Here is a thread a started on rec.bicycles.tech
>>
>> BobT wrote:
>> I'm having difficulty installing my Polar power sensor.
>>
>> "Qui si parla Campagnolo" <
[email protected]> wrote in message
>>
news:[email protected]...
>> Probably don't want to hear this but get a refund and get a Powertap
>> Pro rear wheel. More accurate, easier to set up, all around a better
>> system that relies on chain frequency.
Thanks, but you are right, I didn't want to hear that. In fact, I would love to have a Powertap Pro (or SRM for that matter) but I paid $250.00 for my Polar unit compared to $900.00 plus a wheel build. Based on head-to-head comparisons I've seen on the web, I'm hoping to get reasonable results with this much less expensive product.
"JayofMontreal" <
[email protected]> wrote in message
news:[email protected]...
> There is no rule with regards to the mounting of the magnet, nor what
> magnet to use. Try a rare earth magnet. They are very powerful and you can
> mount it quite a distance from the pickup and still get a reading.
>
I tried using several rare earth magnets I purchased from Radio Shack to no avail. The problem is that the chainstay is 4 cm from the inside of the crankarm where the cadence sensor needs to be. If I mount the power / cadence sensor on top of and parallel to the chain stay, I'm going to need a really strong magnet. In fact, when I put 4 of the 1/8" Radio Shack rare earth magnets in place, they pulled the chain against the crankarm magnets but didn't trigger the cadence sensor.
I have reached a solution that I will post here for others who might have this problem in the future. For the shape of my chainstay and my chainline (Onix Orbea, Shimano Ultegra 10-speed triple), I need to mount the power / cadence sensor at an angle to the chainstay with the front of the sensor outboard. I made a spacer that I zip-tied to the outside of the front of the chainstay. I then zip-tied the front of the sensor to the top of the spacer positioning the front of the sensor much closer to the crankarm. I think one could make a spacer to move the front or back of the sensor up or down or inboard or outboard.
I made the spacer out of wood. Plastic like Nylon or Delrin might be better but I couldn't find any locally. First, I measured how much above the top and how much outboard of the outside of the chainstay I needed to position the sensor. I used a contour gage to transfer the shape of the chainstay to a small block of wood. I then used a Dremel tool to shape the inboard side of the wood to fit the chainstay. I then shaped the upper outboard part of the block to fit the sensor at the correct position. I cut a shallow channel for the zip tie. I finished the wood to protect it from the elements. Now the system works!
BobT