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-   -   Tandem Power Measurement (http://www.bikeforums.net/tandem-cycling/582309-tandem-power-measurement.html)

rdtompki 09-06-09 09:58 PM

Tandem Power Measurement
 
Any info out there in BF land on options available for tandem power measurement (wireless) that would be compatible with a Garmin (ANT+)? I looked on the Saris website and nothing jumped out that appeared to be compatible with a rear-disc equipped, 145mm spacing tandem.

andyman 09-07-09 09:07 AM

I have not tried it, but it seems the iBike Power meter should work with your Garmin 705 Edge. The following link might be useful.
http://www.worldcycles.com/index.htm...rget=d184.html

Alex & Deya 09-08-09 02:07 PM

rdtompki,

andyman is correct, we use the iBike with a 705 for the stoker to see realtime power, the set up works great.

mburchard 09-08-09 02:42 PM

Quote:

Originally Posted by rdtompki (Post 9627076)
Any info out there in BF land on options available for tandem power measurement (wireless) that would be compatible with a Garmin (ANT+)? I looked on the Saris website and nothing jumped out that appeared to be compatible with a rear-disc equipped, 145mm spacing tandem.

Cinqo(s) could probably be rigged up.

I don't think anyone in the TdF is using an iBike to measure power. SRM, Cinqo, and Powertap are the only real options for those guys.

Alex & Deya 09-08-09 09:20 PM

Quote:

Originally Posted by mburchard (Post 9636788)
Cinqo(s) could probably be rigged up.

I don't think anyone in the TdF is using an iBike to measure power. SRM, Cinqo, and Powertap are the only real options for those guys.

I don't see any tandems on the tour. Rick is asking about options for a tandem. We actually have experience with all types of power meters and we found that the iBike works without having it "rigged up" plus the iBike is about half the cost and not just "probalily" may work, we know it works on a tandem.

Hermes 09-09-09 10:47 AM

Both my wife and I train and race with power on our single bikes. We considered the Ibike a couple of years ago and passed. We use both the Quarq Cinqo and PowerTap with a Garmin 705. I thought about using the Ibike for the tandem. Since we have not been riding the tandem much this summer it fell off the radar screen. I think everyone is familiar with Ibike's shortcomings. I can see how it could be of some value on the tandem. Speaking for myself, once you train with power, one gets good at estimating power based upon perceived effort. Obviously, not very accurate and on a tandem there are two people coordinating their effort. I can see how an Ibike feeding both Garmin 705s could add some value.

There is a new power meter coming out next year. Here are some details.

"Clark Foy of San Jose Bike Club has invented a new powermeter. It's
a bunch of accelerometers, stuffed into the hollow pedal spindle of a
Speedplay pedal. Not only does it yield power information measured
directly, it also measures left/right, and in each of the pedal circle
quadrants, so that feedback can be incorporated to improve
efficiency. It's wireless, and communicates to existing "head" units
which use the ANT protocol, which most use. Garmin is one such unit;
there are close to 10 brands that could work.

There are computer chips inside which are electrically reprogrammable,
so as the algorithms improve, the pedals can get "software upgraded".

Retail price will be something like $899, which includes the pedals
($200 retail price). You'll need to purchase one of the head units
separately, like a Garmin.

Product will be launched at Interbike, early production late Q4'09,
broader distribution in Q1'10."


This looks interesting for the tandem. When I first heard about this, I thought tandem and track. Speedplays are fine for tandem but I would not use them on the track.

I can see it now. Go out for a tandem ride and then download the individual power data to Training Peaks and let the discussion begin.:D

merlinextraligh 09-09-09 10:55 AM

I have a Powertap (that doesn't see much use these days) and a Quarq/705 setup for my single bikes.

One problem with riding the tandem a lot, without a power meter is that it throws off tracking the cummulative matrices in Cycling Peaks. Hence, I would love a power meter that gives the power for both riders on the Tandem.

We thought about the I Bike, but in addition to the setup, and extrapolation issues, it wouldn't solve my problem of getting the Captain's only power.

Perhaps a Quarq for the captain, and a I bike? You'd need a crank, with a removable spider. I don't see an intrinsic reason you couldn't run an FSA Team issue, set up backwards, with some locktite on the pedal threads.

Also, there was a guy on here that had a tandem set up with dual SRM's. Rather pricey, but it was for a study presumably supported by a grant.

merlinextraligh 09-09-09 11:02 AM

Quote:

Originally Posted by Hermes (Post 9642066)

There is a new power meter coming out next year. Here are some details.

"Clark Foy of San Jose Bike Club has invented a new powermeter. It's
a bunch of accelerometers, stuffed into the hollow pedal spindle of a
Speedplay pedal. Not only does it yield power information measured
directly, it also measures left/right, and in each of the pedal circle
quadrants, so that feedback can be incorporated to improve
efficiency. It's wireless, and communicates to existing "head" units
which use the ANT protocol, which most use. Garmin is one such unit;
there are close to 10 brands that could work.

There are computer chips inside which are electrically reprogrammable,
so as the algorithms improve, the pedals can get "software upgraded".

Retail price will be something like $899, which includes the pedals
($200 retail price). You'll need to purchase one of the head units
separately, like a Garmin.

Product will be launched at Interbike, early production late Q4'09,
broader distribution in Q1'10."



This sounds similar in concept to the Brim Brothers shoe based system. http://www.brimbrothers.com/

However, they've had trouble apparently with working it all out.

One problem would appear to be how the meter measures force in the up stroke, which would likely be a similar problem for the pedal based system.

I hope the Speedplay system makes it to production.

[Edit] actually reading it, it appears its a different system based on acceleromaters, not, pressure on the pedals.

Alex & Deya 09-09-09 10:14 PM

Quote:

Originally Posted by Hermes (Post 9642066)
Both my wife and I train and race with power on our single bikes. We considered the Ibike a couple of years ago and passed. We use both the Quarq Cinqo and PowerTap with a Garmin 705. I thought about using the Ibike for the tandem. Since we have not been riding the tandem much this summer it fell off the radar screen. I think everyone is familiar with Ibike's shortcomings. I can see how it could be of some value on the tandem. Speaking for myself, once you train with power, one gets good at estimating power based upon perceived effort. Obviously, not very accurate and on a tandem there are two people coordinating their effort. I can see how an Ibike feeding both Garmin 705s could add some value.

There is a new power meter coming out next year. Here are some details.

"Clark Foy of San Jose Bike Club has invented a new powermeter. It's
a bunch of accelerometers, stuffed into the hollow pedal spindle of a
Speedplay pedal. Not only does it yield power information measured
directly, it also measures left/right, and in each of the pedal circle
quadrants, so that feedback can be incorporated to improve
efficiency. It's wireless, and communicates to existing "head" units
which use the ANT protocol, which most use. Garmin is one such unit;
there are close to 10 brands that could work.

There are computer chips inside which are electrically reprogrammable,
so as the algorithms improve, the pedals can get "software upgraded".

Retail price will be something like $899, which includes the pedals
($200 retail price). You'll need to purchase one of the head units
separately, like a Garmin.

Product will be launched at Interbike, early production late Q4'09,
broader distribution in Q1'10."


This looks interesting for the tandem. When I first heard about this, I thought tandem and track. Speedplays are fine for tandem but I would not use them on the track.

I can see it now. Go out for a tandem ride and then download the individual power data to Training Peaks and let the discussion begin.:D

Hermes, you should give the iBike a try on your tandem, we also ride and train with power on our singles, and we've compared the numbers with the power tap and the Gen 3 iBike, the power numbers are almost identical! (the iBike of 2 years ago is not at all as good as the new Gen 3) You'll be surprise how much you can use power on the tandem, as you mentioned one gets good at estimating power based upon perceived effort, so we know how endurance power zone feels on our single and is not different on the tandem, all of our training on the tandem is with power and it really works. We have a combined FTP for the tandem, we got it by doing FTP tests and the numbers came almost identical to our individually FTP numbers (Adding the FTP of the two of us).

mburchard 09-10-09 08:33 AM

Quote:

Originally Posted by Alex & Deya (Post 9639263)
I don't see any tandems on the tour. Rick is asking about options for a tandem. We actually have experience with all types of power meters and we found that the iBike works without having it "rigged up" plus the iBike is about half the cost and not just "probalily" may work, we know it works on a tandem.

You missed the point. I think crank-based power meter options are probably possible on a tandem, and if so would be a superior solution to an iBike (assuming $$ not an issue for you). Of course you would need two head units too, maybe pair captain with stoker power, and stoker with captain, to have some fun!

rdtompki 09-10-09 08:55 AM

On our Davinci we would need identical crank-based power measurement units each of which needs to support a single, 36t chainring (on the left side). This is probably too expensive a solution given we're never going to race, but intriguing nevertheless. A better solution might be a Powetap hub for our single bikes which have identical 12-27 cassettes. I will look into the iBike as well. It appears it may develop useful information at a reasonable price, but I certainly wish the website were more forthcoming about the nature of the algorithms used short of revealing any of their precious IP.

Hermes 09-10-09 03:13 PM

Quote:

Originally Posted by Alex & Deya (Post 9646697)
Hermes, you should give the iBike a try on your tandem, we also ride and train with power on our singles, and we've compared the numbers with the power tap and the Gen 3 iBike, the power numbers are almost identical! (the iBike of 2 years ago is not at all as good as the new Gen 3) You'll be surprise how much you can use power on the tandem, as you mentioned one gets good at estimating power based upon perceived effort, so we know how endurance power zone feels on our single and is not different on the tandem, all of our training on the tandem is with power and it really works. We have a combined FTP for the tandem, we got it by doing FTP tests and the numbers came almost identical to our individually FTP numbers (Adding the FTP of the two of us).

Thanks for the info. We will look into it.

WebsterBikeMan 09-11-09 07:32 AM

Quote:

Originally Posted by rdtompki (Post 9648413)
On our Davinci we would need identical crank-based power measurement units each of which needs to support a single, 36t chainring (on the left side). This is probably too expensive a solution given we're never going to race, but intriguing nevertheless. A better solution might be a Powetap hub for our single bikes which have identical 12-27 cassettes. I will look into the iBike as well. It appears it may develop useful information at a reasonable price, but I certainly wish the website were more forthcoming about the nature of the algorithms used short of revealing any of their precious IP.

While it may be somewhat out of date, they do have several patents, which, by their very nature, reveal their "precious IP". If you look up the company name at the bottom of the web site, then go look for patents with that assignee name, there are only three hits (possibly more applications not yet issued, I didn't look). Now the patent describes what they were envisioning when the patent was written, and not necessarily what they wound up doing, but it would appear that they use a MEMS accelerometer and calculated acceleration (from the wheel sensor) to compute actual acceleration and tilt. They also use two air pressure sensors, one with a port facing forward and another to the side to measure wind speed (this isn't right, but the error could probably be calibrated out). The main remaining input is cadence, measured conventionally. Optional other measurements include altitude and temperature, which appear to be used either to improve accuracy in other measurements or to fine tune things. A roll-down calibration followed by a curve fit allows a measurement of rolling resistance and air resistance. Pretty much the rest is a matter of math.

To the original question, as far as I can tell, since there's no crank or pedal based pressure sensor, you can only get total power, so if you're looking for something tandem-specific, you're not really getting it here. You can compute the total power, but you can't separate captain from stoker. If that's what you're looking for.

rdtompki 09-11-09 09:08 AM

Quote:

Originally Posted by WebsterBikeMan (Post 9654711)
...but it would appear that they use a MEMS accelerometer and calculated acceleration (from the wheel sensor) to compute actual acceleration and tilt. They also use two air pressure sensors, one with a port facing forward and another to the side to measure wind speed (this isn't right, but the error could probably be calibrated out). The main remaining input is cadence, measured conventionally. Optional other measurements include altitude and temperature, which appear to be used either to improve accuracy in other measurements or to fine tune things. A roll-down calibration followed by a curve fit allows a measurement of rolling resistance and air resistance. ...

Thanks for the information. You're describing what I would envision their approach. Devil is in the details in terms of how the various measurements are combined, weighted, filtered ,etc. It's surprising that their website is more of the "trust me" variety. When I get some time I'll look up the patents; might be interesting.

masiman 09-12-09 05:25 PM

If you have some extra cash laying around you could try this out.

SRM Dura Ace

Hermes 09-12-09 08:42 PM

Quote:

Originally Posted by masiman (Post 9663680)
If you have some extra cash laying around you could try this out.

SRM Dura Ace

Cash is always and issue but the SRM solution is not that straight forward. You need a timing chain on the captain and stoker cranks and typically a triple. I suppose one could be motivated and have some special work done on the SRMs to make it work.

I think the Ibike is great or hopefully a pedal based system that will still be expensive but will also work on the road bikes.

And if I were going to use a crank based system and figure out a way to "make it work", I would use the Quarq. We have this technology on road bikes and it works well for less money than an SRM.

masiman 09-14-09 10:40 AM

Quote:

Originally Posted by Hermes (Post 9664666)
Cash is always and issue but the SRM solution is not that straight forward. You need a timing chain on the captain and stoker cranks and typically a triple. I suppose one could be motivated and have some special work done on the SRMs to make it work.

I think the Ibike is great or hopefully a pedal based system that will still be expensive but will also work on the road bikes.

And if I were going to use a crank based system and figure out a way to "make it work", I would use the Quarq. We have this technology on road bikes and it works well for less money than an SRM.

I posted more for the gee whiz of look how much this stuff costs. I was pretty sure that cheaper solutions were available.

I like seeing the power output from other people. I know my power will be similar and I get that information for about zero cost :thumb: :)

Good luck with it. I'd like to see progression numbers over a training season.

This was a good read on the subject.

Hermes 09-14-09 11:13 AM

Quote:

Originally Posted by masiman (Post 9672060)
I posted more for the gee whiz of look how much this stuff costs. I was pretty sure that cheaper solutions were available.

I like seeing the power output from other people. I know my power will be similar and I get that information for about zero cost :thumb: :)

Good luck with it. I'd like to see progression numbers over a training season.

This was a good read on the subject.

A better read is Training and Racing with a Power Meter by Allen and Coggan. Training with power is much more than "knowing" your power or being able to say I produce X watts. It is about hitting power numbers that are meaningful to you over discreet periods of time to improve VO2 Max and Threshold Power as well as others. Downloading individual power numbers into Training Peaks Software and tracking progress becomes very meaningful and motivating. Post ride analysis leads to incite on how to increase performance. This benefit even makes the SRM cost justifiable. The question becomes how many power meters can one have and which bikes to equip to have it make sense when you are paying the cost. For us, we do not ride the tandem enough to justify yet another power meter solution.

If a pedal based power solution becomes available that will work for the track, I would get two setups. Then I could easily swap pedals to the tandem and effectively set up the equivalent of four bikes with power. And BTW, the current SRM solution for a track bike is 3700 Euros if you are looking for a gee whiz factor.:rolleyes:

masiman 09-14-09 11:29 AM

Quote:

Originally Posted by Hermes (Post 9672260)
And BTW, the current SRM solution for a track bike is 3700 Euros if you are looking for a gee whiz factor.:rolleyes:

That is significantly more than the ~$3800 for the NIB Dura-Ace.

I'll just leech for the next decade or so :innocent: :)

merlinextraligh 09-14-09 11:30 AM

Quote:

Originally Posted by Hermes (Post 9664666)
And if I were going to use a crank based system and figure out a way to "make it work", I would use the Quarq. We have this technology on road bikes and it works well for less money than an SRM.

I sent an email to Quarq, and asked if they were aware of any tandem compatible cranks that would work with a Quarq. I haven't gotten a response yet.

I'm betting you could use any of the Quarq cranks now available turned backwards for the captain's crank, and etiher get the pedal threads redone, or use locktite.

Stoker's crank might be more problematic.

Alex & Deya 09-14-09 11:45 AM

Quote:

Originally Posted by Hermes (Post 9672260)
A better read is Training and Racing with a Power Meter by Allen and Coggan. Training with power is much more than "knowing" your power or being able to say I produce X watts. It is about hitting power numbers that are meaningful to you over discreet periods of time to improve VO2 Max and Threshold Power as well as others. Downloading individual power numbers into Training Peaks Software and tracking progress becomes very meaningful and motivating. Post ride analysis leads to incite on how to increase performance. This benefit even makes the SRM cost justifiable. The question becomes how many power meters can one have and which bikes to equip to have it make sense when you are paying the cost. For us, we do not ride the tandem enough to justify yet another power meter solution.

If a pedal based power solution becomes available that will work for the track, I would get two setups. Then I could easily swap pedals to the tandem and effectively set up the equivalent of four bikes with power. And BTW, the current SRM solution for a track bike is 3700 Euros if you are looking for a gee whiz factor.:rolleyes:

Hermes, You are perfectly correct. Most people believes that a power meter is just used to do your workouts or just see your power during the ride, but as most of us that really train with power know that one of the most important aspects of power is the ability to analyze you ride after and keep a real track of your efforts and the amount of stress your body is enduring day by day, week by week and over a whole season, allowing you to train and recover correctly, also the ability to measure your fitness and build a power profile over time. Having a power meter on our tandem stills allow us to get TSS and IF for the rides that we do on tandem, this keeps our data power data without gaps on TSS and IF and really allows us to maximize our training. One of the things we've learned on a tandem is that you are only as good as you are as a team (the two of you). So having the ability to see individual power on the tandem is good, but you are still connected and it is really is one machine with two engines that need to ride as one and at the end of the ride combined power still is going to be super important.

Hermes 09-14-09 11:46 AM

Quote:

Originally Posted by masiman (Post 9672344)
That is significantly more than the ~$3800 for the NIB Dura-Ace.

I'll just leech for the next decade or so :innocent: :)

That is because the track market is small and SRM only makes their "top of the line" Scientific version for fixed gear.

Phantoj 09-14-09 01:42 PM

I would guess the cinqo/SRM would have to be specially calibrated to work with the reverse torque.

mrfish 09-14-09 04:24 PM

Yes, reverse torque is important, particularly on the track.

IIRC I have heard that you can't use an ordinary bike powermeter backwards on the tandem because powermeters are set up to read zero when they see reverse power. For example if you freewheel down a hill then pedal backwards really fast you should see 5 or 10 Watts negative power. My bet is that you don't because it would look confusing so easier to drop the data.

Hermes 09-18-09 09:28 AM

Pedal based power meter...pics from Interbike courtesy of Google wattage group.

Some photos from the pre-Interbike open house:

Information sheet, page 1:
http://www.flickr.com/photos/djconnel/3930884632/

Information sheet, page 2:
http://www.flickr.com/photos/djconnel/3931039857/

Blow-up from wall poster:
http://www.flickr.com/photos/djconnel/3930768660/

Souvenir water bottles :):
http://www.flickr.com/photos/djconnel/3930768710/


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