SRM and the weights On the wattage mailing list on various hidden or open derision towards the delivered by SRM calibration values (slope) was heard. One must Uli (Schoberer) times finally calibrated weights send ...
In September, my SRM in Jülich a guest and was given a new battery and shorter cranks and also calibrated.
That is always good, I thought. However, I had already called the mockery known. The greater was my power, how accurate my SRM would be calibrated.
lack precise weights was dispensed on a first inspection of the slope. However, disappointed me my values. These were well below expectations. I was in that one month really that much weaker?
Analytic Cycling (
http://www.analyticcycling.com/ForcesPower_Page.html ) revealed an error of about 8% ... The slope was not 34 Hz / Nm, but about 31.5 Hz / Nm.
Yesterday, a good month later, an electronic scale finally arrived. Finally could the weight plates are weighed. The review of the now relatively well known weights showed that the slope amounts to 31.7 Hz. Since 31.5 and 31.7 only 0.6% apart, so that two independent methods showed virtually the same were registered 31.7 Hz / Nm and power control.
knowledge After all, have voted in the values of the past few weeks! But I will leave me to SRM will no longer crank and not specifically intended send in for calibration.
calibration The method for calibrating the SRM is simple:
- the zero point of the exhibition at horizontal SRM crank without attached weight. Man
- the root mass with an attached weight, also horizontal crank.
- Man Formula
use (zero with weight minus zero no weight) / (weight in kg * 9.81 * crank length in m) = slope
In my case, the values
(1618 - 381) were / (23:38 * 9.81 * 0.17) = 31 725
It is recommended to use a relatively large mass (about 20 kg) to somewhat realistic values to obtain. 50 kg would probably have been better, but since the one hand, the problem would have existed to raise such a mass, on the other hand, probably would be my work stand collapsed. ;-)
