Power sensors & tandems

[Windbreaker]

I've got plans to do quite a bit of tandem riding in the coming months but this threatens to disrupt my training program (even more) in that I will have no data for the tandem rides.

 

So I've been thinking ... .

 

The Polar Power sensor theoretically could work on the timing chain. I'd have to make up ugly brackets again including one for the chain speed sensor which usually fits to the rear derailleur. But I guesss that should be more accurate than a normal installation as it doesn't have the cassette / chainring combinations to deal with. 

 

And the ErgoMeter could also be used I guess?

 

Anyone see any problems with either option before I start sensitising my wife to the prospect of spending more money on "toys".

[BikeMax]

 

I've got plans to do quite a bit of tandem riding in the coming months but this threatens to disrupt my training program (even more) in that I will have no data for the tandem rides.

 

So I've been thinking ... .

 

The Polar Power sensor theoretically could work on the timing chain. I'd have to make up ugly brackets again including one for the chain speed sensor which usually fits to the rear derailleur. But I guesss that should be more accurate than a normal installation as it doesn't have the cassette / chainring combinations to deal with. 

 

And the ErgoMeter could also be used I guess?

 

Anyone see any problems with either option before I start sensitising my wife to the prospect of spending more money on "toys".

 

Interesting one this - Adrian and I discussed it recently - the problem is that due to the two riders and the timing chain it is tough or even impossible to get a direct accurate reading of both riders power.

 

If you put an ergomo or an SRM at both cranks then the front one would read accurateley for the front rider but the rear one would read the power for both front and back combined - so you would need to subtract front power from back power reading to get a figure for the stoker.

 

Same issues I would imagine with any device due to the different loads through the front and back cranks via the timing chain.

 

I would just estimate TSS for the tandem rides based on a hard L3 ride for that duration.

 

[Cruxpearl]

Ergomo only works with ISIS Cranksets

Polar will be very finicky to set up with Triple Chainring configuration...

iBike???

 

 

[domenic]

 
If you put an ergomo or an SRM at both cranks then the front one would read accurateley for the front rider but the rear one would read the power for both front and back combined - so you would need to subtract front power from back power reading to get a figure for the stoker.

True for the Ergomo, but the SRM surely only measures the crank power?

[BikeMax]

 

Ergomo only works with ISIS Cranksets

Polar will be very finicky to set up with Triple Chainring configuration...

iBike???

 

 

]

 

IBIke is not going to work - the unit on the front will estimate power using CDA of front rider only (as this is all the wind sees) while the rear unit will see no wind and estimate incorrect power as well.

 

Got shares in it Crux ?

 

[Windbreaker]

I've got plans to do quite a bit of tandem riding in the coming months but this threatens to disrupt my training program (even more) in that I will have no data for the tandem rides.

 

So I've been thinking ... .

 

The Polar Power sensor theoretically could work on the timing chain. I'd have to make up ugly brackets again including one for the chain speed sensor which usually fits to the rear derailleur. But I guesss that should be more accurate than a normal installation as it doesn't have the cassette / chainring combinations to deal with. 

 

And the ErgoMeter could also be used I guess?

 

Anyone see any problems with either option before I start sensitising my wife to the prospect of spending more money on "toys".

Interesting one this - Adrian and I discussed it recently - the problem is that due to the two riders and the timing chain it is tough or even impossible to get a direct accurate reading of both riders power.

If you put an ergomo or an SRM at both cranks then the front one would read accurateley for the front rider but the rear one would read the power for both front and back combined - so you would need to subtract front power from back power reading to get a figure for the stoker.

Same issues I would imagine with any device due to the different loads through the front and back cranks via the timing chain.

I would just estimate TSS for the tandem rides based on a hard L3 ride for that duration.

 

I'm only interested in the front riders power. I can probably get my hands on a Polar to test if it is feasible.

[BikeMax]

 

 

If you put an ergomo or an SRM at both cranks then the front one would read accurateley for the front rider but the rear one would read the power for both front and back combined - so you would need to subtract front power from back power reading to get a figure for the stoker.

True for the Ergomo' date=' but the SRM surely only measures the crank power?

[/quote']

 

Yes it does measure at the crank, but due to the timing chain, the power at the crank of the rear rider will also include the power output of the pilot - don't forget that the rear wheel is putting down the power from both riders and this is transmitted through the timing chain from front to back.

 

I did find this slightly confusing but did check it with SRM and they confirmed this to be the case.

 

[Windbreaker]

Ergomo only works with ISIS Cranksets

Polar will be very finicky to set up with Triple Chainring configuration...

iBike???

 

 

Nope, iBike would measure the combined power for both riders and even if that was the goal is still not a good solution as it would require calibration for each different rider combo.

 

The Polar would be measuring from the timing chain so the triple chainring thing is not an issue. 

[bruce]

 

Ergomo only works with ISIS Cranksets

Polar will be very finicky to set up with Triple Chainring configuration...

iBike???

 

 

 

Ergomo works with both ISUS and square taper (ISO).  Does not work with external bearing BB's e.g. Shimano hollowtech, mega-exo etc.

 

[BikeMax]

 

Ergomo only works with ISIS Cranksets

Polar will be very finicky to set up with Triple Chainring configuration...

iBike???

 

 

Nope' date=' iBike would measure the combined power for both riders and even if that was the goal is still not a good solution as it would require calibration for each different rider combo.

 

The Polar would be measuring from the timing chain so the triple chainring thing is not an issue. 

[/quote']

 

I am not convinced that the timing chain will give you pilots power alone in an accurate manner as you may find some bleed over from the stokers chainset ? Get rid of the third chainring and mount on the main chain maybe ?

 

Bruce will be able to give you an "informed" opinion on the logic of measuring from the timing chain.

 

[bruce]

For true power of both riders you could mount SRM/Ergomo on the front, then either SRM/Ergomo or a PT on the rear wheel.  Then when the readings are downloaded, use excel to subtract the pilots power from the rear power - this will give you the stokers power output contribution.

[Guest Michelle]

...while the rear unit will see no wind and estimate incorrect power as well.

 

that's if you're lucky