Forget that. Was that with or without PC's?
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Re: Something borrowed...something FAST! [Tom A.]
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Forget that. Was that with or without PC's?
Re: Something borrowed...something FAST! [RChung]
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I use the original power cranks:
Re: Something borrowed...something FAST! [Andrew Coggan]
[ In reply to ]
Yaw angle is not necessarily close to 0 just because the air is still. If, for example, you are doing power slides (you *are* on a fixed gear), yaw angle could be close to 90 degrees. Please don't forget these important details in the future.
Re: Something borrowed...something FAST! [Tom A.]
[ In reply to ]
(I figured this thread wasn't already long enough...)
OK Tom, I had to pull this out to look at the numbers again. Call me a doubting Thomas, but I really suspect that something else is going on here.
After a season of racing a P3C and comparing the files to last year (P3), I'm seeing little to no difference between the two on most occassions*. I realize that I'm comparing a P3 Aluminum to a P3C, versus the P2, but the bikes just aren't THAT different--more wheel coverage and bladed seat stays worth an extra .023?
The last 40K I just did on Sunday, my stand-alone CxA was actually worse on the P3C, which has me a little perplexed--but either way, it hasn't been demonstrably better on most occassions.
*the 2 exceptions to this were both TT's on very bad pavement, where my P3C seemed faster--so I'm still left wondering if there's some potential rolling resistance advantage.
Thoughts?
OK Tom, I had to pull this out to look at the numbers again. Call me a doubting Thomas, but I really suspect that something else is going on here.
After a season of racing a P3C and comparing the files to last year (P3), I'm seeing little to no difference between the two on most occassions*. I realize that I'm comparing a P3 Aluminum to a P3C, versus the P2, but the bikes just aren't THAT different--more wheel coverage and bladed seat stays worth an extra .023?
The last 40K I just did on Sunday, my stand-alone CxA was actually worse on the P3C, which has me a little perplexed--but either way, it hasn't been demonstrably better on most occassions.
*the 2 exceptions to this were both TT's on very bad pavement, where my P3C seemed faster--so I'm still left wondering if there's some potential rolling resistance advantage.
Thoughts?
Re: Something borrowed...something FAST! [roady]
[ In reply to ]
After a season of racing a P3C and comparing the files to last year (P3), I'm seeing little to no difference between the two on most occassions*...
unless you are recording environmental condititons with power, then there is little that can be assesed ex post facto.
I have been recording weather details for my local tts and gotta say, local data versus even the closest weather station (about 1k away) can be dramatically different. Even from my start time to the last start time...
for ex, from http://wattagetraining.com/betaBlog/?p=66:
and that plot was before I could record wind direction (which I now trace too)...
g
greg
www.wattagetraining.com
unless you are recording environmental condititons with power, then there is little that can be assesed ex post facto.
I have been recording weather details for my local tts and gotta say, local data versus even the closest weather station (about 1k away) can be dramatically different. Even from my start time to the last start time...
for ex, from http://wattagetraining.com/betaBlog/?p=66:
and that plot was before I could record wind direction (which I now trace too)...
g
greg
www.wattagetraining.com
Re: Something borrowed...something FAST! [gregclimbs]
[ In reply to ]
well, a couple of things--one, I'm in the northwest, and it just isn't that windy here. I'm certainly aware of the limitations of comparing files year-to-year, but I do have a handle on the atmospheric conditions, and I wouldn't say that is 'little that can be done' post-facto. I basically use rruff's speadsheet to back-calculate the windspeed, and while it's not a perfect method, it seems to work fairly well, so that my CxA is typically within .005 at the worst
Re: Something borrowed...something FAST! [roady]
[ In reply to ]
1. Unless the TTs were conducted under very similar conditions (w/ respect to wind speed, wind direction, and pavement/rolling resistance), there may be too much variability in the estimated CdA values to detect the difference between frames. IOW, formal testing is probably required.
2. Aerodynamic differences between the carbon and aluminum Cervelo TT bikes are likely to be greatest at yaw.
3. Combining thoughts #1 and #2: in formal tests at/near 0 deg of yaw, my CdA using the equipment and position as shown in the picture above is 0.224 +/- 0.005 m^2. However, back-calculated CdAs from the four TTs I've done using that bike have ranged from 0.198 to 0.222 m^2, depending on how much wind there was.
Re: Something borrowed...something FAST! [roady]
[ In reply to ]
yeah, but you are using one guess to get to another (wind and cda). if ONE of them were known, then you would be in a better situation re: evironmental conditions.
also, my point re: windspeed is not only that it is variable, but that using the best available data (noaa etc weatherstations) will be better than assuming but not as good as measuring (:shock:)
the other thing as I understand from your post is you are comparing a p3 to a p3c whereas tom was comparing a p2k to a p3c. there is a much larger seperation of tom comparison because the p2k is dramatically different than the p3al and p3c - but you knew that...
even cervelo's bike brain data showed the p3al going fairly well against the p3c...
:D
g
greg
www.wattagetraining.com
also, my point re: windspeed is not only that it is variable, but that using the best available data (noaa etc weatherstations) will be better than assuming but not as good as measuring (:shock:)
the other thing as I understand from your post is you are comparing a p3 to a p3c whereas tom was comparing a p2k to a p3c. there is a much larger seperation of tom comparison because the p2k is dramatically different than the p3al and p3c - but you knew that...
even cervelo's bike brain data showed the p3al going fairly well against the p3c...
:D
g
greg
www.wattagetraining.com
Re: Something borrowed...something FAST! [roady]
[ In reply to ]
I don't know...unfortunately, I don't have access to the P3C anymore :-(
All I know is that my CdA on my P2K has been consistent all along, both in the particular testing that resulted in this thread and as judged by performance in various events on it since the spring. I also know that for the races I was able to do on the P3C in the configuration that was tested that started this thread, the CdA/power results matched up pretty well with the difference I measured.
Maybe you're just seeing that at mostly zero yaw the differences between a P3 and a P3C (or a P2C for that matter) just aren't that great...especially if you say that it isn't that windy where you are.
http://bikeblather.blogspot.com/
Re: Something borrowed...something FAST! [Andrew Coggan]
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Re: Something borrowed...something FAST! [Tom A.]
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once i (eventually) get a Quarq and Ibike Aero to measure rolling CdA real-time, i'm going to have a field day comparing my P2SL, P3SL and maybe borrow a P2C/P3C.
Re: Something borrowed...something FAST! [gregclimbs]
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what did this mythical data actually say? I've heard allusions to this, but that's really it.
Re: Something borrowed...something FAST! [footwerx]
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Re: Something borrowed...something FAST! [Tom A.]
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well, I thought about that--but as I mentioned in the post to AC, at 7-9 degrees, it seems my CxA is not better on this bike. I realize that short of going to a wind tunnel with both bikes, I won't be able to reliably figure this out, but I'm confident in saying that it's not way faster. It's funny, at this same TT last year, Jens was scratching his head just as I was (and he made the same P3 to P3C switch that I did). hmm...
Re: Something borrowed...something FAST! [roady]
[ In reply to ]
What do your formal field tests (on the track you mentioned) say?
Re: Something borrowed...something FAST! [Andrew Coggan]
[ In reply to ]
It was inconclusive. Using the Lim method, I didn't get reliable enough data. It appeared that the Crr was a bit lower (using the same tires), and CxA was the same. I didn't really trust the results, so I disregarded it. If I controlled Crr, it showed the P3C to be about .005 faster. The track was just resurfaced at the time of the first test, so it's possible that the track was faster.
Sadly, I didn't test both bikes back-to-back, so I'm just not that confident in the track testing for the frames. I'd suspect that at the low yaw conditions of a flat 400 meter track, they'd be pretty similar.
Re: Something borrowed...something FAST! [Tom A.]
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Re: Something borrowed...something FAST! [ksull]
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Re: Something borrowed...something FAST! [Tom A.]
[ In reply to ]
I just saw it bro ;)
Kerry Sullivan
USAT,USACII, CSCS, NLP practitioner
http://www.triathlonsummit.com
Kerry Sullivan
USAT,USACII, CSCS, NLP practitioner
http://www.triathlonsummit.com
Re: Something borrowed...something FAST! [Tom A.]
[ In reply to ]
Tom, were you ever able to get reliable test data on the Transition versus the P3C?
I never got a chance to field test a Transition...then again, once Mark Cote published his wind tunnel data of that comparison (Transition vs. P3C), I sort of lost any incentive to bother with it since Mark's testing was fairly transparent.
http://bikeblather.blogspot.com/