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Nov
30
comment DIY computational fluid dynamics for aerodynamics?
Yeah, I guess I'm "that" guy. I think your question was a little open-ended but there's an interesting bicycle-related kernel in there. I'm thinking about how best to answer the kernel.
Nov
30
comment DIY computational fluid dynamics for aerodynamics?
Defraeye et al. (2010) did some work with CFD and wind tunnel measurements, and claimed to get reasonably good modeling. Getting quick CFD is the holy grail, of course -- but the problem is "quick."
Nov
29
comment DIY computational fluid dynamics for aerodynamics?
I don't know, I sorta like the reference to "the Chung Method."
Nov
15
comment Is the Power Pilot the only speedometer / computer that will work on a LeMond Revolution Trainer?
An alternative to buying a Power Pilot may be to mount a cheap speedometer using the small magnet attached to the "wheel", then use the information here to calculate power for speed, print that out on a sheet of paper, and tape it to the wall next to your trainer. If you can afford a slightly nicer ANT+ capable speed sensor plus ANT+ USB dongle, you can then use the trainerroad application or Golden Cheetah to display speed and power on a computer screen.
Nov
2
comment Terminology index - a list of bike part names and cycling concepts
@freiheit: It's an English word that is also a French word. That's like saying "Paris" is an English word that's commonly mistaken for a French word. In English, we pronounce "pannier" as "PAN-yer" and "Paris" as "PAIR-iss" but in French they are pronounced "Pan-YAY" and "Pa-REE."
Oct
31
comment Why choose a traditional frame over an aerodynamically streamlined frame?
Speed increased for the same power output. Power output decreased for the same speed. Power and speed were recorded electronically at one-second intervals. The electronic recording device was not influenced by the rider's beliefs, so claiming that the estimation of Crr and CdA was the result of a placebo effect is incorrect.
Oct
31
comment Why choose a traditional frame over an aerodynamically streamlined frame?
@meagar: Exactly. But the metrics are not speed and power. The metrics are CdA and Crr. We're using a power and speed recorder to record the data in order to calculate CdA and Crr, which are independent of speed and power. In fact, it's the variance in speed and power that make CdA and Crr estimable. We could have done the estimation with a powered electric bicycle, varying the throttle and speed and still estimated CdA and Crr. Even if the rider had a prior belief it's the relationship between power and speed that matters -- and that is what is recorded.
Oct
31
comment Why choose a traditional frame over an aerodynamically streamlined frame?
First, how could "a placebo effect" alter the recorded speed and power? Second, the field test was consistent with wind tunnel measurements. How could a placebo effect affect the wind tunnel? Third, I already pointed out that it was an example comparison of two frames that were already considered aero -- I used this example because the difference was smaller than usual. We really should move this to a discussion room if you wish to continue.
Oct
31
comment Why choose a traditional frame over an aerodynamically streamlined frame?
@DanielRHicks - we can (and probably should) move this to a discussion room if you wish but these advantages don't disappear. Here's an example of a field test under real-world conditions that measured the difference between two frames that were already pretty aero. Subsequently the rider raced in a 40K TT and his actual time came within half a second per km of the predicted time.
Oct
31
comment Why choose a traditional frame over an aerodynamically streamlined frame?
@DanielRHicks - You may have doubts but the differences have been measured in wind tunnels (with rotating front wheel) and also in field tests. Whether the difference is large enough to matter is a legitimate question; but whether the frames "provide measurable improvement" is not.
Oct
29
comment What road bike tire pressure is best for speed?
There is an example of rolling resistance on real roads increasing with increasing pressure about two-thirds of the way through this article.
Oct
16
comment Effective breathing for efficient cycling
Unlike weight-lifting or yoga, but like running and swimming, cycling is mostly about aerobic capacity. However, the efforts during cycling tend to be much more variable than running or swimming (especially running on a flat track or swimming in a pool). That means your respiration rate is going to be much more variable than in running or swimming (or weight-lifting or yoga). Sports which are more steady-state allow for more steady-state rhythm in breathing.
Oct
16
comment Velodrome atmospheric conditions
Oh, I was just commenting on your calculation of the power demand. At the speeds you were using in your example, rolling resistance will account for ~50 watts or so. OTOH, if you were just looking at differences in power demand with air density, it's easier to notice that an x% change in air density translates to exactly the same x% difference in aero drag.
Oct
16
comment Velodrome atmospheric conditions
Nice, though you're missing the contribution to total power demanded by rolling resistance, which will be around Crr*mass*g*v where g ~= 9.8 m/sec^2. It appears the Wolfram air density calculation is assuming some barometric pressure and humidity since you didn't put one in. And, as an aside, I recommend method #4 on that cyclingpowermodels.com page.
Oct
7
comment Effective 'equipment minimal' leg strength training for cycling?'
Whoops. You're right. I had intended to write 1.4x their weight at 1RM but somehow it came out as 4x, then I brain-farted and made a calculation based on 4. I'll edit it. Thanks.
Oct
3
comment Is a leather saddle appropriate for all-weather riding?
Proofide is a leather conditioner that helps the break in process and adds weather resistance. I wouldn't leave the bike out in the sun or heavy rain with only Proofide but I would (and do) ride in all weather on a leather saddle conditioned with Proofide.
Oct
1
comment What is the optimal cadence?
@Vorac, thanks for clarifying your question. I've added some discussion of cadence and knee strain.
Sep
27
comment Can Tacx Flow head unit work with old (2002) Basic frame/brake?
I do not know the answer to your question but I have a 2005 Tacx Flow and the load generator for that year was the same as the load generator for the Tacx I-Magic and the Tacx Grand Excel -- and in previous years the Grand Excel and the Basic used the same load generator. The question then, of course, is whether the Grand Excel's load generator changed between 2002 and 2005.
Aug
10
comment Why is BMX gearing so low
It's exactly because of the acceleration. BMX courses put a premium on being the first to the turn so the start is critical. Recently, UCI rules governing BMX have been amended to allow gearing systems but BMX riders have eschewed them, in part because they put out a max instantaneous power in excess of 2000 watts and few bicycle gearing systems can take that much load without risking a missed shift.
Aug
5
comment when does the pace bike leave in Keirin?
I don't think this is quite exactly right. The UCI regulations specify not a distance to be traveled but rather the distance remaining: no matter the length of the track, the pacer pulls off between 600 and 700 meters before the finish line. Thus, if the track is 250 meters long the pacer pulls off about 2.5 laps before the finish; if the track is 333 meters long the pacer pulls off 2 laps before the finish; and if the track is 400 meters long the pacer pulls off 1.5 laps before the finish.