Pedaling Efficiently

[Alex Simmons]

I was referring to using the technique to detect other riders on the track. Not much pracital usefulness to that.

You clearly missed the point.

It wasn't about a way to detect other riders per se, it was to demonstrate how sensitive (and hence how useful) the power meter data actually is in such benign conditions. But also that one needs to know these effects exist so that they correctly interpret the data. (which is exactly what Mike above had discovered from his data) since he was trying to make some fine tuning adjustments to position.

The fact that such small things can be picked up, is of itself exceptionally useful as it means that other small changes, like when I change from one aero wheel to another, or one aero helmet to another, or hands position differences, or saddle height changes, can be quantified for their impact to CdA and some smart decisions made.

For instance, in Jayson's case, I determined one aero helmet would add substantial distance over another (and could quantify it). One helmet (the least effective one) was supplied by a sponsor, but we declined to use it on the basis of the testing. Many Pro riders don't get that option.

For myself I determined my old Shamal front wheel was a better choice on the track than a Zipp 808 (with same tyre, glue and pressure). And my front disk (same tyre, glue and pressure) was only marginally better than the Shamal.

In less benign conditions, one needs to work out to what level of precision you can get to, and there are ways of teasing this out, but eventually wind does become thine enemy (but even then there might be solutions with some pretty clever technology - so watch this space - ultimately the testing will tell us if we are dealing with enemies or frenemies, wind wise that is).

 

[Alex Simmons]

I've seen exactly the same thing as Alex (on the same velodrome....Dunc Gray) when aero testing.

As has Phil McKnight, who's about as anal as you get with nailing down his data and equipment calibration.

Also, when inspecting Jayson's numbers one evening after a session, there was a change in his apparent CdA I couldn't quite understand. It was the exact same set up, equipment etc. Same session, temp etc etc but the numbers said otherwise.

So when I quizzed him as to whether he had made any other change, he let slip that without me knowing he'd changed his saddle height a couple of mm for that one run to see how it felt and didn't tell me. I didn't see him do it at the time as I was doing some track side analysis/planning.

 

[RChung]

Also, when inspecting Jayson's numbers one evening after a session, there was a change in his apparent CdA I couldn't quite understand. It was the exact same set up, equipment etc. Same session, temp etc etc but the numbers said otherwise.

So when I quizzed him as to whether he had made any other change, he let slip that without me knowing he'd changed his saddle height a couple of mm for that one run to see how it felt and didn't tell me. I didn't see him do it at the time as I was doing some track side analysis/planning.

There's your blinded test.

 

[Fday]

You clearly missed the point.

It wasn't about a way to detect other riders per se, it was to demonstrate how sensitive (and hence how useful) the power meter data actually is in such benign conditions. But also that one needs to know these effects exist so that they correctly interpret the data. (which is exactly what Mike above had discovered from his data) since he was trying to make some fine tuning adjustments to position.

The fact that such small things can be picked up, is of itself exceptionally useful as it means that other small changes, like when I change from one aero wheel to another, or one aero helmet to another, or hands position differences, or saddle height changes, can be quantified for their impact to CdA and some smart decisions made.

For instance, in Jayson's case, I determined one aero helmet would add substantial distance over another (and could quantify it). One helmet (the least effective one) was supplied by a sponsor, but we declined to use it on the basis of the testing. Many Pro riders don't get that option.

For myself I determined my old Shamal front wheel was a better choice on the track than a Zipp 808 (with same tyre, glue and pressure). And my front disk (same tyre, glue and pressure) was only marginally better than the Shamal.

In less benign conditions, one needs to work out to what level of precision you can get to, and there are ways of teasing this out, but eventually wind does become thine enemy (but even then there might be solutions with some pretty clever technology - so watch this space - ultimately the testing will tell us if we are dealing with enemies or frenemies, wind wise that is).

This discussion came about because you stated in post 116 that you could detect from your PM when a rider entered the other side of the track. I questioned the basis of that statement. It is now not clear that is exactly what you meant if all you meant was that other riders on the track could interfere with the accuracy of the measurement, the magnitude depending upon where they are and what they are doing. I remain unconvinced that the method is so sensitive that it can detect when a rider enters the other side of the track.

As with most testing it is important to pay attention to the details. It appears this testing is no exception and this is one detail of this testing that is not particularly obvious.

 

[Fday]

There's your blinded test.

Ugh, did he pick up when another rider entered the track that was unknown to the rider? That was the claim, not whether he could pick up aero differences using the technique.

 

[acoggan]

Just to stir the pot D) a little:

Training and Racing With a Power Meter Journal: Does drafting benefit the leading rider?

 

[acoggan]

I have believed in the benefits of field testing of aerodynamics. I have recommended "the Chung method" to many. It has been "advertised" as an accurate method as long as you ride a loop and "know" the rolling resistance. Wind and other issues were seemingly accounted for. My concern here was if the outcome can be made less accurate by something as minor as another rider on the other side of the track

Wind (produced by nature or another rider) is thine enemy.

 

[Fday]

Just to stir the pot D) a little:

Training and Racing With a Power Meter Journal: Does drafting benefit the leading rider?

Interesting and well written. I am not so sure I would call it stirring the pot as much as stirring the air.

I think one thing can be drawn from all this: The closer two riders are to each other the bigger the effect they will have on each other. It remains an open question as to how far away they can be from each other and still detect this effect. I agree with your call for further study although I would think it could also be undertaken by someone who disagreed with the hypothesis.

 

[Fday]

Wind (produced by nature or another rider) is thine enemy.

Or, friend

 

[Fday]

Interesting and well written. I am not so sure I would call it stirring the pot as much as stirring the air.

I think one thing can be drawn from all this: The closer two riders are to each other the bigger the effect they will have on each other. It remains an open question as to how far away they can be from each other and still detect this effect. I agree with your call for further study although I would think it could also be undertaken by someone who disagreed with the hypothesis.

One more thing, I believe several years ago the World Triathlon Corp did some wind tunnel testing to determine where the benefits of a draft ended for the purpose of ending controversy regarding the drafting rules and I believe they came up with the benefits becoming insignificant at 7 meters. Now, insignificant from a race perspective doesn't mean undetectable but surely, the effects at 125 m must truly be tiny.

 

[RChung]

Wind (produced by nature or another rider) is thine enemy.

Especially when the other rider had a beer and burrito.

 

[RChung]

Now, insignificant from a race perspective doesn't mean undetectable but surely, the effects at 125 m must truly be tiny.

Yup, it is tiny. That's why it's so cool.

 

[Fday]

One more thing, I believe several years ago the World Triathlon Corp did some wind tunnel testing to determine where the benefits of a draft ended for the purpose of ending controversy regarding the drafting rules and I believe they came up with the benefits becoming insignificant at 7 meters. Now, insignificant from a race perspective doesn't mean undetectable but surely, the effects at 125 m must truly be tiny.

One more thing that might make for an "easy" experiment to address some of these issues. Take a smoke generator, something like a "punk" used for lighting firecrackers, where the smoke rises and is easily seen. It would be relatively easy to put it behind the rider after he goes by (and move it out of the way before he comes by again) and see how long the air remains disturbed. It could also be done with two riders on the track opposite each other to see what happens. Might even be able to calculate the air speed by the angle the smoke is rising. I suspect that one would find the disturbance lasts longer on the straights than the curves (because of the tendency of the following wind to travel in a straight line). Anyhow, might answer the question as to how far away one really needs to be from someone if doing this testing and one wants really clean air.

 

[Fday]

Yup, it is tiny. That's why it's so cool.

But, Coggan said he didn't see an effect when two riders were taking care to stay opposite each other. There is no question the technique is sensitive. It seems the question is how close do the riders have to be to impact this analysis?

 

[acoggan]

But, Coggan said he didn't see an effect when two riders were taking care to stay opposite each other.

Not quite. What I observed was that 1) there were no obvious temporal trends in the data from the 1 km efforts performed on day 1, and 2) the CdA calculated from these tests agreed with that measured in the wind tunnel. This doesn't completely rule out the possibility that the two riders were interacting with each other.

 

[Fday]

Not quite. What I observed was that 1) there were no obvious temporal trends in the data from the 1 km efforts performed on day 1, and 2) the CdA calculated from these tests agreed with that measured in the wind tunnel. This doesn't completely rule out the possibility that the two riders were interacting with each other.

Well, I agree that it doesn't completely eliminate the possibility but in your discussion you commented that your data seemed to go against what others had reported.

 

[Alex Simmons]

Especially when the other rider had a beer and burrito.

 

[swampy1970]

Especially when the other rider had a beer and burrito.

If the effects at 125m are tiny, what are the positive effects of the beer and burrito with regards to speed? Could it be possible to redistribute this gaseous flow to achieve a more laminar airflow over the rider in the same way that F1 cars used to attempt to increase downforce by using exhaust gasses to speed airflow in underbody tunnels?

As a side note, would any increase in speed come from said gaseous release or from any extra pedal 'pressure' from the 'squeeze and push' required?

I can say from years of PowerCrank use that it is easier to relax and fart during hard efforts.

 

[Alex Simmons]

I can say from years of PowerCrank use that it is easier to relax and fart during hard efforts.

Looking forward to having another pint with you to hear more such war stories

 

[RChung]

Looking forward to having another pint with you to hear more such war stories

Seems like something that shouldn't be passed.