Hi
CompuTrainer
Did a small ramp test on the CompuTrainer at the cottage using my Winter bike PowerTap wheel. I'd been suspecting that the PowerTap might be reading a bit low and this proved to be the case. Between about 175W and 300W the PowerTap was reading about 10W below the CompuTrainer Lab Pro.
I'm not going to worry about this as I use the PowerTap as a data gathering tool rather than as a tool to guide my training or to do my tests with, I'd be more concerned also if the PowerTap was telling me my output was higher rather than lower! After the performance of sending the unit to Prague to have the bearings replaced I'm sure not going to send it again to be calibrated, I might if a UK agent opens up but not before as it's not essential.
I can't help but wonder if the apparent reading difference might be due to the lengthy period of very low temperatures we have been experiencing and the temperature sensitivity of strain gauges. My gut feeling is that this variation might just disappear when/if the warm weather comes, we shall see.
[Uploaded 24/01/2009 22:01:06]
Showing posts with label Power Meter Tests. Show all posts
Showing posts with label Power Meter Tests. Show all posts
Saturday, 24 January 2009
Monday, 26 May 2008
Monday Training
Hi
This was not really a proper training session but the last of my series of comparisons between the PowerTap and the CompuTrainer. I wanted to do a simple ramp type test covering the more commonly used wattage range in 25W steps going from 175W to 300W, riding for 5 minutes at each load setting, The whole proces was controlled by a .erg file in the CompuTrainer. The outcome was that the average wattage for the workout on the CompuTrainer was 225W and on the PowerTap 226W, the 2 units tracked each other very closely though as in previous tests the PowerTap recorded higher and lower very short duration wattages. The CompuTrainer when in ergo mode I understand adjusts the load x30 per second so who knows whether the CompuTrainer or the PowerTap is "right" - but they are certainly close enough over the most commonly used wattages and stable over 5 minute periods. The CompuTrainer calibrations were again checked before and after the test and there was no discernable drift at all. So, you will be pleased to know that that's the testing over!
The graph of the wattages recorded by the 2 units is shown below:
[Uploaded 26/05/2008 18:32:06]
This was not really a proper training session but the last of my series of comparisons between the PowerTap and the CompuTrainer. I wanted to do a simple ramp type test covering the more commonly used wattage range in 25W steps going from 175W to 300W, riding for 5 minutes at each load setting, The whole proces was controlled by a .erg file in the CompuTrainer. The outcome was that the average wattage for the workout on the CompuTrainer was 225W and on the PowerTap 226W, the 2 units tracked each other very closely though as in previous tests the PowerTap recorded higher and lower very short duration wattages. The CompuTrainer when in ergo mode I understand adjusts the load x30 per second so who knows whether the CompuTrainer or the PowerTap is "right" - but they are certainly close enough over the most commonly used wattages and stable over 5 minute periods. The CompuTrainer calibrations were again checked before and after the test and there was no discernable drift at all. So, you will be pleased to know that that's the testing over!
The graph of the wattages recorded by the 2 units is shown below:
[Uploaded 26/05/2008 18:32:06]
Friday, 23 May 2008
FTP Test - PowerTap vs CompuTrainer Comparison
Hi
I have now had the chance to sort out the data from last night's test and produce comparison graphs of wattage against time for the PowerTap and the CompuTrainer during my FTP test. As you can see from the graphs below the units tracked each other very closely, certainly not a large enough difference to be significant especially when the vast variations in day-to-day athletic performances which can't readily be explained are taken into consideration.
From the data I calculated my best 5 minute and 20 minute powers and from the 20 minute power my estimated FTP, the results are shown below:
PowerTap Data:
MP5 - 357W
MP20 - 310W
FTP - 294.5W
CompuTrainer Data:
MP5 - 361W
MP20 - 312W
FTP - 296.4W
So, if the FTP is the pearl I am looking for the difference between the 2 values is 1.9W, or 0.64%, that's accurate enough for me!
I have now had the chance to sort out the data from last night's test and produce comparison graphs of wattage against time for the PowerTap and the CompuTrainer during my FTP test. As you can see from the graphs below the units tracked each other very closely, certainly not a large enough difference to be significant especially when the vast variations in day-to-day athletic performances which can't readily be explained are taken into consideration.
From the data I calculated my best 5 minute and 20 minute powers and from the 20 minute power my estimated FTP, the results are shown below:
PowerTap Data:
MP5 - 357W
MP20 - 310W
FTP - 294.5W
CompuTrainer Data:
MP5 - 361W
MP20 - 312W
FTP - 296.4W
So, if the FTP is the pearl I am looking for the difference between the 2 values is 1.9W, or 0.64%, that's accurate enough for me!
Tuesday, 20 May 2008
PowerTap vs CompuTrainer Comparison - 2x20 SST Session @ "265W"
Hi
The graph below shows the data from tonight's session as recorded on my CompuTrainer (Lab Pro 3D version) and the loan PowerTap. Important points to note are as follows:
Here are the results:
It can be seen that the PowerTap readings were consistently lower, the overall (whole session) averages for the session recorded were CompuTrainer 233W, PowerTap 224W. The average figures for effort 1 were CompuTrainer 265W, PowerTap 257W and for effort 2 CompuTrainer 264W, PowerTap 258W.
So, there was a difference, who knows which figures are "right". If I assume that the ergo function on the CompuTrainer keeps the load steady there did seem to be more minute by minute fluctuation in the PowerTap readings but that's a bit subjective.
Any thoughts on the matter welcomed!
The graph below shows the data from tonight's session as recorded on my CompuTrainer (Lab Pro 3D version) and the loan PowerTap. Important points to note are as follows:
- Continental trainer tyre inflated to 110psi.
- CompuTrainer warmed up for 10 minutes at 175W prior to calibration.
- CompuTrainer calibrated after warmup, calibration reading (press on force) 2.37.
- CompuTrainer calibration rechecked after session, calibration reading 2.35 (effectively no drift).
- All power (load) settings controlled by CompuTrainer .erg file, no user interference or adjustment.
Here are the results:
It can be seen that the PowerTap readings were consistently lower, the overall (whole session) averages for the session recorded were CompuTrainer 233W, PowerTap 224W. The average figures for effort 1 were CompuTrainer 265W, PowerTap 257W and for effort 2 CompuTrainer 264W, PowerTap 258W.So, there was a difference, who knows which figures are "right". If I assume that the ergo function on the CompuTrainer keeps the load steady there did seem to be more minute by minute fluctuation in the PowerTap readings but that's a bit subjective.
Any thoughts on the matter welcomed!
Saturday, 17 May 2008
Power meter comparison on a 2 hour ride.
Hi
Following on from my comparison between the PowerTap and an uncalibrated CompuTrainer yesterday I have now taken my tests a step further. Today's test was run having firstly calibrated my CompuTrainer properly according to the instructions using an adequate press on force and a proper trainer tyre inflated to 110psi and cleaned with isopropyl alcohol to avoid tyre slip.
The weather here in Northumberland in the UK was poor so, confined indoors, I rode a route on the trainer that I had previously prepared from GPS data and converted to a 3D course. The route is just short of 50 miles and at a steady pace I would be riding for a bit over 2 hours. The plan was to record the ride on both the PowerTap and the CompuTrainer and compare the data sets.
I was pleased with the results which showed what I had hoped, that is that the 2 units were very comparable in terms of data output. There were of course differences but these are almost certainly a function of the different ways in which the units operate and calculate power. I cannot of course be certain which of the units is "right" but that was not the purpose, the purpose was to find out whether the outputs were comparable.
The main observations I made were as follows:
1). The average and normalised power figures obtained from the 2 power meters were pretty much identical, as were the TSS and IF figures calculated. Looking at the overview graph below it is clear that the overall power figures are very similar for this 2+ hour ride, calibration makes a difference!
2). Looking more closely at the data above and for a 5 minute period (below) it can be seen that the PowerTap records a higher value when there is a short, hard, immediate change in power output, as might be the case in a sprint or other sudden power burst. The result of this is that the PowerTap records a higher maximum power for the ride, at 616W compared to the 565W recorded by the CompuTrainer. The following graph shows the recorded outputs during a 5 minute period including one sudden power output change.
3). I observed that during periods where the "speed" was high, riding in a high gear with a lower cadence the CompuTrainer recorded a slightly but consistently lower power figure than the PowerTap.
A summary of the comparative data as extracted by the TrainingPeaks WKO+ package is enclosed below which shows the remarkable consistency of the figures produced by the units. On the basis of the trials so far I have no hesitation in recommending this combination of equipment for indoor and outdoor training. Having spent a lot of money on this setup I'm happy with the data coming out, even though I'd like the numbers to be higher!
Next week I hope to carry out an FTP test, it will be interesting to see which unit gives me the higher FTP, I think on the basis of my investigations so far it will be the PowerTap.
PowerTap vs CompuTrainer Comparison.
Following on from my comparison between the PowerTap and an uncalibrated CompuTrainer yesterday I have now taken my tests a step further. Today's test was run having firstly calibrated my CompuTrainer properly according to the instructions using an adequate press on force and a proper trainer tyre inflated to 110psi and cleaned with isopropyl alcohol to avoid tyre slip.
The weather here in Northumberland in the UK was poor so, confined indoors, I rode a route on the trainer that I had previously prepared from GPS data and converted to a 3D course. The route is just short of 50 miles and at a steady pace I would be riding for a bit over 2 hours. The plan was to record the ride on both the PowerTap and the CompuTrainer and compare the data sets.
I was pleased with the results which showed what I had hoped, that is that the 2 units were very comparable in terms of data output. There were of course differences but these are almost certainly a function of the different ways in which the units operate and calculate power. I cannot of course be certain which of the units is "right" but that was not the purpose, the purpose was to find out whether the outputs were comparable.
The main observations I made were as follows:
1). The average and normalised power figures obtained from the 2 power meters were pretty much identical, as were the TSS and IF figures calculated. Looking at the overview graph below it is clear that the overall power figures are very similar for this 2+ hour ride, calibration makes a difference!
2). Looking more closely at the data above and for a 5 minute period (below) it can be seen that the PowerTap records a higher value when there is a short, hard, immediate change in power output, as might be the case in a sprint or other sudden power burst. The result of this is that the PowerTap records a higher maximum power for the ride, at 616W compared to the 565W recorded by the CompuTrainer. The following graph shows the recorded outputs during a 5 minute period including one sudden power output change.
3). I observed that during periods where the "speed" was high, riding in a high gear with a lower cadence the CompuTrainer recorded a slightly but consistently lower power figure than the PowerTap.A summary of the comparative data as extracted by the TrainingPeaks WKO+ package is enclosed below which shows the remarkable consistency of the figures produced by the units. On the basis of the trials so far I have no hesitation in recommending this combination of equipment for indoor and outdoor training. Having spent a lot of money on this setup I'm happy with the data coming out, even though I'd like the numbers to be higher!
Next week I hope to carry out an FTP test, it will be interesting to see which unit gives me the higher FTP, I think on the basis of my investigations so far it will be the PowerTap.
PowerTap vs CompuTrainer Comparison.
| PowerTap | CompuTrainer | |
| Duration | 2:11:40 | 2:11:40 |
| Work Done | 1723kJ | 1712kJ |
| TSS | 139.1 (IF 0.797) | 138.7 (IF 0.796) |
| NP | 223 | 223 |
| Maximum Power | 616W | 565W |
| Average Power | 218W | 217W |
| Peak 5s Power | 530W | 456W |
| Peak 10s Power | 395W | 386W |
| Peak 20s Power | 318W | 315W |
| Peak 30s Power | 314W | 310W |
| Peak 1m Power | 287W | 290W |
| Peak 2m Power | 271W | 272W |
| Peak 5m Power | 248W | 250W |
| Peak 10m Power | 242W | 244W |
| Peak 20m Power | 231W | 232W |
| Peak 30m Power | 226W | 229W |
| Peak 60m Power | 224W | 225W |
Friday, 16 May 2008
PowerTap vs CompuTrainer Comparison
Hi
I use a CompuTrainer Lab Pro indoors and a PowerTap 2.4 outdoors. In the past I've been involved in discussions about the calibration procedures when using a CompuTrainer. I've always taken great pains to ensure that I follow the recommended procedures and warm up the tyre and drum properly for at least 10 minutes @ 175W before calibrating and starting my training session.
Anyway, I have been fortunate enough to be given the use of a PowerTap hub to use on my CompuTrainer until next Friday as I wanted to do some comparisons just out of interest. I have the hub on a one week loan from the ever generous and ever helpful Breeze Bikes in Amble, Northumberland.
I installed the wheel onto the CompuTrainer today and have done the first of my tests, simply to prove the necessity of proper unit calibration. For this test I simply got onto the trainer and rode in ergo mode for the first 2 minutes @ 100-125W to get going and from then on from minute 2 to the end of approximately a 10 minute period @ 175W.
I then downloaded the PowerTap and copied the file off the CompuTrainer and graphed the power outputs recorded at identical time points. The results are shown below, there are no surprises. There is however clear confirmation that if you don't calibrate your trainer properly after fully warming it up you will think you are about 20W more powerful than you actually are. More comparisons will follow, done with a properly warmed up and calibrated unit!
I use a CompuTrainer Lab Pro indoors and a PowerTap 2.4 outdoors. In the past I've been involved in discussions about the calibration procedures when using a CompuTrainer. I've always taken great pains to ensure that I follow the recommended procedures and warm up the tyre and drum properly for at least 10 minutes @ 175W before calibrating and starting my training session.
Anyway, I have been fortunate enough to be given the use of a PowerTap hub to use on my CompuTrainer until next Friday as I wanted to do some comparisons just out of interest. I have the hub on a one week loan from the ever generous and ever helpful Breeze Bikes in Amble, Northumberland.
I installed the wheel onto the CompuTrainer today and have done the first of my tests, simply to prove the necessity of proper unit calibration. For this test I simply got onto the trainer and rode in ergo mode for the first 2 minutes @ 100-125W to get going and from then on from minute 2 to the end of approximately a 10 minute period @ 175W.
I then downloaded the PowerTap and copied the file off the CompuTrainer and graphed the power outputs recorded at identical time points. The results are shown below, there are no surprises. There is however clear confirmation that if you don't calibrate your trainer properly after fully warming it up you will think you are about 20W more powerful than you actually are. More comparisons will follow, done with a properly warmed up and calibrated unit!
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