For the future...

rob of the og

The hac4 gets (rightly imo) written off lightly here, but it did get me thinking about how far away calc'ed/estimated power measurement might be from accuracy:

hac4 measures velocity and gradient, and compares this with an entered value for total weight of athlete + machine (and a load of estimated values for wind resistance and surface type - which is where it's accuracy crumbles)

surely it's not beyond the realms of possibility to add a front-mounted wind velocity measuring-thingy (worked back to head/tail wind speed by comparing with actual speed and a drag co-efficient), and a 'shaker' to work out energy lost to the ground. Both of these are related to speed by equations so power losses from each can be quantified. The only thing left then is the drag co-efficient of the rider + machine, but this can be iterated by comparing the changes in speed and recorded wind velocity to slight changes in gradient, via the equations of aerodynamics.

er, perhaps I should do some work this afternoon instead

beerco

Won't work. the HAC uses an built in estimate for CdA to calculate power. With only one equation of motion, you cannot solve for both Power and CdA....Math.