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Field test with a PM?
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I've heard some reference to it on ST but haven't seen a specific thread on it. I'm in the market for a PM this year and would possibly like to try some field testing with various equipment or positions once I have a PM. Are there any specific protocols to follow? Do you try to do it when there is little wind? What distance to cover? Try to ride close FTP over X distance? Is single sided PM good enough?

I'm not looking at what's going to save me 0.25 watts but perhaps I'd find some things that might save me 10 watts. I guess I think of it as a poor man's wind tunnel (poor man who can afford $1000+ for something that might get him from 8th place to 4th place in age group in the local small tri that nobody really cares about).

Obviously the PM will primarily be used as a training tool but it might be fun to play around with some field testing.
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Re: Field test with a PM? [Burhed] [ In reply to ]
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See the search box over on the right? You're looking for the "Platypus" thread.
Last edited by: RChung: Jan 28, 15 21:14
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Re: Field test with a PM? [Burhed] [ In reply to ]
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chung method:
https://www.google.com/...s_sm=93&ie=UTF-8

powertap is best for it but any good power meter will do.
it takes a LOT of effort to get good results from this, a single sided power meter is not going to cut it.

a location/time with low wind is also critical



Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter
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Re: Field test with a PM? [RChung] [ In reply to ]
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Cool. Thanks. Would have never guessed to search for 'Platypus'.
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Re: Field test with a PM? [jackmott] [ In reply to ]
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jackmott wrote:
chung method:
https://www.google.com/...s_sm=93&ie=UTF-8

powertap is best for it but any good power meter will do.
it takes a LOT of effort to get good results from this, a single sided power meter is not going to cut it.

a location/time with low wind is also critical

damn you stages :|
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Re: Field test with a PM? [Burhed] [ In reply to ]
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Here are a couple of resources that may prove helpful:

http://www.slideshare.net/...nd-tunnel-compressed

http://www.trainingandracingwithapowermeter.com/...aerodynamicists.html

BTW, when revisting the data from this experiment I discovered that I'd made a mistake in the calculations. Here is a corrected version of Fig. 6:


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Re: Field test with a PM? [Burhed] [ In reply to ]
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One of your biggest challenges will be finding a low-wind area where you can safely ride without using your brakes. Safety first but if you brake you'll have to throw the data from that loop out. Google maps is a decent way to scout locations though you'll find that many loops that look good from the air end up having issues once you see them in person.
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Re: Field test with a PM? [GreenPlease] [ In reply to ]
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GreenPlease wrote:
One of your biggest challenges will be finding a low-wind area where you can safely ride without using your brakes. Safety first but if you brake you'll have to throw the data from that loop out. Google maps is a decent way to scout locations though you'll find that many loops that look good from the air end up having issues once you see them in person.

http://anonymous.coward.free.fr/.../recommendations.pdf
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Re: Field test with a PM? [RChung] [ In reply to ]
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RChung wrote:
GreenPlease wrote:
One of your biggest challenges will be finding a low-wind area where you can safely ride without using your brakes. Safety first but if you brake you'll have to throw the data from that loop out. Google maps is a decent way to scout locations though you'll find that many loops that look good from the air end up having issues once you see them in person.

http://anonymous.coward.free.fr/.../recommendations.pdf

Oh hell I've been going waaaaaay out of my way to do a true loop. This is awesome. Learn something every day.
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Re: Field test with a PM? [Burhed] [ In reply to ]
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Burhed wrote:
Is single sided PM good enough?
Sorry, I missed this question earlier.

Field testing for estimating drag is a pretty demanding application of a power meter. You need both accuracy and precision over a wide range of speed and power, not just at FTP or at one cadence or pedal force. If your power (or speed) isn't right, you *might* still be able to distinguish big changes in CdA or Crr but you almost surely won't be able to distinguish small changes. That's why I generally recommend that you use a power meter and speed sensor that gives reliable high accuracy measurements.

There are two ways to go faster on a bike: you can either maximize the power you can make, or minimize the power you must make. Maximizing your power is mostly about training, and almost any power meter can help almost every rider do this. Minimizing your power is mostly about reducing drag or pacing properly, and for this you probably need a power meter that produces high quality data. But a second faster is a second faster, and the clock doesn't care whether that second came from increased power or reduced drag -- so do both. Power meters are expensive so it seems like a missed opportunity not to do everything you can with one to gain seconds. Get a power meter that lets you do both.
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