Next up is the PAS sensor mounting and configuration.
REV 1 PAS sensor configuration uses a cast hub with four mounting tabs:
The cast hub is then meant to sandwich between the left crank arm and the BB face.
[youtube]gcb5JPNDtlI[/youtube]
The central flange thickness is ~3mm:
For reference, the BB is:
During initial assembly, I noted that the 4 spacers (+spring washer) were still in place on the spider side:
Unfortunately, removing 3mm of spacers from the spider side was not an option due to various clearance issues. With this design adding 3mm to the BB stack (without subsequently removing ~3mm) I was further concerned about the reduced spline engagement on the left crank arm.
Not certain of the material used for this casting. Assuming this part was produced using open pour, judging from the high level of included air (bubbles). Given the general brittle nature of these casting materials (note the fracture in the photo above), further weakened by bubbles - the failure mode in this configuration could be severe. If the hub fractured, the crank could loosen quickly, suddenly having ~3mm of lateral play. Not good under the potential power levels of this system.
I torqued the left crank arm fixing bolt:
[youtube]oQghdv6AD9A[/youtube]
Here is the completed assembly:
[youtube]arD2YEb0GS8[/youtube]
This configuration did not provide a stable PAS signal, primarily due to excessive runout.
Curious about the central flange condition after torque, I disassembled to inspect:
After this one-time torque application and dis-assembly, the central hub flange thickness measured ~2.2mm. Compressed/displaced significantly from the 3.0mm nominal.
Note the displaced material towards the end of the video:
[youtube]KqsjWH5jE5M[/youtube]
For reference, here's the mating face of the left crank arm:
Will update as the REV 2 design progresses...
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