaryland.edu
Very interesting! If I use our model of the power requirements of
cycling and John Cobb's wind tunnel data for the Corima wire-spoked
wheel and the Rolf Vector Pro (the only two wheels tested by both),
here's what I get:
Corima wheelset:
Power = 384 W (measured by Tour magazine)
Calculated total aero drag @ 30 mph (20 deg C, zero wind) = 7.02 lbs.
Rolf Vector Pro wheelset:
Power = 407 W (again, measured by Tour)
Calculated total aero drag @ 30 mph (20 deg C, zero wind) = 7.48 lbs.
IOW, based on the Tour data and our model, using Corima wheels instead
of Rolf wheels reduces your overall drag by 0.46 lbs, or 0.23 lbs/wheel.
This corresponds almost EXACTLY with what John measured in the wind
tunnel: average drag for the Corima wheel at 0 to 10 degrees of yaw was
0.16 lbs, whereas the average drag of the Rolf wheel at 0 to 10 degrees
of yaw was 0.38 lbs, a difference of 0.22 lbs.
I also did the calculations for the SPOX R2 wheelset (which to my
knowledge John has not tested in the wind tunnel):
SPOX R2 wheelset:
Power = 413 W (again, measured by Tour)
Calculated total aero drag @ 30 mph (20 deg C, zero wind) = 7.60 lbs
Thus, the SPOX R2 wheelset apparently generates 0.12 lbs more drag than
the Rolf wheelset, or a difference of 0.06 lbs/wheel. This is about
one-half of the 0.13 lbs difference that John found for the original
SPOX, which lacked the R2's aero rim.
I think the above calculations support several conclusions:
1) w/ care, testing of wheels on an indoor velodrome and a power
measuring device can give reasonably precise results.
2) our model is able to predict fairly small differences in overall drag
with good accuracy.
3) extrapolation from results of wind tunnel testing to the so-called
real world is (as expected) valid.
4) the fat SPOX found on the Spinergy wheels create additional
aerodynamic drag, just as you'd expect.
(Note: for the above calculations, I assumed a bike + rider weight of
183 lbs, and a oefficient of rolling resistance of 0.003, but these
assumptions - and the others listed above - have very little impact on
the overall conclusion. The use of drag data averaged over 0 to 10
degrees of yaw is justified on the basis of Project 96 measurements
showing that yaw angle varies over that range as one circles a
velodrome.)
Bob Mitke
>Following table shows the power needed to sustain a velocity of
>45 Km/h for some current aerowheel sets. The numbers are from the
>German magazine "Tour" (April 2000). The tests were carried by a
>professional rider using an SRM-equiped bicycle in a track.
>
>Wheel Set Power in Watts (for v=45 Km/h)
>
>Corima 4-Spoke HM 381.9
>Corima Spokewheel 384.5
>Lightweight 385.0
>Citec 3000 390.0
>Mavic Ksyrium 391.8
>Zipp 530 394.7
>Ritchey OCR 395.7
>Shimano Dura Ace 399.7
>Rolf Vector Pro Carbon 407.0
>Spinergy Spox R2 413.3
I don't think I even need to comment on the uncertainty of this test.
Yes, don't use SPOX during a TT. Use double disks if you can
handle it. I don't think Spinergy was trying to offer an aerodynamic
product with the SPOX.
At 30 mph the best aero wheels put out about .2 lbs of drag and typical
6 ftrs put out about 10 lbs of drag in their aero position. I think it is
obvious where you should spend your time and money if you _really_
want to go faster. Even Andrew Coggan would probably back me on this
one.
Buy a set of "aero" wheels and then get in a wind tunnel and work on
your position. Working on your position can often times lead to a couple
of pounds (or more) of drag reduction at 30 mph. Seems like a bigger
gain than the .05 lbs gained (maybe) by switching your wheels.
-Bob Mitke
cog...@grecc.umaryland.edu
> Emilio Lopes wrote:
>
> >Following table shows the power needed to sustain a velocity of
> >45 Km/h for some current aerowheel sets. The numbers are from the
> >German magazine "Tour" (April 2000). The tests were carried by a
> >professional rider using an SRM-equiped bicycle in a track.
> >
> >Wheel Set Power in Watts (for v=45 Km/h)
> >
> >Corima 4-Spoke HM 381.9
> >Corima Spokewheel 384.5
> >Lightweight 385.0
> >Citec 3000 390.0
> >Mavic Ksyrium 391.8
> >Zipp 530 394.7
> >Ritchey OCR 395.7
> >Shimano Dura Ace 399.7
> >Rolf Vector Pro Carbon 407.0
> >Spinergy Spox R2 413.3
>
> I don't think I even need to comment on the uncertainty of this test.
I don't think it is nearly as uncertain as you imply - see my other
posts for the calculations that led me to this conclusion.
> At 30 mph the best aero wheels put out about .2 lbs of drag and
typical
> 6 ftrs put out about 10 lbs of drag in their aero position.
If your drag is that high you might as well stay home...I'm 6 feet tall,
but my total aerodynamic drag at 30 mph is just over 5 lbs. That's
better than most people, but even with 6 lbs of drag a difference of 0.6
lbs (which is about the difference between a pair of SPOX R2 and a pair
of Corima wheels) amounts to 10% of the total. Perhaps more importantly,
a 0.6 lbs difference in drag amounts to almost 2 min in a 40k TT at
typical racing speeds.
> I think it
is
> obvious where you should spend your time and money if you _really_
> want to go faster. Even Andrew Coggan would probably back me on this
> one.
If the choice were spend $500 on new wheels vs. spend the same amount to
get tested in the wind tunnel under John Cobb's watchful eye, then yes,
I'd opt to spend the money on going to the wind tunnel. But position and
wheels are really totally independent, so comparing one to the other
really isn't all that relevant.
> Buy a set of "aero" wheels and then get in a wind tunnel and work on
> your position. Working on your position can often times lead to a
couple
> of pounds (or more) of drag reduction at 30 mph. Seems like a bigger
> gain than the .05 lbs gained (maybe) by switching your wheels.
I generally agree, but again, aside from $$ spent on wind tunnel testing
(which may not be all that necessary, e.g., do you think Obree developed
his positions in the wind tunnel?) the two are totally independent.
Jon Isaacs
>
Please do, however do so with actual information. Do you actually know what
the uncertainty in these tests are? It is interesting that both the drag data
that I presented and this data show the same results.
I did not do these tests so I don't actually know the errors involved. Typical
data reporting is done in terms of significant figures.
This data supports my conjectures in the original post, ie that these
"boutique" wheels are actually "posers." They look like "serious" wheels, they
cost like "serious" wheels but they don't provide the benefits of "serious"
wheels.
Regarding the Spox. Certainly you now must admit that they are inferior from
a performance standpoint. The justification for Spox is that they "ride"
better. I suggest that switching to one size larger tire will provide a
greater increase in ride quality and by using a standard rim, there will not be
a aerodynamic loss.
>Buy a set of "aero" wheels and then get in a wind tunnel and work on
>your position.
I have seen people using Spox for Triathleons and time trials. I imagine they
would be disappointed if they knew that a SPOX required about 8.5% more effort
than a true aerowheel like a Corima 4 spoke.
Developing ones position is a bit more complicated than just getting in a wind
tunnel. Position is a compromise between comfort, biomechanical efficiency,
and aerodynamics. The wind tunnel only measures one of these factors.
Wheels are easy, good ones will help you. Just hope you don't buy some
"posers" thinking they will actually help you.
Jon Isaacs
John Verheul
cog...@grecc.umaryland.edu wrote:
<snip>
> 4) the fat SPOX found on the Spinergy wheels create additional
> aerodynamic drag, just as you'd expect.
> >
> >
> > Corima 4-Spoke HM 381.9
> > Corima Spokewheel 384.5
> > Lightweight 385.0
> > Citec 3000 390.0
> > Mavic Ksyrium 391.8
> > Zipp 530 394.7
> > Ritchey OCR 395.7
> > Shimano Dura Ace 399.7
> > Rolf Vector Pro Carbon 407.0
> > Spinergy Spox R2 413.3
You conclude the fat spokes on the Spinergy are what creates the
additional drag, how then does the (also fat-spoked) Ksyrium do so well
in the "Tour" test? I was shocked to see it ahead of the Rolf Carbon
and the Dura Ace. Could the difference between the Ksyrium and the Spox
be attributable to rim shape (U vs. V)?
John Verheul
cog...@grecc.umaryland.edu
> You conclude the fat spokes on the Spinergy are what creates the
> additional drag, how then does the (also fat-spoked) Ksyrium do so
well
> in the "Tour" test? I was shocked to see it ahead of the Rolf Carbon
> and the Dura Ace. Could the difference between the Ksyrium and the
Spox
> be attributable to rim shape (U vs. V)?
I haven't looked closely at a set of Ksyrium wheels, but my
understanding is that they used bladed spokes, not round. IOW, while
they may look larger than normal when viewed from the side, when viewed
head-on they have much less frontal area than a SPOX (and a better
shape, to boot). A number of tests have shown that bladed spokes are
better than round spokes at realistic yaw angles (despite dataless
claims to the contrary).
Andrew Coggan
John Verheul
cog...@grecc.umaryland.edu wrote:
> I haven't looked closely at a set of Ksyrium wheels, but my
> understanding is that they used bladed spokes, not round.
I have. While they are really big, you are correct that they are
bladed, although they're not flat like steel "bladed" spokes.
> IOW, while
> they may look larger than normal when viewed from the side, when
viewed
> head-on they have much less frontal area than a SPOX (and a better
> shape, to boot). A number of tests have shown that bladed spokes are
> better than round spokes at realistic yaw angles (despite dataless
> claims to the contrary).
I haven't examined Spox closely. I had no idea the spokes were (besides
being huge) round.
John Verheul
Michael Murphey
>bikes...@aol.comnojunk (Bob Mitke) wrote:
>> Emilio Lopes wrote:
>>
>> >Following table shows the power needed to sustain a velocity of
>> >45 Km/h for some current aerowheel sets. The numbers are from the
>> >German magazine "Tour" (April 2000). The tests were carried by a
>> >professional rider using an SRM-equiped bicycle in a track.
>> >
>> >Wheel Set Power in Watts (for v=45 Km/h)
>> >
>> >Corima 4-Spoke HM 381.9
>> >Corima Spokewheel 384.5
>> >Lightweight 385.0
>> >Citec 3000 390.0
>> >Mavic Ksyrium 391.8
>> >Zipp 530 394.7
>> >Ritchey OCR 395.7
>> >Shimano Dura Ace 399.7
>> >Rolf Vector Pro Carbon 407.0
>> >Spinergy Spox R2 413.3
>>
>> I don't think I even need to comment on the uncertainty of this test.
>
>I don't think it is nearly as uncertain as you imply - see my other
>posts for the calculations that led me to this conclusion.
You surprise me. Consider what we know about the test procedure; a
pro rider on a track with a SRM equipped bicycle. Then the power
differences are all within 10% of each other, sometimes less then 1%.
And to top it all off, these results are given with a precision of
four places. I suggest that the agreement with John Cobb's data is
coincidence and that these results are not worth much.
>
>> At 30 mph the best aero wheels put out about .2 lbs of drag and
>typical
>> 6 ftrs put out about 10 lbs of drag in their aero position.
>
>If your drag is that high you might as well stay home...I'm 6 feet tall,
>but my total aerodynamic drag at 30 mph is just over 5 lbs. That's
>better than most people, but even with 6 lbs of drag a difference of 0.6
>lbs (which is about the difference between a pair of SPOX R2 and a pair
>of Corima wheels) amounts to 10% of the total. Perhaps more importantly,
>a 0.6 lbs difference in drag amounts to almost 2 min in a 40k TT at
>typical racing speeds.
>
>> I think it
>is
>> obvious where you should spend your time and money if you _really_
>> want to go faster. Even Andrew Coggan would probably back me on this
>> one.
>
>If the choice were spend $500 on new wheels vs. spend the same amount to
>get tested in the wind tunnel under John Cobb's watchful eye, then yes,
>I'd opt to spend the money on going to the wind tunnel. But position and
>wheels are really totally independent, so comparing one to the other
>really isn't all that relevant.
>
>> Buy a set of "aero" wheels and then get in a wind tunnel and work on
>> your position. Working on your position can often times lead to a
>couple
>> of pounds (or more) of drag reduction at 30 mph. Seems like a bigger
>> gain than the .05 lbs gained (maybe) by switching your wheels.
>
>I generally agree, but again, aside from $$ spent on wind tunnel testing
>(which may not be all that necessary, e.g., do you think Obree developed
>his positions in the wind tunnel?) the two are totally independent.
--
Michael Murphey
The Bicycle Shop
Starkville, MS
cog...@grecc.umaryland.edu
You're right, it could be coincidence, since we only have two data
points to compare between the two approachs to testing (i.e., velodrome
vs. wind tunnel). But, my comment was based in part on other studies
that have used the velodrome approach, i.e., Peter Keen's experiments
with Chris Boardman in anticipation of his hour record attempt, the
testing done as part of Project 96, a couple of European investigations
published in scientific journals, etc. Now, I'm not about to argue that
you can measure the power requirement to the nearest 0.1 W, or that you
should, e.g., buy a Citec wheel instead of a Mavic Ksyrium because the
reported differences in aero drag, but nonetheless I do think that this
approach and these data tell us something (and, to show you that I put
my money and performance where my mouth is, am currently investigating
to see how much a Corima rim would cost me).
It might be worth mentioning that, if the above data were generated
using the same approach that Tour magazine has used in the past, they
are based on measurement at multiple velocities, with the power
requirement at exactly 45 km/h obtained by interpolation (or least
that's how I recall the protocol went).
Andrew Coggan
Mark McMaster
>
> John Verheul <John.an...@worldnet.att.net> wrote:
>
> > You conclude the fat spokes on the Spinergy are what creates the
> > additional drag, how then does the (also fat-spoked) Ksyrium do so
> well
> > in the "Tour" test? I was shocked to see it ahead of the Rolf Carbon
> > and the Dura Ace. Could the difference between the Ksyrium and the
> Spox
> > be attributable to rim shape (U vs. V)?
>
> they may look larger than normal when viewed from the side, when viewed
> head-on they have much less frontal area than a SPOX (and a better
> shape, to boot). A number of tests have shown that bladed spokes are
> better than round spokes at realistic yaw angles (despite dataless
> claims to the contrary).
Indeed, the Ksyriums spokes are bladed. In addition, the
deeper rim and fewer spokes on the Ksyriums probably also
help.
Mark McMaster
MMc...@ix.netcom.com
Markku Tuomi
> You conclude the fat spokes on the Spinergy are what creates the
> additional drag, how then does the (also fat-spoked) Ksyrium do so
> well in the "Tour" test? I was shocked to see it ahead of the Rolf
> Carbon and the Dura Ace. Could the difference between the Ksyrium
> and the Spox be attributable to rim shape (U vs. V)?
"Tour" also expresses surprise at the poor showing of the Rolf and
Shimano wheels, despite their pronounced aero look. They suggest that
this may be caused by the fact that these wheels have pairs of spokes
exiting the rim next to each other, thus creating extra turbulence.
To quote: "Die Überraschung aber liefern Shimano und Rolf. Beide
Laufräder sind ausgewiesene Aero-Räder, beide schneiden überraschend
schlect ab. Gemeinsames Merkmal: nahe der Felge überkreuzte,
beziehungsweise dicht hintereinander vernippelte Speichen. Offenbar wird
durch diese Bauform die anströmende Luft besonders stark verwirbelt."
(Tour, April 2000, p. 76)
--
Markku Tuomi <m...@cc.jyu.fi>
Emilio Lopes
> > >> >Corima 4-Spoke HM 381.9
> > >> >Corima Spokewheel 384.5
> > >> >Lightweight 385.0
> > >> >Citec 3000 390.0
> > >> >Mavic Ksyrium 391.8
> > >> >Zipp 530 394.7
> > >> >Ritchey OCR 395.7
> > >> >Shimano Dura Ace 399.7
> > >> >Rolf Vector Pro Carbon 407.0
> > >> >Spinergy Spox R2 413.3
> > >>
> > You surprise me. Consider what we know about the test procedure; a
> > pro rider on a track with a SRM equipped bicycle. Then the power
> > differences are all within 10% of each other, sometimes less then 1%.
> > And to top it all off, these results are given with a precision of
> > four places. I suggest that the agreement with John Cobb's data is
> > coincidence and that these results are not worth much.
> You're right, it could be coincidence, since we only have two data
> points to compare between the two approachs to testing (i.e., velodrome
> vs. wind tunnel). But, my comment was based in part on other studies
> that have used the velodrome approach, i.e., Peter Keen's experiments
> with Chris Boardman in anticipation of his hour record attempt, the
> testing done as part of Project 96, a couple of European investigations
> published in scientific journals, etc. Now, I'm not about to argue that
> you can measure the power requirement to the nearest 0.1 W, or that you
> should, e.g., buy a Citec wheel instead of a Mavic Ksyrium because the
> reported differences in aero drag, but nonetheless I do think that this
> approach and these data tell us something (and, to show you that I put
> my money and performance where my mouth is, am currently investigating
> to see how much a Corima rim would cost me).
They quoted a price of DEM 2265,- for the Corima four-spokes wheel.
That would be about US$ 1130.
> It might be worth mentioning that, if the above data were generated
> using the same approach that Tour magazine has used in the past, they
> are based on measurement at multiple velocities, with the power
> requirement at exactly 45 km/h obtained by interpolation (or least
> that's how I recall the protocol went).
This seems to be the case in this test too. They say the values for
the power were numerically "normalized" to a velocity of 45 Km/h.
Also small variations of air temperature and pressure were taken in
account.
The uncertainty of the numbers presented in the test results from the
combination of the uncertainty in the measure and the interpolation
errors. They don't mention this at all, so we don't know how large it
really is. Considering this and also that the difference between a
four-spokes carbon wheel and a wheel with relatively many thick round
spokes is "just" of the order of 10% *I* would stick to a home-built
wheel with deep section rims and maybe bladed or elliptical spokes.
But that's just my opinion.
The difference is still smaller for smaller values of velocity, since
power is proportional to the cube of the velocity.
ECL.