Fat Boab Posted March 5, 2019 Posted March 5, 2019 Well, that was helpful I thought it was. And it was arguably the most concise post in this thread...
obree Posted March 5, 2019 Posted March 5, 2019 Stop messing around and get yourself an InfoCrank. Not as expensive as you think and at least it works. Calculate over the years how much all the pedals and hubs are costing you and just spend the money wisely.
J Wakefield Posted March 5, 2019 Posted March 5, 2019 What happens if you decrease cadence by selecting a bigger gear for the same road speed etc? Secondly, is the behaviour you've noted consistent at other constant power levels? You go from Watts (hi cadence value) to NM of torque (Low cadence) as a value.
DieselnDust Posted March 5, 2019 Posted March 5, 2019 You go from Watts (hi cadence value) to NM of torque (Low cadence) as a value. Huh?Can you explain what you are thinking here please
s14phoenix Posted March 28, 2019 Author Posted March 28, 2019 What happens if you decrease cadence by selecting a bigger gear for the same road speed etc? Secondly, is the behaviour you've noted consistent at other constant power levels? If I select a bigger gear and drop cadence but keep the same "wheel speed" the crank based power meter also increases power output but wheel power meter remain the same. I have now tested single sided crank arm power vs hub and also tested dual sided pedal based power. 1. I seem to have a lazy left leg when it seems to feel like not helping as much anymore - fatigue seem to affect power drop on left side only power meters. 2. Dual sided pedal based power seems as consistent as hub based and I have fluctuating balance numbers - due to definite lazy left leg. This explains some overuse injuries to my right knee each time I have increased my training load and quantity due to the right leg doing so much more of the work when the left leg tires. 3. when fresh left leg is stronger than the right and balance goes in the opposite direction to fatigued... I can seem to manage better overall power output when actively monitoring power balance. Seem I am going to need to focus on strengthening left leg and also cadence drills focussing on keeping balance numbers such that I train left slightly more than right try fix this issue. This is why I am not so sure about riding on "feel" without ever checking to make sure there is not other issues in your power delivery and efficiency. As a obvious gizmo nut I love the tech but it is very confusing also... and more is definitely more and better when it comes to information.
DieselnDust Posted March 28, 2019 Posted March 28, 2019 If I select a bigger gear and drop cadence but keep the same "wheel speed" the crank based power meter also increases power output but wheel power meter remain the same. I have now tested single sided crank arm power vs hub and also tested dual sided pedal based power. 1. I seem to have a lazy left leg when it seems to feel like not helping as much anymore - fatigue seem to affect power drop on left side only power meters. 2. Dual sided pedal based power seems as consistent as hub based and I have fluctuating balance numbers - due to definite lazy left leg. This explains some overuse injuries to my right knee each time I have increased my training load and quantity due to the right leg doing so much more of the work when the left leg tires. 3. when fresh left leg is stronger than the right and balance goes in the opposite direction to fatigued... I can seem to manage better overall power output when actively monitoring power balance. Seem I am going to need to focus on strengthening left leg and also cadence drills focussing on keeping balance numbers such that I train left slightly more than right try fix this issue. This is why I am not so sure about riding on "feel" without ever checking to make sure there is not other issues in your power delivery and efficiency. As a obvious gizmo nut I love the tech but it is very confusing also... and more is definitely more and better when it comes to information. the bit in bold I find intriguing. Which head unit are you using as the sample rate, and also whether you are using 3s power average or instantaneous power. IF the latter then somethings wrong.If you increase the gearing you will increase the chain tension which will increase the twist in the torque tube which translates to an increase power value. the jump may ot be as big as for a crank or pedal based system but it should be there. Which power meter are you now using as your go to tool?
s14phoenix Posted March 28, 2019 Author Posted March 28, 2019 I have tested the following power meters with 3s and instantaneous display but that did not make much difference as I used static or rather constant output trying to stay as stable as possible - accelerating or decelerating would obviously change power figures so when changing cadence levels I would allow time for the value to settle at the new constant velocity. 4iiii left only crank arm power and stages left only power meter - power increase with cadence drop and torque increase - reverse when increasing cadence - cadence in power calculation seems to make up a small margin of the reported power Garmin vector 2 pedals - stable power output at same wheel speed and various cadence against the same set load.- be it within error margin with hub and trainer Tacx Vortex Smart indoor trainer - no power increase at same wheel speed and various cadence against the same set load. - set same load setting and various cadence 1. the load or braking effect decreases when cadence increases in same gear to keep at the goal power 2. the load or braking effect increases with cadence decrease in same gear to try reach the goal power Hub output - stable power output at same wheel speed- be it within error margin of pedals and trainer Head unit used Garmin Edge 520, Edge 810. Same test done on Zwift with each of the different power meters as well. What I have not tried is the software used by DCRainmaker where they have compared various power meters in their review using the data from the headunit uploads etc. but I cannot understand my results compared to their comparative tests where all the power meters tested roughly tracked at the same power (within error margin) The reason I am doing all this is that the pedals are not mine. the stages and 4iiii is also not mine and the hub and trainer is. So I am looking for a new power meter to replace the hub based power meter that has thus far been trouble free. I do not want to rebuild a new wheelset with a power hub every time I buy a new wheelset. I will otherwise look at investing in a set of Garmin Vector 3 or similar as that seemed to address most of my issues including my left/right imbalances etc.
Schnavel Posted March 28, 2019 Posted March 28, 2019 Stay away from the Vector 3 pedals. I know many people who are on their third set of pedals as they keep going for warranty replacement. Rather get a crank based option - I have had trouble free power readings from my Quarq over the years. Battery seems to last longer when compared with my powertap hub on my other bike.
Barend de Arend Posted March 28, 2019 Posted March 28, 2019 If I select a bigger gear and drop cadence but keep the same "wheel speed" the crank based power meter also increases power output but wheel power meter remain the same. I have now tested single sided crank arm power vs hub and also tested dual sided pedal based power. 1. I seem to have a lazy left leg when it seems to feel like not helping as much anymore - fatigue seem to affect power drop on left side only power meters. 2. Dual sided pedal based power seems as consistent as hub based and I have fluctuating balance numbers - due to definite lazy left leg. This explains some overuse injuries to my right knee each time I have increased my training load and quantity due to the right leg doing so much more of the work when the left leg tires. 3. when fresh left leg is stronger than the right and balance goes in the opposite direction to fatigued... I can seem to manage better overall power output when actively monitoring power balance. Seem I am going to need to focus on strengthening left leg and also cadence drills focussing on keeping balance numbers such that I train left slightly more than right try fix this issue. This is why I am not so sure about riding on "feel" without ever checking to make sure there is not other issues in your power delivery and efficiency. As a obvious gizmo nut I love the tech but it is very confusing also... and more is definitely more and better when it comes to information. This is why I posted about the error bars and statistics. Comparing power meters isn't always easy. Error bars aren't necessarily constant across cadence. They could be -2% at 50 cadence and +2% at 150 cadence. They could also fluctuate heavily with temperature and low-torque and high-torque changes. Single-sided power meters exacerbate this. If the left reads +2% and doubles, you'll think you're producing extra power when you aren't. This can make you favour conditions where the power meter misreads, and you end up doing exercises that give you a false sense of result. I also think it's a mistake to look at the balance unless you're specifically trying to fix a leg imbalance. There's no science that says that achieving 50/50 balance makes you faster. It's easily possible that the left reads -2% and the right +2%, making you think you have an imbalance when in fact you have balance. On the other hand one lazy leg could be because of a medical condition like a constricted artery, so do take note of that.
DieselnDust Posted March 28, 2019 Posted March 28, 2019 I have tested the following power meters with 3s and instantaneous display but that did not make much difference as I used static or rather constant output trying to stay as stable as possible - accelerating or decelerating would obviously change power figures so when changing cadence levels I would allow time for the value to settle at the new constant velocity. 4iiii left only crank arm power and stages left only power meter - power increase with cadence drop and torque increase - reverse when increasing cadence - cadence in power calculation seems to make up a small margin of the reported power Garmin vector 2 pedals - stable power output at same wheel speed and various cadence against the same set load.- be it within error margin with hub and trainer Tacx Vortex Smart indoor trainer - no power increase at same wheel speed and various cadence against the same set load. - set same load setting and various cadence 1. the load or braking effect decreases when cadence increases in same gear to keep at the goal power 2. the load or braking effect increases with cadence decrease in same gear to try reach the goal power Hub output - stable power output at same wheel speed- be it within error margin of pedals and trainer Head unit used Garmin Edge 520, Edge 810. Same test done on Zwift with each of the different power meters as well. What I have not tried is the software used by DCRainmaker where they have compared various power meters in their review using the data from the headunit uploads etc. but I cannot understand my results compared to their comparative tests where all the power meters tested roughly tracked at the same power (within error margin) The reason I am doing all this is that the pedals are not mine. the stages and 4iiii is also not mine and the hub and trainer is. So I am looking for a new power meter to replace the hub based power meter that has thus far been trouble free. I do not want to rebuild a new wheelset with a power hub every time I buy a new wheelset. I will otherwise look at investing in a set of Garmin Vector 3 or similar as that seemed to address most of my issues including my left/right imbalances etc. I am thinking the Tacx Vortex is where the skewing of the data is showing up. Its a wheel on trainer if I recall correctly and the problem with that is that you don't get very consistent results as it is not really measuring power output directly but rather using the electro motor force calculation. The difference between it and the cranks based units is that tyre slip but also drum inertia becomes a factor that will also skew your hub based unit results as the drum inertia is not the same as your inertia on the road. I woul be interested to see if the results are consistent if you replace the vortex with a Neo, Kickr or Hammer
s14phoenix Posted March 28, 2019 Author Posted March 28, 2019 I am thinking the Tacx Vortex is where the skewing of the data is showing up. Its a wheel on trainer if I recall correctly and the problem with that is that you don't get very consistent results as it is not really measuring power output directly but rather using the electro motor force calculation. The difference between it and the cranks based units is that tyre slip but also drum inertia becomes a factor that will also skew your hub based unit results as the drum inertia is not the same as your inertia on the road. I woul be interested to see if the results are consistent if you replace the vortex with a Neo, Kickr or Hammer Well when the lotto pays out I will look at the Neo or similar... would love to but I want to sort out the power meter for use everywhere first. then next is replacing the trainer to direct drive... Would love to compare also... this is very confusing and interesting all at the same time. For now I think a set of power pedals then next the I will look at the trainer...
DieselnDust Posted March 28, 2019 Posted March 28, 2019 Well when the lotto pays out I will look at the Neo or similar... would love to but I want to sort out the power meter for use everywhere first. then next is replacing the trainer to direct drive... Would love to compare also... this is very confusing and interesting all at the same time. For now I think a set of power pedals then next the I will look at the trainer... Yeah I think based on the trainer you're using, pedals or crank based PM as the main measurement device, and also to feedback to your desktop or mobile software is going to be the best.Tacx Flux is really pretty good too and drive drive
Schnavel Posted March 28, 2019 Posted March 28, 2019 https://www.bikehub.co.za/classifieds/354718-cycle-ops-hammer-direct-drive/
mecheng89 Posted March 30, 2019 Posted March 30, 2019 Been using PowerTap hub since '17. Replaced the coin battery a few times, and did one full service on it. Been dependable, will never switch to anything else. Pity is it's only one one wheelset, but will probably build a second wheelset soon. Training on a smart trainer using a different FTP.
V18 Posted March 30, 2019 Posted March 30, 2019 New one at tapei cycle show based on tyre pressure oscillations. 5% variance. Don't shoot the messenger. www.aroflybike.com
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