Monday, July 15, 2013
New boards from AP circuits, SRM takes pot shots at Garmin
From left to right: V4.1, V4, V3, V3 circuit boards.
I like the purple ones best but they just don’t have the turn around time of APC.
In other news SRM seems to be taking pot shots at Garmin / Look Keo Power.
“Rider contact points, like the pedal, were initially looked at for prime PowerMeter placement. After extensive testing, SRM determined the pedal option would not give the same durable performance and accurate torque measurements as the crank spider”
This isn’t Garmin’s arrangement. Garmin is using a differential bending beam arrangement with piezo strain sensors. The differential bending beam would reduce much of the error in SRM’s design which is highly sensitive to pedal offset and angle torqueing as my experiments showed for the shear gauge on the crank arm.
However, measuring at the crank arm seemed like they couldn’t find fault. In fact it’s written as if this is their comparison case, but didn’t like that it only measured one leg each.
“In order to accurately measure power, SRM tested torque measurements in the crank arm, against the measurements in the spider. The crank spider is the first point where pedaling forces from the left and right leg meet, before that force is transmitted to the drive train”
Seems like they don’t have anything negative to say on this type of instrumentation. That’s at least a positive for me. As it should be as this is how a professional load cell would be setup essentially.