Just out of interest......how does BKool actually calculate your power?
Power is just a straight calculation from speed and resistance.
Power is force times speed. Force is the force you are applying to overcome the trainers resistance, in an equal and opposite Newtonian kind of way.
Since there is no power meter in the Bkool units, the actual resistance being applied must be presumed to be the same as the software requests. Clearly, there will be variations between bkool units when a certain resistance level is requested electronically as to what actual resistance is applied, and this will vary anyway depending on the speed of the roller.
Anyway, presuming a certain level of resistance, power can be calculated from that resistance and the speed of the roller.
Weight, wind, rolling resistance, etc. are not factors in the power being produced, power is just force times speed.
On a trainer there is no gravity, wind or indeed movement along the road, but in the real world they do factor in the resistance, and hence affect the the power required to achieve a speed, as they affect the resistance and hence the force needed to overcome the resistance.
So weight comes in, along with any factors applied for presumed wind and/or rolling resistance, in calculating the resistance to apply to simulate a desired gradient, wind, road surface, etc.
Hence if you tell it you weigh more it will apply more resistance to simulate the same gradient, and hence more power will be required to achieve the same speed at the higher resistance. So weight is not a factor in calculating the power, rather it is a factor in calculating the resistance to apply.
I have done repeated tests of the bkool pro against first a Powertap G3 and then a KICKR and also real life rides on the same circuits and the Bkool was not great at applying the correct resistance, a very difficult job as speed, gearing, cadence, temperature, strength of magnets, etc. all have such an impact. This meant that the calculation of power is done using an estimated level of resistance that can vary from actual resistance by differing amounts depending on speed, cadence, gearing, temperature and from Bkool unit to bkool unit.
Even highly calibrated power meters will struggle to agree with each other and only claim to be with +-2% or so, but my bkool figures differed by up to +-15% or more from my Powertap, and the KICKR reinforced this when I used it for the same sessions. I found at slow speeds the Bkool read too low, and at high speeds it read too high.
There is also the issue of resistance limits, as there is no doubt that the Bkool units, as with any trainer, has limits as to how much resistance it can supply. This means that in effect, when a certain gradient, weight, wind speed and road surface are simulated, at various points it will fail to apply enough resistance and the variation between presumed resistance and actual resistance will break down and the power figures will become much less accurate. This will depend on gearing, cadence, weight, etc. but on gradients much above 10-15% you can usually tell the resistance is not sufficient. What seems to happen is as you apply power against the resistance, if you supply enough power you overcome the limited resistance and it becomes easier to pedal.
So don't take the power figures too seriously, they are a very useful indicator and can give you a good idea of progress and a reasonable approximation of the probable power give or take 10% or 20% or so, but they are only an approximation.
Geoff
. I forgot to ask you if you went to pro1 or did you jump straight to pro2? I'll be amazed if I ever get past pro1.
) , but a blue jersey would make me a real contender.
