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Old 08-22-14, 09:08 PM
  #6326  
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Originally Posted by tetonrider
a magnet is always going to be more accurate, no?
Sure. My point about accuracy was just that any crank-based system will measure cadence more accurately than a powertap, because a powertap isn't using its accelerometer (or any other mechanism) to measure cadence, it's inferring cadence from peaks in torque. My comment was intended to mildly refute shovelhd's statement that a powertap uses its accelerometer to measure cadence if there's no cadence sensor installed.

It's all pretty pedantic.
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Old 08-22-14, 09:29 PM
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Originally Posted by globecanvas
Sure. My point about accuracy was just that any crank-based system will measure cadence more accurately than a powertap, because a powertap isn't using its accelerometer (or any other mechanism) to measure cadence, it's inferring cadence from peaks in torque. My comment was intended to mildly refute shovelhd's statement that a powertap uses its accelerometer to measure cadence if there's no cadence sensor installed.

It's all pretty pedantic.
agree that it's pedantic, but there's still some learning involved.

magnet > accelerometer on the crank (inferring position and making a calculation) > the PT method of using torque and speed to take a guess at instantaneous cadence.

lots of folks rushing out to ditch their magnets when it's a worse solution in many ways. funny to see so many people talking about what a pain a magnet is. i don't get that one. saw lots of talk about destroyed RDs. really?
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Old 08-22-14, 10:10 PM
  #6328  
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Originally Posted by tetonrider
destroyed RDs. really?
yup. I had one.
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Old 08-22-14, 10:15 PM
  #6329  
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Originally Posted by Ygduf
yup. I had one.
i believe it's happening but am surprised by how many people are claiming it.

how are you attaching the magnet to the frame....hot glue or something else that gets brittle?

2-part epoxy on the frame works really well (the worst roads one can ride...and even MTB), lasts for years, and is also easy to remove with a tap from a screwdriver when someone is ready.

just curious if there is some common thread for those who are losing a magnet and having it take out a derailleur.
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Old 08-23-14, 05:24 AM
  #6330  
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Originally Posted by tetonrider
how are you attaching the magnet to the frame....hot glue or something else that gets brittle?
insufficient epoxy and having a chain drop to the frame on the inside, dragging it directly over the magnet.

when I re-did the epoxy I used way more and positioned it more carefully toward the back to if the chain came off it would not/would have less direct contact.

I guess the bigger point is not that it's likely, but that with a minimal mistake you end up with a situation where you tear your rear derailleur off the bike and put the rider in pretty serious jeopardy.

All for cadence, which while sometimes interesting after the fact, is def something I could live without.
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Old 08-23-14, 07:56 AM
  #6331  
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Changed the battery in the G3 this morning, went out for a ride and still switched betweem auto pause/resume. I turned off the auto pause so I didn't have to keep dealing with it, but still this shouldn't be happening correct? Calibrated at 514 this morning.
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Old 08-23-14, 10:36 AM
  #6332  
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Originally Posted by Ygduf
insufficient epoxy and having a chain drop to the frame on the inside, dragging it directly over the magnet.

when I re-did the epoxy I used way more and positioned it more carefully toward the back to if the chain came off it would not/would have less direct contact.

I guess the bigger point is not that it's likely, but that with a minimal mistake you end up with a situation where you tear your rear derailleur off the bike and put the rider in pretty serious jeopardy.

All for cadence, which while sometimes interesting after the fact, is def something I could live without.
yes, you're right--that is a terrible way for something to fail.

2 points:
1) you couldn't live without cadence, even if you don't want to look at it. cadence is a key component of the way power is calculated; no cadence, no power, and i'm assuming you don't want to live without that. (i know you know that, just saying it's more a component of a functioning crank-based system than it is for display.)

2) sounds like your installation was messed up. i'm my own mechanic and have made my share of mistakes along the way, but if one isn't 100% sure of what they're doing they should take it to a pro who has learned how to do it right w/o risking the derailleur. e.g., as you discovered you put a magnet behind the crank, on the chain stay, where a derailed chain would still not take it out; no amount of epoxy will protect a magnet if a chain hits it. if one improperly installs their stem there could be dire consequences, too, but that's not the fault of the system.
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Old 08-25-14, 10:23 PM
  #6333  
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Where the heck are the release notes for the Powertap G3 updates?

I just went from version 3.7 to 5.8 and I have no idea if my Powertap is going to be more awesome(more awesome as in showing higher #'s of course).

Anyone know where I can find this very valuable information?
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Old 08-26-14, 05:46 AM
  #6334  
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ovoleg - You have to download Powertap's Power Agent first. Then this video walks you through the process.
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Old 08-26-14, 09:21 AM
  #6335  
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Originally Posted by revchuck
ovoleg - You have to download Powertap's Power Agent first. Then this video walks you through the process.
I did I just want to find a location of the release notes. It's all updated to 5.8.
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Old 08-27-14, 02:06 PM
  #6336  
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quick one, as this thread is getting pretty long and a view/search of the recent pages didn't turn anything up.

I've got one of the first-gen Quarq's (s975), and I'm wanting to confirm whether or not it has become inaccurate (drift, offset, etc)
Where is the instructions on how to check that?

A few years ago when I checked it every week or so with a Garmin, the offset was stable. However, I don't have a Garmin, only have my PC7.

Anyone?
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Old 08-27-14, 02:21 PM
  #6337  
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Do you have a wahoo key?

alternatively, borrow someone's garmin
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Old 08-27-14, 02:43 PM
  #6338  
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Originally Posted by echappist
Do you have a wahoo key?

A-HA!! I knew I was missing something obvious-
yup, of course, now that I don't have an iphone, my wahoo key won't work anymore... @!#$$%^

yeah- I'll sort it out- thanks.
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Old 08-27-14, 03:06 PM
  #6339  
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Quarq just came out with a new Qualvin. Check the site.
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Old 08-28-14, 06:56 AM
  #6340  
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I'm assuming everyone trains by time here. I know some of you train without auto pause on. How does that work? You just roughly know when to turn around? Or do you shoot for your time moving + non moving time reference? I would assume then you would end up short on time though.

My ride yesterday had over 10 minutes of stopping time. So I was considering maybe trying no auto pause for a bit.
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Old 08-28-14, 07:31 AM
  #6341  
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Can't help you there... I don't use auto pause, but it is a rare ride that has more than a minute or two of stopped time.
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Old 08-28-14, 07:40 AM
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Yeah now that I'm training earlier in the afternoon there is more traffic and I hit more red lights. It's a bummer for sure.
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Old 08-28-14, 10:12 AM
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Originally Posted by Creatre
I'm assuming everyone trains by time here. I know some of you train without auto pause on. How does that work? You just roughly know when to turn around? Or do you shoot for your time moving + non moving time reference? I would assume then you would end up short on time though.

My ride yesterday had over 10 minutes of stopping time. So I was considering maybe trying no auto pause for a bit.
Originally Posted by Creatre
Yeah now that I'm training earlier in the afternoon there is more traffic and I hit more red lights. It's a bummer for sure.
I always use autopause cause all my numbers are thrown off because I typically have AT LEAST 10 mins of stopped time over a 1.5 hour ride.

Why wouldn't you guys use autopause?
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Old 08-28-14, 10:18 AM
  #6344  
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Originally Posted by Creatre
I'm assuming everyone trains by time here. I know some of you train without auto pause on. How does that work? You just roughly know when to turn around? Or do you shoot for your time moving + non moving time reference? I would assume then you would end up short on time though.

My ride yesterday had over 10 minutes of stopping time. So I was considering maybe trying no auto pause for a bit.
there's a data field called "riding time", which one'd presume to be different from "elapsed time"

when i have autopause on, they are different (as in Garmin is keeping track of the time stopped), and i'd imagine them to be different when you have it off

also, autopause off inflates numbers, especially when you have a 30 min cafe break. Overall NP drops by very little, but duration now gets inflated
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Old 08-28-14, 10:22 AM
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Originally Posted by echappist
also, autopause off inflates numbers, especially when you have a 30 min cafe break. Overall NP drops by very little, but duration now gets inflated
I'd go a little farther just to try and make sure people get how important this is - autopause basically invalidates the accuracy of any data for any given time period, during which autopause took effect.

don't use autopause.
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Old 08-28-14, 01:38 PM
  #6346  
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Originally Posted by globecanvas
Can't help you there... I don't use auto pause, but it is a rare ride that has more than a minute or two of stopped time.

Yea, if I want to get any sort of real training in than I do it on my commute into work which = zero stopped time. The commute home is just a Z2 ride. Weekend workouts I can find areas without lights easy enough.
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Old 08-28-14, 07:27 PM
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Originally Posted by Creatre
I'm assuming everyone trains by time here. I know some of you train without auto pause on. How does that work? You just roughly know when to turn around? Or do you shoot for your time moving + non moving time reference? I would assume then you would end up short on time though.

My ride yesterday had over 10 minutes of stopping time. So I was considering maybe trying no auto pause for a bit.
I don't worry about it. If I'm doing z4+ intervals, I tend to do those where I don't have to stop. If I'm doing longer ones I tend not to worry about it too much, although I have done hour+ z3 "intervals" (usually as part of a longer workout) on a 10-min or so loop I usually use for shorter intervals just to avoid stopping during the z3 interval.

Of course I'm slow so maybe you should ignore what I say...
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Old 08-30-14, 07:01 PM
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Potentially stupid question

Powertap G3 with Joule 1.0. Joule 1.0 appears to record all data properly. When data is uploaded to power agent, when I look at ride files ride time is inaccurate, as is avg wattage, etc. A couple of pictures attached...you can see the discrepancy between viewing the ride by distance versus by time, and all of the data for this ride is incomplete relative to the joule 1.0's on board data (rolling time on the joule = ~2:02, avg spd = 16.9, kj burned is higher, total climbed is lower...).

Anyway, if anyone has an idea as to what's going on I'd love to know what I'm doing wrong. If not I'll bug powertap after the weekend is over.



Edit: Actually, I just got a "low battery" warning when I just turned on my head unit, so I'd wager that's probably what's causing this weirdness.
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power_by_distance.jpg (99.5 KB, 13 views)
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power_by_time.jpg (99.0 KB, 18 views)

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Old 09-05-14, 05:20 AM
  #6349  
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I'm getting a set of ten speed Reynolds 46 tubulars to replace my Open Pro/Powertap wheels for racing, and will probably end up with a Stages power meter. Are they as simple as Powertap (calibrate pre-ride and forget) to use, or is more involved? Also, any issues with using Stages with a Garmin 500?
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Old 09-05-14, 06:11 AM
  #6350  
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Originally Posted by revchuck
Also, any issues with using Stages with a Garmin 500?
A friend of mine has been using Stages since it came out with his 500 with no issues
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