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2011-10-27 5:55 PM
in reply to: #3741397

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2011-10-27 5:57 PM
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2011-10-27 6:38 PM
in reply to: #3741415

Master
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Subject: RE: Power meter question!
Fred D - 2011-10-27 6:55 PM
colinphillips - 2011-10-27 6:31 PM
Fred D - 2011-10-27 2:54 PM 

You are misled.

Thanks. (I do follow those ST discussions, and try to filter out the noise; and I also use analyticcycling etc. for ballpark figures.)

If being misled saves me $1500 on an unnecessary purchase, then that's the kind of ignorance I can live with.

honestly buying a powertap for dirt cheap would be a great option for anyone. Again comparing watts to someone else's watts is a fun but not useful exercise.

 

x2

This thread has become completely de-railed from the OP question but I agree that a PT is probably the best buy I have made. I bought a used wired unit for ~$250 when it was popular to switch to wireless. I have had no problems with the unit and it gives me reproducible results. My power has increased more than I ever dreamed possible with focused training. I am hoping that the introduction of the Vector will bring down the price of Quarq on the used market. The actual entry of the pedal based powermeter is long overdue considering it was supposed to be available over 3 years ago. I imagine some of the people who were holding out have left the sport by now.

2011-10-27 8:21 PM
in reply to: #3741456

Champion
7595
50002000500252525
Columbia, South Carolina
Subject: RE: Power meter question!

pschriver - 2011-10-27 7:38 PM 

I agree that a PT is probably the best buy I have made. I bought a used wired unit for ~$250 when it was popular to switch to wireless. I have had no problems with the unit and it gives me reproducible results. My power has increased more than I ever dreamed possible with focused training. I am hoping that the introduction of the Vector will bring down the price of Quarq on the used market. The actual entry of the pedal based powermeter is long overdue considering it was supposed to be available over 3 years ago. I imagine some of the people who were holding out have left the sport by now.

x whatever.

I also got a very cheap wired PT (and race with a wheel cover), and although I'd like to go wireless some day, I can hide the wire from the wind pretty well, so I'm happy with the setup for now.

And I completely agree that the numbers are meaningful only comparing your present self to your earlier self, including for calculating (improvements in) CdA and so on (and anyway doing a roll-down test might be a better plan there, though they have their own set of difficulties, especially comparing results from different days).  As Fred said, it's an expensive hood ornament unless you take the time to educate yourself a bit.

2011-10-27 8:26 PM
in reply to: #3741572

Elite
3779
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Ontario
Subject: RE: Power meter question!
Experior - 2011-10-27 9:21 PM

pschriver - 2011-10-27 7:38 PM 

I agree that a PT is probably the best buy I have made. I bought a used wired unit for ~$250 when it was popular to switch to wireless. I have had no problems with the unit and it gives me reproducible results. My power has increased more than I ever dreamed possible with focused training. I am hoping that the introduction of the Vector will bring down the price of Quarq on the used market. The actual entry of the pedal based powermeter is long overdue considering it was supposed to be available over 3 years ago. I imagine some of the people who were holding out have left the sport by now.

x whatever.

I also got a very cheap wired PT (and race with a wheel cover), and although I'd like to go wireless some day, I can hide the wire from the wind pretty well, so I'm happy with the setup for now.

Love to see how you have your wires setup on our SC.  Trying to figure out how to do this.

Thanks

2011-10-27 9:01 PM
in reply to: #3741580

Champion
7595
50002000500252525
Columbia, South Carolina
Subject: RE: Power meter question!
GoFaster - 2011-10-27 9:26 PM
Experior - 2011-10-27 9:21 PM

pschriver - 2011-10-27 7:38 PM 

I agree that a PT is probably the best buy I have made. I bought a used wired unit for ~$250 when it was popular to switch to wireless. I have had no problems with the unit and it gives me reproducible results. My power has increased more than I ever dreamed possible with focused training. I am hoping that the introduction of the Vector will bring down the price of Quarq on the used market. The actual entry of the pedal based powermeter is long overdue considering it was supposed to be available over 3 years ago. I imagine some of the people who were holding out have left the sport by now.

x whatever.

I also got a very cheap wired PT (and race with a wheel cover), and although I'd like to go wireless some day, I can hide the wire from the wind pretty well, so I'm happy with the setup for now.

Love to see how you have your wires setup on our SC.  Trying to figure out how to do this.

Thanks

 

I'll try to remember to take pictures (or PM me to remind me).  Right now it is in pieces getting all gussied up for a race.  But here's the basic idea.  I run it up up the top of the seat stay, then up the back of seat tube between the seat tube and the draft box, and then along the top tube right alongisde the seat post, moving it to the middle of the top tube right in front of the seat post.  Then it goes along the center of the top tube until it reaches the stem.  I put clear tape (sliced down packing tape) over it the entire way.  Then it runs over the rubber thingy that covers the spot where the bars connect to the fork (no tape there), up on top of the stem, and then over to the aero bar (right or left -- depends on how you've got the head unit mounted), and along there until it gets to the spot where the PT head unit is mounted on the aero bar.  You have to leave a little slack at the rubber thingy for steering, but otherwise the whole length of the wire can be taped down, and if you do a neat job of it, it comes out looking pretty good (and I believe that the aero penalty is basically zero -- I did some roll-down tests (granted, no steering was involved in these tests) and saw no significant effect).



2011-10-27 10:40 PM
in reply to: #3740795

Master
2372
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Subject: RE: Power meter question!
JohnnyKay - 2011-10-27 12:38 PM
Tom Demerly. - 2011-10-27 1:23 PM

"At this stage, it remains very unclear to me what is 'superior' about a pedal based system aside from it offering incrementally more flexibility in switching between bikes."

A compromise to current power measurement units in cycling is the existing strain gauge technology used in current power meters.

Current brands and models use a foil strain gauge. Here is an introduction to strain guage technology and a discussion of the foil strain gauge developed in 1938:

http://www.omega.com/prodinfo/StrainGages.html

The newer strain guages are silicone strain gauges and "provide an accurate, stable signal over a wide operating temperature range (-40 to +140°C), as well as temperature compensation." (source: sensata technologies, microfused silicon strain gauge for hermetic pressure sensing)

Silicone strain gauges are more stable and produce more repeatable data for an elastic force application such as power measurement through an elastic drivetrain, like a pedal axle that flexs some. In automotive high end, such as BMW, Volvo and Mercedes, these silicone strain guages monitor brake pressure, vehicle ride control such as stability systems, transmission behavior and even sense the changing weight of passengers to adjust the suspension of the car (BMW).

Other brands will switch to silicone sensors and bring their power measurement closer to where the force is appllied- at the pedals- instead of where the result occurs- at the wheel. This closer proximity to the origin of the forces will provide a much more accurate, repeatable and detailed insight into how forces are being applied.

Another huge capability, in addition to independent measurement of force application where it is applied, is an accurate measurement of tangenital and radial force. In other words- the quality of your pedal stroke: Are you applying force to the pedal with the best angular relationship? The Garmin unit has the capability to provide an accurate and precise measurement of those force tangents.

I don't need -40 to +140°C range.  More like 10 to +110F.  I have not seen any noticible change in my PT across temps, but I'll concede there might be a small advantage here to the silicone (not likley one that would drive a purchase decision unless the difference is clearly measureable on a bike).

The 'source of force' application advantage is still not readily apparent to me.  What matters is the force moving the wheel.  I do not see how the the drive trian loss impacts how I look at the data.  Might matter for academic studies, but that's certainly not the mass market.

The pedal storke stuff opens up another can-of-worms debate, but I see absolutely no value in that.  It's like spinscan.  Sounds cool.  Helps me go faster, how? (Please don't answer that, it was rhetorical--it doesn't.)

Tom,

For the love of all that is holy, please drop the 'e' from silicone.  It is a silicon (i.e. semiconductor), not silicone (i.e. window caulk), strain gauge.  I'd also argue with the marketing hype placed on the SG type.  In typical mild conditions - not in the middle of a power turbine, etc., foil strain gauges are just fine.   Nothing wrong with semiconductor gauges, though.  Nice to see they have engineered some temperature compensation to keep the reading stable over a typical temperature range - I have seen effects in my PT.

And, I, for one, find the left/right capability to be highly intriguing.  One of my legs is surgically "enhanced" and it would be nice to see what I'm doing in each leg separately.  It would actually be pretty useful for me.  What rate of capture is offered with these?  That matters a lot in its ultimate usefulness.

2011-10-29 3:58 PM
in reply to: #3739351

Champion
7595
50002000500252525
Columbia, South Carolina
Subject: RE: Power meter question!

Alright, I took a video of installing the PT wiring on my bike, here:

http://www.youtube.com/watch?v=UJfQegfa8Cw

Sorry that took a while -- my bike was in pieces and it took a while to clean it and get it back together.

2011-10-29 8:44 PM
in reply to: #3743725

Elite
3779
20001000500100100252525
Ontario
Subject: RE: Power meter question!

Michael, that was a great video - thanks for taking the time to put that together.  Love the stem on the 9 series.

I have a white 7 series, so I think I'll try to run the wire under the frame rather than on top just to hide it a bit - or waybe I'll try it on top.  The only benefit of the 7 series is that I can wrap some of the extra wire around the cables in front of the stem.

Bike is in the shop for the next week since it came with the old stem clamp and BBCG.  By the time I get it back I'll have ridden it for a total of 60min in the three weeks I've owned it.  Oh well, looking forward to a long future together.  You have any issues with the drop outs and mounting to a trainer?

2011-10-29 11:13 PM
in reply to: #3743915

Champion
7595
50002000500252525
Columbia, South Carolina
Subject: RE: Power meter question!
GoFaster - 2011-10-29 9:44 PM

Michael, that was a great video - thanks for taking the time to put that together.  Love the stem on the 9 series.

I have a white 7 series, so I think I'll try to run the wire under the frame rather than on top just to hide it a bit - or waybe I'll try it on top.  The only benefit of the 7 series is that I can wrap some of the extra wire around the cables in front of the stem.

Bike is in the shop for the next week since it came with the old stem clamp and BBCG.  By the time I get it back I'll have ridden it for a total of 60min in the three weeks I've owned it.  Oh well, looking forward to a long future together.  You have any issues with the drop outs and mounting to a trainer?

It mounts to my trainer (Cyclpos) fine.  I can't use the the SC skewer, but I have a cheap metal skewer that works fine.

(edited to make it English)



Edited by Experior 2011-10-29 11:26 PM
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