So you want to train with power on a budget?

[ratz]

It's that time again. The 6 month itch is here and we did upgrades which of course means you can too.

Items for sale this time:

Qty 2: Wahoo Fitness Speed/Cadence Sensor BlueTooth Version. $30ea
Reason: We went garmin gps and need ANT+ sensors. These work perfectly still.

Qty 2: Stages Power Meters. SRAM Rival Version 165mm. $550 ea.
Reason: We are going to shorter custom Cranks and these cannot be shortened. Compatible with all SRAM 165mm Cranksets including: Apex, Rival, Force, and RED. Both are calibrated and tested against Wahoo Kickr to confirm accuracy.

Qty 4: SRAM Rival 165mm 110BCD Compact Crank sets. Cranks only; no Rings no Bottom Bracket. $80 ea

Qty 2: SRAM Aero Ring set 110 BCD 50T/34T $45 new unused.

Shipping by USPS. Buyer selects shipping speed; I cover the first $5 of shipping cost.

 

[Martinius Berg]

Could you publish photos of the items your selling please , that would help a lot to identify your objects ?

Martinius.

 

[super slim]

Are you selling a well used rubber mallet?

 

[ratz]

Are you selling a well used rubber mallet?

For you I'll include that for free with the meter

 

[super slim]

I am afraid that I am waiting for the Watteam Powerbeat unit to come out that can be glued to the top of my FSA Gossamer triple 153 mm long cranks.
I am willing to make an offer for such a FAMOUS rubber mallet as yours!!!

 

[ratz]

I am afraid that I am waiting for the Watteam Powerbeat unit to come out that can be glued to the top of my FSA Gossamer triple 153 mm long cranks.
I am willing to make an offer for such a FAMOUS rubber mallet as yours!!!

With great mallet comes great responsibility. You would have to include funds for me to travel downunder to train you on the proper usage. I think based on Minnesota weather that I could fit that into my schedule in January

 

[ratz]

glued to the top of my FSA Gossamer triple 153 mm long

Be advise I checked on those; the back of your crank has to be flat to use those; the strain gauges install on the back face of the crank and it has to be flat; it won't work on concave cranks. So far my conclusion has been that to use sub 165mm cranks and a power meter you need a pedal based solution until power tapes ships their "C1" solution. And the C1 only works with round rings.

 

[super slim]

Ratz is a 5 mm wide flat wide enough???

 

[super slim]

With great mallet comes great responsibility. You would have to include funds for me to travel downunder to train you on the proper usage. I think based on Minnesota weather that I could fit that into my schedule in January

With great AGE, comes great abilities to handle the honor of working with tools of great historic importance and rarity!
If I win the X Lotto I will be able to afford your travel arrangements, 1st class of course!

 

[ratz]

Ratz is a 5 mm wide flat wide enough???

Which direction? Lengthwise or latterly? Got a photo?

 

[super slim]

-

I was hoping that the strain gauge could fit on the 5 mm flat area on the top of the crank

 

[ratz]

Unfortunately for me Stages has slashed the prices on the SRAM Rival OCT version of their power meters.
This is good news for you; because now I get to do the same.
Guess these won't be going on Ebay for a few weeks now.

So You want to train with Power? The time has never been better.


Qty 1: Full Rival 165mm Crank Set with Power Meter
110 Compact Double. 50/34 Rings.
Stages Power Meters in 165mm Rival
$350 + Shipping.


Qty 1: Stages SRAM Rival OCT 165mm Crank Arm Power Meter
$300 + Shipping.


The rest of the items have been sold.

 

[hamishbarker]

Wow what a deal! Too bad i have an old wired powertap so cannot justify a purchase but someone will be happy with it!

 

[ratz]

We are now down to:

Qty 1: Stages SRAM Rival OCT 165mm Crank Arm Power Meter
$300 + Shipping

Compatible with SRAM Cranksets of type: Apex, Rival, Force, and RED in the 165mm size.

 

[BentAero]

Be advise I checked on those; the back of your crank has to be flat to use those; the strain gauges install on the back face of the crank and it has to be flat; it won't work on concave cranks. So far my conclusion has been that to use sub 165mm cranks and a power meter you need a pedal based solution until power tapes ships their "C1" solution. And the C1 only works with round rings.

From watteam.com faq page:
Is POWERBEAT compatible with Rotor 3D+ cranks (like 160, 165 mm)?
Yes, POWERBEAT can be calibrated to work with all crank types.
I have a carbon crank; will I have to replace it?
POWERBEAT is an add-on power meter, which means you won’t need to replace any of your favorite bike parts. It works with both carbon and aluminum cranks.

From watteam.com/benefits:
"...without having to replace a single component on your bike."

"Installation requires no technical knowhow – only the pedals needs to be removed. Simply follow the video tutorials on the app and you shall be done in less than 30 minutes. The only catch is that the sensors need to dry for 24 hours after they’re glued."

I can't find anything on their site about the crank needing a flat surface, nor do the photos of the sensor installed appear that it needs anything other than a common thread-on pedal.
"...calibrated to work with all crank types." -is a pretty strong statement.
What am I missing?

 

[ratz]

I can't find anything on their site about the crank needing a flat surface, nor do the photos of the sensor installed appear that it needs anything other than a common thread-on pedal.
"...calibrated to work with all crank types." -is a pretty strong statement.
What am I missing?

They have a Strain gauge that has to be on the crank; then they use pedal pods like Garmin for the electronics. All those strain gauges get glued on to a flat and level surface. Usually that's on the back side of the crank. If that was the only spot then for example APEX cranks wouldn't work. .....But..... I did remember seeing a photo of them mounting on the top edge of the arm I just couldn't find it until now. Here it is
http://www.dcrainmaker.com/2014/09/watteams-powerbeat-prototypebeta.html

That's gotta be a heck of good gauge to measure on the strongest/stiffest dimension of the crank like that. Also look like you can put the gauges on multiple bikes and just move the pods. Not sure about that wire though if you decided without the pods.

 

[hamishbarker]

the most extreme fibre of a beam (i.e. the part of the beam furthest from the centreline) is the one with the largest strain. Measuring where the strain is largest makes sense to me, because then the signal to noise ratio will be best. Where they glued it in the DC rainmaker video makes sense in that regard, but is exposed to impacts etc in a way that ones glued to the rear of the crank are probably not.

A crank is probably partly a beam and partly a torque member. Don't know if the strains from the beam action ( the crank is "fixed" at the BB and the load is cantilevered from there to the point load at the pedal threads 165-175mm away from the BB) or the torque action ( the load on the pedal is circa 50mm out along the pedal shaft, twisting the crank when it is at 3 and 9 oclock, but bending it when at 12 and 6 oclock are larger.

One could probably glue the gauge anywhere in the middle of the crank, calibrate it at 3, 6 9, and 12 oclock and then be able to calculate the force at any point.

The watt team boxes probably also include accelerometers to sense where the pedal is in the circle in order to be able to sense what forces are radial (along the long axis of the pedal , such as when standing on a pedal remaining at 6 oclock) since they do nothing to produce chain tension (useful force) and what forces are tangential (pushing the pedals around).

 

[BentAero]

Disappointing news from Watteam.
A week ago, DC Rainmaker reported that Watteam's Powerbeat first release this winter would not be Carbon crank compatible. Also, the initial production which is calibrated by their own App showed 165mm as being the shortest crank option available. Uh-oh...

Today the company sent emails to everyone who was registered on their site on how to 'get in line' for the first batch. Next red-flag was this sentence in the press release-email: “POWERBEAT 1.0 for hollow aluminum cranks will be released in the end of the month. The public announcement will be made today as well.”

Did you catch that word hollow? Uh-oh #2

I replied to Ofir's (Ofir Gal On, Founder & CEO) email with the following question: “Ofir, I use Sram Apex cranks shortened to 155mm.
They aren’t hollow, (can’t redrill hollow cranks) and the preliminary app doesn’t show length shorter than 165.
Am I precluded from using power beat?”

He replied to me: “Yep… sorry but at the moment this is correct.
We’ll keep you posted for changes
Thanks”

That's a deal-breaker.

Can’t begin to describe how disappointed I am. Like everyone else, been waiting nearly a year for a (quote from website) “Supports all aluminum & carbon crank types.” meter, only to have them backpedal (sorry!) on fitment. First we lost carbon, now we’ve lost non-hollow aluminum cranks.
I’m sure it’s just growing pains and they’ll get it figured out eventually, but it doesn’t sound like it will work for me anytime soon.

 

[mzweili]

First we lost carbon, now we’ve lost non-hollow aluminum cranks

From an engineering point of view it's understandable. As I see, their powermeter measures the deflection of the crank (elongation of the outer fiber). Probably the deflection of carbon- and solid aluminum cranks is too small to give a reliable measurement. That is the risk with R&D products, they sometimes do not behave as expected.

 

[ratz]

Ergo for Short cranks it's a power-tap hub or P1 Pedals