Is there anyone that can service PowerTap hubs on here?

[vkonradi]

Thank you Pierre. Gutted.

Just stumbled upon this as I typed 'Powertap disassembly' in to Google search. I have a few failed hubs with different failure manifestations from which I might build some frankenhubs. And/or check PCBs for cracked solder joints and re-solder.

That was a very nice sequence of assembly photos on dcrainmaker's page.

Photo 7 on this page https://www.bikeradar.com/news/saris-cycleops-powertap-launch-2009-range/ indicates the screw thread attaching the torque tube assembly into the hub body is left hand threaded. As it must be, yes? Even though the photo on dcrainmaker seems to show torquing it CW direction.

https://www.singletracks.com/progression/cycleops-powertap-sl-mountain-bike/ has a useful cross section view. You can see where the torque tube outside seems to slide on a simple (not ball) bearing surface inside the hub, probably metal on nylon or teflon. This bearing is necessary because of course the torque tube must twist just an infinitesimal bit in order for its strain gauges to register.

Seems a main impediment to disassembly is needing a special wrench to engage the torque tube for threading into the hub body. There are two internal recesses in the torque tube cylindrical threaded section which evidently accept the wrench head. A mating tool could be fabricated by cutting/welding/filing with some fiddling to fine tune the fit.

 

[rjsdavis]

Thanks for this...

Are you volunteering to repair the Powertap hubs on here??

 

[vkonradi]

Um, yeah, of course, sure. Or maybe if I learn I can teach others to fish?

 

[vkonradi]

One fundamental challenge to making repairs is evident even before inspection. A resistor or op amp replacement in the strain gauge amplifier circuit will require adjusting the amplifier offset. Which is no doubt a register in the microcontroller flash memory. Easy enough if you have the programming tool which does the secret handshake. Or possible with significant effort if you have the documentation to implement the protocol. Next to impossible otherwise.

Or maybe adjust two offset values. The coarse value being the analog offset adder, and the fine value being the residual ADC offset after the analog offset has been set. Strain gauges... fiddly things, but they do work great once they are dialed in.

I suspect repairs would be mostly limited to mix and match of good sensor PCB and radio modules. Possibly repair of cracked solder joints, but likely not replacement of cracked components on the sensor PCB, for the noted offset calibration reason.