iBike Power sensor

[Wheelsuck]

Windbreaker: What was wrong with the Polar stuff? I was asking Mother Xmas for a Polar Power sensor and cadence meter, now looks like I wil have do a christmas list recall.   

[bruce]

 

really don't know as much as bruce / bikemax on the subject' date='  but i have been doing a fair amount of reading on powermeters as i want to be well informed before i put my money down.

 

i really cant see how the iBike can be equal to the ergomo / srm / powertap.  there is just way to many variables to consider. 

 

what happens when you go on a long downhill for example? 

 

your normal polar HR monitor will still register your HR as high because of your heartrate lag after the big climb,  the ergomo / srm / powertap should not register any power because you are not doing any pedaling so you are in true fact not doing any work,  the iBike will for sure register some impressive power as you are now going @ 80 - 90 km/h!

 

i think that with the iBike you will only be toying with the idea of power training,  but with the others you will be doing it seriously.

 

 

[/quote']

 

The iBike has an accelerometer and an altitude sensor.  If know that the force that is making you move is gravity, and when that force balances wind resistance it knows that you are not pedalling.

 

As an engineer - I think it is a really clever piece of equipment.  My concern about it is with regards to some of the assumptions made e.g. the wind speed at the handlebars is the same as the wind speed hitting your upper torso when riding in a bunch.

 

[nikki]

Will riding in windy and humid condions  like at the coast affect the reliability the power readings?

[BikeMax]

 

 

Bottom line - it has serious flaws. Too many variables to deal with. I'd be pleasantly surprised if the iBike turns out to be as accurate as the Polar even. 

The PowerMeters that Hunter Allen was comparing it to' date=' and found it "damn close to my other power meters." was actually SRM & PowerTap... not to bad for a flawed little thingy with too many variables to deal with... [/quote']

 

What does "damn close" mean ? - the comparisons that I have seen have shown the overall data, particularly the NP to be significantly out if there have been any spikes caused by misreadings of any sort - a short spike in a power file causes mayhem in the overall analysis of NP/IF & TSS

 

The fact that the frontal area is estimated means that if you change position (and as such change frontal area) then you need to recalibrate in that new position..

 

On top of that, in a bunch the unit is flawed due to the change in wind resistance caused by the draft..

 

Then there is the problem with using it on a TT bike due to the airflow change caused by the TT position..

 

It is always good to see new products that encourage people to train with power, but IMO to compare a device that estimates power (and with significant margin for error) to a device such as PT or SRM that actually measures power is a big mistake.

 

It is a fine device as long as you are happy with it's shortcomings and are prepared to pay as much as a PT for the unit.

 

[101%]

But wouldn't a strong cross wind affect the readings .

[Marius]

wonder what they were smooking when they came up with  the whole concept of the iBike PowerMeter, I mean you just don't come up with somehting like that, it had to be GoodSh*t!!!

[bruce]

 

Will riding in windy and humid condions  like at the coast affect the reliability the power readings?

 

THe iBike will use a standard value for air density etc so any changes from that value will cause errors.  The magnitude of those errors should be fairly small though at cycling speeds.

 

They probably use the values at sea-level, so it would be at altitude that there might be errors.

 

[101%]

wonder what they were smooking when they came up with  the whole concept of the iBike PowerMeter' date=' I mean you just don't come up with somehting like that, it had to be GoodSh*t!!![/quote']

 

They've invented gadgets that can cut a piece of hair into a 1000 pieces ...so why not.

[bruce]

 

But wouldn't a strong cross wind affect the readings .

 

Theoretically it shouldn't.  If you break the cross wind up into vectors then it would be measuring the equivalent of a lighter headwind.

 

If the wind speed sensor becomes sheltered - e.g. if you put it on the bars of a TT bike and your arms shelter the unit, then errors would definitely occur.

 

[bruce]

 

wonder what they were smooking when they came up with  the whole concept of the iBike PowerMeter' date=' I mean you just don't come up with somehting like that, it had to be GoodSh*t!!![/quote']

 

They've invented gadgets that can cut a piece of hair into a 1000 pieces ...so why not.

 

101% plays with serious lasers - I reckon there is some good sh!t there!!

 

[101%]

let say:

 

You where riding on a flat rode at 15km/h at the same wind intake as ......lets say 15km/h up 7% gradient climb ..how the hell does it no you climbing and that your power usage has just doubled.

[Marius]

wonder what they were smooking when they came up with  the whole concept of the iBike PowerMeter' date=' I mean you just don't come up with somehting like that, it had to be GoodSh*t!!![/quote']

 

They've invented gadgets that can cut a piece of hair into a 1000 pieces ...so why not.

101% plays with serious lasers - I reckon there is some good sh!t there!!

 

Well said!

[Dr. Seuss]

 

let say:

 

You where riding on a flat rode at 15km/h at the same wind intake as ......lets say 15km/h up 7% gradient climb ..how the hell does it no you climbing and that your power usage has just doubled.

 

the little hamster inside is telling it so!

 

 

 

[bruce]

 

 

let say:

 

You where riding on a flat rode at 15km/h at the same wind intake as ......lets say 15km/h up 7% gradient climb ..how the hell does it no you climbing and that your power usage has just doubled.

 

It calculates power using the following:

1. It has an accelerometer, which calculates the force you are applying to accelerate.

2. It has a wind speed sensor, which is uses to calculate the force you are applying to overcome wind resistance.

3. It has an altimeter, which is uses to calculate changes in altitude and hence work out what the gradient is that you are riding on.  Either positive or negative depending on whether you are going uphill or downhill.  Using your body mass, it works out what force you muct be applying to overcome gravity.

 

Using all of these sensors it calculates what your power output should be to overcome all of these forces.  This is the criticism.

 

[Droster_Renoster]

Bruce

 

Surely the other products also CALCULATES your power output, they just use other inputs? Do you have any specifics available on how the polar unit calculates power?

[domenic]

The iBike is calibrated by coasting from a fixed speed. It measures the incline so it does not matter what the gradient is.

So if you want to use it for TT's you calibrate it using a TT position, for sea level you calibrate at sea level, for altitude you calibrate at altitude. It only becomes less accurate when you use it in circumstances other than what you calibrated for.

It is a sofisticated power calculating device based on measured parameters. The fears about it not being accurate are largely unfounded.

The only two real problems, for me, are that its measuring becomes compromised on corrugated roads, and that cannot work on an indoor trainer.