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 Post subject: Re: Garmin Vector Usage
PostPosted: Sun Dec 01, 2013 11:52 pm 
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Joined: Sun Nov 10, 2002 6:03 pm
Posts: 310
Location: Belfast
Thanks for all the replies
I used the pedals in anger on Friday. I decided to carry out an FTP test on myself; I used the protocol as advised in Hunter Allen & Andrew Coggan's EXCELLENT book Training and Racing with a Power Meter. This is a structured warm-up followed by a max 5 minute piece and then the crucial 20 minute maximum steady piece and a wind-down.
I had the Garmin Edge 500 reading the data from the Vectors and my old Cat-Eye computer set on speed and cadence for everything.
The upshot was that the Vectors/Edge did not drop out (go to "0:00W") BUT they did fluctuate throughout the session (320 -280W). Meanwhile I and the Cat-Eye held a steady speed and cadence throughout the session.
At this point I have two questions:
1. Are such fluctuations normal (even when speed and cadence are steady) ....or is it the dished/uneven cranks .... or is it me?
2. Any thoughts on how to solve the problem [new cranks? smoothing existing cranks?]


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 Post subject: Re: Garmin Vector Usage
PostPosted: Mon Dec 02, 2013 12:42 am 
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Joined: Fri Oct 05, 2012 3:52 am
Posts: 220
Are you asking if displayed wattages would vary like that in this kind of test? The answer is yes, on any power meter/head unit combo.

You can change the "smoothing" (sampling shown on the screen. i.e. 1/3/5 secs typically.....although your head unit will still record all data for later download) displayed so the fluctuations are less pronounced. Still, you will get minor fluctuations like you stated based on terrain or even on a trainer, because, well, you aren't a robot.


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 Post subject: Re: Garmin Vector Usage
Posted: Mon Dec 02, 2013 12:42 am 


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PostPosted: Fri Jan 24, 2014 6:37 pm 
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Joined: Thu Dec 09, 2004 5:51 pm
Posts: 135
Has anyone tried the vectors with THM clavicula's. If I remember correctly the cranks can't be more than 15mm thick to work.

Does anyone know the thickness of the clavicula's or if they work ?


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 Post subject: Re: Garmin Vector Usage
PostPosted: Fri Jan 24, 2014 7:01 pm 
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Joined: Wed Feb 27, 2013 6:47 pm
Posts: 2
Enda Marron wrote:
Thanks for all the replies
I used the pedals in anger on Friday. I decided to carry out an FTP test on myself; I used the protocol as advised in Hunter Allen & Andrew Coggan's EXCELLENT book Training and Racing with a Power Meter. This is a structured warm-up followed by a max 5 minute piece and then the crucial 20 minute maximum steady piece and a wind-down.
I had the Garmin Edge 500 reading the data from the Vectors and my old Cat-Eye computer set on speed and cadence for everything.
The upshot was that the Vectors/Edge did not drop out (go to "0:00W") BUT they did fluctuate throughout the session (320 -280W). Meanwhile I and the Cat-Eye held a steady speed and cadence throughout the session.
At this point I have two questions:
1. Are such fluctuations normal (even when speed and cadence are steady) ....or is it the dished/uneven cranks .... or is it me?
2. Any thoughts on how to solve the problem [new cranks? smoothing existing cranks?]


I'm sure it is You, why? becasue I have the same. Try testing at half of your FTP and you will see you will be able to keep power within 10W, but it takes time before you learn such a steady pedaling.
Post link to garmin connenct from that ride.


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 Post subject: Re: Garmin Vector Usage
PostPosted: Sun Jun 01, 2014 1:47 am 
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Joined: Wed Sep 26, 2007 1:57 pm
Posts: 7366
Location: San Francisco, CA
I think I made a mistake in not installing those washers:

Image
Image
Image

It's remarkably consistent in its wrongness, though. L-R balance is probably fairly good. I see this every single ride I check: right-leg dominant at lower power, 50-50 at higher power. Note the power axis is approximately 84% actual:

Image

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Fuji SL/1
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 Post subject: Re: Garmin Vector Usage
PostPosted: Sun Jun 01, 2014 2:29 am 
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Joined: Tue Apr 18, 2006 3:03 am
Posts: 1890
Location: Islip, NY
I hear there is a version of the pedals that will be designed for thicker crank arms. Should be out soon enough.

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 Post subject: Re: Garmin Vector Usage
PostPosted: Sun Jun 01, 2014 11:58 pm 
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Joined: Wed Sep 26, 2007 1:57 pm
Posts: 7366
Location: San Francisco, CA
I think I solved my problem. I went into Vector Updater and it said my cranks were 144.5 mm, rather than 170 mm. I have no idea how that happened.... That's 85% the correct crank length.

Curiously, after I added a spacer and did a ride I got 91% ratio Vector:Powertap. So divide that by 85% and I get 1.07, which would be 7% power lost to drivetrain. That seems like a lot, but certainly it's in ball-park. I'll do another ride with the revised crank length.

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Fuji SL/1
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 Post subject:
PostPosted: Mon Jun 02, 2014 4:30 am 
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Joined: Tue Apr 17, 2012 11:20 am
Posts: 325
.


Last edited by Causidicus on Wed Jun 18, 2014 1:33 am, edited 1 time in total.

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 Post subject: Re: Garmin Vector Usage
PostPosted: Tue Jun 03, 2014 3:52 pm 
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Joined: Wed Sep 26, 2007 1:57 pm
Posts: 7366
Location: San Francisco, CA
This is after adding a spacer but before fixing the crank length:

Image

The power ratio increased from 0.84 to 0.91. After adjusting for this, the curves are impressively similar. Note you'd expect the ratio to drop slightly at higher power, since drivetrains are fractionally more efficient at higher power (there's fixed losses from pulleys spinning, etc). Here's the LR-balance, which is remarkably reproducible:

Image

I tried a ride after fixing the crank length but I had a problem with my Edge 800 and didn't get a record of the Vector power.

_________________
http://djconnel.blogspot.com/
Fuji SL/1
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 Post subject: Re: Garmin Vector Usage
PostPosted: Thu Jun 05, 2014 4:40 am 
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Joined: Wed Sep 26, 2007 1:57 pm
Posts: 7366
Location: San Francisco, CA
Problem solved! I found the "crank length" line under the bike properties. In my Edge 500 this was set to "auto", which makes sense, but under the Edge 800 it was set to 144.5 mm, which seems (ahem) not the most common crank length around. I don't know how that happened.

Anyway, I set it to 170 mm so should be seeing great agreement next ride with the two meters.

_________________
http://djconnel.blogspot.com/
Fuji SL/1
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