Mar 20, 2011
Some pictures up in the prototype section of the intermediate ring idea. I might do some decision matricies. It's seeming like there is a vast amount of things I could do with microcontrollers like Arduino if I can get it down to a small package. ANT+ logger, general data logging, low cost cycle computer that can be modified and changed. Running my athlete math model from my CTE project (reduced functionality, would require power meter).
Mar 18, 2011
Crank arm instrumentation looks like it will work. Sram Rival makes a good candidate but...
I didn't realize SRAM Force's crank arms are carbon fiber (I knew Red was, but didn't realize Force was too). I've been in contact with a company regarding applying strain gages to carbon fiber for permanent installation. They have yet to get back to me. They would potentially have a non linear curve. Why: Carbon fiber or Carbon reinforced polymer is essentially woven rope + plastic. Rope doesn't hold shape well, or deal with compressive stress well so it's held in shape by the epoxy. When taking up force the epoxy takes load first and then the carbon takes over primarily, but still some force is taken by the epoxy. At very low forces you get flex until the carbon gets stress and it sky rockets.
I'm looking at another avenue, an intermediary crank spider ring. CAD pictures will be uploaded in the prototype area in the next few days. My idea is instrument a intermediate aluminum assembly that connects between the crank and the rings, the rings are effectively rotated 36 degrees. To get pedal stroke the crank "BB tube" needs to be instrumented with a torque strain gage setup. For any engineers, installing strain gages on 45 degrees inside a tube is hard. Special gages for it, but still complex for building. A lot harder than exterior on the crank arms.
Mar 3, 2011
RF noise in my home has been ruining my measurements of the gages. Added a filter after the wheatstone bridge and it's cleared it up a lot. Some still left that can be found by touching the Arduino board. I'm doing to get my MCP3201 IC from the university and interface it tomorrow I think.
Feb 27, 2011
Page Launch - not much here!