No problem, glad it worked
And to answer your original question, maybe it’s an urban legend, but Robert does not use GC/Aerolab. Us mere mortals can do mental addition and subtraction. Robert does mental VE.
Thank you so much. What was weird is last night it bounced and then about 15 minutes later it just opened. It seems to sit there for a while saying, “Application is not responding”. Then it opens right up, but I will try those other versions. You guys are amazing thanks for all of your help.
Very strange. I went back and retried 3.5 versions that did the same “bouncing” as you. They opened up immediately this morning. As if there is some type of “initialization” that had to be done, and now that’s it’s done, everything is fine.
Other than the train option not working Golden Cheetah seems to be working just fine. Question about the VE testing. Can I just use any home weather station that measures barometric pressure? I am thinking the home ones that you see that measure inside and outside temperature and then humidity and pressure. Those that do a lot of VE testing thoughts?
I’m hoping to get a little help troubleshooting my protocol. I am currently setup using a wahoo elemnt bolt as my ride recorder, garmin vector 3s as my power meter, and a garmin speed sensor 2 as my speed sensor.
My course is an out and back with an initial climb and then a short downhill and immediate uphill, both of which I coast to lose enough speed to turn around on the uphill without using any brakes. I’ve got my start/finish position chalked on the road as well as the start, apex, and finish of my turnaround point. I use the lap button on each start and finish and use that to cut out the turnaround back (in red) to the start as I have to break hard to turnaround on the start/finish portion of my test area.
I’ve been out testing a single position on 3 different days so far and have yet to come up with consistent results from any of them. Each day of testing has had very little wind. I recognize that I’m on a single sided powermeter which isn’t the best, but is I would think that having a muscle imbalance would skew the cda results and that I wouldn’t have an inconsistent enough imbalance to make the results as unreliable as they are.
Any ideas on what could be making my lap not symmetrical comparing pre-turnaround to after turnaround? My first guess would be maybe some wind but each lap being non-symmetrical in almost the same way makes me doubt it. Could I have missed a recording setting that smells like smart recording? I’ve got my speed sensor set to use the specific wheel circumference but haven’t found any settings for the powermeter that would suggest fishy recording. Or does it all come down to using a single sided powermeter?
Any help would be greatly appreciated. Happy New Year.
I’m hoping to get a little help troubleshooting my protocol. I am currently setup using a wahoo elemnt bolt as my ride recorder, garmin vector 3s as my power meter, and a garmin speed sensor 2 as my speed sensor.
My course is an out and back with an initial climb and then a short downhill and immediate uphill, both of which I coast to lose enough speed to turn around on the uphill without using any brakes. I’ve got my start/finish position chalked on the road as well as the start, apex, and finish of my turnaround point. I use the lap button on each start and finish and use that to cut out the turnaround back (in red) to the start as I have to break hard to turnaround on the start/finish portion of my test area.
I’ve been out testing a single position on 3 different days so far and have yet to come up with consistent results from any of them. Each day of testing has had very little wind. I recognize that I’m on a single sided powermeter which isn’t the best, but is I would think that having a muscle imbalance would skew the cda results and that I wouldn’t have an inconsistent enough imbalance to make the results as unreliable as they are.
Any ideas on what could be making my lap not symmetrical comparing pre-turnaround to after turnaround? My first guess would be maybe some wind but each lap being non-symmetrical in almost the same way makes me doubt it. Could I have missed a recording setting that smells like smart recording? I’ve got my speed sensor set to use the specific wheel circumference but haven’t found any settings for the powermeter that would suggest fishy recording. Or does it all come down to using a single sided powermeter?
Any help would be greatly appreciated. Happy New Year.
Happy new Year too.
In you precise description, you didn’t mention if you ride on the middle of the road, which is a necessary condition (but potentialy unsafe one) to have symmetrical elevation profile.
I also have non-symmetrical elevation profile here (red curve: use of a barometer with a +/-10 cm precision) during a low wind day (virtual elevations corrected by airspeed from an anenometer). It may be explained cause a road is not perfectly level from a side to other (or some other reason that I am also interested to know too).
Just to clarify, it looks like the 2nd image was a Golden Cheetah screenshot? What was used for the first image?
The first one was mycda.app. Golden Cheetah doesn’t seem to import my laps in the correct spot and mycda.app does while also automatically isolating the laps. Using mycda just makes it so I don’t have to manipulate my data to remove the between laps section.
Oh, I didn’t realize that I was supposed to be going center but that makes sense for the asymmetry, thank you. As far as the lack of precision in results, I am beginning to suspect either my speed sensor accuracy or how the elemnt bolt uses the speed sensor. I have the elemnt set to use the wheel circumference instead of the “auto” setting which still uses some gps. However, my lap distances still vary by up to 26 feet in a set. What sensor do you use and/or is there a gold standard that people tend to use for aero testing? I’ve seen a lot of mentions for the gsc 10 but was having trouble getting my hands on one so I had settled for the garmin speed sensor 2.
I personally could never get remotely decent data with a single sided power meter, but that may just have been me!
Oh, I didn’t realize that I was supposed to be going center but that makes sense for the asymmetry, thank you. As far as the lack of precision in results, I am beginning to suspect either my speed sensor accuracy or how the elemnt bolt uses the speed sensor. I have the elemnt set to use the wheel circumference instead of the “auto” setting which still uses some gps. However, my lap distances still vary by up to 26 feet in a set. What sensor do you use and/or is there a gold standard that people tend to use for aero testing? I’ve seen a lot of mentions for the gsc 10 but was having trouble getting my hands on one so I had settled for the garmin speed sensor 2.
What speed sensor are you using?
Do not use magnet-less speed sensor.PowerTap G3 hub may have some (rare) oddities (velocity spikes). Gsc 10 is an old speed sensor.I am using this cheap one (magnet sensor) with good success: https://www.amazon.com/Cadence-Bluetooth-Cycling-Indicators-Waterproof/dp/B099KHWXKP/ref=sr_1_3?crid=1G655ZO74ORF8&keywords=Coospo+speed+sensor&qid=1641065567&sprefix=coospo+speed+sensor%2Caps%2C163&sr=8-3
Unfortunately I have been using a magnet less sensor. Garmin Speed Sensor 2.
https://www.garmin.com/en-US/p/641230
I’ve now got a magnet one in the mail. Arrives Tuesday. Thanks for the help. Hopefully the next round of testing has me closer to quality results.
Any ideas on what could be making my lap not symmetrical comparing pre-turnaround to after turnaround?
All happy aero tests are alike, all unhappy aero tests are unhappy in their own way. There are so many ways that failure to fit can occur that you need to dive into the actual data to see what happened. It’s hard to diagnose just from a VE profile. That is, VE is a very sensitive diagnostic but because so many things go into it, it’s hard just from the profile alone to figure out which of those many things went wrong.
Usually when there’s a lack of fit, I have to go through a checklist of things that may have gone wrong. Unfortunately, right now, diagnosing lack of fit is sort of like drawing an owl.
At some point those of us who know what to do have to fill in a bit more about step 2.
Robert, tow quick questions for you.
- Can I use a hub mounted speed sensor. Some have said yes, some have said no.
- I have a Garmin Edge 130, I did a route with the GPS and I just got a straight line for elevation. There was about 6ft of gain/loss in the 250ish Meter loop I did. Is this enough elevation or do I need more? Will that computer work?
Thank you.
Robert, tow quick questions for you.
- Can I use a hub mounted speed sensor. Some have said yes, some have said no.
- I have a Garmin Edge 130, I did a route with the GPS and I just got a straight line for elevation. There was about 6ft of gain/loss in the 250ish Meter loop I did. Is this enough elevation or do I need more? Will that computer work?
Thank you.
I’m no Dr. Chung, so take what I say with a grain of salt, but I would try multiple loops of that track. You should see the elevation rise and fall periodically. The 130 has a barometer for barometric elevation so should work OK. As for the hub sensor I have used one and it worked for me but make sure you set the correct wheel circumference (use a weighted roll out meaning sit on the bike full weight and roll out 1 wheel revolution measure the distance).
Awesome, thanks!! I did 4 laps in a high school parking lot that has about 6ft’. Thanks again!
I wrote some simple code to implement the VE method. And tested whether it revealed the difference with a visor (and without). I rode a lumpy 1km “half-pipe” loop about 30-odd times, varying the speeds a bit. I do have a braking zone at one end as I turn around. So I hit the Lap button each time on my Garmin. My code inspects the .tcx file and throws out brake zone laps and keeps the “loop”.
My code can flatten the graph automatically etc. Seems very straightforward to code up and I get a family of solutions (Crr, cdA).
I also find a difference without/with visor. (Not a tri-bike or regular bike but still method applies.) So far, so good.
Then, because I have varying speed runs, see histogram, I graph all the (Crr, cdA) pair solutions over a range of Crr.
I pick the pair that has the least overall deviation for the top3 fastest and slowest runs.
Problem is, the best Crr I get is perhaps unrealistically low, around 0.0035, 0,004.
(Continental GP 5000 S TR 32-622 tubeless with Vittoria Airliner on the back and Contact Urban 32-406 with super thin butyl in front. Not a regular bike.)
Hmm, I have good rho data from our university’s dept of Hydrology and Atmospheric Sciences weather station.
(I live at elevation and rho < 1 usually, so it’s a good sign it’s station pressure.)
I use a wireless Garmin Speed Sensor 2, and don’t rely on GPS speed.
The data is recorded one per second by my Garmin computer.
I do not correct for the initial data point, as it requires the data point 1 sec before my start, but I rely on hitting Lap.
I do use the velocity correction for the lag detailed in the slides.
I have the Assioma powermeter pedals. I modify the watts reported, multiplying by a factor bit less than one to account for drivetrain inefficiency.
I didn’t detect significant wind during my run, but perhaps I’m mistaken and there was some wind.
(So last week, I bought the Bluetooth windmeter mentioned in the other thread and threw together 5 min code to extract the wind speed. Next time, I can mount the windmeter in front and get V_air.)
Anyway, I have a simple question about the slope equation formula. I notice the Crr part doesn’t take slope into account for simplicity.
Given an incline, Crr is conventionally defined with respect to force normal to the incline, so shouldn’t we multiply by the cosine of the slope?
If I do that, the VE curves look significantly different. So I must be missing something.
See handwritten picture with f(s) = 0 and f’(s) for the revised formula. I solve numerically for s (slope).
Plotted, the deviations are initially small, but as you can see in the last picture, they add up and the VE graph looks different, formula vs. formula2.
Garmin GPS profile is also shown here, but of course, I don’t use it in my calculations.
Sorry, I forgot to append the slope formula and modified with cosine slope formula to the previous post.
Here’s the code in Python, I can write it in any programming language, but Python is accessible to anyone and easy to read.
Just in case I made a silly error.
CdA values are not in the expected range for a cyclist, what unities do you use?
Not that it’s relevant, but I’m using something a bit more aerodynamic than my road bikes.
It’s the same principle at work.
I’m testing the effectiveness of the visor in this picture.
can you post the .fit file?