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Power Tap
 

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

5/21/17 5:27 PM

Power Tap

Got a Wheel with w 2.4+ version of the hub.

What wakes it up for a scan to see it? Spin of the cassette, spin of the axle?

Anyone have a spare used Joule they have moved on from??

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walter
Joined: 11 Jan 2004
Posts: 4391
Location: metro-motown-area

5/22/17 6:00 AM

spin of axle

there's a magnet fixed in place on the axle, when the hub-shell rotates the magnet closes a contact w/ each revolution waking up the electrics...voila!

what that also means is you dont need a separate speed-sensor when using PTs. in fact, if using a PT head + hub pairing, the CPU ignores a standalone speed-sensor.

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

5/22/17 10:29 AM

Hey, I remember a user here named Walter, is that you? ;)

Are you up on Joule 1.0 VS 2.0. is one HRM compatible and the other not? Getting dizzy googling for the tons of ambiguity... ;)

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walter
Joined: 11 Jan 2004
Posts: 4391
Location: metro-motown-area

5/24/17 7:17 AM

i use a Joule GPS. it's not bad, but the UI could use some work -- better button configs.

we just completed our move this week, into a smaller house of which only half is finished/livable...so we're living out of boxes and amid construction dust.

but the view amongst the treetops makes it easier to bear!

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

5/28/17 12:59 PM

What are you sitting down for? Get to work!

Got the tool and put new batteries in. Woke right up. I have no idea as far calibration is concerned.

But my iP-Bike Android App picked it up as generic power radio, not as a PT specifically.

Quick ride showed, what I would consider appropriate avg and max reading for my little test effort up a little hill and a mash.

I think the Madone is going to be dedicated for the purpose. Move the DuoTrap from the Domane over to it. iP-Bike app likes that too.

Are 32 spoke PT hubs more accurate than lower spoke wheels?

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 5096
Location: Nashua, NH

5/29/17 1:22 PM

Why should spoke count matter?

I don't see the connection.

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

5/29/17 2:04 PM

Asking as I know specific cross is required, wondered if more spoke may mean less variance..

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

6/14/17 2:55 PM

Learn something new every day. My Android was showing cadence. So I googled some more after the first real ride with it. It does do cadence, I did not know that. It is a little jumpy but levels out once you get a steady pedaling/power going.

Two things are apparent; 1) when you get to see your output, you tend to go faster. ;) 2) it takes more watts to get my fat ars up hills than I guessed it took. No wonder I git so tired going up. ;(

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walter
Joined: 11 Jan 2004
Posts: 4391
Location: metro-motown-area

6/18/17 7:45 AM

i think 2X is the minimum required...

...and must be crossed the same on both flanges.

asymmetrical lacing can lead to shell twisting, which causes inaccurate torque/power readings. more crossings are not better after meeting the 2X requirement.

re: cadence, i use the inferred cadence you're using while on the road, it's good enough for gubment work. but i have a proper cadence sensor fitted to the trainer bike just for grins

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dddd
Joined: 11 Jan 2004
Posts: 3345
Location: NorCal

6/18/17 3:13 PM

Any shell twist will be because of uneven spoke tensioning, sometimes the result of one's hasty build and tensioning sequence. I occasionally come across wheels that have been tensioned so as to put very great net twisting force through the shell, and I've seen hubshells crack for presumably that reason.

Spoke crossing should attempt to approach the tangent condition for best flange durability, so the preferred spoke crossing count also depends on the spoke count.
Some rear wheels are designed so as to put radial spokes on one side, so as to either optimize the bracing angle and stiffness or to reduce spoke fatigue and loosening problems. These lacing choices both depend on and affect the wheel component's designs.

I don't use power meters because my output has it's own random variability, and because my ability to pull ahead or even to keep up depends on how I am feeling in real time. What brain activity I would devote to tracking my power output number might better be spent evaluating my situation on the road, my hydration/fueling and on known conditions that lie ahead, including those that affect safety. I also often devote mental resources to effecting perfect, and optimally-timed friction shifts, which hmmm, maybe provides enough of the sort of technical entertainment that I might be missing without a meter.;-)

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walter
Joined: 11 Jan 2004
Posts: 4391
Location: metro-motown-area

6/18/17 5:54 PM

i think the twist warning is for knuckleheads like me that like to run radial NDS in the back -- definitely twist issues when only crossed on 1 side!

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dddd
Joined: 11 Jan 2004
Posts: 3345
Location: NorCal

6/19/17 12:45 AM

Now I understand what you meant, that the torque would be in response to pedaling, or could similarly be in response to braking.

I was thinking only of static torque from uneven spoke tensions, where each flange imparts opposing torque to the other with the wheel not even mounted to the bike yet!

I still say go for as many crosses as possible, short of going below tangency to the spoke hole circle. This minimizes spoke tension cyclic variation and thus fatigue on the rim, nipples, spokes and flanges. A shallow spoke crossing angle might literally double the fatigue loading in some cases, but not with 2x and a low spoke count.
3x spoking with 28 or 32h count is as good as you can do.

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