On Feb 27, 7:06 pm, Dan Connelly <d_j_c_o_n_n_e_l@y_a_h_o_o_._c_o_m>
wrote:
> [email protected] wrote:
> > On Feb 27, 4:04 pm, Dan Connelly <d_j_c_o_n_n_e_l@y_a_h_o_o_._c_o_m>
> > wrote:
> >> Which is better?
> >> (approx same price)
>
> > It seems like the Ergomo measures only the left side and extrapolates
> > the right. That seems unfortunate to me.
>
> > Joseph
>
> I agree. Some data posted to the wattage lists on google groups... pedaling
> left leg only results in more than double the reading from PowerTap. Since
> left-right balance can vary for a variety of reasons, this is a real weakness of
> the Ergomo:
> -------------------------
>
> PT Ergomo diff diff DE* %error Ergomo v PT
> 1* 145 58 87 29 150.00%
> 2* 186 81 105 24 129.63%
> 3* 192 91 101 10 110.99%
> 4* 239 97 142 45 146.39%
> 5* 288 124 164 40 132.26%
>
> 6 96 109 -13 -11.93%
> 7 118 133 -15 -11.28%
> 8 141 143 -2 -1.40%
> 9 165 160 5 3.13%
> 10 180 182 -2 -1.10%
> 11 216 211 5 2.37%
> 11 236 228 8 3.51%
> 12 256 245 11 4.49%
>
> * = pedaling left leg only
> DE* = difference of power for single leg reading on Ergomo doubled
> compared to PT
It is unfortunate that all of these systems have either one glaring
flaw, or tie you in to a single specific (expensive) component.
If I knew more about embeded programming I'd think about trying to
roll my own. I'd like to use force sensors in my shoes, and then based
on wheel speed, cadence, and calibrated crank length I could figure
out the power. If I did something like that I'd be limited by having
to use a full fledged system like Linux, while somebody who knew what
they were doing could program a chip to do it. This way the system
would be accurate (ideally at least) and would not be dependant upon
any one component, so it could be used on multiple bikes with multiple
wheels, cranks, etc.
I wonder if you could get reasonable readings with sensors like these
sadwiched between the shoe and cleat:
http://www.tekscan.com/flexiforce/specs_flexiforce.html
Joseph
